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Sample records for advanced thermal spray

  1. Advances in Thermal Spray Coatings for Gas Turbines and Energy Generation: A Review

    NASA Astrophysics Data System (ADS)

    Hardwicke, Canan U.; Lau, Yuk-Chiu

    2013-06-01

    Functional coatings are widely used in energy generation equipment in industries such as renewables, oil and gas, propulsion engines, and gas turbines. Intelligent thermal spray processing is vital in many of these areas for efficient manufacturing. Advanced thermal spray coating applications include thermal management, wear, oxidation, corrosion resistance, sealing systems, vibration and sound absorbance, and component repair. This paper reviews the current status of materials, equipment, processing, and properties' aspects for key coatings in the energy industry, especially the developments in large-scale gas turbines. In addition to the most recent industrial advances in thermal spray technologies, future technical needs are also highlighted.

  2. Thermal spray: Advances in coatings technology; Proceedings of the National Thermal Spray Conference, Orlando, FL, Sept. 14-17, 1987

    SciTech Connect

    Houck, D.L.

    1988-01-01

    Papers are presented on particle injection in plasma spraying, cored tube wires for arc and flame spraying, new plasma gun technology, and grit-blasting as a surface preparation before plasma spraying. Also considered are hypervelocity applications of tribological coatings, the variability in strength of thermally sprayed coatings, automated powder mass flow monitoring and control, and coated abrasive superfinishing. Other topics include wire-sprayed aluminum coating services in a SIMA corrosion-control shop, cerium oxide stabilized thermal barrier coatings, and strength enhancement of plasma sprayed coatings.

  3. Thermal Arc Spray Overview

    NASA Astrophysics Data System (ADS)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  4. Advances in Thermal Spray Deposition of Billets for Particle Reinforced Light Metals

    SciTech Connect

    Wenzelburger, Martin; Zimmermann, Christian; Gadow, Rainer

    2007-04-07

    Forming of light-metals in semi-solid state offers some advantages like low process temperatures, improved mould durability, good flow behavior and fine, globular microstructure of the final material. By the introduction of ceramic particles, increased elastic modulus and yield strength as well as wear resistance and creep behavior can be obtained. By semi-solid forging or semi-solid casting, particle reinforced metals (PRM) can be produced with improved matrix microstructure and beneficial forming process parameters compared to conventional MMC manufacturing techniques. The production of this kind of light metal matrix composites requires the supply of dense semi-finished parts with well defined volume fractions of homogeneously distributed particulate reinforcement. A manufacturing method for cylindrical light metal billets is described that applies thermal spraying as a build-up process for simultaneous deposition of matrix and reinforcement phase with cored wires as spraying material. Thermal spraying leads to small grain sizes and prevents dendrite formation. However, long process cycle times lead to billet heating and recrystallization of the matrix microstructure. In order to preserve small grain sizes that enable semi-solid forming, the thermal spraying process was analyzed by in-flight particle analysis and thermography. As a consequence, the deposition process was optimized by adaptation of the thermal spraying parameters and by application of additional cooling, leading to lower billet temperatures and finer PRM billet microstructure.

  5. Thermally sprayed coatings

    SciTech Connect

    Diaz, D.J.; Blann, G.A. )

    1991-05-01

    Standardization of specimen preparation for microstructural evaluation of thermally sprayed coatings is considered. Metallographic specimen preparation procedures including sectioning, encapsulation, planar grinding, and power lapping of thermally sprayed coatings are described. A Co-Ni-Cr-W coating on an AISI 410 stainless steel substrate is used as a control sample. Specimen-preparation techniques have been evaluated through scanning electron microscopy for determining the percentage of apparent porosity and energy dispersive spectroscopy for determining elemental composition.

  6. The future of thermal spray technology

    SciTech Connect

    Smith, R.W. ); Fast, R.D. )

    1994-07-01

    Thermal spray technology is emerging as an important processing tool for both surface protection and advanced materials forming. Despite the technology having been in use for over 100 years, much of its advancement, driven by aerospace applications, has occurred in the past 15 years. Increased understanding of process/structure/property relationships has resulted in the growing application of thermal spray coating technology resulting in new processes; for example, low-pressure plasma spray, high-velocity oxyfuel (HVOF) spray and reactive plasma spray. New equipment, automation and materials have been introduced. This article reviews many of the commercial thermal spray processes, borrowing from educational programs at ASM International and the Hobart Institute of Welding Technology, and reviews the applications and growth potential for emerging thermal spray processing technologies. A review of the needs in education and standardization and comparisons to programs on other countries is also presented.

  7. Thermal spray processing

    SciTech Connect

    Herman, H.; Berndt, C.C.

    1995-03-01

    Thermal spray processing has been used for a number of years to cost-effecticely apply TBC`s for a wide range of heat engine applications. In particular, bond coats are applied by plasma spray and HVOF techniques and partially-stabilized zirconia top coats are applied by plasma spray methods. Thermal spray involves melting and rapid transport of the molten particles to the substrate, where high-rate solidification and coating build-up occur. It is the very nature of this melt processing that leads to the unique layered microstructure, as well as the apparent imperfections, so readily identified with thermal spray. Modeling the process, process-induced residual stresses, and thermal conductivity will be discussed in light of a new understanding of porosity and its anisotropy. Microcracking can be understood using new approaches, allowing a fuller view of the processing-performance connection. Detailed electron microscopic, novel neutron diffraction and fracture analysis of the deposits can lead to a better understanding of how overall microstructure can be controlled to influence critical properties of the deposited TBC system.

  8. Thermal spray processing

    NASA Technical Reports Server (NTRS)

    Herman, H.; Berndt, C. C.

    1995-01-01

    Thermal spray processing has been used for a number of years to cost-effecticely apply TBC's for a wide range of heat engine applications. In particular, bond coats are applied by plasma spray and HVOF techniques and partially-stabilized zirconia top coats are applied by plasma spray methods. Thermal spray involves melting and rapid transport of the molten particles to the substrate, where high-rate solidification and coating build-up occur. It is the very nature of this melt processing that leads to the unique layered microstructure, as well as the apparent imperfections, so readily identified with thermal spray. Modeling the process, process-induced residual stresses, and thermal conductivity will be discussed in light of a new understanding of porosity and its anisotropy. Microcracking can be understood using new approaches, allowing a fuller view of the processing-performance connection. Detailed electron microscopic, novel neutron diffraction and fracture analysis of the deposits can lead to a better understanding of how overall microstructure can be controlled to influence critical properties of the deposited TBC system.

  9. Method and Process Development of Advanced Atmospheric Plasma Spraying for Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Mihm, Sebastian; Duda, Thomas; Gruner, Heiko; Thomas, Georg; Dzur, Birger

    2012-06-01

    Over the last few years, global economic growth has triggered a dramatic increase in the demand for resources, resulting in steady rise in prices for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened potential of savings and form the basis for securing future competitive advantages in the market. In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the optimization of the APS coating process is the use of the existing coating equipment. Furthermore, the current coating quality and characteristics must not change so as to avoid new qualification and testing. Using experience in APS and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow-rate, the electrical power, the arrangement and angle of the powder injectors in relation to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedures such as spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity and temperature), powder injection conditions (injection point, injection speed, grain size and distribution) and the coating lamination (coating pattern and spraying distance) are examined. The optimized process and resulting coating were compared to the current situation using several diagnostic methods. The improved process significantly reduces costs and achieves the requirement of comparable coating quality. Furthermore, a contribution was made towards better comprehension of the APS of ceramics and the definition of a better method for future process developments.

  10. Characterization of thermal spray coatings

    SciTech Connect

    Schorr, B.S.; Stein, K.J.; Marder, A.R.

    1999-02-01

    The ability to characterize fully the microstructure of a coating is paramount for understanding the in-service properties and eventual optimization of the coating. This article discusses sample preparation and subsequent analytical techniques (LOM, SEM, XRD, WDS, and QIA) for several cermet thermal spray coatings and provides a detailed analysis of as-sprayed microstructures in addition to processing trends for several FeCrAIY-carbide coatings. It was found that the splats produced in these high velocity oxy-fuel (HVOF) coatings tended to exhibit a predominantly dendritic structure most likely retained from the gas atomization process that produced the original powder. Chemical analysis showed that the carbides tend to break down during spraying producing a complex mixture of oxides and various carbides. Finally, image analysis revealed that as the carbides in the pre-sprayed powder were increased, more carbides and oxides with less FeCrAIY and thinner coatings were found. These techniques allow the thorough characterization of thermal spray cermet coatings, which in turn should further the understanding of the thermal spray processes and help provide superior coatings in the future.

  11. Cermet composite thermal spray coatings for erosion and corrosion protection in combustion environments of advanced coal-fired boilers

    SciTech Connect

    Levin, B.F.; DuPont, J.N.; Marder, A.R.

    1996-05-01

    Research is presently being initiated to determine the optimum ceramic/metal combination in thermally sprayed metal matrix composite coatings for erosion and corrosion resistance in new coal-fired boilers. The research will be accomplished by producing model cermet composites using powder metallurgy and electrodeposition methods in which the effect of ceramic/metal combination for the erosion and corrosion resistance will be determined. These results will provide the basis for determining the optimum hard phase constituents` size and volume percent in thermal spray coatings. Thermal spray coatings will be applied by our industrial sponsor and tested in our erosion and corrosion laboratories. During the last quarter, model Ni-Al{sub 2}O{sub 3} powder cermet composites were produced at Idaho National Engineering Laboratory by the Hot Isostatic Pressing (HIP) technique. The composite samples contained 0, 21, 27, 37, and 45 volume percent of Al{sub 2}O{sub 2} in a nickel matrix with an average size of alumina particles of 12 micrometers. The increase in volume fraction of alumina in the nickel matrix from 0 to 45% led to an increase in hardness of these composites from 85 to 180 HV{sub 1000}. The experimental procedure and preliminary microstructural characterization of Ni-Al{sub 2}O{sub 3} composites are presented in this progress report along with plans for the research in coming year. 3 figs.

  12. Thermal Spray Coatings for Coastal Infrastructure

    SciTech Connect

    Holcomb, G.R.; Covino, BernardS. Jr.; Cramer, S.D.; Bullard, S.J.

    1997-11-01

    Several protection strategies for coastal infrastructure using thermal-spray technology are presented from research at the Albany Research Center. Thermal-sprayed zinc coatings for anodes in impressed current cathodic protection systems are used to extend the service lives of reinforced concrete bridges along the Oregon coast. Thermal-sprayed Ti is examined as an alternative to the consumable zinc anode. Sealed thermal-sprayed Al is examined as an alternative coating to zinc dust filled polyurethane paint for steel structures.

  13. HVOF thermal spray process for internal diameter applications

    SciTech Connect

    Poe, M.W.

    1994-12-31

    Thermal spray has been selected as the coating process of choice for many OEM and repair/restoration applications. Although the thermal spray process has historically been limited to coating `line-of-sight` surfaces, advances in thermal spray equipment design now allow protective and/or restorative coatings to be applied to deep internal diameters utilizing state-of-the-art HVOF processing. The advanced designs include both `standard` and `mini` torches to coat rotating components, plus a rotating extension for coating stationary ID`s. In addition, a wide range of coating materials has been developed and engineered to combat the deleterious effects of wear found in severe service environments. The resultant coatings have exceptionally high bond strength with no interconnected porosity and low residual stress. This unique process provides an important adjunct to the field of thermal spray process capabilities.

  14. Thermal Spraying Coatings Assisted by Laser Treatment

    SciTech Connect

    Fenineche, N. E.; Cherigui, M.

    2008-09-23

    Coatings produced by air plasma spraying (APS) are widely used to protect components against abrasive wear and corrosion. However, APS coatings contain porosities and the properties of these coatings may thereby be reduced. To improve these properties, various methods could be proposed, including post-laser irradiation [1-4]. Firstly, PROTAL process (thermal spraying assisted by laser) has been developed as a palliative technique to degreasing and grit-blasting prior to thermal spraying. Secondly, thermal spray coatings are densified and remelted using Laser treatment. In this study, a review of microstructure coatings prepared by laser-assisted air plasma spraying will be presented. Mechanical and magnetic properties will be evaluated in relation to changes in the coating microstructure and the properties of such coatings will be compared with those of as-sprayed APS coatings.

  15. Thermal spraying of nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Lau, Maggy L.

    The present research addresses the fundamental synergism between thermal spray synthesis, microstructural evolution and mechanical behavior of Ni, Inconel 718 and Fe based 316-stainless steel nanocrystalline materials. Nanocrystalline Ni powders produced by mechanical milling in liquid nitrogen were investigated under isothermal and non-isothermal conditions. Significant grain growth occurred in the case of cryomilled Ni powders even when annealing at lower temperatures (equivalent to about 0.17 Tm), indicating the poor thermal stability of these powders. The activation energy for grain growth was calculated to be 146.2 kJ/mol. The values of the time exponent, n, were very close to 4.0, implying that grain growth was controlled by grain boundary diffusion mechanism. The grain growth behavior of the nanocrystalline Ni powders under non-isothermal annealing conditions showed good correspondence between the experimental results and the theoretical simulation. The grain growth behavior of the milled Inconel 718 powders and coatings, under isothermal annealing indicated that the nanocrystalline powders and coatings exhibited thermal stability against grain growth up to 1073 K (0.67Tm). The average grain sizes of methanol milled powders after annealing at 1273 K for 1 hr, cryomilled powders, HVOF coating of the methanol milled powders and HVOF coatings of the cryomilled Inconel 718 powders were 91, 84, 137 and 102 nm, respectively. In the present study, Zener pinning of nanoscale oxides of (Cr,Fe) contributed to the stability against grain growth during thermal annealing of the nanocrystalline Inconel 718 powders and coatings. (Abstract shortened by UMI.)

  16. Thermal spray applications for power plant components

    SciTech Connect

    Sampson, E.R.

    2000-03-01

    Power plants usually are located near water and many are in salt water environments. Corrosion occurring in these environments is a problem often solved with thermal spray coatings. The use of thermal spray aluminum and zinc in three power plants for various components is reviewed. Special emphasis is on the cooling tower at the Seabrook, New Hampshire plant. A guide to selection of the coating and process also is given.

  17. Laser modification of thermally sprayed coatings

    NASA Astrophysics Data System (ADS)

    Uglov, A. A.; Fomin, A. D.; Naumkin, A. O.; Pekshev, P. Iu.; Smurov, I. Iu.

    1987-08-01

    Experimental results are reported on the modification of thermally sprayed coatings on steels and aluminum alloys using pulsed YAG and CW CO2 lasers. In particular, results obtained for self-fluxing Ni9CrBSi powders, ZRO2 ceramic, and titanium are examined. It is shown that the laser treatment of thermally sprayed coatings significantly improves their physicomechanical properties; it also makes it possible to obtain refractory coatings on low-melting substrates with good coating-substrate adhesion.

  18. Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Ganvir, Ashish; Curry, Nicholas; Markocsan, Nicolaie; Nylén, Per; Joshi, Shrikant; Vilemova, Monika; Pala, Zdenek

    2016-01-01

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  19. Wear mechanisms in thermally-sprayed Mo-based coatings

    NASA Astrophysics Data System (ADS)

    Wayne, S. F.; Sampath, S.; Anand, V.

    1994-07-01

    The successful development of advanced diesel engines relies heavily on piston ring coating materials which can withstand elevated temperatures and reduce friction. Traditional hard chrome plating and flame-sprayed Mo-wire materials have reached their potential in the diesel engine environment, and alternatives are needed. Thermally-sprayed Mo-based alloys and composites are being evaluated for applications as next-generation ring-face coatings. The alloy development task of producing complex Mo-based alloy powders for use as thermally-sprayed coating materials requires an understanding of their wear resistance under contact stress conditions. In this paper, the wear behavior of Mo and Mo + NiCrBSi thermally sprayed coatings is exmined by pin-on-disc and single-point scratch-test methods. Microstructural analysis beneath worn regions have revealed that fracture of splats and their decohesion constitute the mode of failure. Improved wear resistance and stability of low friction coefficient was obtained by prealloying Mo with NiCrBSi prior to thermal spraying.

  20. Thermal spray manual for machinery components

    SciTech Connect

    Travis, R.; Ginther, C.; Herbstritt, M.; Herbstritt, J.

    1995-12-31

    The Thermal Spray Manual For Machinery Components is a National Shipbuilding Research (SP-7) Project. This Manual is being developed by Puget Sound Naval Shipyard with the help of other government thermal spray facilities and SP-7 panel members. The purpose of the manual is to provide marine repair facilities with a ``how to do`` document that will be ``user friendly`` and known to be technically sound through production experience. The manual`s intent is to give marine repair facilities the ability to maximize the thermal spray process as a repair method for machinery components and to give these facilities guidelines on how to become qualified to receive certification that they meet the requirements of Military Standard 1687A.

  1. Thermal sprayed zirconium coatings for corrosion resistance

    SciTech Connect

    Bamola, R.K.

    1992-01-01

    Vacuum Plasma Spraying (VPS) is conducted in inert reduced pressures. This results in higher particle velocities than in atmospheric plasma spraying. Reverse arc sputter cleaning and pre-heating of the workpiece lead to elevated substrate temperatures during deposition, allowing sintering of the coating and, thus, enhanced densities and bond strengths. Inert Environment Electric Arc Spraying (IEAS) is performed in inert gas chambers, utilizing wire as the feedstock. This leads to lower gas content in the coating, since the initial gas content in wire is lower than that of the powder feedstock used in VPS. Controlled atmosphere sprayed zirconium coatings had inferior mechanical and corrosion properties when compared with bulk zirconium. The VPS coatings displayed higher bond strengths and better cavitation erosion resistance than did the IEAS coatings. The IEAS coatings had lower gas content and showed better electrochemical and corrosion behavior. The lower gas content for IEAS was due to a lower initial gas level in the wire feedstock used in this process. Also, scanning electron microscopy revealed that larger particles result in the IEAS process. Thus, a smaller surface-area-to-volume ratio is available for gas-metal reactions to occur. Improvements in mechanical and corrosion properties for the IEAS coatings were due to elevated substrate temperatures during deposition. Compressive surface stresses induced by post-spray shot-peening enhanced corrosion and cavitation resistance of IEAS coatings. Coating porosity caused failure during immersion testing. Therefore, it was concluded that controlled environment thermal spraying of zirconium is not suitable for forming corrosion resistant coatings on steel. ZrN coatings were formed by electric arc spraying using a nitrogen shroud and post-spray nitriding. Two phases; ZrN and zirconium solid solution, exist in the as-sprayed coating. Nitriding increases the proportion of ZrN.

  2. Stereological analysis of thermally sprayed deposits

    SciTech Connect

    Montavon, G.; Coddet, C.; Leigh, S.H.; Sampath, S.; Herman, H.; Berndt, C.C.

    1995-12-31

    Thermal spray deposits can be described by several characteristics including the porosity, the fraction of unmolten particles and the microhardness. These physical and structural characteristics are general and little quantitative information is available to fully describe the microstructure of such deposits. Stereological analysis is one of the microscopic methods which provides quantitative relationships. Hence, it allows a better understanding of correlations between spray parameters and deposit microstructure. Stereology, in the most strict sense, is able to describe a 3-D space from 2-D sections through solid bodies. The aim of this paper is to review the numerical formulations of methods that can be applied on 2-D cross-sections of thermal spray deposits. A historical perspective of several approaches is given, and two methods (i.e., DeHoff`s and Cruz-Orive`s protocols) are detailed.

  3. Cermet composite thermal spray coatings for erosion and corrosion protection in combustion environments of advanced coal-fired boilers. Semiannual technical report, January 14, 1997--August 14, 1997

    SciTech Connect

    Schorr, B.S.; Levin, B.F.; DuPont, J.N.; Marder, A.R.

    1997-08-31

    Research is presently being conducted to determine the optimum ceramic/metal combination in thermally sprayed metal matrix composite coatings for erosion and corrosion resistance in new coal-fired boilers. The research will be accomplished by producing model cermet composites using powder metallurgy and electrodeposition methods in which the effect of ceramic/metal combination for the erosion and corrosion resistance will be determined. These results will provide the basis for determining the optimum hard phase constituent size and volume percent in thermal spray coatings. Thermal spray coatings will be applied by our industrial sponsor and tested in our erosion and corrosion laboratories. Bulk powder processed Ni-Al{sub 2}O{sub 3} composites were produced at Idaho National Engineering Laboratory. The composite samples contained 0, 21, 27, 37, and 45 volume percent Al{sub 2}O{sub 3} with an average particle size of 12 um. Also, to deposit model Ni-Al{sub 2}O{sub 3} coatings, an electrodeposition technique was developed and coatings with various volume fractions (0-35%) of Al{sub 2}O{sub 3} were produced. The powder and electrodeposition processing of Ni-Al{sub 2}O{sub 3} Composites provide the ability to produce two phase microstructure without changing the microstructure of the matrix material. Therefore, the effect of hard second phase particles size and volume fraction on erosion resistance could be analyzed.

  4. Thermal spray coatings on Yankee dryers

    SciTech Connect

    Bowers, D.F. )

    1994-08-01

    Several failure investigations and recent research on thermal spray coatings on Yankee dryer surfaces show at least three modes of environmentally induced degradation. Corrosion may occur with the ingress of certain chemicals into coating pores. Erosion or corrosion is manifested by streaks at local sites of high doctor blade loading. Erosion and cracking occur due to coating parameters, thermal stress, and differential expansion. While most of the results described in this paper are from investigations of molybdenum, stainless steel coatings also are discussed.

  5. A new HVOF thermal spray concept

    SciTech Connect

    Browning, J.A.; Matus, R.J.; Richter, H.J.

    1995-12-31

    HVOF plays an important role in the commercial production of thermal spray coatings from powder. Initially, both the chamber and duct modes were used. Today, the best coatings are produced by high-pressure chamber guns with some manufacturers having switched their designs from the duct to the chamber mode. There has been little or no spraying of wire with HVOF equipment. A new HVOF process -- the shock-stabilized mode -- compliments chamber powder spraying by offering the user a very simple device for wire use. Calculations show that the much higher jet velocities of the chamber mode make that design the better suited for use with powder. Conversely, the greatly increased jet temperatures offered by shock-stabilized combustion give extremely high wire melt-off rates.

  6. High velocity pulsed plasma thermal spray

    NASA Astrophysics Data System (ADS)

    Witherspoon, F. D.; Massey, D. W.; Kincaid, R. W.; Whichard, G. C.; Mozhi, T. A.

    2002-03-01

    The quality and durability of coatings produced by many thermal spray techniques could be improved by increasing the velocity with which coating particles impact the substrate. Additionally, better control of the chemical and thermal environment seen by the particles during flight is crucial to the quality of the coating. A high velocity thermal spray device is under development through a Ballistic Missile Defense Organization Small Business Innovation Research (SBIR) project, which provides significantly higher impact velocity for accelerated particles than is currently available with existing thermal spray devices. This device utilizes a pulsed plasma as the accelerative medium for powders introduced into the barrel. Recent experiments using a particle imaging diagnostic system showed that the device can accelerate stainless steel and WC-Co powders to velocities ranging from 1500 to 2200 m/s. These high velocities are accomplished without the use of combustible gases and without the need of a vacuum chamber, while maintaining an inert atmosphere for the particles during acceleration. The high velocities corresponded well to modeling predictions, and these same models suggest that velocities as high as 3000 m/s or higher are possible.

  7. Thermal Spray Formation of Polymer Coatings

    NASA Technical Reports Server (NTRS)

    Coquill, Scott; Galbraith, Stephen L.; Tuss. Darren L.; Ivosevic, Milan

    2008-01-01

    This innovation forms a sprayable polymer film using powdered precursor materials and an in-process heating method. This device directly applies a powdered polymer onto a substrate to form an adherent, mechanically-sound, and thickness-regulated film. The process can be used to lay down both fully dense and porous, e.g., foam, coatings. This system is field-deployable and includes power distribution, heater controls, polymer constituent material bins, flow controls, material transportation functions, and a thermal spray apparatus. The only thing required for operation in the field is a power source. Because this method does not require solvents, it does not release the toxic, volatile organic compounds of previous methods. Also, the sprayed polymer material is not degraded because this method does not use hot combustion gas or hot plasma gas. This keeps the polymer from becoming rough, porous, or poorly bonded.

  8. Method of producing thermally sprayed metallic coating

    DOEpatents

    Byrnes, Larry Edward; Kramer, Martin Stephen; Neiser, Richard A.

    2003-08-26

    The cylinder walls of light metal engine blocks are thermally spray coated with a ferrous-based coating using an HVOF device. A ferrous-based wire is fed to the HVOF device to locate a tip end of the wire in a high temperature zone of the device. Jet flows of oxygen and gaseous fuel are fed to the high temperature zone and are combusted to generate heat to melt the tip end. The oxygen is oversupplied in relation to the gaseous fuel. The excess oxygen reacts with and burns a fraction of the ferrous-based feed wire in an exothermic reaction to generate substantial supplemental heat to the HVOF device. The molten/combusted metal is sprayed by the device onto the walls of the cylinder by the jet flow of gases.

  9. Thermal Expansion of Vacuum Plasma Sprayed Coatings

    NASA Technical Reports Server (NTRS)

    Raj, S V.; Palczer, A. R.

    2010-01-01

    Metallic Cu-8%Cr, Cu-26%Cr, Cu-8%Cr-1%Al, NiAl and NiCrAlY monolithic coatings were fabricated by vacuum plasma spray deposition processes for thermal expansion property measurements between 293 and 1223 K. The corrected thermal expansion, (DL/L(sub 0) varies with the absolute temperature, T, as (DL/L(sub 0) = A(T - 293)(sup 3) + BIT - 293)(sup 2) + C(T - 293) + D, where, A, B, C and D are thermal, regression constants. Excellent reproducibility was observed for all of the coatings except for data obtained on the Cu-8%Cr and Cu-26%Cr coatings in the first heat-up cycle, which deviated from those determined in the subsequent cycles. This deviation is attributed to the presence of residual stresses developed during the spraying of the coatings, which are relieved after the first heat-up cycle. In the cases of Cu-8%Cr and NiAl, the thermal expansion data were observed to be reproducible for three specimens. The linear expansion data for Cu-8% Cr and Cu-26%Cr agree extremely well with rule of mixture (ROM) predictions. Comparison of the data for the Cu-8%Cr coating with literature data for Cr and Cu revealed that the thermal expansion behavior of this alloy is determined by the Cu-rich matrix. The data for NiAl and NiCrAlY are in excellent agreement with published results irrespective of composition and the methods used for processing the materials. The implications of these results on coating GRCop-84 copper alloy combustor liners for reusable launch vehicles are discussed.

  10. Thermal Conductivity and Sintering Behavior of Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2002-01-01

    Advanced thermal barrier coatings, having significantly reduced long-term thermal conductivities, are being developed using an approach that emphasizes real-time monitoring of thermal conductivity under conditions that are engine-like in terms of temperatures and heat fluxes. This is in contrast to the traditional approach where coatings are initially optimized in terms of furnace and burner rig durability with subsequent measurement in the as-processed or furnace-sintered condition. The present work establishes a laser high-heat-flux test as the basis for evaluating advanced plasma-sprayed and physical vapor-deposited thermal barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) Program. The candidate coating materials for this program are novel thermal barrier coatings that are found to have significantly reduced thermal conductivities due to an oxide-defect-cluster design. Critical issues for designing advanced low conductivity coatings with improved coating durability are also discussed.

  11. Cold Sprayed Intermetallic Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Leshchinsky, Evgeny

    Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bond coat and a ceramic heat-isolative topcoat. Several recent research activities are concentrated on the development of improved multilayer bond coat and TBC materials. This study represents an investigation performed for the aluminum based bond coats, especially those with reduced thermal conductivities. Using alternative TBC materials, such as metal alloys and intermetallics, their processing methods can be further optimized to achieve the best thermal physical parameters. One example is the ten-layer system in which cold sprayed aluminum based intermetallics are synthesized. These systems demonstrated improved heat insulation and thermal fatigue capabilities compared to conventional TBC. The microstructures and properties of the laminar coatings were characterized by SEM, EDS, XRD; micromechanical and durability tests were performed to define the structure and coating formation mechanisms. Application prospects for HCCI engines are discussed. Fuel energy can be utilized more efficiently with the concept of low heat rejection engines with applied TBC.

  12. Chromium coatings by HVOF thermal spraying: Simulation and practical results

    SciTech Connect

    Knotek, O.; Lugscheider, E.; Jokiel, P.; Schnaut, U.; Wiemers, A.

    1994-12-31

    Within recent years High Velocity Oxygen-Fuel (HVOF) thermal spraying has been considered an asset to the family of thermal spraying processes. Especially for spray materials with melting points below 3,000 K it has proven successful, since it shows advantages when compared to coating processes that produce similar qualities. In order to enlarge the fields of thermal spraying applications into regions with rather low thickness, e.g. about 50--100 {micro}m, especially HVOF thermally sprayed coatings seem to be advantageous. The usual evaluation of optimized spraying parameters, including spray distance, traverse speed, gas flow rates etc. is, however, based on numerous and extensive experiments laid out by trial-and-error or statistical experimental design and thus being expensive: man-power and material is required, spray systems are occupied for experimental works and the optimal solution is questioned, for instance, when a new powder fraction or nozzle is used. In this paper the possibility of reducing such experimental efforts by using modeling and simulation is exemplified for producing thin chromium coatings with a CDS{trademark}-HVOF system. The aim is the production of thermally sprayed chromium coatings competing with galvanic hard chromium platings, which are applied to reduce friction and corrosion but are environmentally disadvantageous during their production.

  13. Experimental Analysis of Spray Dryer Used in Hydroxyapatite Thermal Spray Powder

    NASA Astrophysics Data System (ADS)

    Murtaza, Q.; Stokes, J.; Ardhaoui, M.

    2012-09-01

    The spray drying process of hydroxyapatite (HA) powder used as a plasma spray powder on human hip implants was examined. The Niro-Minor mixed spray dryer was studied because it incorporates both co-current and counter-current air mixing systems. The process parameters of the spray drying were investigated: temperature, flow rate of the inlet hot air in the spray dryer, viscosity of feed/HA slurry, and responses (chamber and cyclone powder size, deposition of powder on the wall of spray dryer, and overall thermal efficiency). The statistical analysis (ANOVA test) showed that for the chamber particle size, viscosity was the most significant parameter, while for the cyclone particle size, the main effects were temperature, viscosity, and flow rate, but also their interaction effects were significant. The spray dried HA powder showed the two main shapes were a doughnut and solid sphere shape as a result of the different input.

  14. Thermal spray and cold spray analysis of density, porosity, and tensile Specimens for use with LIGA applications

    SciTech Connect

    DECKER,MERLIN K.; SMITH,MARK F.

    2000-02-01

    This analysis provides a preliminary investigation into using Twin-Wire Arc Thermal Spray and Cold Spray as material deposition processes for LIGA applications. These spray material processes were studied to make an initial determination of their potential as alternatives to producing mechanical parts via the electroplating process. Three materials, UltraMachinable{reg_sign} Stainless Steel, BondArc{reg_sign}, and aluminum, were sprayed using Thermal Spray. Only aluminum was sprayed using the Cold Spray process. Following the spray procedure, the test specimens were released from a copper mold and then tested. Three tests, density, tensile strength, and porosity, were performed on the specimens to determine the spray effect on material properties. Twin-Wire Arc Thermal Spray did not demonstrate adequate deposition properties and does not appear to be a good process candidate for LIGA. However, Cold Spray yielded better density results and warrants further investigation to analyze the minimum feature size produced by the process.

  15. Thermal spray ceramic coatings. (Latest citations from METADEX). Published Search

    SciTech Connect

    Not Available

    1994-10-01

    The bibliography contains citations concerning the application of ceramic coatings by thermal spraying. The coatings discussed include alumina, yttrium oxide, carbides, and nitrides. Citations focus on plasma spraying, tribology, processing, and contact fatigue. (Contains 250 citations and includes a subject term index and title list.)

  16. Structurally Integrated, Damage-Tolerant, Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Vackel, Andrew; Dwivedi, Gopal; Sampath, Sanjay

    2015-07-01

    Thermal spray coatings are used extensively for the protection and life extension of engineering components exposed to harsh wear and/or corrosion during service in aerospace, energy, and heavy machinery sectors. Cermet coatings applied via high-velocity thermal spray are used in aggressive wear situations almost always coupled with corrosive environments. In several instances (e.g., landing gear), coatings are considered as part of the structure requiring system-level considerations. Despite their widespread use, the technology has lacked generalized scientific principles for robust coating design, manufacturing, and performance analysis. Advances in process and in situ diagnostics have provided significant insights into the process-structure-property-performance correlations providing a framework-enhanced design. In this overview, critical aspects of materials, process, parametrics, and performance are discussed through exemplary studies on relevant compositions. The underlying connective theme is understanding and controlling residual stresses generation, which not only addresses process dynamics but also provides linkage for process-property relationship for both the system (e.g., fatigue) and the surface (wear and corrosion). The anisotropic microstructure also invokes the need for damage-tolerant material design to meet future goals.

  17. Thermal spray deposition and evaluation of low-Z coatings

    SciTech Connect

    Seals, R.D.; Swindeman, C.J.; White, R.L.

    1996-09-01

    Thermally sprayed low-Z coatings of B{sub 4}C on Al substrates were investigated as candidate materials for first-wall reactor protective surfaces. Comparisons were made to thermally sprayed coatings of B, MgAl{sub 2}O{sub 4}, Al{sub 2}O{sub 3}, and composites. Graded bond layers were applied to mitigate coefficient of thermal expansion mismatch. Microstructures, thermal diffusivity before and after thermal shock loading, steel ball impact resistance, CO{sub 2} pellet cleaning and erosion tolerance, phase content, stoichiometry by Rutherford backscattering spectroscopy, and relative tensile strengths were measured.

  18. Trajectory Generation and Coupled Numerical Simulation for Thermal Spraying Applications on Complex Geometries

    NASA Astrophysics Data System (ADS)

    Candel, A.; Gadow, R.

    2009-12-01

    For high process reproducibility and optimized coating quality in thermal spray applications on complex geometries, atmospheric plasma spraying and high-velocity oxygen fuel torches are guided by advanced robot systems. The trajectory of the torch, the spray angle, and the relative speed between torch and component are crucial factors which affect the coating microstructure, properties, and, especially, the residual stress distribution. Thus, the requirement of high-performance thermally sprayed coatings with narrow dimensional tolerances leads to challenges in the field of robot-assisted handling, and software tools for efficient trajectory generation and robot programming are demanded. By appropriate data exchange, the automatically generated torch trajectory and speed profile can be integrated in finite element method models to analyze their influence on the heat and mass transfer during deposition. Coating experiments assisted by online diagnostics were performed to validate the developed software tools.

  19. Thermal properties of plasma-sprayed tungsten deposits

    NASA Astrophysics Data System (ADS)

    Kang, Hyun-Ki

    2004-10-01

    Tungsten powder was plasma-sprayed onto a graphite substrate in order to examine the microstructures, porosities, and thermal conductivities of tungsten deposits. Tungsten was partially oxidized to tungsten oxide (WO 3) after plasma spraying. Most pores were found in the vicinity of lamellar layers in association with oxidation. It was revealed that both tungsten oxide and the lamellar structure with pores have a significant influence on the electrical and thermal conductivity.

  20. Efficiency of Pulsed Detonation Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Cannon, Jacob E.; Alkam, Mohammad; Butler, P. Barry

    2008-12-01

    Pulsed detonation thermal spray coating is used to enhance the material properties at the surface of an object. The present research implements computational fluid dynamic modeling to identify the efficiency of energy and mass delivered to potential target locations. Six cases of a hydrogen-air mixture are used to investigate the gas flow from the instant of ignition to the instant of flow reversal at the tube exit. Flow monitors are included in the model to represent potential target locations. These monitors are placed at different axial locations in order to record mass flow rate and the flow rate of enthalpy over time. The results indicate that there exists a quasi-steady jet that is efficient and predictable in delivery of energy and mass from the tube exit to potential target locations positioned on the centerline. The duration of the quasi-steady jet is dependent on the fraction of combustible gas (i.e., % fill). Much of the initial energy and mass delivered from the jet avoids the flow monitors. This is found to be related to the evolution of the jet behind the blast wave where energy is lost in expansion and vorticity production. It is also found that nearly 11-18% of the available energy and 20-23% of the available mass remains in the tube after flow reversal.

  1. Cermet composite thermal spray coatings for erosion and corrosion protection in combustion environments of advanced coal-fired boilers. Semi-annual technical progress report, February 1996--July 1996

    SciTech Connect

    Banovic, S.W.; Levin, B.F.; DuPont, J.N.; Marder, A.R.

    1996-08-01

    Present coal-fired boiler environments remain hostile to the materials of choice since corrosion and erosion can be a serious problem in certain regions of the boiler. Recently, the Clean Air Act Amendment is requiring electric power plants to reduce NO{sub x}, emissions to the environment. To reduce NO{sub x}, emissions, new low NO{sub x}, combustors are utilized which burn fuel with a substoichiometric amount of oxygen (i.e., low oxygen partial pressure). In these low NO{sub x} environments, H{sub 2}S gas is a major source of sulfur. Due to the sulfidation process, corrosion rates in reducing parts of boilers have increased significantly and existing boiler tube materials do not always provide adequate corrosion resistance. Combined attack due to corrosion and erosion is a concern because of the significantly increased operating costs which result in material failures. One method to combat corrosion and erosion in coal-fired boilers is to apply coatings to the components subjected to aggressive environments. Thermal spray coatings, a cermet composite comprised of hard ceramic phases of oxide and/or carbide in a metal binder, have been used with some success as a solution to the corrosion and erosion problems in boilers. However, little is known on the effect of the volume fraction, size, and shape of the hard ceramic phase on the erosion and corrosion resistance of the thermally sprayed coatings. It is the objective of this research to investigate metal matrix composite (cermet) coatings in order to determine the optimum ceramic/metal combination that will give the best erosion and corrosion resistance in new advanced coal-fired boilers.

  2. Measuring of residual stresses in thermal sprayed coatings

    SciTech Connect

    Brandt, O.C.

    1995-12-31

    The Modified Almen Method (MAM) uses the deformation of test samples for measuring the residual stress and with small mathematical expenditure it yields the distribution in the coating. This paper presents the basic theory of MAM and the boundary conditions for using this method for the classification of thermal sprayed coatings with respect to the residual stress. The residual stress distribution of different HVOF coatings are shown in this work. Typical spray parameters are compared. The results are also compared with the ones calculated with other methods for the determination of the residual stress in thermal sprayed coatings.

  3. Reactive Plasma Nitriding of AL2O3 Powder in Thermal Spray

    NASA Astrophysics Data System (ADS)

    Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

    Among advanced ceramics, aluminum nitride (AlN) had attracted much attention in the field of electrical and structural applications due to its outstanding properties. However, it is difficult to fabricate AlN coating by conventional thermal spray processes directly. Due to the thermal decomposition of feedstock AlN powder during spraying without a stable melting phase (which is required for deposition in thermal spray). Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of AlN thermally sprayed coatings. In this study the possibility of fabrication of AlN coating by reactive plasma nitriding of alumina (Al2O3) powder using N2/H2 plasma was investigated. It was possible to fabricate a cubic-AlN (c-AlN) based coating and the fabricated coating consists of c-AlN, α-Al2O3, Al5O6N and γ-Al2O3. It was difficult to understand the nitriding process from the fabricated coatings. Therefore, the Al2O3 powders were sprayed and collected in water. The microstructure observation of the collected powder and its cross section indicate that the reaction started from the surface. Thus, the sprayed particles were melted and reacted in high temperature reactive plasma and formed aluminum oxynitride which has cubic structure and easily nitride to c-AlN. During the coatings process the particles collide, flatten, and rapidly solidified on a substrate surface. The rapid solidification on the substrate surface due to the high quenching rate of the plasma flame prevents AlN crystal growth to form the hexagonal phase. Therefore, it was possible to fabricate c-AlN/Al2O3 based coatings through reactive plasma nitriding reaction of Al2O3 powder in thermal spray.

  4. Advanced manufacturing by spray forming: Aluminum strip and microelectromechanical systems

    SciTech Connect

    McHugh, K.M.

    1994-12-31

    Spray forming is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. By combining rapid solidification processing with product shape control, spray forming can reduce manufacturing costs while improving product quality. INEL is developing a unique spray-forming method based on de Laval (converging/diverging) nozzle designs to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Properties of the spray-formed material are tailored by controlling the characteristics of the spray plume and substrate. Two examples are described: high-volume production of aluminum alloy strip, and the replication of micron-scale features in micropatterned polymers during the production of microelectromechanical systems.

  5. Fuel thermal stability effects on spray characteristics

    NASA Technical Reports Server (NTRS)

    Lefebvre, A. H.; Nickolaus, D.

    1987-01-01

    The propensity of a heated hydrocarbon fuel toward solids deposition within a fuel injector is investigated experimentally. Fuel is arranged to flow through the injector at constant temperature, pressure, and flow rate and the pressure drop across the nozzle is monitored to provide an indication of the amount of deposition. After deposits have formed, the nozzle is removed from the test rig and its spray performance is compared with its performance before deposition. The spray characteristics measured include mean drop size, drop-size distribution, and radial and circumferential fuel distribution. It is found that small amounts of deposition can produce severe distortion of the fuel spray pattern. More extensive deposition restores spray uniformity, but the nozzle flow rate is seriously curtailed.

  6. Photocatalytic Iron Oxide Coatings Produced by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Navidpour, A. H.; Salehi, M.; Amirnasr, M.; Salimijazi, H. R.; Azarpour Siahkali, M.; Kalantari, Y.; Mohammadnezhad, M.

    2015-12-01

    Recently, hematite coatings with semiconductor properties have received attention for photocatalytic applications. In this study, plasma and flame spraying techniques were used for hematite deposition on 316 stainless steel plates. X-ray diffraction was used for phase composition analysis, and methylene blue was used as an organic pollutant to evaluate the photocatalytic activity of thermally sprayed coatings. The results showed that all these coatings could act under visible-light irradiation but the one deposited by flame spraying at 20 cm stand-off distance showed the highest photocatalytic activity. The results showed that wavelength of the light source and pH of the solution affected the photocatalytic activity significantly. It was also shown that thermally sprayed iron oxide coatings could have a high photo-absorption ability, which could positively affect the photocatalytic activity.

  7. Quality optimization of thermally sprayed coatings produced by the JP-5000 (HVOF) gun using mathematical modeling

    NASA Technical Reports Server (NTRS)

    Tawfik, Hazem

    1994-01-01

    Currently, thermal barrier coatings (TBC) of gas-turbine blades and similar applications have centered around the use of zirconia as a protective coating for high thermal applications. The advantages of zirconia include low thermal conductivity and good thermal shock resistance. Thermally sprayed tungsten carbide hardface coatings are used for a wide range of applications spanning both the aerospace and other industrial markets. Major aircraft engine manufacturers and repair facilities use hardface coatings for original engine manufacture (OEM), as well as in the overhaul of critical engine components. The principle function of these coatings is to resist severe wear environments for such wear mechanisms as abrasion, adhesion, fretting, and erosion. The (JP-5000) thermal spray gun is the most advanced in the High Velocity Oxygen Fuel (HVOF) systems. Recently, it has received considerable attention because of its relative low cost and its production of quality coatings that challenge the very successful but yet very expensive Vacuum Plasma Spraying (VPS) system. The quality of thermal spray coatings is enhanced as porosity, oxidation, residual stress, and surface roughness are reduced or minimized. Higher densification, interfacial bonding strength, hardness and wear resistance of coating are desirable features for quality improvement.

  8. Plasma Spray-PVD: A New Thermal Spray Process to Deposit Out of the Vapor Phase

    NASA Astrophysics Data System (ADS)

    von Niessen, Konstantin; Gindrat, Malko

    2011-06-01

    Plasma spray-physical vapor deposition (PS-PVD) is a low pressure plasma spray technology recently developed by Sulzer Metco AG (Switzerland). Even though it is a thermal spray process, it can deposit coatings out of the vapor phase. The basis of PS-PVD is the low pressure plasma spraying (LPPS) technology that has been well established in industry for several years. In comparison to conventional vacuum plasma spraying (VPS) or low pressure plasma spraying (LPPS), the new proposed process uses a high energy plasma gun operated at a reduced work pressure of 0.1 kPa (1 mbar). Owing to the high energy plasma and further reduced work pressure, PS-PVD is able to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional physical vapor deposition (PVD) technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and electron beam-physical vapor deposition (EB-PVD) coatings. In contrast to EB-PVD, PS-PVD incorporates the vaporized coating material into a supersonic plasma plume. Owing to the forced gas stream of the plasma jet, complex shaped parts such as multi-airfoil turbine vanes can be coated with columnar thermal barrier coatings using PS-PVD. Even shadowed areas and areas which are not in the line of sight of the coating source can be coated homogeneously. This article reports on the progress made by Sulzer Metco in developing a thermal spray process to produce coatings out of the vapor phase. Columnar thermal barrier coatings made of Yttria-stabilized Zircona (YSZ) are optimized to serve in a turbine engine. This process includes not only preferable coating properties such as strain tolerance and erosion

  9. High-Performance Corrosion-Resistant Materials: Iron-Based Amorphous-Metal Thermal-Spray Coatings: SAM HPCRM Program ? FY04 Annual Report ? Rev. 0 - DARPA DSO & DOE OCRWM Co-Sponsored Advanced Materials Program

    SciTech Connect

    Farmer, J; Haslam, J; Wong, F; Ji, S; Day, S; Branagan, D; Marshall, M; Meacham, B; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Weaver, D; Aprigliano, L; Kohler, L; Bayles, R; Lemieux, E; Wolejsza, T; Martin, F; Yang, N; Lucadamo, G; Perepezko, J; Hildal, K; Kaufman, L; Heuer, A; Ernst, F; Michal, G; Kahn, H; Lavernia, E

    2007-09-19

    The multi-institutional High Performance Corrosion Resistant Materials (HPCRM) Team is cosponsored by the Defense Advanced Projects Agency (DARPA) Defense Science Office (DSO) and the Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM), and has developed new corrosion-resistant, iron-based amorphous metals that can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The Fe-based corrosion-resistant, amorphous-metal coatings under development may prove of importance for applications on ships. Such coatings could be used as an 'integral drip shield' on spent fuel containers, as well as protective coatings that could be applied over welds, thereby preventing exposure to environments that might cause stress corrosion cracking. In the future, such new high-performance iron-based materials could be substituted for more-expensive nickel-based alloys, thereby enabling a reduction in the $58-billion life cycle cost for the long-term storage of the Nation's spent nuclear fuel by tens of percent.

  10. Analysis of biofluids by paper spray MS: advances and challenges.

    PubMed

    Manicke, Nicholas E; Bills, Brandon J; Zhang, Chengsen

    2016-03-01

    Paper spray MS is part of a cohort of ambient ionization or direct analysis methods that seek to analyze complex samples without prior sample preparation. Extraction and electrospray ionization occur directly from the paper substrate upon which a dried matrix spot is stored. Paper spray MS is capable of detecting drugs directly from dried blood, plasma and urine spots at the low ng/ml to pg/ml levels without sample preparation. No front end separation is performed, so MS/MS or high-resolution MS is required. Here, we discuss paper spray methodology, give a comprehensive literature review of the use of paper spray MS for bioanalysis, discuss technological advancements and variations on this technique and discuss some of its limitations. PMID:26916068

  11. Thermal Spray Coatings for Blast Furnace Tuyere Application

    NASA Astrophysics Data System (ADS)

    Pathak, A.; Sivakumar, G.; Prusty, D.; Shalini, J.; Dutta, M.; Joshi, S. V.

    2015-12-01

    The components in an integrated steel plant are invariably exposed to harsh working environments involving exposure to high temperatures, corrosive gases, and erosion/wear conditions. One such critical component in the blast furnace is the tuyere, which is prone to thermal damage by splashing of molten metal/slag, erosive damage by falling burden material, and corrosion from the ensuing gases. All the above, collectively or independently, accelerate tuyere failure, which presents a potential explosion hazard in a blast furnace. Recently, thermal spray coatings have emerged as an effective solution to mitigate such severe operational challenges. In the present work, five different coatings deposited using detonation spray and air plasma spray techniques were comprehensively characterized. Performance evaluation involving thermal cycling, hot corrosion, and erosion tests was also carried out. Based on the studies, a coating system was suggested for possible tuyere applications and found to yield substantial improvement in service life during actual field trials.

  12. Advanced Diagnostics for High Pressure Spray Combustion.

    SciTech Connect

    Skeen, Scott A.; Manin, Julien Luc; Pickett, Lyle M.

    2014-06-01

    The development of accurate predictive engine simulations requires experimental data to both inform and validate the models, but very limited information is presently available about the chemical structure of high pressure spray flames under engine- relevant conditions. Probing such flames for chemical information using non- intrusive optical methods or intrusive sampling techniques, however, is challenging because of the physical and optical harshness of the environment. This work details two new diagnostics that have been developed and deployed to obtain quantitative species concentrations and soot volume fractions from a high-pressure combusting spray. A high-speed, high-pressure sampling system was developed to extract gaseous species (including soot precursor species) from within the flame for offline analysis by time-of-flight mass spectrometry. A high-speed multi-wavelength optical extinction diagnostic was also developed to quantify transient and quasi-steady soot processes. High-pressure sampling and offline characterization of gas-phase species formed following the pre-burn event was accomplished as well as characterization of gas-phase species present in the lift-off region of a high-pressure n-dodecane spray flame. For the initial samples discussed in this work several species were identified, including polycyclic aromatic hydrocarbons (PAH); however, quantitative mole fractions were not determined. Nevertheless, the diagnostic developed here does have this capability. Quantitative, time-resolved measurements of soot extinction were also accomplished and the novel use of multiple incident wavelengths proved valuable toward characterizing changes in soot optical properties within different regions of the spray flame.

  13. Manual HVOF thermal spray repair of nickel aluminum bronze castings

    SciTech Connect

    Brenna, R.T.; McCaw, R.L.; Pugh, J.L.

    1994-12-31

    Manual high velocity oxyfuel (HVOF) thermal spray repairs were accomplished on a large nickel aluminum bronze propeller castings. The repairs were done on three different configurations of surface defects of up to 100 square inches and as deep as 90 mils. Nickel aluminum bronze alloy powder, sieve sized for the HVOF process, was sprayed. High quality, high coating density, repairs were achieved even on porous areas of the castings. Prior to performance of the repairs, a procedure was qualified in accordance with MIL-STD-1687 and a mock-up simulating the repair was produced. After HVOF spraying of the mock-up, the sprayed surface was sanded, milled, and drilled to determine how finishing of the actual castings would be done. After successful procedure qualification, the HVOF equipment was moved to the job site, metal masking was devised for the spray areas and grit blasting and manual HVOF spraying was done. Results of HVOF coating chemical analyses, bend tests, coating tensile bond strength tests, coating microscopic examinations, and mock-up evaluations are reported along with the spray procedures and techniques used in the repairs.

  14. Comparison of the characteristics of HVOF and plasma thermal spray

    SciTech Connect

    Fincke, J.R.; Swank, W.D.; Haggard, D.C.

    1994-12-31

    In spraying oxygen sensitive materials, such as WC:Co it is often observed that the carbide fraction present in the deposit is significantly less than in the original particles. This lowers the hardness of the coating, resulting in inferior wear resistance. The cause is the in-flight, high temperature decomposition of carbides by reaction with entrained oxygen. The degree of decomposition is determined by a combination of particle temperature, residence time and entrainment characteristics of the jet. The fundamental differences between HVOF and plasma thermal spray are examined in this context. Even though the HVOF process may actually subject a particle to greater oxygen exposure than plasma spraying, the lower particle temperatures experienced lead to coatings which exhibit less carbide loss than plasma sprayed coatings fabricated in air.

  15. Gas detonation gun for thermal spraying

    SciTech Connect

    Kadyrov, E.; Kadyrov, V.

    1995-08-01

    High-velocity oxy-fuel and gas detonation are competing spray coating processes well known for providing premium quality coatings with low porosity and high adhesion. They are favored for applications in environments of extreme wear, heat, and aggressive corrosion. Nevertheless, they both have limitations. For the HVOF process, these include excessive gas consumption, high rate of heat transfer to the sprayed substrate, and the short life of the (supersonic) Laval nozzle. On the other hand, the traditional gas detonation gun also has drawbacks, and the purpose of this article is to outline some factors that led to the design of an improved gas detonation coating process called Demeton, produced by Demeton USA Inc., Garden City Park, N.Y.

  16. Quality Considerations for the Evaluation of Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Wigren, Jan; Täng, Kristina

    2007-12-01

    Revealing the true structural and mechanical properties is of utmost importance for the optimized use of thermal sprayed coatings. Only the true properties can be expected to correlate to the spray parameters. During the recent decade, the gas turbine industry has experienced a focus on the laboratory procedures being the weakest link in a frozen and robust process. This article will show several results indicating that the laboratory procedures are more essential to the evaluation results than the spray parameters themselves. With new and robust laboratory techniques, the true properties of thermal spray coatings are revealed, causing a major problem with respect to the quality standards developed 30-40 years ago. In many cases, these old specifications need updates, which is a difficult task from a cost, time, and quality perspective for OEM’s. Coatings that have been successfully used for almost half a century no longer conform to the specification they were optimized to, because of these new appropriate laboratory techniques and procedures. What is actually meant when stating the following? (1) The coating has 5% porosity; (2) No cracks are allowed; (3) Tensile bond is 50 Mpa; (4) Hardness is 1000 HV; and (5) Coating thickness is 100 μm. This article also initiates a discussion on the measurement inaccuracies, for testing of thermally sprayed coatings, with respect to the commonly used general international standards (such as QS9000, ISO17025, AS9003, and ISO10012), as well as with respect to recommendations from the Six Sigma methodology.

  17. Effect of Starting Microstructure on Thermal Properties forAs-Sprayed and Thermally Exposed Plasma-Sprayed YSZ Coatings

    SciTech Connect

    Wang, Hsin; Tan, Y; Longtin, J P; Sampath, S

    2009-01-01

    Thermal barrier coatings (TBCs) experience thermal gradients, excessive temperature, and high heat flux from hot gases in turbines during service. These extended thermal effects induce sin-tering and significant microstructure changes, which alter the resulting thermal conductivity within the TBCs. In this study plasma-sprayed Yttria Stabilized Zirconia (YSZ) TBCs using dif-ferent starting powders and process parameters were subjected to thermal aging at several tem-peratures and time intervals, after which their thermal conductivity was measured at room tem-perature. The thermal conductivity results are analyzed by introducing the Larson-Miller pa-rameter describing the creep behavior of thermal conductivity increase with annealing tempera-ture and time. One set of selected coatings was also annealed under the same conditions and the thermal conductivity was measured at elevated temperatures. The temperature-dependent ther-mal conductivity data is analyzed and used to predict long-term thermal behavior for general YSZ coating design.

  18. Latest Developments in Suspension and Liquid Precursor Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Fauchais, Pierre; Montavon, Ghislain

    2010-01-01

    The interest to manufacture onto large surfaces thick (i.e., 10-20 μm, average thickness) finely structured or nanostructured layers is increasingly growing since the past 10 years. This explains the interest for suspension thermal spraying (STS) and solution precursor thermal spraying (SPTS), both allowing manufacturing finely structured layers of thicknesses varying between a few micrometers up to a few hundreds of micrometers. STS aims at processing a suspension of sub-micrometer-sized or even nanometer-sized solid particles dispersed in a liquid phase. The liquid phase permits the injection of particles in the thermal flow (i.e., due to their size, a carrier gas cannot play this role). SPTS aims at processing a solution of precursors under the same conditions. Upon evaporation of the liquid phase, the precursor concentration increases until precipitation, pyrolysis, and melting of small droplets occur. Compared to conventional thermal spray routes, STS and SPTS are by far more complex because fragmentation and vaporization of the liquid control the coating build-up mechanisms. Numerous studies are still necessary to reach a better understanding of the involved phenomena and to further develop the technology, among which are injection systems, suspension and solution optimizations, spray kinematics, etc. This review presents some recent developments and our present knowledge in this field together with the available tools implemented to characterize the plasma-liquid interaction and the coating formation.

  19. Determination of Thermal Spray Coating Property with Curvature Measurements

    NASA Astrophysics Data System (ADS)

    Dwivedi, Gopal; Nakamura, Toshio; Sampath, Sanjay

    2013-12-01

    Real-time curvature measurement of a coating-substrate system during deposition has facilitated the monitoring of coating stresses and provided additional insights into thermal spray deposition mechanisms. However, the non-equilibrium state of coating formation along with harsh spray booth environment introduces complexity not only in data interpretation but also in the coating properties estimation. In this paper, a new procedure is proposed to estimate the elastic modulus of thermal sprayed ceramic coatings using in situ curvature and temperature measurements. In order to correlate the measurable parameters to coating elastic modulus, a systematic study is conducted to develop a suitable methodology. First, various finite element model analyses are carried out to formulate suitable relations between the measurements and elastic modulus. Subsequently, experiments are conducted to validate the procedure to estimate coating moduli. The results are compared with more accurate measurements obtained from post-deposition characterization technique under low temperature thermal cycles. The comparison suggests that the moduli estimated using the proposed procedure are in good agreements with those obtained from the post-deposition technique. Further, the nonlinear response of coatings are evaluated from the estimated moduli during deposition and cool down, which offer additional information on the characteristics of thermal spray coatings.

  20. Milestones in Functional Titanium Dioxide Thermal Spray Coatings: A Review

    NASA Astrophysics Data System (ADS)

    Gardon, M.; Guilemany, J. M.

    2014-04-01

    Titanium dioxide has been the most investigated metal oxide due to its outstanding performance in a wide range of applications, chemical stability and low cost. Coating processes that can produce surfaces based on this material have been deeply studied. Nevertheless, the necessity of coating large areas by means of rapid manufacturing processes renders laboratory-scale techniques unsuitable, leading to a noteworthy interest from the thermal spray (TS) community in the development of significant intellectual property and a large number of scientific publications. This review unravels the relationship between titanium dioxide and TS technologies with the aim of providing detailed information related to the most significant achievements, lack of knowhow, and performance of TS TiO2 functional coatings in photocatalytic, biomedical, and other applications. The influence of thermally activated techniques such as atmospheric plasma spray and high-velocity oxygen fuel spray on TiO2 feedstock based on powders and suspensions is revised; the influence of spraying parameters on the microstructural and compositional changes and the final active behavior of the coating have been analyzed. Recent findings on titanium dioxide coatings deposited by cold gas spray and the capacity of this technology to prevent loss of the nanostructured anatase metastable phase are also reviewed.

  1. Progress in Advanced Spray Combustion Code Integration

    NASA Technical Reports Server (NTRS)

    Liang, Pak-Yan

    1993-01-01

    A multiyear project to assemble a robust, muitiphase spray combustion code is now underway and gradually building up to full speed. The overall effort involves several university and government research teams as well as Rocketdyne. The first part of this paper will give an overview of the respective roles of the different participants involved, the master strategy, the evolutionary milestones, and an assessment of the state-of-the-art of various key components. The second half of this paper will highlight the progress made to date in extending the baseline Navier-Stokes solver to handle multiphase, multispecies, chemically reactive sub- to supersonic flows. The major hurdles to overcome in order to achieve significant speed ups are delineated and the approaches to overcoming them will be discussed.

  2. Fabrication and Characterization of Thermal-Sprayed Fe-Based Amorphous/Nanocrystalline Composite Coatings: An Overview

    NASA Astrophysics Data System (ADS)

    Guo, Wenmin; Wu, Yuping; Zhang, Jianfeng; Hong, Sheng; Li, Gaiye; Ying, Guobing; Guo, Ji; Qin, Yujiao

    2014-10-01

    This review focuses on the recent development of iron (Fe)-based amorphous/nanocrystalline composite coatings, which have attracted much attention due to their attractive combination of high hardness/strength, elevated abrasive wear resistance, and enhanced corrosion resistance. Accompanying the advancements in various thermal spray technologies, industrial application fields of Fe-based amorphous/nanocrystalline composite coatings are becoming more diverse. In the main part, the typical empirical rules for the design of amorphous alloys with high glass-forming ability are generalized and discussed at first. Then various thermal spray technologies for the fabrication of Fe-based amorphous/nanocrystalline composite coatings, such as high velocity oxygen/air spray (HVOF/HVAF), air plasma spray (APS), low-pressure plasma spray (LPPS), high-energy plasma spray (HPS), and high velocity arc spray (HVAS) processes, are introduced. The microstructures, hardness, wear resistance, and corrosion resistance of Fe-based amorphous/nanocrystalline composite coatings formed using these thermal spray technologies are reviewed and compared. Finally, the existing challenges and future prospects are proposed.

  3. Thermal analysis simulation for a spin-motor used in the advanced main combustion chamber vacuum plasma spray project using the SINDA computer program

    NASA Technical Reports Server (NTRS)

    Mcdonald, Gary H.

    1990-01-01

    One of the many design challenges of this project is predicting the thermal effects due to the environment inside the vacuum chamber on the turntable and spin motor spindle assembly. The objective of the study is to model the spin motor using the computer program System Improved Numerical Differencing Analyzer (SINDA). By formulating the appropriate input information concerning the motor's geometry, coolant flow path, material composition, and bearing and motor winding characteristics, SINDA should predict temperatures at various predefined nodes. From these temperatures, hopefully, one can predict if the coolant flow rate is sufficient or if certain mechanical elements such as bearings, O ring seals, or motor windings will exceed maximum design temperatures.

  4. Microstructural and Mechanical Properties of Ni-Base Thermal Spray Coatings Deposited by Flame Spraying

    NASA Astrophysics Data System (ADS)

    Amokrane, Bradai Mohand; Abdelhamid, Sadeddine; Youcef, Mouadji; Abderrahim, Benabbas; Nedjemeddine, Bounar; Ahmed, Mammeri

    2011-10-01

    In this work, two different Ni-base powders, namely, ProXon 21021 (P21) and ProXon 21031 (P31), were sprayed onto a steel substrate 35CrMo4 using a thermal flame spray technique. The morphology and chemical composition of the phases that are present in the powders and coatings were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The hardness and wear resistance of the coatings were investigated. The XRD analysis revealed that the phases present in the coatings are different from the initial powders. In addition, some inhomogeneities such as oxides, porosity, and unmelted particles were observed by SEM. It was found that the P31 spray-coated exhibited higher microhardness, higher wear resistance, and significantly lower friction coefficient in comparison with those of P21 coatings.

  5. Cermet composite thermal spray coatings for erosion and corrosion protection in combustion environments of advanced coal-fired boilers. Semiannual technical progress report, August 14, 1996--January 14, 1997

    SciTech Connect

    Levin, B.F.; DuPont, J.N.; Marder, A.R.

    1997-02-01

    Research is presently being conducted to determine the optimum ceramic/metal combination in thermally sprayed metal matrix composite coatings for erosion and corrosion resistance in new coal-fired boilers. The research will be accomplished by producing model cermet composites using powder metallurgy and electrodeposition methods in which the effect of ceramic/metal combination for the erosion and corrosion resistance will be determined. These results will provide the basis for determining the optimum hard phase constituent size and volume percent in thermal spray coatings. Thermal spray coatings will be applied by our industrial sponsor and tested in our erosion and corrosion laboratories. In the first six months of this project, bulk powder processed Ni-Al{sub 2}O{sub 3} composites were produced at Idaho National Engineering Laboratory. The results of microstructural characterization of these alloys were presented in the first semiannual report. The composite samples contained 0, 21, 27, 37, and 45 volume percent Al{sub 2}O{sub 3} with an average particle size of 12 um. An increase in the volume fraction of alumina in the nickel matrix from 0 to 45% led to a significant increase in hardness of these composites.

  6. HVOF thermal spraying: An alternative to hard chrome plating

    SciTech Connect

    Bolles, D.C.

    1995-10-01

    In recent years pressure to find alternatives to chromium electroplating has accelerated dramatically. While it is not likely that the process will be banned completely, the trend points to severe limitations. Industries must now look closely at their applications, and actively consider alternatives to hard chrome plaint. One of the most viable alternatives in thermal spraying. Recent advances in high-velocity oxygen fuel (HVOF) technology offer an environmentally safer, cleaner and less-expensive alternative to chromium plating. It has been shown here that HVOF coatings can be used as chromium plating alternatives for many different applications. The HVOF process offers several advantages over chromium plaint including thicker coating capability, no part size restrictions and no hazardous waste products. A number of HVOF coatings have had excellent results in laboratory and field testing, and can be considered as effective replacements for hard chrome. The choice for a suitable replacement can only be made after careful assessment of the conditions associated with the application in question.

  7. Quantitative analysis of thermal spray deposits using stereology

    SciTech Connect

    Leigh, S.H.; Sampath, S.; Herman, H.; Berndt, C.C.; Montavon, G.; Coddet, C.

    1995-12-31

    Stereology deals with protocols for describing a 3-D space, when only 2-D sections through solid bodies are available. This paper describes a stereological characterization of the microstructure of a thermal spray deposit. The aim of this work is to present results on the stereological characterization of a thermal spray deposit, using two approaches known as DeHoff`s and Cruz-Orive`s protocols. The individual splats are assumed to have an oblate spheroidal shape. The splat size distribution and elongation ratio distribution of splats are calculated using quantitative information from 2-D plane sections. The stereological methods are implemented to investigate the microstructure of a water stabilized plasma spray-formed Al{sub 2}O{sub 3}-13wt.%TiO{sub 2}. Results are obtained with both protocols. The splat sizes range from 0 to 60 {micro}m and shape factors from 0.4 to 1.0. The splats within the deposit seem to be much smaller and thicker (i.e., lower spreading) than those of the first layer deposited onto the substrate. The approach described in this work provides helpful quantitative information on the 3-D microstructure of thermal spray deposit.

  8. Diagnostics of thermal spraying plasma jets

    SciTech Connect

    Fauchais, P.; Coudert, J.F.; Vardelle, M.; Vardelle, A.; Denoirjean, A. )

    1992-06-01

    The development of diagnostic techniques for dc plasma spraying is reviewed with attention given to the need for thick highly reproducible coatings of good quality for aeronautic and other uses. Among the techniques examined are fast cameras, laser-Doppler anemometry (LDA), coherent anti-Stokes Raman spectroscopy (CARS), enthalpy probes, and emission spectroscopy. Particular emphasis is given to the effect of arc fluctuations on the spectroscopic measurements, and a method is introduced for obtaining temperature and species density of vapor clouds traveling with each particle in flight. Coating properties can be deduced from data on single particles, and statistical approaches are often unreliable without added data on surface temperature and particle velocity. Also presented is a method for deriving the temperature evolution of a cooled splat and successive layers and passes. These methods are of interest to the control of adhesion and cohesion in coatings for critical aerospace applications. 70 refs.

  9. Diagnostics of thermal spraying plasma jets

    NASA Astrophysics Data System (ADS)

    Fauchais, P.; Coudert, J. F.; Vardelle, M.; Vardelle, A.; Denoirjean, A.

    1992-06-01

    The development of diagnostic techniques for dc plasma spraying is reviewed with attention given to the need for thick highly reproducible coatings of good quality for aeronautic and other uses. Among the techniques examined are fast cameras, laser-Doppler anemometry (LDA), coherent anti-Stokes Raman spectroscopy (CARS), enthalpy probes, and emission spectroscopy. Particular emphasis is given to the effect of arc fluctuations on the spectroscopic measurements, and a method is introduced for obtaining temperature and species density of vapor clouds traveling with each particle in flight. Coating properties can be deduced from data on single particles, and statistical approaches are often unreliable without added data on surface temperature and particle velocity. Also presented is a method for deriving the temperature evolution of a cooled splat and successive layers and passes. These methods are of interest to the control of adhesion and cohesion in coatings for critical aerospace applications.

  10. Effects of plasma spray parameters on two layer thermal barrier

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1981-01-01

    The power level and the type of arc gas used during plasma spraying of a two layer thermal barrier system (TBS) were found to affect the life of the system. Life at 1095 C in a cyclic furnace test was improved by about 140 percent by increasing the power during plasma spray applications of the bond and thermal barrier coatings. This improvement is due to increases in the densities of the bond and thermal barrier coatings by 3 and 5 percent, respectively. These increases in densities are equivalent to about 45 and 30 percent reduction in mean porosities, respectively. The addition of hydrogen to the argon arc gas had the same effect as the reduction in power level and caused a reduction in TBS life.

  11. Rolling contact fatigue testing of thermally sprayed coatings

    SciTech Connect

    Maekelae, A.; Vuoristo, P.; Lahdensuo, M.; Niemi, K.; Maentylae, T.

    1994-12-31

    Two Rolling Contact Fatigue (RCF) test systems have been developed in order to compare coatings according to their service lives under high-load rolling contact. Experimental testing facilities of the three-roller and the two-roller type RCF test equipment are presented and problems involved with testing of thermally sprayed coatings are discussed. The aim of this three-year-project is to study reasons for development of coating micropitting and delamination of high-velocity oxyfuel (HVOF) and detonation gun sprayed coatings. Some observations of rolling contact fatigue behavior of detonation gun sprayed WC+12% Co coating subjected to a nearly pure rolling line contact at cyclic Hertzian stress level of approximately 410 MPa are made, but interpreting the results requires still more work.

  12. Thermal Spray Coating of Tungsten for Tokamak Device

    NASA Astrophysics Data System (ADS)

    Jiang, Xianliang; F, Gitzhofer; M, I. Boulos

    2006-03-01

    Thermal spray, such as direct current (d.c.) plasma spray or radio frequency induced plasma spray, was used to deposit tungsten coatings on the copper electrodes of a tokamak device. The tungsten coating on the outer surface of one copper electrode was formed directly through d.c. plasma spraying of fine tungsten powder. The tungsten coating/lining on the inner surface of another copper electrode could be formed indirectly through induced plasma spraying of coarse tungsten powder. Scanning electron microscopy (SEM) was used to examine the cross section and the interface of the tungsten coating. Energy Dispersive Analysis of X-ray (EDAX) was used to analyze the metallic elements attached to a separated interface. The influence of the particle size of the tungsten powder on the density, cracking behavior and adhesion of the coating is discussed. It is found that the coarse tungsten powder with the particle size of 45 ~ 75 μm can be melted and the coating can be formed only by using induced plasma. The coating deposited from the coarse powder has much higher cohesive strength, adhesive strength and crack resistance than the coating made from the fine powder with a particle size of 5 μm.

  13. Vision-aided Monitoring and Control of Thermal Spray, Spray Forming, and Welding Processes

    NASA Technical Reports Server (NTRS)

    Agapakis, John E.; Bolstad, Jon

    1993-01-01

    Vision is one of the most powerful forms of non-contact sensing for monitoring and control of manufacturing processes. However, processes involving an arc plasma or flame such as welding or thermal spraying pose particularly challenging problems to conventional vision sensing and processing techniques. The arc or plasma is not typically limited to a single spectral region and thus cannot be easily filtered out optically. This paper presents an innovative vision sensing system that uses intense stroboscopic illumination to overpower the arc light and produce a video image that is free of arc light or glare and dedicated image processing and analysis schemes that can enhance the video images or extract features of interest and produce quantitative process measures which can be used for process monitoring and control. Results of two SBIR programs sponsored by NASA and DOE and focusing on the application of this innovative vision sensing and processing technology to thermal spraying and welding process monitoring and control are discussed.

  14. Front surface thermal property measurements of air plasma spray coatings

    SciTech Connect

    Bennett, Ted; Kakuda, Tyler; Kulkarni, Anand

    2009-04-15

    A front-surface measurement for determining the thermal properties of thermal barrier coatings has been applied to air plasma spray coatings. The measurement is used to determine all independent thermal properties of the coating simultaneously. Furthermore, with minimal requirements placed on the sample and zero sample preparation, measurements can be made under previously impossible conditions, such as on serviceable engine parts. Previous application of this technique was limited to relatively thin coatings, where a one-dimensional heat transfer model is applied. In this paper, the influence of heat spreading on the measurement of thicker coatings is investigated with the development of a two-dimensional heat transfer model.

  15. Hierarchical Formation of Intrasplat Cracks in Thermal Spray Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2016-06-01

    Intrasplat cracks, an essential feature of thermally sprayed ceramic coatings, play important roles in determining coating properties. However, final intrasplat crack patterns are always considered to be disordered and irregular, resulting from random cracking during splat cooling, since the detailed formation process of intrasplat cracks has scarcely been considered. In the present study, the primary formation mechanism for intrasplat cracking was explored based on both experimental observations and mechanical analysis. The results show that the intrasplat crack pattern in thermally sprayed ceramic splats presents a hierarchical structure with four sides and six neighbors, indicating that intrasplat crack patterns arise from successive domain divisions due to sequential cracking during splat cooling. The driving forces for intrasplat cracking are discussed, and the experimental data quantitatively agree well with theoretical results. This will provide insight for further coating structure designs and tailoring by tuning of intrasplat cracks.

  16. Tensile adhesion testing methodology for thermally sprayed coatings

    NASA Technical Reports Server (NTRS)

    Berndt, Christopher C.

    1990-01-01

    The structure of thermally sprayed coatings consists of lamellae which are oriented parallel to the substrate surface. The lamellae separate and fracture by distinctive mechanisms which are reflected in the failure morphology, and these may be described as adhesive (between the coating and substrate), cohesive (within the coating), or mixed mode. There is a large variability in the failure stress for any nominally identical group of coatings. A lower bound for the fracture toughness of alumina coatings can be calculated as 0.2 MNm exp -3/2. The coating strength values may also be treated as belonging to the statistical distribution of the Weibull function. The Weibull modulus of the coating strength varied from 1.4 to 3.8. This analysis infers that the flaw size within coatings is highly variable and that the flaws are nonuniformly dispersed. The present work focuses on the question of whether tensile adhesion tests are an appropriate testing method for thermally sprayed materials.

  17. Thermoelectric Device Fabrication Using Thermal Spray and Laser Micromachining

    NASA Astrophysics Data System (ADS)

    Tewolde, Mahder; Fu, Gaosheng; Hwang, David J.; Zuo, Lei; Sampath, Sanjay; Longtin, Jon P.

    2016-02-01

    Thermoelectric generators (TEGs) are solid-state devices that convert heat directly into electricity. They are used in many engineering applications such as vehicle and industrial waste-heat recovery systems to provide electrical power, improve operating efficiency and reduce costs. State-of-art TEG manufacturing is based on prefabricated materials and a labor-intensive process involving soldering, epoxy bonding, and mechanical clamping for assembly. This reduces their durability and raises costs. Additive manufacturing technologies, such as thermal spray, present opportunities to overcome these challenges. In this work, TEGs have been fabricated for the first time using thermal spray technology and laser micromachining. The TEGs are fabricated directly onto engineering component surfaces. First, current fabrication techniques of TEGs are presented. Next, the steps required to fabricate a thermal spray-based TEG module, including the formation of the metallic interconnect layers and the thermoelectric legs are presented. A technique for bridging the air gap between two adjacent thermoelectric elements for the top layer using a sacrificial filler material is also demonstrated. A flat 50.8 mm × 50.8 mm TEG module is fabricated using this method and its performance is experimentally characterized and found to be in agreement with expected values of open-circuit voltage based on the materials used.

  18. Thermal Plasma Spraying Applied on Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Soysal, D.; Arnold, J.; Szabo, P.; Henne, R.; Ansar, S. A.

    2013-06-01

    Solid oxide fuel cells (SOFCs), attractive for diverse applications in a broad range from small portable and auxiliary power units, up to central power systems, are conventionally produced by sintering methods. However, plasma spraying promises some advantages particularly for cells with metal support. In the present paper, research activities conducted in recent years at DLR as well as latest developments on plasma sprayed functional layers for SOFC as cathodes, electrolytes, and anodes are reported. Power densities of more than 800 mW/cm2 were achieved for plasma sprayed single cells of 12.56 cm2 size, and 300 mW/cm2, respectively, with a 250 W stack made of 10 cells. These values were attained at 0.7 V and 800 °C, with H2:N2 = 1:1 as fuel gas and air as oxidizing gas. Furthermore, continuous operation of more than 5000 h was attained with a plasma sprayed metal-supported SOFC stack which could also withstand more than 30 redox and thermal cycles.

  19. Thermal sprayed composite melt containment tubular component and method of making same

    DOEpatents

    Besser, Matthew F.; Terpstra, Robert L.; Sordelet, Daniel J.; Anderson, Iver E.

    2002-03-19

    A tubular thermal sprayed melt containment component for transient containment of molten metal or alloy wherein the tubular member includes a thermal sprayed inner melt-contacting layer for contacting molten metal or alloy to be processed, a thermal sprayed heat-generating layer deposited on the inner layer, and an optional thermal sprayed outer thermal insulating layer. The thermal sprayed heat-generating layer is inductively heated as a susceptor of an induction field or electrical resistively heated by passing electrical current therethrough. The tubular thermal sprayed melt containment component can comprise an elongated melt pour tube of a gas atomization apparatus where the melt pour tube supplies molten material from a crucible to an underlying melt atomization nozzle.

  20. Application of thermal spray coatings using high deposition rate equipment

    SciTech Connect

    Novak, H.L.

    1995-12-01

    Reusable launch vehicles located by the ocean are subject to harsh seacoast environments before launch and immersion after splashdown at sea and towback to the refurbishment facility. High strength aluminum and non-corrosion resistant steel alloys are prone to general corrosion and pitting due to galvanic couples and protective coating damage. Additional protection of structural materials with thermally sprayed pure aluminum coatings was evaluated for plasma, arc spray and high velocity oxy-fuel (HVOF) processes. Comparisons are made for corrosion rates of various coated aluminum alloy and steel substrates when exposed to ASTM B-117 neutral salt fog testing and also to beach exposure tests performed at Kennedy Space Center, Florida. Recent development work involved the use of high deposition rate thermal arc-spray equipment. The use of an inverter power supply reduced powdering and enhanced operator visibility. Deposition rates of 45.36--68.04 kilograms/hour are obtainable using 4.76--6.35 millimeter diameter wire electrodes.

  1. Microstructural influence on erosion behaviour of thermal spray coatings

    SciTech Connect

    Matthews, S.J.; James, B.J. . E-mail: b.james@auckland.ac.nz; Hyland, M.M.

    2007-01-15

    The influence of structure on erosion performance of thermally sprayed Cr{sub 3}C{sub 2}-NiCr coatings under industrial turbine conditions has been investigated. Thermal spraying of these materials results in substantial variation in composition and microstructure due to exposure of the coating powders to the high temperature accelerating gas. Coatings were characterised using Back Scatter Electron imaging in conjunction with X-ray diffraction which showed carbide dissolution into the matrix of varying extent depending on deposition technique. Heat treatment at 900 deg. C caused carbide precipitation and matrix refinement. Erosion testing of as-sprayed and heat treated coatings was conducted at ambient and elevated temperature. Single impacts were characterised using Scanning Electron Microscopy in order to determine the erosion mechanism. At ambient temperature the single impacts caused a brittle response with both carbide grains and matrix being cleaved by the erodent particle. Brittle cracks surrounded each impact and intersected with splat boundaries leading to a significant contribution to erosion rate from splat structure. Following heat treatment the erosion response of the coatings was more ductile with mounds of plastically deformed material surrounding each impact, this significantly reduced erosion rate.

  2. Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

    NASA Astrophysics Data System (ADS)

    Podlesak, Harry; Pawlowski, Lech; D'Haese, Romain; Laureyns, Jacky; Lampke, Thomas; Bellayer, Severine

    2010-03-01

    Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 n experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.

  3. The effect of thermal aging on the thermal conductivity of plasma sprayed and EB-PVD thermal barrier coatings

    SciTech Connect

    Dinwiddie, R.B.; Beecher, S.C.; Porter, W.D.; Nagaraj, B.A.

    1996-05-01

    Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EV-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The density of the APS coatings was controlled by varying the spray parameters. The low density APS yttria-partially stabilized zirconia (yttria-PSZ) coatings yielded a thermal conductivity that is lower than both the high density APS coatings and the EB-PVD coatings. The thermal aging of both fully and partially stabilized zirconia are compared. The thermal conductivity of the coatings permanently increases upon exposure to high temperatures. These increases are attributed to microstructural changes within the coatings. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the EB-PVD coatings are less susceptible to thermal aging effects, results suggest that they typically have a higher thermal conductivity than APS coatings before thermal aging. The increases in thermal conductivity due to thermal aging for plasma sprayed partially stabilized zirconia have been found to be less than for plasma sprayed fully stabilized zirconia coatings.

  4. Investigation of defects in thermal sprayed coatings using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Marzban, Ali

    Thermal spray (TS) coatings and materials including thermal barrier, tribological and anti-corrosive coatings have established application across a number of engineering fields. TS is attractive for these systems due to its low cost, ability to coat large areas and flexibility in material feedstock. These attributes, along with improvements in process diagnostics have spurred the exploration of TS for more functional applications including fuel cells, conformal electronic sensors and biomedical implants. Successful implementation of TS coatings in these systems will require more robust characterization of their mechanical behavior; to date this has been limited and in practice most measurements are carried out in a pass/fail manner. Little is known about the intrinsic or progressive behavior of the coatings under repeated loading. This is important as the microstructure of TS coatings comprises layers of micron-thick flattened particles ('splats') separated by interfaces, the bonding between which is not well understood. These interfaces represent potential short crack growth sites throughout the material. A lot of works has demonstrated that microstructurally short cracks propagate at substantially higher growth rates than long cracks at equivalent driving forces under both quasi-static and cycling loading conditions in ceramics and their composites and metals. Short cracks in a naturally broken material like TS will have a different mechanism. Mechanical properties and fracture behavior have been examined in TS, but via conventional methods. That is to say, a large notch is introduced and allowed to propagate. This method completely neglects the existing microstructure of a TS material, which is lamellar and contains a number of near-horizontal cracks. In this study, a new approach to damage monitoring in TS coatings, using through thickness impedance spectroscopy to detect changes in dielectric properties is introduced. The goal of this research is to understand

  5. The development of ASTM standards for metallographic preparation practices of thermally sprayed coatings

    SciTech Connect

    Blann, G.A.; Diaz, D.J.

    1994-12-31

    The primary objective of metallographic examinations of thermally sprayed coatings is to reveal the constituents and structure of the coatings and substrates by means of the microscope after proper metallographic preparation is performed. Because of the diversity of coating types and the personal element, the standardization of metallographic preparation of thermally sprayed coatings is essential. An ASTM subcommittee was formed with the support of the ASM Thermal Spray Committee to provide the laboratories involved in coating characterization with guidelines that will provide consistent metallographic procedures that produce an accurate evaluation of the wide range of thermally sprayed coatings. The methods used to establish this standard will be discussed in this paper.

  6. Investigation of water spray to reduce collateral thermal damage during laser resection of soft tissue

    NASA Astrophysics Data System (ADS)

    Theisen-Kunde, D.; Wolken, H.; Ellebrecht, D.; Danicke, V.; Wurster, L.; Kleemann, M.; Birngruber, R.

    2013-06-01

    To reduce unwanted collateral thermal damage to surrounding tissue and organs during laparoscopic laser dissection (cw, wavelength: 1.9μm) of porcine liver water spray was used. Size and amount of the produced water droplets of the water spray were photographed by short time imaging and analyzed by imaging software. At in vivo measurements on fresh porcine liver the depth of thermal damage was reduced by 85 % with water spray and the lateral size of thermal damage at the tissue surface could be reduced by 67%. This results show that especially for laparoscopic laser surgery water spray application might be a useful tool to avoid unwanted collateral thermal damage.

  7. Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review

    NASA Astrophysics Data System (ADS)

    Feuerstein, Albert; Knapp, James; Taylor, Thomas; Ashary, Adil; Bolcavage, Ann; Hitchman, Neil

    2008-06-01

    The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of electron beam physical vapor deposition (EBPVD) applied yttria-stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This article highlights the key features of plasma spray and HVOF, diffusion aluminizing, and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bond coat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.

  8. Advanced Thermally Stable Jet Fuels

    SciTech Connect

    A. Boehman; C. Song; H. H. Schobert; M. M. Coleman; P. G. Hatcher; S. Eser

    1998-01-01

    The Penn State program in advanced thermally stable jet fuels has five components: 1) development of mechanisms of degradation and solids formation; 2) quantitative measurement of growth of sub-micrometer and micrometer-sized particles during thermal stressing; 3) characterization of carbonaceous deposits by various instrumental and microscopic methods; 4) elucidation of the role of additives in retarding the formation of carbonaceous solids; and 5) assessment of the potential of producing high yields of cycloalkanes and hydroaromatics from coal.

  9. Thermal spray manufacturing issues in coating IGT hot section components

    NASA Astrophysics Data System (ADS)

    Sahoo, P.; Carr, T.; Martin, R.; Dinh, F.

    1998-12-01

    The desire to improve the performance of gas turbine engines has led to higher operating temperatures in the turbine sections of the engine. Materials used for hot section turbine blades and vanes are not resistant to hot corrosion, and therefore require protective coatings. This paper reviews the current art and technology of thermally sprayed MCrAlY and TB coatings onto hot section components. The issues in applying such coatings will be discussed, along with references to manufacturing issues on the shop floor. The difficulties inherent in applying a line-of-sight coating to complex geometries will be discussed. The testing, evaluation, and performance characteristics of typical coatings are discussed.

  10. Robust hydrophobic Fe-based amorphous coating by thermal spraying

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, Y.; Liu, L.

    2012-09-01

    Metallic surface is intrinsically hydrophilic due to its high surface energy. In this work, we present a different picture that highly hydrophobic metallic coatings could be directly fabricated by thermal spraying of Fe-based amorphous powders through the surface roughness control. These hydrophobic coatings are amorphous, exhibiting super-high hardness and excellent corrosion resistance. With low surface energy modification, the coatings become superhydrophobic and exhibit clearly self-cleaning effect. The present work opens a window for the applications of the amorphous coatings.

  11. Advanced Wellbore Thermal Simulator

    1992-03-04

    GEOTEMP2, which is based on the earlier GEOTEMP program, is a wellbore thermal simulator designed for geothermal well drilling and production applications. The code treats natural and forced convection and conduction within the wellbore and heat conduction within the surrounding rock matrix. A variety of well operations can be modeled including injection, production, forward and reverse circulation with gas or liquid, gas or liquid drilling, and two-phase steam injection and production. Well completion with severalmore » different casing sizes and cement intervals can be modeled. The code allows variables, such as flow rate, to change with time enabling a realistic treatment of well operations. Provision is made in the flow equations to allow the flow areas of the tubing to vary with depth in the wellbore. Multiple liquids can exist in GEOTEMP2 simulations. Liquid interfaces are tracked through the tubing and annulus as one liquid displaces another. GEOTEMP2, however, does not attempt to simulate displacement of liquids with a gas or two-phase steam or vice versa. This means that it is not possible to simulate an operation where the type of drilling fluid changes, e.g. mud going to air. GEOTEMP2 was designed primarily for use in predicting the behavior of geothermal wells, but it is flexible enough to handle many typical drilling, production, and injection problems in the oil industry as well. However, GEOTEMP2 does not allow the modeling of gas-filled annuli in production or injection problems. In gas or mist drilling, no radiation losses are included in the energy balance. No attempt is made to model flow in the formation. Average execution time is 50 CP seconds on a CDC CYBER170. This edition of GEOTEMP2 is designated as Version 2.0 by the contributors.« less

  12. Corrosion Characterization of Iron-Based High-Performance Amorphous-Metal Thermal-Spray Coatings

    SciTech Connect

    Farmer, J C; Haslam, J J; Day, S D; Branagan, D J; Blue, C A; Rivard, J K; Aprigliano, L F; Yang, N; Perepezko, J H; Beardsley, M B

    2005-03-21

    New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative corrosion resistance. Many of these materials can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. One of these compositions, SAM1651, is discussed in detail to illustrate the promise of this general class of materials.

  13. Failure of PVD/plasma sprayed thermal barrier coatings during thermal cycling

    SciTech Connect

    Teixeria, V.; Andritschky, M.; Gruhn, H.; Mallener, W.; Buchkremer, H.; Stoever, D.

    1995-12-31

    ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high temperature Ni-based alloys precoated by Physical Vapor Deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by Atmospheric Plasma Spraying (APS) and Inert gas Plasma Spraying (IPS at 2 bar) for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1,000 C and 1,150 C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables the authors to calculate the transient thermal strains and stresses which contribute to a better understanding of the failure mechanisms of the TBC during thermal cycling. They have also studied experimentally the adherence and failure modes of these coating systems during this high temperature testing. The TBC failure mechanism during thermal cycling is discussed in the light of coating transient stresses and substrate oxidation.

  14. Failure of physical vapor deposition/plasma-sprayed thermal barrier coatings during thermal cycling

    NASA Astrophysics Data System (ADS)

    Teixeira, V.; Andritschky, M.; Gruhn, H.; Malléner, W.; Buchkremer, H. P.; Stöver, D.

    2000-06-01

    ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS) and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1000 and 1150 °C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables calculation of the transient thermal strains and stresses, which contributes to a better understanding of the failure mechanisms of the TBC during thermal cycling. The adherence and failure modes of these coating systems were experimentally studied during the high-temperature testing. The TBC failure mechanism during thermal cycling is discussed in light of coating transient stresses and substrate oxidation.

  15. Process gases for high velocity oxy-fuel thermal spraying

    SciTech Connect

    Creffield, G.K.; Chapman, I.F.; Cole, M.A.; Page, W.J.; McDonough, T.

    1994-12-31

    The importance of fuel and other process gases for high velocity oxy-fuel (HVOF) thermal spraying and especially the delivery of them to the point of use is well recognized. Problems associated with the supply of liquid fuel gases, at the high flow rates and pressures required by this process, have been addressed. Considerable development work has gone into designing an appropriate liquid withdrawal and vaporizer system for propylene, which overcomes these previous difficulties and enables users to maintain adequate fuel gas flow rates in order to ensure optimum operating conditions for the production of high quality coatings. A feature of the thermal spray process is that the temperature of the workpiece is kept low, typically below 150 C, in order to reduce residual stresses in the coating and to protect heat sensitive substrates. Traditionally this has been by compressed air, however, improved cooling has been achieved using carbon dioxide. Specially designed equipment is now available which provides and directs a cold mixture of carbon dioxide gas and solid particles (snow) via suitable nozzles, on the workpiece. The position of the cooling stream can be varied, depending on the application. These developments emphasize the importance now attached to providing dedicated gas installation packages for HVOF.

  16. Industrial applications of thermal sprayed coatings in Venezuelan steelmaking industry

    NASA Astrophysics Data System (ADS)

    Liscano, S.; Nuñez, E.; Gil, L.; Zerpa, R.

    2013-11-01

    The metal components subjected to high temperature conditions, abrasive wear, corrosion, impact, etc.; tend to present degradation of manufacturing material, causing the failure imminent of the component. One of the alternatives to minimize or eliminate such effect is the application of ceramic coatings, which are thermal insulators and exhibit high mechanical strength. Its extreme hardness, coupled with the low friction properties and chemical stability, allowing its use in a wide variety of applications. Therefore, the following paper describes the application of thermal sprayed coatings obtained by HVOF and Plasma technologies like alternative to protect the metallic equipment in different venezuelan industrial sectors, such as to operate under aggressive conditions of service, such as the steelmaking nationals industries. This study presents applications cases of ceramic-based coatings, in order to minimize the sticking of metallic material in components of reduction reactor of FINMET® and MIDREXTM process.

  17. Mechanical and Thermal Transport Properties of Suspension Thermal-Sprayed Alumina-Zirconia Composite Coatings

    NASA Astrophysics Data System (ADS)

    Oberste Berghaus, Jörg; Legoux, Jean-Gabriel; Moreau, Christian; Tarasi, Fariba; Chráska, Tomas

    2008-03-01

    Micro-laminates and nanocomposites of Al2O3 and ZrO2 can potentially exhibit higher hardness and fracture toughness and lower thermal conductivity than alumina or zirconia alone. The potential of these improvements for abrasion protection and thermal barrier coatings is generating considerable interest in developing techniques for producing these functional coatings with optimized microstructures. Al2O3-ZrO2 composite coatings were deposited by suspension thermal spraying (APS and HVOF) of submicron feedstock powders. The liquid carrier employed in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to unique and novel fine-scaled microstructures. The suspensions were injected internally using a Mettech Axial III plasma torch and a Sulzer-Metco DJ-2700 HVOF gun. The different spray processes induced a variety of structures ranging from finely segregated ceramic laminates to highly alloyed amorphous composites. Mechanisms leading to these structures are related to the feedstock size and in-flight particle states upon their impact. Mechanical and thermal transport properties of the coatings were compared. Compositionally segregated crystalline coatings, obtained by plasma spraying, showed the highest hardness of up to 1125 VHN3 N, as well as the highest abrasion wear resistance (following ASTM G65). The HVOF coating exhibited the highest erosion wear resistance (following ASTM G75), which was related to the toughening effect of small dispersed zirconia particles in the alumina-zirconia-alloyed matrix. This microstructure also exhibited the lowest thermal diffusivity, which is explained by the amorphous phase content and limited particle bonding, generating local thermal resistances within the structure.

  18. Advanced solar thermal receiver technology

    NASA Technical Reports Server (NTRS)

    Kudirka, A. A.; Leibowitz, L. P.

    1980-01-01

    Development of advanced receiver technology for solar thermal receivers designed for electric power generation or for industrial applications, such as fuels and chemical production or industrial process heat, is described. The development of this technology is focused on receivers that operate from 1000 F to 3000 F and above. Development strategy is mapped in terms of application requirements, and the related system and technical requirements. Receiver performance requirements and current development efforts are covered for five classes of receiver applications: high temperature, advanced Brayton, Stirling, and Rankine cycle engines, and fuels and chemicals.

  19. Production of spherical apatite powders—the first step for optimized thermal-sprayed apatite coatings

    NASA Astrophysics Data System (ADS)

    Lugscheider, E.; Knepper, M.; Gross, K. A.

    1992-09-01

    Regardless of the thermal spraying system, a coating can only be as good as the quality of the input powders. Powder quality in turn is dependent on the manufacturing process and conditions. Thus, it is possible to alter characteristics such as morphology, porosity, phase composition, and the mechanical strength of the individual particles. This article looks at powder agglomerations using the spray drying technique. Two different spray drying configurations were used to produce spherical apatite powders. Apatite powders could be produced with variable densities. Rotary-atomized powders possessed internal porosity as well as open porosity. More applicable for thermal spraying are the nozzle-atomized powders, which are more dense. The particle size range produced is dependent on the many parameters in the spray drying process. Hydroxyapatite is more sensitive than fluorapatite to alterations in process conditions. The powders produced were clean, free of other phases, and possessed good flowability for thermal spraying purposes.

  20. Superior Thermal Barrier Coatings Using Solution Precursor Plasma Spray

    NASA Astrophysics Data System (ADS)

    Jordan, E. H.; Xie, L.; Gell, M.; Padture, N. P.; Cetegen, B.; Ozturk, A.; Ma, X.; Roth, J.; Xiao, T. D.; Bryant, P. E. C.

    2004-03-01

    A novel process, solution precursor plasma spray (SPPS), is presented for depositing thermal barrier coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting coatings microstructure has three unique features: (1) ultra fine splats (1 µm), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) coatings. The conductivity of SPPS coatings is lower than EB-PVD coatings and higher than the best APS coatings. Manufacturing cost is expected to be similar to APS coatings and much lower than EB-PVD coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.

  1. Fabrication of low cost cutting wheel via thermal spray process

    NASA Astrophysics Data System (ADS)

    Anasyida, A. S.; Nurulakmal, M. S.

    2012-09-01

    The present study is mainly focused on development of metal cutting wheel. The process involved hard particles (abrasives) being bonded on the wheel to enhance the cutting capability by thermal spraying process and followed by polymer bonding. The purpose of this work is to produce low cost cutting wheel and study the performance of cutting behavior. Two different types of powders; silicon carbide (SiC) as bonding agent and chromium carbide (Cr3C2) as abrasives were used. Wear loss and depth of cut as function of load, cutting time and cutting speed were evaluated. The results showed that the speed and load were the main factors that affected the cutting efficiency and the optimum cutting process can be performed at low cutting speed and high load or at high cutting speed and low load.

  2. Surface preparation via grit-blasting for thermal spraying

    SciTech Connect

    Varacalle, D.J. Jr.; Lundberg, L.B.; Hartley, R.S.

    1995-11-01

    The major reason for grit blasting for thermal spray applications is to ensure a strong mechanical bond between the substrate and the coating by the enhanced roughening of the substrate material. This study presents five statistically designed experiments that were accomplished to investigate the grit blasting process. The experiments were conducted using a Box statistical design of experiment (SDE) approach. A substantial range of grit blasting parameters and their effect on the resultant substrate roughness were investigated, including grit type, pressure, working distance, and exposure time. The substrates were characterized for surface characteristics using image analysis. These attributes are correlated with the changes in operating parameters. Optimized process parameters for the two machines used in this study as predicted by the SDE analysis are presented.

  3. Wear resistance of composite coatings produced by thermal spraying

    SciTech Connect

    Klinskaya, N.A.

    1995-12-31

    Injection of refractory additions (carbides, borides, oxides etc.) into self-fluxing alloys is a well-known technique for their hardening. Nevertheless the matter of influence of refractory components on the structure and characteristics of composite coatings is not studied well enough. This paper presents the results of investigations of gas thermal coatings (plasma and detonation ones) on the base of stellite with refractory components in the form of borides such as CrB{sub 2}, TiB{sub 2}, (TiCr)B{sub 2}. This study is concerned with the influence of refractory additions (carbides, borides, oxides) on the wear resistance sprayed coatings based on self-fluxing alloys NiCrBSi and CoCrBSi.

  4. Electrochemical Aging of Thermal-Sprayed Zinc Anodes on Concrete

    SciTech Connect

    Holcomb, G.R.; Bullard, S.J.; Covino, B.S. Jr.; Cramer, S.D.; Cryer, C.B.; McGill, G.E.

    1996-10-01

    Thermal-sprayed zinc anodes are used in impressed current cathodic protection systems for some of Oregon's coastal reinforced concrete bridges. Electrochemical aging of zinc anodes results in physical and chemical changes at the zinc-concrete interface. Concrete surfaces heated prior to thermal-spraying had initial adhesion strengths 80 pct higher than unheated surfaces. For electrochemical aging greater than 200 kC/m{sup 2} (5.2 A h/ft{sup 2}), there was no difference in adhesion strengths for zinc on preheated and unheated concrete. Adhesion strengths decreased monotonically after about 400 to 600 kC/m{sup 2} (10.4 to 15.6 A-h/ft{sup 2}) as a result of the reaction zones at the zinc-concrete interface. A zone adjacent to the metallic zinc (and originally part of the zinc coating) was primarily zincite (ZnO), with minor constituents of wulfingite (Zn(OH){sub 2}), simonkolleite (Zn{sub 5}(OH) {sub 8}C{sub l2}{sup .}H{sub 2}O), and hydrated zinc hydroxide sulfates (Zn{sub 4}SO{sub 4}(OH){sub 6}{sup .}xH{sub 2}O). This zone is the locus for cohesive fracture when the zinc coating separates from the concrete during adhesion tests. Zinc ions substitute for calcium in the cement paste adjacent to the coating as the result of secondary mineralization. The initial estimate of the coating service life based on adhesion strength measurements in accelerated impressed current cathodic protection tests is about 27 years.

  5. Simulation of surface roughness during the formation of thermal spray coatings

    SciTech Connect

    Kanouff, M.P.

    1996-07-01

    The formation of a thermal spray coating was analyzed to identify methods to reduce the surface roughness of the coating. A new methodology was developed which uses a string of equally spaced node points to define the shape of the coating surface and to track the shape change as the thermal spray mass is deposited. This allows the calculation of arbitrary shapes for the coating surface which may be very complex. The model simulates the stochastic deposition of a large number of thermal spray droplets, where experimental data is used for the mass flux distribution on the target surface. This data shows that when the thermal spray mass impinges on the target surface, a large fraction of it (over-spray) splashes off the target and is re-deposited with a small spray angle, resulting in a large coating roughness. This analysis was used in a parameter study to identify methods for reducing the coating roughness. Effect of the shape of the profile for the pre-roughened substrate was found to be small. Decreasing the droplet size by a factor of 2 decreased the roughness by 13%. Increasing the spray angle for the over-spray by a factor of 2 decreased the roughness by 50%, and decreasing the amount of over- spray by a factor of 2 decreased the roughness by 51%.

  6. Thermophysical properties of thermal sprayed coatings on carbon steel substrates by photothermal radiometry

    SciTech Connect

    Garcia, J.A.; Mandelis, A.; Farahbakhsh, B.; Lebowitz, C.; Harris, I.

    1999-09-01

    Laser infrared photothermal radiometry (PTR) was used to measure the thermophysical properties (thermal diffusivity and conductivity) of various thermal sprayed coatings on carbon steel. A one-dimensional photothermal model of a three-layered system in the backscattered mode was introduced and compared with experimental measurements. The uppermost layer was used to represent a roughness-equivalent layer, a second layer represented the substrate. The thermophysical parameters of thermal sprayed coatings examined in this work were obtained when a multiparameter-fit optimization algorithm was used with the backscattered PTR experimental results. The results also suggested a good method to determine the thickness of tungsten carbide and stainless-steel thermal spray coatings once the thermal physical properties are known. The ability of PTR to measure the thermophysical properties and the coating thickness has a strong potential as a method for in situ characterization of thermal spray coatings.

  7. Advanced thermally stable jet fuels

    SciTech Connect

    Schobert, H.H.

    1999-01-31

    The Pennsylvania State University program in advanced thermally stable coal-based jet fuels has five broad objectives: (1) Development of mechanisms of degradation and solids formation; (2) Quantitative measurement of growth of sub-micrometer and micrometer-sized particles suspended in fuels during thermal stressing; (3) Characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) Elucidation of the role of additives in retarding the formation of carbonaceous solids; (5) Assessment of the potential of production of high yields of cycloalkanes by direct liquefaction of coal. Future high-Mach aircraft will place severe thermal demands on jet fuels, requiring the development of novel, hybrid fuel mixtures capable of withstanding temperatures in the range of 400--500 C. In the new aircraft, jet fuel will serve as both an energy source and a heat sink for cooling the airframe, engine, and system components. The ultimate development of such advanced fuels requires a thorough understanding of the thermal decomposition behavior of jet fuels under supercritical conditions. Considering that jet fuels consist of hundreds of compounds, this task must begin with a study of the thermal degradation behavior of select model compounds under supercritical conditions. The research performed by The Pennsylvania State University was focused on five major tasks that reflect the objectives stated above: Task 1: Investigation of the Quantitative Degradation of Fuels; Task 2: Investigation of Incipient Deposition; Task 3: Characterization of Solid Gums, Sediments, and Carbonaceous Deposits; Task 4: Coal-Based Fuel Stabilization Studies; and Task 5: Exploratory Studies on the Direct Conversion of Coal to High Quality Jet Fuels. The major findings of each of these tasks are presented in this executive summary. A description of the sub-tasks performed under each of these tasks and the findings of those studies are provided in the remainder of this volume

  8. Fatigue Crack Growth in Bodies with Thermally Sprayed Coating

    NASA Astrophysics Data System (ADS)

    Kovářík, O.; Haušild, P.; Medřický, J.; Tomek, L.; Siegl, J.; Mušálek, R.; Curry, N.; Björklund, S.

    2016-01-01

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the localization of crack initiation sites and the dynamics of crack propagation are studied. The resonance bending fatigue test was employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical thermal barrier coating consisting of yttria stabilized zirconia and NiCoCrAlY layers. The strain distribution on the coating surface was evaluated by the Digital Image Correlation method through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e., the changes of material properties, crack initiation, and crack propagation, were identified. The tested coatings strongly influenced the first two phases, and the influence on the crack propagation was less significant. In general, the presented crack detection method can be used as a sensitive nondestructive testing method well suited for coated parts.

  9. Structure Analysis Of Corrosion Resistant Thermal Sprayed Coatings On Low Alloy Steels

    SciTech Connect

    Chaliampalias, D.; Vourlias, G.; Pistofidis, N.; Pavlidou, E.; Stergiou, A.; Stergioudis, G.; Polychroniadis, E. K.

    2007-04-23

    Metallic coatings have been proved to reduce the rate of corrosion of steel in various atmospheres. In this work the structure of Al, Cu-Al and Zn thermal sprayed coatings is examined. The as formed coatings are extremely rough, and they are composed of several phases which increase corrosion resistance as it was determined Salt Spray Chamber tests.

  10. Methods for coating conduit interior surfaces utilizing a thermal spray gun with extension arm

    DOEpatents

    Moore, Karen A.; Zatorski, Raymond A.

    2007-10-02

    Systems and methods for applying a coating to an interior surface of a conduit. In one embodiment, a spray gun configured to apply a coating is attached to an extension arm which may be inserted into the bore of a pipe. The spray gun may be a thermal spray gun adapted to apply a powder coating. An evacuation system may be used to provide a volume area of reduced air pressure for drawing overspray out of the pipe interior during coating. The extension arm as well as the spray gun may be cooled to maintain a consistent temperature in the system, allowing for more consistent coating.

  11. Systems and methods for coating conduit interior surfaces utilizing a thermal spray gun with extension arm

    DOEpatents

    Moore, Karen A.; Zatorski, Raymond A.

    2005-07-12

    Systems and methods for applying a coating to an interior surface of a conduit. In one embodiment, a spray gun configured to apply a coating is attached to an extension arm which may be inserted into the bore of a pipe. The spray gun may be a thermal spray gun adapted to apply a powder coating. An evacuation system may be used to provide a volume area of reduced air pressure for drawing overspray out of the pipe interior during coating. The extension arm as well as the spray gun may be cooled to maintain a consistent temperature in the system, allowing for more consistent coating.

  12. Review of US Nanocorp - SNL Joint Development of Thermal-Sprayed Thin-Film Cathodes for Thermal Batteries

    SciTech Connect

    GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; DAI,JINXIANG; XIAO,T. DANNY; REISNER,DAVID E.

    2000-11-14

    The use of plasma spray to deposit thin metal-sulfide cathode films is described in this paper. Conventional electroactive stack components in thermal batteries are constructed from pressed-powder parts that are difficult to fabricate in large diameters in thicknesses <0.010. Plasma-sprayed electrodes do not steer from this difficulty, allowing greater energy densities and specific energies to be realized. Various co-spraying agents have been found suitable for improving the mechanical as well as electrochemical properties of plasma-sprayed cathodes for thermal batteries. These electrodes generally show equal or improved performance over conventional pressed-powder electrodes. A number of areas for future growth and development of plasma-spray technology is discussed.

  13. An Assessment of the Residual Stresses in Low Pressure Plasma Sprayed Coatings on an Advanced Copper Alloy

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.; Agarwal, A.; Lachtrupp, T. P.

    2002-01-01

    Modeling studies were conducted on low pressure plasma sprayed (LPPS) NiAl top coat applied to an advanced Cu-8(at.%)Cr-4%Nb alloy (GRCop-84) substrate using Ni as a bond coat. A thermal analysis suggested that the NiAl and Ni top and bond coats, respectively, would provide adequate thermal protection to the GRCop-84 substrate in a rocket engine operating under high heat flux conditions. Residual stress measurements were conducted at different depths from the free surface on coated and uncoated GRCop-84 specimens by x-ray diffraction. These data are compared with theoretically estimated values assessed by a finite element analysis simulating the development of these stresses as the coated substrate cools down from the plasma spraying temperature to room temperature.

  14. Corrosion properties of stainless steel coatings made by different methods of thermal spraying

    SciTech Connect

    Siitonen, P.; Konos, T.; Kettunen, P.O.

    1994-12-31

    The corrosion protection ability of thermally sprayed stainless steel coatings in aggressive environments is considerably limited as compared to bulk materials of the same composition. The two main reasons for the decrease in corrosion resistance are the porosity in the coatings and the oxidation of elements, particularly chromium, during spraying process. The corrosion resistance and structure of stainless steel coatings, ANVAL 254 SMO, made by different methods of thermal spraying were evaluated in this work. The coatings were produced by atmospheric plasma spraying (APS), atmospheric plasma spraying using gas shielding around the plasma (APS/S), low pressure plasma spraying (LPPS), detonation gun spraying (DGS) and high velocity oxyfuel spraying (HVOF). Electrochemical methods were used for determining the corrosion protection ability of coatings in 3.5% NaCl-solution and in sulfur acid solution (pH 3 and 1). The structure and composition of coatings were studied by optical microscopy and scanning electron microscopy/energy dispersive analysator (SEM/EDS). The porosity of the coatings was determined by water impregnation method, optical microscopy and mercury porosimeter. The results showed that the best coating quality can be achieved by LPPS- and HVOF-coatings. Oxidation and porosity restrict the use of APS-coatings in corrosive environments. The oxidation can be avoided by using argon gas shield around the plasma flame during spraying. Due to porosity all studied coatings suffered crevice corrosion in chloride solution. Despite high Mo-alloying the best coatings reached only the corrosion resistance of AISI 316.

  15. A Review of Thermal Spray Metallization of Polymer-Based Structures

    NASA Astrophysics Data System (ADS)

    Gonzalez, R.; Ashrafizadeh, H.; Lopera, A.; Mertiny, P.; McDonald, A.

    2016-06-01

    A literature review on the thermal spray deposition of metals onto polymer-based structures is presented. The deposition of metals onto polymer-based structures has been developed to enhance the thermal and electrical properties of the resulting metal-polymer material system. First, the description of the thermal spray metallization processes and technologies for polymer-based materials are outlined. Then, polymer surface preparation methods and the deposition of metal bond-coats are explored. Moreover, the thermal spray process parameters that affect the properties of metal deposits on polymers are described, followed by studies on the temperature distribution within the polymer substrate during the thermal spray process. The objective of this review is devoted to testing and potential applications of thermal-sprayed metal coatings deposited onto polymer-based substrates. This review aims to summarize the state-of-the-art contributions to research on the thermal spray metallization of polymer-based materials, which has gained recent attention for potential and novel applications.

  16. A Review of Thermal Spray Metallization of Polymer-Based Structures

    NASA Astrophysics Data System (ADS)

    Gonzalez, R.; Ashrafizadeh, H.; Lopera, A.; Mertiny, P.; McDonald, A.

    2016-05-01

    A literature review on the thermal spray deposition of metals onto polymer-based structures is presented. The deposition of metals onto polymer-based structures has been developed to enhance the thermal and electrical properties of the resulting metal-polymer material system. First, the description of the thermal spray metallization processes and technologies for polymer-based materials are outlined. Then, polymer surface preparation methods and the deposition of metal bond-coats are explored. Moreover, the thermal spray process parameters that affect the properties of metal deposits on polymers are described, followed by studies on the temperature distribution within the polymer substrate during the thermal spray process. The objective of this review is devoted to testing and potential applications of thermal-sprayed metal coatings deposited onto polymer-based substrates. This review aims to summarize the state-of-the-art contributions to research on the thermal spray metallization of polymer-based materials, which has gained recent attention for potential and novel applications.

  17. Computer-Aided Robot Trajectory Auto-generation Strategy in Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Cai, Zhenhua; Liang, Hong; Quan, Shuhai; Deng, Sihao; Zeng, Chunnian; Zhang, Feng

    2015-10-01

    This paper is concerned with a new methodology which is designed to auto-generate the robotic trajectory for thermal spraying process. Based on it, a software package named Thermal Spray Toolkit is developed and integrated in the main frame of off-line programming software RobotStudio™ (Product of ABB Company, Sweden). This toolkit implements the robotic trajectory planning in an interactive manner between RobotStudio™ and the finite element analysis software (FES). It allows rearranging the imported node index created on the surface of workpiece by FES and in turn generating the thermal spraying needed robot trajectories. Several parameters in thermal spraying, such as scanning step and torch-substrate relative velocity which have major influence on the coating deposition, are considered in the trajectory generation process. Experiment is carried out to check the reliability of the generated robot trajectory.

  18. Performance of thermal-sprayed zinc anodes treated with humectants in cathodic protection systems

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Russell, James H.; Bennett, John E.; Milius, John K.; Cryer, Curtis B.; Soltesz, Steven M.

    2001-01-01

    Thermal-sprayed Zn anodes are used for impressed current cathodic protection (ICCP) systems in Oregon's reinforced concrete coastal bridges to minimize corrosion damage. Thermal-sprayed Zn performs well as an ICCP anode but the voltage requirement can increase with increasing electrochemical age. It also performs well as a galvanic (GCP) anode but current output can decrease with increasing electrochemical age. Past research has shown that increasing moisture at the Zn anode-concrete interface improves the operation of the thermal-sprayed Zn anode. Humectants, hygroscopic materials that are applied to the surface of the Zn-anode, can increase the moisture at the zinc-concrete interface, thereby improving the performance and extending the anode service life. Results are given for humectant-treated (LiBr and LiNO3) thermal-sprayed Zn anodes used in the laboratory electrochemical aging studies and in field studies on the Yaquina Bay Bridge, Oregon, USA.

  19. Analytical and mechanical testing of high velocity oxy-fuel thermal sprayed and plasma sprayed calcium phosphate coatings.

    PubMed

    Haman, J D; Chittur, K K; Crawmer, D E; Lucas, L C

    1999-01-01

    Plasma spraying (PS) is the most frequently used coating technique for implants; however, in other industries a cheaper, more efficient process, high-velocity oxy-fuel thermal spraying (HVOF), is in use. This process provides higher purity, denser, more adherent coatings than plasma spraying. The primary objective of this work was to determine if the use of HVOF could improve the mechanical properties of calcium phosphate coatings. Previous studies have shown that HVOF calcium phosphate coatings are more crystalline than plasma sprayed coatings. In addition, because the coatings are exposed to more complex loading profiles in vivo than standard ASTM tensile tests provide, a secondary objective of this study was to determine the applicability of four-point bend testing for these coatings. Coatings produced by HVOF and PS were analyzed by profilometry, diffuse reflectance Fourier transform infrared spectroscopy, X-ray diffraction, four-point bend, and ASTM C633 tensile testing. HVOF coatings were found to have lower amorphous calcium phosphate content, higher roughness values, and lower ASTM C633 bond strengths than PS coatings; however, both coatings had similar crystal unit cell sizes, phases present (including hydroxyapatite, beta-tricalcium phosphate, and tetracalcium phosphate), and four-point bend bond strengths. Thus, the chemical, structural, and mechanical results of this study, in general, indicate that the use of HVOF to produce calcium phosphate coatings is equivalent to those produced by plasma spraying. PMID:10556851

  20. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  1. Quantifying Thermal Spray Coating Architecture by Stereological Protocols: Part II. Key Points to be Addressed

    NASA Astrophysics Data System (ADS)

    Antou, Guy; Montavon, Ghislain

    2007-06-01

    This commentary aims at presenting, from a practical viewpoint, some key points to assess when implementing image analysis coupled to stereological protocols to quantify statistically the architecture of thermal spray coatings and their relevant features (pores, lamellae, and so forth.). This article is the second of a two-part commentary; the first one, published in Journal of Thermal Spray Technology, Vol 16 (No. 1), 2007, detailed those stereological protocols from a historical perspective.

  2. Wear Analysis of Thermal Spray Coatings on 3D Surfaces

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Luo, W.; Selvadurai, U.

    2014-01-01

    Even though the application of thermal spray coatings on complex geometries gained a greater interest in the last decade, the effect of different geometrical features on the wear behavior is still ill-defined. In this study, the wear resistance of FTC-FeCSiMn coated 3D surfaces was investigated. The wear test was carried out by means of two innovative testing procedures. The first test is a Pin-on-Tubes test where the rotating motion is realized by a lathe chuck. The specimens in the second test were fixed on the table and a robot arm operated the pin. This wear test was applied on specimens with concave or convex surfaces. The residual stresses, which were determined by means of an incremental hole-drilling method, show a dependency on the substrate geometry. The obtained stresses were put in relation to the different radii. After the wear test, a 3D-profilometer determined the wear volume and the sections of the coatings were characterized by a scanning electron microscope. The results indicate that the wear resistance is strongly influenced by the geometry of the substrate.

  3. Development of Advanced Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    Advanced multi-component, low conductivity oxide thermal barrier coatings have been developed using an approach that emphasizes real-time monitoring of thermal conductivity under conditions that are engine-like in terms of temperatures and heat fluxes. This is in contrast to the traditional approach where coatings are initially optimized in terms of furnace and burner rig durability with subsequent measurement in the as-processed or furnace-sintered condition. The present work establishes a laser high-heat-flux test as the basis for evaluating advanced plasma-sprayed and electron beam-physical vapor deposited (EB-PVD) thermal barrier coatings under the NASA Ultra-Efficient Engine Technology (UEET) Program. The candidate coating materials for this program are novel thermal barrier coatings that are found to have significantly reduced thermal conductivities and improved thermal stability due to an oxide-defect-cluster design. Critical issues for designing advanced low conductivity coatings with improved coating durability are also discussed.

  4. Application of commercially pure titanium coatings using HVOF thermal spray for machinery component restoration

    SciTech Connect

    McCaw, R.L.; Hays, R.A.; Brenna, R.T.

    1994-12-31

    Alloy 625 has been shown to be susceptible to crevice corrosion under tight metal to nonmetal crevices in both natural and treated seawater. Under similar conditions, commercially pure titanium (CP Ti) has been shown to be immune. Therefore, coating alloy 625 sealing areas with CP Ti is a potentially effective crevice corrosion countermeasure. Specialized thermal spray techniques were developed utilizing the high velocity oxy-fuel (HVOF) process to apply coatings of CP Ti to alloy 625 substrates in atmosphere. Coating quality was similar to plasma sprayed coatings of other less reactive, metals. Crevice corrosion tests were conducted and issues relating to implementation of HVOF thermal spraying on a production basis were considered.

  5. Laboratory report—thermal spraying at the shanghai institute of ceramics

    NASA Astrophysics Data System (ADS)

    Chuanxian, D.; Zhaohe, T.

    1992-09-01

    Plasma spraying has received considerable attention as a process for obtaining protective coatings. In this article, experiments and results obtained at the Shanghai Institute of Ceramics pertaining to the developments and application of plasma-sprayed coating materials such as thermal barrier, wear resistance, infrared radiation, electrode materials, biomedical materials, and diamond films are presented. The physical, mechanical, and thermal properties of the coatings were measured. The microstructural features of the coatings were also examined. Examples of applications of plasma-sprayed coatings in various industries are illustrated. In addition, the manufacture of some oxide powders and their characteristics are discussed.

  6. Particle In-Flight and Coating Properties of Fe-Based Feedstock Materials Sprayed with Modern Thermal Spray Systems

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Kopp, Nils; Warda, Thomas; Petkovic, Ivica; Schaefer, Marcel; Landes, Klaus Dieter; Forster, Guenter; Zimmermann, Stephan; Marques, Jose-Luis; Kirner, Stefan; Kauffeldt, Marina; Schein, Jochen

    2013-03-01

    New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coatings. Innovations in the field of feedstock materials are supporting this trend. The combination of both has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni-basis or metal-matrix composites. This study intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry. Resulting coatings are analyzed and a correlation with the particle in-flight properties is given. The experiments are accompanied by computational fluid dynamics simulations of spray jet and particle velocities, leading to a comprehensive analysis of the achievable particle properties with state-of-the-art HVOF and APS systems.

  7. Thermal Spraying of Bioactive Polymer Coatings for Orthopaedic Applications

    NASA Astrophysics Data System (ADS)

    Chebbi, A.; Stokes, J.

    2012-06-01

    Flame sprayed biocompatible polymer coatings, made of biodegradable and non-biodegradable polymers, were investigated as single coatings on titanium and as top coatings on plasma sprayed Hydroxyapatite. Biocompatible polymers can act as drug carriers for localized drug release following implantation. The polymer matrix consisted of a biodegradable polymer, polyhydroxybutyrate 98%/ polyhydroxyvalerate 2% (PHBV) and a non-biodegradable polymer, polymethylmethacrylate (PMMA). Screening tests were performed to determine the suitable range of spraying parameters, followed by a Design of Experiments study to determine the effects of spraying parameters on coating characteristics (thickness, roughness, adhesion, wettability), and to optimize the coating properties accordingly. Coatings characterization showed that optimized flame sprayed biocompatible polymers underwent little chemical degradation, did not produce acidic by-products in vitro, and that cells proliferated well on their surface.

  8. Columnar-Structured Thermal Barrier Coatings (TBCs) by Thin Film Low-Pressure Plasma Spraying (LPPS-TF)

    NASA Astrophysics Data System (ADS)

    Hospach, Andreas; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

    2011-01-01

    The very low-pressure plasma Spray (VLPPS) process has been developed with the aim of depositing uniform and thin coatings with coverage of a large area by plasma spraying. At typical pressures of 100-200 Pa, the characteristics of the plasma jet change compared to conventional low-pressure plasma-spraying processes (LPPS) operating at 5-20 kPa. The combination of plasma spraying at low pressures with enhanced electrical input power has led to the development of the LPPS-TF process (TF = thin film). At appropriate parameters, it is possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This technique offers new possibilities for the manufacturing of thermal barrier coatings (TBCs). Besides the material composition, the microstructure is an important key to reduce thermal conductivity and to increase strain tolerance. In this regard, columnar microstructures deposited from the vapor phase show considerable advantages. Therefore, physical vapor deposition by electron beam evaporation (EB-PVD) is applied to achieve such columnar-structured TBCs. However, the deposition rate is low, and the line-of-sight nature of the process involves specific restrictions. In this article, the deposition of TBCs by the LPPS-TF process is shown. How the evaporation of the feedstock powder could be improved and to what extent the deposition rates could be increased were investigated.

  9. Advanced Microscopic Study of Suspension Plasma-Sprayed Zirconia Coatings with Different Microstructures

    NASA Astrophysics Data System (ADS)

    Sokołowski, Paweł; Pawłowski, Lech; Dietrich, Dagmar; Lampke, Thomas; Jech, David

    2016-01-01

    The present paper is focused on the characterization of the differences between two microstructures that can be obtained using SPS technology, namely (i) columnar and (ii) two-zone microstructure including lamellas and fine unmelted particulates. The optimization of spray parameters was made, and the advanced microstructural studies of obtained coatings were performed. The work was focused on zirconia stabilized by yttria (YSZ, ZrO2 + 14 wt.% Y2O3) and both by yttria and ceria (YCSZ, ZrO2 + 24 wt.% CeO2 + 2.5 wt.% Y2O3) which are frequently used as thermal barrier coatings. Two types of microstructure were achieved using two different plasma torches, namely SG-100 of Praxair and Triplex of Oerlikon Metco. The microstructure of prepared coatings was analyzed using scanning electron microscopy with secondary electrons detector and backscattered electrons. Energy dispersive spectroscopy was performed to analyze the chemical composition of sprayed coatings. By electron backscatter diffraction grain shape, size, and crystal orientation were determined. The analysis enabled the discussion of the coatings growth mechanism. Finally, the Shape From Shading technique was applied to recreate and to analyze 3D views of coatings' topographies, and using laser confocal microscopy, the surface roughness was examined.

  10. Fracture toughness of plasma-sprayed thermal barrier ceramics: Influence of processing, microstructure, and thermal aging

    SciTech Connect

    Dwivedi, Gopal; Viswanathan, Vaishak; Sampath, Sanjay; Shyam, Amit; Lara-Curzio, Edgar

    2014-06-09

    Fracture toughness has become one of the dominant design parameters that dictates the selection of materials and their microstructure to obtain durable thermal barrier coatings (TBCs). Much progress has been made in characterizing the fracture toughness of relevant TBC compositions in bulk form, and it has become apparent that this property is significantly affected by process-induced microstructural defects. In this investigation, a systematic study of the influence of coating microstructure on the fracture toughness of atmospheric plasma sprayed (APS) TBCs has been carried out. Yttria partially stabilized zirconia (YSZ) coatings were fabricated under different spray process conditions inducing different levels of porosity and interfacial defects. Fracture toughness was measured on free standing coatings in as-processed and thermally aged conditions using the double torsion technique. Results indicate significant variance in fracture toughness among coatings with different microstructures including changes induced by thermal aging. Comparative studies were also conducted on an alternative TBC composition, Gd2Zr2O7 (GDZ), which as anticipated shows significantly lower fracture toughness compared to YSZ. Furthermore, the results from these studies not only point towards a need for process and microstructure optimization for enhanced TBC performance but also a framework for establishing performance metrics for promising new TBC compositions.

  11. Fracture toughness of plasma-sprayed thermal barrier ceramics: Influence of processing, microstructure, and thermal aging

    DOE PAGESBeta

    Dwivedi, Gopal; Viswanathan, Vaishak; Sampath, Sanjay; Shyam, Amit; Lara-Curzio, Edgar

    2014-06-09

    Fracture toughness has become one of the dominant design parameters that dictates the selection of materials and their microstructure to obtain durable thermal barrier coatings (TBCs). Much progress has been made in characterizing the fracture toughness of relevant TBC compositions in bulk form, and it has become apparent that this property is significantly affected by process-induced microstructural defects. In this investigation, a systematic study of the influence of coating microstructure on the fracture toughness of atmospheric plasma sprayed (APS) TBCs has been carried out. Yttria partially stabilized zirconia (YSZ) coatings were fabricated under different spray process conditions inducing different levelsmore » of porosity and interfacial defects. Fracture toughness was measured on free standing coatings in as-processed and thermally aged conditions using the double torsion technique. Results indicate significant variance in fracture toughness among coatings with different microstructures including changes induced by thermal aging. Comparative studies were also conducted on an alternative TBC composition, Gd2Zr2O7 (GDZ), which as anticipated shows significantly lower fracture toughness compared to YSZ. Furthermore, the results from these studies not only point towards a need for process and microstructure optimization for enhanced TBC performance but also a framework for establishing performance metrics for promising new TBC compositions.« less

  12. FeAI and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Terry C. Totemeier; Richard N. Wright; W. David Swank

    2004-12-01

    FeAl and Mo–Si–B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe–24Al (wt%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 to 700 m/s. Mo–13.4Si–2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo–Si–B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity. For Mo–Si–B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and a-Mo. The T1 phase was retained after spraying at 350 m/s.

  13. FeAl and Mo-Si-B Intermetallic Coatings Prepared by Thermal Spraying

    SciTech Connect

    Totemeier, T.C.; Wright, R.N.; Swank, W.D.

    2003-04-22

    FeAl and Mo-Si-B intermetallic coatings for elevated temperature environmental resistance were prepared using high-velocity oxy-fuel (HVOF) and air plasma spray (APS) techniques. For both coating types, the effect of coating parameters (spray particle velocity and temperature) on the microstructure and physical properties of the coatings was assessed. Fe-24Al (wt.%) coatings were prepared using HVOF thermal spraying at spray particle velocities varying from 540 m/s to 700 m/s. Mo-13.4Si-2.6B coatings were prepared using APS at particle velocities of 180 and 350 m/s. Residual stresses in the HVOF FeAl coatings were compressive, while stresses in the APS Mo-Si-B coatings were tensile. In both cases, residual stresses became more compressive with increasing spray particle velocity due to increased peening imparted by the spray particles. The hardness and elastic moduli of FeAl coatings also increased with increasing particle velocity, again due to an increased peening effect. For Mo-Si-B coatings, plasma spraying at 180 m/s resulted in significant oxidation of the spray particles and conversion of the T1 phase into amorphous silica and {alpha}-Mo. The T1 phase was retained after spraying at 350 m/s.

  14. Synthesis and Microstructural Evolution of Amorphous/Nanocrystalline Steel Coatings by Different Thermal-Spray Processes

    NASA Astrophysics Data System (ADS)

    Varadaraajan, V.; Guduru, Ramesh K.; Mohanty, P. S.

    2013-04-01

    Amorphous/nanocrystalline coatings are useful in high strength and wear-resistant applications. In the present study, the microstructural evolution of a nanocrystalline high performance steel coatings developed by different spray processes along with a novel "hybrid thermal spray" technique was studied. The hybrid-spray process combines arc and high-velocity oxy-fuel (HVOF) techniques, in which the molten metal at the arcing tip is atomized and rapidly propelled toward the substrate by HVOF jet. This so-called hybrid concept offers the benefits of productivity of electric arc spray combined with improved coating densities of HVOF. The microstructural characterization of the hybrid-spray coatings was performed by x-ray diffraction, electron microscopy, and differential scanning calorimetry, and then compared with coatings of the similar material developed by plasma-, HVOF-, and arc-spray processes individually. The HVOF- and plasma-spray coatings showed amorphous structures with very fine nanocrystals embedded, whereas hybrid- and arc-spray techniques yielded completely crystalline coatings with grain size in the range of several nanometers. The final microstructures in different spray processes could be attributed to the precursor materials employed, process temperatures, and cooling rates during the deposition process.

  15. Characterization of Magnesium Silicide Processed with Thermal Spray for Thermoelectric Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Nie, Chao

    Mg2Si has long been recognized as one of the promising thermoelectric materials; the fabrication methods are hot press, spark plasma sintering, high temperature sintering, etc. however, application of thermoelectric materials requires large scale manufacturing but traditional manufacturing process cannot reach this goal by its nature; thus we employed thermal spray technology to fabricate such thermoelectric material. In collaboration with Thermal Spray Center in Stony Brook University, we manufactured Mg 2Si coatings on titanium substrate by plasma thermal spray technology. Samples were further characterized in various methods: scanning electron microscopy (SEM) exhibits the micro structures of sprayed Mg2Si coatings; X-ray spectroscopy (XRD) analysis examined the content and various thermoelectric properties by electrical conductivity measurement, thermal conductivity measurement, Seebeck Effect measurement and Hall Effect measurement. The result showed that vacuum plasma thermal spray so far has better thermoelectric properties than atmospheric plasma spray and Mg2Si has potential to increase its thermoelectric properties if proper fabrication environment and post-fabrication processes are employed.

  16. Diagnostics and Control in the Thermal Spray Process

    SciTech Connect

    Fincke, James Russell; Swank, William David; Bewley, Randy Lee; Haggard, Delon C; Gevelber, M.; Wroblewski, D.

    2001-12-01

    The plasma-spray process features complex plasma-particle interactions that can result in process variations that limit process repeatability and coating performance. This paper reports our work on the development of real-time diagnostics and control for the plasma spray process. The strategy is to directly monitor and control those degrees of freedom of the process that are observable, controllable and affect resulting coating properties. This includes monitoring of particle velocity and temperature as well as the shape and trajectory of the spray pattern. Diagnostics that have been developed specifically for this purpose are described along with the demonstration of a closed loop process controller based on these measurements.

  17. Use of Iba Techniques to Characterize High Velocity Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Trompetter, W.; Markwitz, A.; Hyland, M.

    Spray coatings are being used in an increasingly wide range of industries to improve the abrasive, erosive and sliding wear of machine components. Over the past decade industries have moved to the application of supersonic high velocity thermal spray techniques. These coating techniques produce superior coating quality in comparison to other traditional techniques such as plasma spraying. To date the knowledge of the bonding processes and the structure of the particles within thermal spray coatings is very subjective. The aim of this research is to improve our understanding of these materials through the use of IBA techniques in conjunction with other materials analysis techniques. Samples were prepared by spraying a widely used commercial NiCr powder onto substrates using a HVAF (high velocity air fuel) thermal spraying technique. Detailed analysis of the composition and structure of the power particles revealed two distinct types of particles. The majority was NiCr particles with a significant minority of particles composing of SiO2/CrO3. When the particles were investigated both as raw powder and in the sprayed coating, it was surprising to find that the composition of the coating meterial remained unchanged during the coating process despite the high velocity application.

  18. Rolling contact fatigue characteristics of thermal sprayed tungsten carbide coatings

    SciTech Connect

    Nieminen, R.; Vuoristo, P.; Niemi, K.; Maentylae, T.

    1995-12-31

    The rolling contact fatigue (RCF) behavior of tungsten carbide (WC) based cermet coatings (WC-12% Co) deposited by plasma and HVOF spraying was studied. The RCF testing was carried out with a two-roll configuration testing machine under unlubricated rolling conditions without sliding. Loads applied in the tests resulted to Hertzian contact pressures of 420--600 MPa. The influence of spraying method on the RCF behavior of the coatings was studied as a function of Hertzian contact stress. Plasma sprayed coating showed severe surface roughening and subsurface cracking of the coating under all studied load levels. HVOF sprayed coating behavior was clearly different from the plasma coating with smaller structural changes. HVOF coating retained its original surface roughness but vertical cracks penetrating the coating appeared in this coating.

  19. Fireside Corrosion Behavior of HVOF and Plasma-Sprayed Coatings in Advanced Coal/Biomass Co-Fired Power Plants

    NASA Astrophysics Data System (ADS)

    Hussain, T.; Dudziak, T.; Simms, N. J.; Nicholls, J. R.

    2013-06-01

    This article presents a systematic evaluation of coatings for advanced fossil fuel plants and addresses fireside corrosion in coal/biomass-derived flue gases. A selection of four candidate coatings: alloy 625, NiCr, FeCrAl and NiCrAlY were deposited onto superheaters/reheaters alloy (T91) using high-velocity oxy-fuel (HVOF) and plasma spraying. A series of laboratory-based fireside corrosion exposures were carried out on these coated samples in furnaces under controlled atmosphere for 1000 h at 650 °C. The tests were carried out using the "deposit-recoat" test method to simulate the environment that was anticipated from air-firing 20 wt.% cereal co-product mixed with a UK coal. The exposures were carried out using a deposit containing Na2SO4, K2SO4, and Fe2O3 to produce alkali-iron tri-sulfates, which had been identified as the principal cause of fireside corrosion on superheaters/reheaters in pulverized coal-fired power plants. The exposed samples were examined in an ESEM with EDX analysis to characterize the damage. Pre- and post-exposure dimensional metrologies were used to quantify the metal damage in terms of metal loss distributions. The thermally sprayed coatings suffered significant corrosion attack from a combination of aggressive combustion gases and deposit mixtures. In this study, all the four plasma-sprayed coatings studied performed better than the HVOF-sprayed coatings because of a lower level of porosity. NiCr was found to be the best performing coating material with a median metal loss of ~87 μm (HVOF sprayed) and ~13 μm (plasma sprayed). In general, the median metal damage for coatings had the following ranking (in the descending order: most to the least damage): NiCrAlY > alloy 625 > FeCrAl > NiCr.

  20. Thermal and flow measurements of continuous cryogenic spray cooling.

    PubMed

    Hsieh, Shou-Shing; Tsai, Huang-Hsiu

    2006-07-01

    The performance of single sprays for high heat flux cooling using R-134a was studied. The heat flux and heat transfer coefficient at the surface of a sprayed jet based on measurements of steady-state temperature gradients on a thin copper plate during continuous spraying. Meanwhile, the spray droplets flow characteristics was also quantified through laser doppler velocimetry (LDV) measurements to obtain the local velocity distributions. The effects of mass flow rate and average droplet velocity, and spray exit-to-target distance on the surface heat flux including the corresponding critical heat flux (CHF) were explored through three different nozzle diameters of 0.2, 0.3, and 0.4 mm. Finally, the effective use of the fluid being delivered based on the cooling efficiency and cooling effectiveness was also examined. The relationship between CHF and nozzle performance in terms of cooling efficiency and cooling effectiveness was found. The heat transfer removal rate can reach up to 140 W/cm(2) for the present nozzle size of d (j)=0.2 and 0.3 mm, which may enhance the current cryogen spray cooling (CSC) technique that assists laser therapy of dermatoses. PMID:16598481

  1. Advanced nuclear thermal propulsion concepts

    NASA Technical Reports Server (NTRS)

    Howe, Steven D.

    1993-01-01

    In 1989, a Presidential directive created the Space Exploration Initiative (SEI) which had a goal of placing mankind on Mars in the early 21st century. The SEI was effectively terminated in 1992 with the election of a new administration. Although the initiative did not exist long enough to allow substantial technology development, it did provide a venue, for the first time in 20 years, to comprehensively evaluate advanced propulsion concepts which could enable fast, manned transits to Mars. As part of the SEI based investigations, scientists from NASA, DoE National Laboratories, universities, and industry met regularly and proceeded to examine a variety of innovative ideas. Most of the effort was directed toward developing a solid-core, nuclear thermal rocket and examining a high-power nuclear electric propulsion system. In addition, however, an Innovative Concepts committee was formed and charged with evaluating concepts that offered a much higher performance but were less technologically mature. The committee considered several concepts and eventually recommended that further work be performed in the areas of gas core fission rockets, inertial confinement fusion systems, antimatter based rockets, and gas core fission electric systems. Following the committee's recommendations, some computational modeling work has been performed at Los Alamos in certain of these areas and critical issues have been identified.

  2. Thermal Spray Applications in Electronics and Sensors: Past, Present, and Future

    NASA Astrophysics Data System (ADS)

    Sampath, Sanjay

    2010-09-01

    Thermal spray has enjoyed unprecedented growth and has emerged as an innovative and multifaceted deposition technology. Thermal spray coatings are crucial to the enhanced utilization of various engineering systems. Industries, in recognition of thermal spray's versatility and economics, have introduced it into manufacturing environments. The majority of modern thermal spray applications are "passive" protective coatings, and they rarely perform an electronic function. The ability to consolidate dissimilar material multilayers without substrate thermal loading has long been considered a virtue for thick-film electronics. However, the complexity of understanding/controlling materials functions especially those resulting from rapid solidification and layered assemblage has stymied expansion into electronics. That situation is changing: enhancements in process/material science are allowing reconsideration for novel electronic/sensor devices. This review critically examines past efforts in terms of materials functionality from a device perspective, along with ongoing/future concepts addressing the aforementioned deficiencies. The analysis points to intriguing future possibilities for thermal spray technology in the world of thick-film sensors.

  3. The HVOF process - the hottest topic in the thermal spray industry

    SciTech Connect

    Smith, R.W. . Center for the Plasma Processing of Materials); Irving, B.; Knight, R.

    1993-07-01

    High-velocity combustion or oxyfuel spraying started up more than 35 years ago with the development of the detonation gun or D-Gun process. Described as the newest and fastest growing member of the family of coating, or surfacing, technologies known collectively as thermal spray'', HVOF processes have carved out a significant, specialized niche in the thermal spray coating business, particularly for the deposition of wear-resistant carbide coatings. HVOF processes are able to deposit very dense coatings, typically with reduced changes in the phase composition of the material, compared with plasma arc spray processes. HVOF also offers a number of potential advantages over, and alternatives to, competing processes, including lower capital costs, portability, and ease of use in the field.

  4. Advanced thermal control for spacecraft applications

    NASA Astrophysics Data System (ADS)

    Hardesty, Robert; Parker, Kelsey

    2015-09-01

    In optical systems just like any other space borne system, thermal control plays an important role. In fact, most advanced designs are plagued with volume constraints that further complicate the thermal control challenges for even the most experienced systems engineers. Peregrine will present advances in satellite thermal control based upon passive heat transfer technologies to dissipate large thermal loads. This will address the use of 700 W/m K and higher conducting products that are five times better than aluminum on a specific basis providing enabling thermal control while maintaining structural support.

  5. Microstructure and properties of thermally sprayed silicon nitride-based coatings

    NASA Astrophysics Data System (ADS)

    Thiele, S.; Berger, L.-M.; Herrmann, M.; Nebelung, M.; Heimann, R. B.; Schnick, T.; Wielage, B.; Vuoristo, P.; Schnick, T.

    2002-06-01

    The preparation of thermally sprayed, dense, Si3N4-based coatings can be accomplished using composite spray powders with Si3N4 embedded in a complex oxide binder matrix. Powders with excellent processability were developed and produced by agglomeration (spray drying) and sintering. Optimization of the heat transfer into the powder particles was found to be the most decisive factor necessary for the production of dense and well-adhering coatings. In the present work, different thermal spray processes such as detonation gun spraying (DGS), atmospheric plasma spraying (APS) with axial powder injection, and high-velocity oxyfuel spraying (HVOF) were used. The coatings were characterized using optical and scanning electron microscopy (SEM), x-ray diffraction (XRD), and microhardness testing. The wear resistance was tested using a rubber wheel abrasion wear test (ASTM G65). In addition, thermoshock and corrosion resistances were determined. The microstructure and the performance of the best coatings were found to be sufficient, suggesting the technical applicability of this new type of coating.

  6. Comparison of the photocatalytic behavior of TiO2 coatings elaborated by different thermal spraying processes

    NASA Astrophysics Data System (ADS)

    Toma, Filofteia-Laura; Sokolov, Dmitry; Bertrand, Ghislaine; Klein, Didier; Coddet, Christian; Meunier, Cathy

    2006-12-01

    This paper proposes a comparative study on the microstructure and photocatalytic performances of titanium dioxide coatings elaborated by various thermal spraying methods (plasma spraying in atmospheric conditions, suspension plasma spraying, and high-velocity oxyfuel spraying). Agglomerated spray dried anatase TiO2 powder was used as feedstock material for spraying. Morphology and microstructural characteristics of the coatings were studied mainly by scanning electron microscopy and x-ray diffraction. The photocatalytic behavior of the TiO2-base surfaces was evaluated from the conversion rate of gaseous nitrogen oxides (NOx). It was found that the crystalline structure depended strongly on the technique of thermal spraying deposition. Moreover, a high amount of anatase was suitable for the photocatalytic degradation of the pollutants. Suspension plasma spraying has allowed retention of the original anatase phase and for very reactive TiO2 surfaces to be obtained for the removal of nitrogen oxides.

  7. Fatigue testing of plasma-sprayed thermal barrier coatings, volume 2

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Nagy, A.; Popelar, C. F.

    1990-01-01

    A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

  8. Method and apparatus for the application of thermal spray coatings onto aluminum engine cylinder bores

    SciTech Connect

    Byrnes, L.; Kramer, M.

    1994-12-31

    This paper presents background and detail information concerning the application of thermally sprayed metal alloy coatings onto the I.D. surfaces of aluminum block engine cylinder bores using a rotating extension HVOF spray gun. A fixturing method that provides block temperature stabilization and the elimination of fixture cleaning and part masking is described. A new approach and technique that replaces grit blasting for surface preparation is also discussed.

  9. Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Argarwal, P.; Duderstadt, E. C.

    1984-01-01

    The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.

  10. Effect of layer thickness on the properties of nickel thermal sprayed steel

    NASA Astrophysics Data System (ADS)

    Nurisna, Zuhri; Triyono, Muhayat, Nurul; Wijayanta, Agung Tri

    2016-03-01

    Thermal arc spray nickel coating is widely used for decorative and functional applications, by improving corrosion resistance, wear resistance, heat resistence or by modifying other properties of the coated materials. There are several properties have been studied. Layer thickness of nickel thermal sprayed steel may be make harder the substrate surface. In this study, the effect of layer thickness of nickel thermal sprayed steel has been investigated. The rectangular substrate specimens were coated by Ni-5 wt.% Al using wire arc spray method. The thickness of coating layers were in range from 0.4 to 1.0 mm. Different thickness of coating layers were conducted to investigate their effect on hardness and morphology. The coating layer was examined by using microvickers and scanning electron microscope with EDX attachment. Generally, the hardness at the interface increased with increasing thickness of coating layers for all specimens due to higher heat input during spraying process. Morphology analysis result that during spraying process aluminum would react with surrounding oxygen and form aluminum oxide at outer surface of splat. Moreover, porosity was formed in coating layers. However, presence porosity is not related to thickness of coating material. The thicker coating layer resulted highesr of hardness and bond strength.

  11. Laser ultrasound technique applied in material characterization of thermally sprayed nickel aluminum coatings

    NASA Astrophysics Data System (ADS)

    Yeh, C. H.; Yang, C. H.; Hsiao, W. T.; Su, C.-Y.

    2012-05-01

    Thermal spraying processing usually uses a nickel-aluminum alloy system as the major powder due to its strong adhesion to substrates. The contents of powder material and the processing parameters used in the spraying process cause material properties of coatings exhibiting a wide variation. This research aims at nondestructive characterization of thermal spraying coatings. A laser-generation/laser-detection laser ultrasound technique (LUT) is used for the measurements of dispersion spectra of surface waves propagating along the coated surfaces. Theoretical model for surface waves propagating along a multi-layered structure with coating and substrate is used to model the sprayed coatings. An inversion algorithm based on Shuffled Complex Evolution (SCE-UA) is used to extract mechanical properties from the measured dispersion spectra cooperating with theoretical model. Three coatings with different sprayed powders and powder processing are investigated. Results indicate that substantial linear scatterings are observed for the inverted properties due to the measured dispersion spectra with limited bandwidth inherited from the relatively high attenuations. The slope of linear scattering can be used to distinguish the coating properties. The ANiBNb sample with ball-milled coating has the best properties based on its highest velocity and least attenuation. This method is potentially useful to characterize the mechanical properties of thermally spraying coating in a nondestructive way.

  12. Microstructure and wear behavior of quasicrystalline thermal sprayed

    SciTech Connect

    Sordelet, D.J.; Krotz, P.D.; Daniel, R.L.; Smith, M.F.

    1994-12-31

    An Al-Cu-Fe alloy coating which forms a quasicrystalline phase is a potential candidate for replacing electro-deposited chromium on various components in the Space Shuttle Main Engine. Coatings were deposited by air and vacuum plasma spraying and by high-velocity oxygen-fuel spraying. Finer starting powders tended to lose Al during spraying, which affected the phase equilibrium of the coatings. Coatings which retained the starting powder composition were richer in the desired quasicrystalline phase. Ball-on-disk wear tests between 440 C stainless steel ball and the Al-Cu-Fe coatings were performed. Coefficients of friction ranged from 0.60 to 1.2 for the different coatings.

  13. COMPARISON OF THERMAL PROPERTIES OF THERMAL BARRIER COATING DEPOSITED ON IN738 USING STANDARD AIR PLASMA SPRAY WITH 100HE PLASMA SPRAY SYSTEM

    SciTech Connect

    Uppu, N.; Mensah, P.F.; Ofori, D.

    2006-07-01

    A typical blade material is made of Nickel super alloy and can bear temperatures up to 950°C. But the operating temperature of a gas turbine is above the melting point of super alloy nearly at 1500°C. This could lead to hot corrosions, high temperature oxidation, creep, thermal fatigue may takes place on the blade material. Though the turbine has an internal cooling system, the cooling is not adequate to reduce the temperature of the blade substrate. Therefore to protect the blade material as well as increase the efficiency of the turbine, thermal barrier coatings (TBCs) must be used. A TBC coating of 250 μm thick can reduce the temperature by up to 200° C. Air Plasma Spray Process (APS) and High Enthalpy Plasma Spray Process (100HE) were the processes used for coating the blades with the TBCs. Because thermal conductivity increases with increase in temperature, it is desired that these processes yield very low thermal conductivities at high temperatures in order not to damage the blade. An experiment was carried out using Flash line 5000 apparatus to compare the thermal conductivity of both processes.The apparatus could also be used to determine the thermal diffusivity and specific heat of the TBCs. 75 to 2800 K was the temperature range used in the experimentation. It was found out that though 100HE has high deposition efficiency, the thermal conductivity increases with increase in temperatures whiles APS yielded low thermal conductivities.

  14. Analysis of particle dynamics and heat transfer in detonation thermal spraying systems

    NASA Astrophysics Data System (ADS)

    Ramadan, K.; Butler, P. Barry

    2004-06-01

    A computational study of pulsed detonation thermal spraying is conducted using an axisymmetric two-dimensional transient gaseous detonation model. The variations of the particle velocity and temperature at impact on the target surface with the particle initial loading location are analyzed for different conditions. The geometry of the system and the loading locations of the particulate phase are key parameters in pulsed detonation thermal spraying. Since the process is extremely transient and the gas phase experiences a wide range of transient stages all on a timescale of a millisecond, the particle characteristics are strongly dependent on the instantaneous location in the gas stream. One cycle of detonation thermal spraying occurs on a time scale on the order of a millisecond due to the high gas velocities associated with detonation. Thus, a precise control of the process variable parameters is required to have a successful detonation coating process.

  15. Electronic speckle pattern shearing interferometry for nondestructive testing of thermal sprayed alloy coatings

    NASA Astrophysics Data System (ADS)

    Xue, Yueqiang; Kennedy, David; Mihaylova, Emilia

    2005-06-01

    Thermal sprayed coatings have wide engineering applications. There now exists a wide range of destructive and nondestructive testing (NDT) methods for surface coating inspections. This paper describes an application of Electronic Speckle Pattern Shearing Interferometry (ESPSI) for NDT of thermal sprayed surface coatings. In contrast to other conventional methods such as eddy current, ultrasonic or X-ray, ESPSI allows fast and large survey area inspection. Experimental results of shearographic measurements are presented. Thermal sprayed coatings were tested using ESPSI. Delaminations of the coatings were detected and the fringe patterns were captured using this method. It is shown that the shearography technique can be applied successfully to surface coating quality inspection and it is very effective for delamination detection.

  16. Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

    2014-10-01

    This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

  17. Abrasion, erosion and scuffing resistance of carbide and oxide ceramic thermal sprayed coatings for different applications

    NASA Astrophysics Data System (ADS)

    Barbezat, G.; Nicoll, A. R.; Sickinger, A.

    1993-04-01

    In the area of antiwear coatings, carbide-containing coatings and oxide ceramic coatings are applied using different thermal spray processes in the form of individual layers. In many industries these coatings have become technically significant on components where wear and friction can cause critical damage in the form of abrasion, erosion and scuffing together with corrosion. Carbide-containing and ceramic coatings have been produced with different thermal spray processes for the determination of abrasive, adhesive and erosive wear resistance. Two types of abrasion test, namely an adhesion wear test and an erosion test in water at a high velocity, were used for the characterization of wear resistance under different conditions. The coatings were also characterized with regard to microstructure, composition and fracture toughness. The influence of the thermal spraying process parameters on the microstructure is presented together with the influence of the microstructure on the behavior of the coatings under simulated service conditions.

  18. Quality control of thermal sprayed coatings with an optoelectric sensor

    SciTech Connect

    Rothe, H.; Brandt, O.; Kasper, A.

    1995-12-31

    This paper reports on the development of a fully optoelectronic optical sensor that has been used for investigations concerning quality control of the high velocity oxygen fuel (HVOF) flame spraying process. The authors focused on the following parameters: WoC with Co, CoCr, Ni at T < 500 C, and Cr{sub 3}C{sub 2} with Ni-Cr, Ni at T < 900 C. Until recently, there was no non-destructive testing (NDT) approach for flame spraying available, which is a major drawback for many critical applications, like in the aerospace industry. For instance, while cooling down after spraying, cracks in the coatings may occur caused by strain. Furthermore, edges may cause similar damage to the coating. The idea was to provide the flame spraying industry with a measurement technology that is applicable in the workshop, has a contactless principle of operation and is fast compared to the commonly used metallography or scanning electron microscopy. The approach is designed for use close to the process, i.e. coating morphology was not the focus of the investigations. On the contrary, they tried to extract quality related information from surface microtopography which can be obtained in a non-destructive and affordable manner. Main points covered in this paper are theoretical considerations, the operational principles and construction of the sensor head, and quantitative metrology of surface damage such as variations in rms-roughness and cracks.

  19. Suspension thermal spraying of hydroxyapatite: microstructure and in vitro behaviour.

    PubMed

    Bolelli, Giovanni; Bellucci, Devis; Cannillo, Valeria; Lusvarghi, Luca; Sola, Antonella; Stiegler, Nico; Müller, Philipp; Killinger, Andreas; Gadow, Rainer; Altomare, Lina; De Nardo, Luigi

    2014-01-01

    In cementless fixation of metallic prostheses, bony ingrowth onto the implant surface is often promoted by osteoconductive plasma-sprayed hydroxyapatite coatings. The present work explores the use of the innovative High Velocity Suspension Flame Spraying (HVSFS) process to coat Ti substrates with thin homogeneous hydroxyapatite coatings. The HVSFS hydroxyapatite coatings studied were dense, 27-37μm thick, with some transverse microcracks. Lamellae were sintered together and nearly unidentifiable, unlike conventional plasma-sprayed hydroxyapatite. Crystallinities of 10%-70% were obtained, depending on the deposition parameters and the use of a TiO2 bond coat. The average hardness of layers with low (<24%) and high (70%) crystallinity was ≈3.5GPa and ≈4.5GPa respectively. The distributions of hardness values, all characterised by Weibull modulus in the 5-7 range, were narrower than that of conventional plasma-sprayed hydroxyapatite, with a Weibull modulus of ≈3.3. During soaking in simulated body fluid, glassy coatings were progressively resorbed and replaced by a new, precipitated hydroxyapatite layer, whereas coatings with 70% crystallinity were stable up to 14days of immersion. The interpretation of the precipitation behaviour was also assisted by surface charge assessments, performed through Z-potential measurements. During in vitro tests, HA coatings showed no cytotoxicity towards the SAOS-2 osteoblast cell line, and surface cell proliferation was comparable with proliferation on reference polystyrene culture plates. PMID:24268261

  20. Low Thermal Conductivity Yttria-Stabilized Zirconia Thermal Barrier Coatings Using the Solution Precursor Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Jordan, Eric H.; Jiang, Chen; Roth, Jeffrey; Gell, Maurice

    2014-06-01

    The primary function of thermal barrier coatings (TBCs) is to insulate the underlying metal from high temperature gases in gas turbine engines. As a consequence, low thermal conductivity and high durability are the primary properties of interest. In this work, the solution precursor plasma spray (SPPS) process was used to create layered porosity, called inter-pass boundaries, in yttria-stabilized zirconia (YSZ) TBCs. IPBs have been shown to be effective in reducing thermal conductivity. Optimization of the IPB microstructure by the SPPS process produced YSZ TBCs with a thermal conductivity of 0.6 W/mK, an approximately 50% reduction compared to standard air plasma sprayed (APS) coatings. In preliminary tests, SPPS YSZ with IPBs exhibited equal or greater furnace thermal cycles and erosion resistance compared to regular SPPS and commercially made APS YSZ TBCs.

  1. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  2. Thermal spray forming of refractory sample ampoule cartridges for single crystal growth space furnaces

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank; Poorman, Richard; Holmes, Richard; Mckechnie, Timothy; Krotz, Phil; Liaw, Yoon

    1993-01-01

    A thermal spray process is being used to build up refractory metals and ceramics into a containment cartridge for high temperature, single crystal semiconductor growth experiments. This process uses high energy plasma inside a low pressure (100-200 torr) inert environment to apply layers of material onto a removable mandrel. A variety of materials are being characterized and evaluated against a demanding set of requirements, including high service temperature (1700 C), oxidation resistance, and resistance to liquid metal attack. Techniques to spray form refractory metals (tungsten, molybdenum, niobium, tantalum) and ceramics (alumina, boron nitride) are being developed in the Plasma Spray Cell at Marshall Space Flight Center. These plasma spray formed materials have been evaluated for mechanical properties, density, microstructure, and resistance to liquid metal attack. Forming techniques and the resultant mechanical and metallurgical properties will be presented.

  3. Thermal spray forming of refractory sample ampoule cartridges for single crystal growth space furnaces

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank; Poorman, Richard; Holmes, Richard; Mckechnie, Timothy; Krotz, Phil; Liaw, Yoon

    1993-01-01

    A thermal spray process is being used to build up refractory metals and ceramics into a containment cartridge for high temperature, single crystal semiconductor growth experiments. This process uses high energy plasma inside a low pressure (100-200 torr) inert environment to apply layers of material onto a removable mandrel. A variety of materials are being characterized and evaluated against a demanding set of requirements, including high service temperature (1700 C), oxidation resistance, and resistance to liquid metal attack. Techniques to spray form refractory metals (tungsten, molybdenum, niobium, tantalum) and ceramics (alumina, boron nitride) are being developed in the Plasma Spray Cell at Marshall Space Flight Center. These plasma spray formed materials have been evaluated for mechanical properties, density, microstructure, and resistance to liquid metal attack. Forming techniques and the resultant mechanical and metallurgical properties are presented.

  4. A sputtered zirconia primer for improved thermal shock resistance of plasma-sprayed ceramic turbine seals

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Sovey, J.; Allen, G. P.

    1981-01-01

    It is shown that the application of sputtered Y2O3-stabilized ZrO2 (YSZ) primer in plasma-sprayed YSZ ceramic-coated turbine blades results in an improvement, by a factor of 5-6, in the thermal shock life of specimens with a sprayed, porous, Ni-Cr-Al-Y intermediate layer. Species with and without the primer were found to be able to survive 1000 cycles when the intermediate layer was used, but reduced laminar cracking was observed in the specimen with the primer. It is suggested that the sputtered YZS primer-induced properties are due to (1) more effective wetting and adherence of the plasma-sprayed YZS particles to the primer, and (2) the primer's retardation of impinging, molten plasma sprayed particles solidification rates, which result in a less detrimental residual stress distribution.

  5. The Gas Dynamics of High-Velocity Oxy-Fuel Thermal Sprays

    NASA Astrophysics Data System (ADS)

    Hackett, Charles Marcou

    An experimental study of the gas dynamics of the High-Velocity Oxy-Fuel (HVOF) thermal spray process has been performed. With this process, a hot, combustion-driven, supersonic jet is used to propel particles onto a surface, thus forming metal coatings that provide wear, temperature, and corrosion resistance. The fundamental physics of the spray process were studied and several key areas of interest were identified for in-depth study. Optical diagnostic techniques, including microsecond -exposure schlieren and shadowgraph imaging, were used to visualize the hot supersonic jet produced during the spray process. Energetic turbulent mixing of the jet with the surrounding atmosphere was observed. Measurements of oxide levels in aluminum and mild steel coatings sprayed for a range of conditions indicated that the turbulent mixing influences coating oxidation. However, experiments conducted with a low-speed coaxial shroud of inert gas demonstrated that coating oxide formation can be effectively controlled during the spray process. A simple numerical model was developed to predict the behavior of a spray particle in the HVOF jet. The results of computations indicated that independent control of spray particle velocity and temperature was possible through systematic variations in combustion chamber pressure and particle injection location within the nozzle. This hypothesis was confirmed through a series of experiments in which stainless steel particle velocity and temperature were measured using trace velocimetry and two-color radiative pyrometry, respectively. Combustion chamber pressure had a strong effect on particle velocity. Injection location was used to control the residence time of a particle within the flow, thus allowing manipulation of particle temperature without a measurable effect on velocity. Thus, the results of these experiments revealed that the gas dynamics--the behavior of the compressible gas flow--of the HVOF spray process strongly influenced spray

  6. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, P.; Ruka, R.J.

    1995-02-14

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

  7. Process of high temperature synthesis in producing composite carbide powders for thermally sprayed coatings

    NASA Astrophysics Data System (ADS)

    Szymański, K.; Formanek, B.

    2011-05-01

    The paper presents the characterization of powders containing hard phases of chromium carbides in a NiCr matrix, intended for thermal spraying coatings. The synthesized composite powder containing hard phases and plastic matrix, produced in high-temperature synthesis with chosen powder metallurgy processes has been presented. Commercial materials, such as NiCr- CrxCy, are fabricated by means of agglomeration and sintering method. Processes of high temperature synthesis of Cr3C2, Cr7C3, Cr23C6 carbides combined with NiCr powder mechanical alloying are presented in the article. Parameters of the carbides synthesis were determined in the reactive -protective atmosphere. In the rotation- vibration mill, processes were conducted using grinding and appropriate mechanical alloying at variable amplitude. The standard and synthesized powders were thermally sprayed by HVOF method in Jet Kote II and Diamond Jet system. The structure and phase composition of the powders and coatings were determined by: light and scanning microscopy, X-ray phase analysis (RTG) and energy dispersive X-ray analysis (EDX). The structure and wear properties of HVOF sprayed coatings containing chromium carbides has been presented. The thermally sprayed coatings are characterized of wear resistance in abrasion and erosion tests. The sprayed coatings characterized high resistance in wear conditions.

  8. Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2014-08-01

    High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.

  9. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1995-01-01

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

  10. JPL Advanced Thermal Control Technology Roadmap - 2012

    NASA Technical Reports Server (NTRS)

    Birur, Gaj; Rodriguez, Jose I.

    2012-01-01

    NASA's new emphasis on human exploration program for missions beyond LEO requires development of innovative and revolutionary technologies. Thermal control requirements of future NASA science instruments and missions are very challenging and require advanced thermal control technologies. Limited resources requires organizations to cooperate and collaborate; government, industry, universities all need to work together for the successful development of these technologies.

  11. A Numerical Study of Sea-Spray Aerosol Motion in a Coastal Thermal Internal Boundary Layer

    NASA Astrophysics Data System (ADS)

    Liang, Tinghao; Yu, Xiping

    2016-03-01

    A three-dimensional large-eddy simulation model is applied to the study of sea-spray aerosol transport, dispersion and settling in the coastal thermal internal boundary layer (IBL) formed by cool airflow from the open sea to the warm land. An idealized situation with constant inflow from the ocean and constant heat flux over the coastal land is considered. The numerical results confirm that the thickness of the coastal thermal IBL increases with the distance from the coastline until the outer edge of the IBL penetrates into the capping inversion layer. The thickness increases also with time until a fully-developed thermal boundary layer is formed. In addition, the thickness of the coastal thermal IBL increases more rapidly when the heat flux over the land is greater. Existence of large-scale eddies within the thermal IBL is identified and the turbulence intensity within the thermal IBL is also found to be significantly higher than that above. It is also indicated that the vertical position of the maximum concentration does not occur at the surface but increases as sea-spray aerosols are transported inland. The vertical position of the maximum flux of sea-spray aerosols within the coastal thermal IBL is shown to coincide with that of the maximum vertical velocity fluctuations when the coastal thermal IBL is fully developed with increased distance in the airflow direction.

  12. A Numerical Study of Sea-Spray Aerosol Motion in a Coastal Thermal Internal Boundary Layer

    NASA Astrophysics Data System (ADS)

    Liang, Tinghao; Yu, Xiping

    2016-08-01

    A three-dimensional large-eddy simulation model is applied to the study of sea-spray aerosol transport, dispersion and settling in the coastal thermal internal boundary layer (IBL) formed by cool airflow from the open sea to the warm land. An idealized situation with constant inflow from the ocean and constant heat flux over the coastal land is considered. The numerical results confirm that the thickness of the coastal thermal IBL increases with the distance from the coastline until the outer edge of the IBL penetrates into the capping inversion layer. The thickness increases also with time until a fully-developed thermal boundary layer is formed. In addition, the thickness of the coastal thermal IBL increases more rapidly when the heat flux over the land is greater. Existence of large-scale eddies within the thermal IBL is identified and the turbulence intensity within the thermal IBL is also found to be significantly higher than that above. It is also indicated that the vertical position of the maximum concentration does not occur at the surface but increases as sea-spray aerosols are transported inland. The vertical position of the maximum flux of sea-spray aerosols within the coastal thermal IBL is shown to coincide with that of the maximum vertical velocity fluctuations when the coastal thermal IBL is fully developed with increased distance in the airflow direction.

  13. Multi-scale Phenomena and Structures Observed in Fabrication of Thermal Barrier Coatings by Using Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Kuroda, Seiji; Murakami, Hideyuki; Watanabe, Makoto; Itoh, Kaita; Shinoda, Kentaro; Zhang, Xiancheng

    Thermal barrier coatings (TBC) fabricated by plasma spray can exhibit a wide range of microstructures due to differences in feedstock powders and spraying conditions. Since different microstructures naturally result in different thermal and mechanical properties and service life as thermal barrier coatings, it is of great importance to understand the relationship among the feedstock characteristics, spray conditions and the coating microstructures. Recent research efforts of the author's group to understand fundamental phenomena in plasma spraying of TBC are reviewed from microscopic to macroscopic viewpoints, i.e., direct observation of single droplet impact of molten zirconia by an ultra fast video camera, detection of acoustic emission (AE) signals during plasma spraying by using laser AE technique, and in-situ measurement of the curvature and temperature of a substrate during plasma spraying, from which strain-stress relationships and residual stresses of TBC can be evaluated.

  14. Polarization characteristics of four types of coating films by thermal spray in seawater solution

    NASA Astrophysics Data System (ADS)

    Moon, Kyung-Man; Kim, Yun-Hae; Lee, Myeong-Hoon; Baek, Tae-Sil

    2015-03-01

    Thermal spray coating method has been known to be an attractive technique due to its relatively high coating speed. However, a high corrosion resistance of the coating film deposited by thermal spray method should be improved to prolong its lifetime. In this study, four types of coated films (DFT: 400 μm), that is, pure zinc, pure aluminum and two Al - Zn alloy (Al:Zn = 85:15 and Al:Zn = 95:5) films were coated onto a carbon steel (SS401) with arc spraying, and the corrosion behaviors of these samples were investigated using the electrochemical method. The pure aluminum sample had the best corrosion resistance in seawater solution and alloy (Al:Zn = 85:15) film, so called galvalume followed the pure aluminum sample, moreover, the alloy (Al:Zn = 95:5) sample exhibited the worst corrosion resistance.

  15. Preparation of cross sections of thermal spray coatings for TEM investigation

    SciTech Connect

    Zhang, H. )

    1992-03-01

    A technique for the preparation of cross sections for transmission electron microscopy (TEM) of thermal spray coatings has been developed. The procedure is designed to minimize specimen damage during mechanical thinning and to reduce the effect of differential thinning during ion milling. Specimens were made by two different coating systems - WC-Co coating produced by the FARE Gun process on a mild steel substrate and Tribaloy T-800 sprayed by the HVOF process on a nickel-base superalloy. These specimens have large areas that are electron transparent on either side of the interface, and the results have shown the atomic scale microstructure of the interface between the thermal spray coating and the substrate. 9 refs.

  16. Ultrafine particles emitted by flame and electric arc guns for thermal spraying of metals.

    PubMed

    Bémer, Denis; Régnier, Roland; Subra, Isabelle; Sutter, Benjamin; Lecler, Marie T; Morele, Yves

    2010-08-01

    The ultrafine aerosol emitted by thermal spraying of metals using flame and electric arc processes has been characterized in terms of particle size distribution and emission rates based on both particle number and mass. Thermal spraying of Zn, Zn/Al, and Al was studied. Measurements taken using an electrical low pressure impactor and a condensation nucleus counter reveal an aerosol made up of very fine particles (80-95% of number distribution <100 nm). Ultrafine particle emission rates produced by the electric arc process are very high, the largest values being recorded during spraying of pure aluminium. This process generates high particle emissions and therefore requires careful consideration and possible rethinking of currently implemented protection measures: ventilated cabins, dust collectors, and personal protective equipment. PMID:20685717

  17. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality By Eddy Current Method

    SciTech Connect

    B. Mi; G. Zhao; R. Bayles

    2006-08-10

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  18. Advancement of Shock-wave Induced Spraying Process through the Study of Gas and Particle Flow Fields

    NASA Astrophysics Data System (ADS)

    Karimi Esfahani, Mohammad

    This research advances the knowledge of the working principles of the Shock-wave Induced Spraying Process (SISP), a thermal spray material deposition technique. Pulses created by a fast acting valve pass through a heated line increasing energy content and interacting with metered batches of heated or non-heated powder introduced into the line. The powder is accelerated to high velocities before bonding to the substrate upon impact. Advantages over other cold spray processes include cost savings and a more effective transfer of thermal energy to the powder. The shock-wave occurring near the substrate in other cold spray processes is avoided. The SISP flow field is resolved by using a computational model. The two-dimensional model accounts for the valve, gas heater, a tapered nozzle at the tip of the device, and preheating of the powder. It is implemented with a commercial computational fluid dynamics code. Comparisons are made with one-dimensional predictions, and measurements of pressure and temperature. Particle flow predictions are validated using particle velocity and adhesion measurements. A flow region of both high temperature and velocity gas, favorable to material deposition, forms which is not present in comparable steady-state cold spray processes. Increasing gas pressure increases the gas speed, while increasing temperature increases speed and temperature of this region. Using helium results in greater energy levels but for shorter periods of time. This indicates the need for a powder feeder which places particles in the flow at correct instants and durations of time. The effects of particle flow parameters on system performance are examined. It is found that the device must be operated at very high main heater and powder heater temperatures: 900 °C and 700 °C respectively to achieve a coating with stainless steel using nitrogen as the driving gas. It is also shown that a heater length range of 0.9 m to 1.4 m results in the greatest likelihood of

  19. Investigation of wear and scuffing behaviour of ferrous thermal spray coatings for aluminum engines

    NASA Astrophysics Data System (ADS)

    Edrisy, Afsaneh

    The development of lightweight internal combustion engines using materials such as cast aluminum alloys represents one of the most significant technological developments in the automotive industry. These engines reduce weight, which in turn reduce fuel consumption and emission. However, poor wear resistance and low seizure load of unprotected Al-Si alloys are a major drawback for applications involving sliding contact in automotive engine blocks. The wear resistance of cast aluminum parts can be improved by depositing coatings on the sliding surfaces. In this respect, iron based coatings deposited through a thermal spray process may play an important role in improving wear resistances of aluminium parts used in the automotive industry. These coatings can be produced economically and be easily deposited on the curved surfaces in ambient air atmosphere. In this research, two promising thermal spray deposition processes were considered: These were (i) plasma transfer wire arc thermal spraying (PTWA) process, and (ii) high velocity oxy-fuel (HVOF) process. The research work presented in this dissertation primarily focussed on the wear behaviour of low carbon steel thermal spray coatings which were applied using PTWA and HVOF processes deposited on engine grade cast aluminum alloy substrates. The main objective of the work was to characterize the micromechanisms of wear that control the wear rates of the coatings. Several new wear mechanisms that were previously unknown in thermal spray coatings were identified. In addition, the effect of the environment on the wear performance of coatings was investigated. The importance of controlling the atmospheric conditions during the sliding contact of coated aluminum components was established. Detailed analyses of compositions and microstructures of iron based coatings that were produced using PTWA and HVOF thermal deposition processes showed that the wear resistances of the coatings were sensitive to the production method. A

  20. Laser fusing of HVOF thermal sprayed alloy 625 on nickel-aluminum bronze

    SciTech Connect

    Brenna, R.T.; Pugh, J.L.; Denney, P.E.

    1994-12-31

    A preliminary study has been conducted to determine the feasibility of laser fusing alloy 625 onto nickel-aluminum-bronze base metal. Laser fusing was performed by melting a pre-coated surface of alloy 625 that had been applied by the high velocity oxyfuel (HVOF) thermal spray process. The laser fusing was successful in producing a metallurigical bond between alloy 625 and the substrate. Minor modification to the heat-affected zone of the base metal was observed by microhardness measurements, and defect-free interfaces were produced between alloy 625 and nickel-aluminum-bronze by the process. The laser is a high energy density source that can be used for precise thermal processing of materials including surface modification. Laser fusing is the full or partial melting of a coating material that has been previously applied in some fashion to the substrate. Thermal spray coating of nickel-aluminum-bronze material with alloy 625 was conducted at the David Taylor Research Center. Nickel-aluminum-bronze specimens 2 x 3-in. by 1/2-in. thick were coated with alloy 25 utilizing the HVOF equipment. Coating thicknesses of approximately 0.014-in. (0.3 mm) were produced for subsequent laser fusing experiments. A preliminary study has been conducted to determine the feasibility of laser fusing a HVOF thermal sprayed alloy 625 coating onto nickel-aluminum-bronze base metal. Conclusions of this investigation were as follows: (1) Laser fusing was successful in producing a metallurgical bond between HVOF thermal sprayed alloy 625 and the nickel-aluminum-bronze. (2) Only minor microstructural modification to the heat-affected zone of the base metal ws observed by microhardness measurements. (3) Defect-free interfaces were produced between thermal sprayed alloy 625 and nickel-aluminum-bronze by laser fusing.

  1. Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers

    NASA Astrophysics Data System (ADS)

    van Every, Kent J.

    The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current commericial YSZ coatings generated using micron-sized powders. The coatings for this research were made via the recently developed suspension plasma spraying (SPS) process. With SPS, powders are suspended in a solvent containing dispersing agents; the suspension is then injected directly into a plasma flow that evaporates the solvent and melts the powder while transporting it to the substrate. Although related to the industrial TBC production method of air plasma spraying (APS), SPS has two important differences---the ability to spray sub-micron diameter ceramic particles, and the ability to alloy the particles with chemicals dissolved in the solvent. These aspects of SPS were employed to generate a series of coatings from suspensions containing ˜100 nm diameter YSZ powder particles, some of which were alloyed with neodymium and ytterbium ions from the solvent. The SPS coatings contained columnar structures not observed in APS TBCs; thus, a theory was developed to explain the formation of these features. The thermal conductivity of the coatings was tested to evaluate the effects of these unique microstructures and the effects of the alloying process. The results for samples in the as-sprayed and heat-treated conditions were compared to conventional YSZ TBCs. This comparison showed that, relative to APS YSZ coatings, the unalloyed SPS samples typically exhibited higher as-sprayed and lower heat-treated thermal conductivities. All thermal conductivity values for the alloyed samples were lower than conventional YSZ TBCs

  2. Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)

    NASA Astrophysics Data System (ADS)

    Ganvir, Ashish; Curry, Nicholas; Björklund, Stefan; Markocsan, Nicolaie; Nylén, Per

    2015-10-01

    The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower.

  3. Sprayed coatings

    NASA Astrophysics Data System (ADS)

    Steffens, H. D.

    1980-03-01

    Thermal spraying is shown to be an efficient means for the protection of surface areas against elevated temperature, wear, corrosion, hot gas corrosion, and erosion in structural aircraft components. Particularly in jet engines, numerous parts are coated by flame, detonation, or plasma spraying techniques. The applied methods of flame, detonation, and plasma spraying are explained, as well as electric arc spraying. Possibilities for spray coatings which meet aircraft service requirements are discussed, as well as methods for quality control, especially nondestructive test methods. In particular, coating characteristics and properties obtained by different spray methods are described, and special attention is paid to low pressure plasma spraying.

  4. Advanced thermal management technologies for defense electronics

    NASA Astrophysics Data System (ADS)

    Bloschock, Kristen P.; Bar-Cohen, Avram

    2012-05-01

    Thermal management technology plays a key role in the continuing miniaturization, performance improvements, and higher reliability of electronic systems. For the past decade, and particularly, the past 4 years, the Defense Advanced Research Projects Agency (DARPA) has aggressively pursued the application of micro- and nano-technology to reduce or remove thermal constraints on the performance of defense electronic systems. The DARPA Thermal Management Technologies (TMT) portfolio is comprised of five technical thrust areas: Thermal Ground Plane (TGP), Microtechnologies for Air-Cooled Exchangers (MACE), NanoThermal Interfaces (NTI), Active Cooling Modules (ACM), and Near Junction Thermal Transport (NJTT). An overview of the TMT program will be presented with emphasis on the goals and status of these efforts relative to the current State-of-the-Art. The presentation will close with future challenges and opportunities in the thermal management of defense electronics.

  5. A sputtered zirconia primer for improved thermal shock resistance of plasma sprayed ceramic turbine seals

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Sovey, J.; Allen, G. P.

    1981-01-01

    The development of plasma-sprayed yttria stabilized zirconia (YSZ) ceramic turbine blade tip seal components is discussed. The YSZ layers are quite thick (0.040 to 0.090 in.). The service potential of seal components with such thick ceramic layers is cyclic thermal shock limited. The most usual failure mode is ceramic layer delamination at or very near the interface between the plasma sprayed YSZ layer and the NiCrAlY bondcoat. Deposition of a thin RF sputtered YSZ primer to the bondcoat prior to deposition of the thick plasma sprayed YSZ layer was found to reduce laminar cracking in cyclic thermal shock testing. The cyclic thermal shock life of one ceramic seal design was increased by a factor of 5 to 6 when the sputtered YSZ primer was incorporated. A model based on thermal response of plasma sprayed YSZ particles impinging on the bondcoat surface with and without the sputtered YSZ primer provides a basis for understanding the function of the primer.

  6. Advanced Active Thermal Control Systems Architecture Study

    NASA Technical Reports Server (NTRS)

    Hanford, Anthony J.; Ewert, Michael K.

    1996-01-01

    The Johnson Space Center (JSC) initiated a dynamic study to determine possible improvements available through advanced technologies (not used on previous or current human vehicles), identify promising development initiatives for advanced active thermal control systems (ATCS's), and help prioritize funding and personnel distribution among many research projects by providing a common basis to compare several diverse technologies. Some technologies included were two-phase thermal control systems, light-weight radiators, phase-change thermal storage, rotary fluid coupler, and heat pumps. JSC designed the study to estimate potential benefits from these various proposed and under-development thermal control technologies for five possible human missions early in the next century. The study compared all the technologies to a baseline mission using mass as a basis. Each baseline mission assumed an internal thermal control system; an external thermal control system; and aluminum, flow-through radiators. Solar vapor compression heat pumps and light-weight radiators showed the greatest promise as general advanced thermal technologies which can be applied across a range of missions. This initial study identified several other promising ATCS technologies which offer mass savings and other savings compared to traditional thermal control systems. Because the study format compares various architectures with a commonly defined baseline, it is versatile and expandable, and is expected to be updated as needed.

  7. Relationship Between Lamellar Structure and Elastic Modulus of Thermally Sprayed Thermal Barrier Coatings with Intra-splat Cracks

    NASA Astrophysics Data System (ADS)

    Li, Guang-Rong; Lv, Bo-Wen; Yang, Guan-Jun; Zhang, Wei-Xu; Li, Cheng-Xin; Li, Chang-Jiu

    2015-12-01

    The elastic modulus of plasma-sprayed top coating plays an important role in thermal cyclic lifetime of thermally sprayed thermal barrier coatings (TBCs), since the thermal stress is determined by the substrate/coating thermal mismatch and the elastic modulus of top coating. Consequently, much attention had been paid to understanding the relationship between elastic modulus and lamellar structure of top coating. However, neglecting the intra-splat cracks connected with inter-splat pores often leads to poor prediction in in-plane modulus. In this study, a modified model taking account of intra-splat cracks and other main structural characteristics of plasma-sprayed yttria-stabilized zirconia coating was proposed. Based on establishing the relationship between elastic modulus and structural parameters of basic unit, effects of structural parameters on the elastic modulus of coatings were discussed. The predicted results are well consistent with experimental data on coating elastic modulus in both out-plane direction and in-plane direction. This study would benefit the further comprehensive understanding of failure mechanism of TBCs in thermal cyclic condition.

  8. Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

    NASA Technical Reports Server (NTRS)

    Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

    2001-01-01

    A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

  9. Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

    NASA Technical Reports Server (NTRS)

    Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

    2000-01-01

    A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

  10. Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying

    SciTech Connect

    Helminiak, M A; Yanar, N M; Pettit, F S; Taylor, T A; Meier, G H

    2012-10-01

    The high-temperature behavior of high-purity, low-density (HP-LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The high purity yttria-stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as-processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP-LD coatings is compared with that of state-of-the-art electron beam physical vapor deposition TBCs.

  11. Infrared-thermal wave scanner for NDE of naval thermal spray coatings

    SciTech Connect

    Green, D.R.; Wandling, C.R.; Gatto, F.B.

    1984-02-27

    An engineering prototype scanning system has been completed and evaluated in shop tests. This paper describes the system and shows examples of bond defects that have been detected. The system uses advanced emissivity independent infrared scanning and thermal wave techniques to detect nonbonds and differentiate them from variations in coating density and thickness. A computer is used to control the scanning process, analyze the data and produce pseudo three-dimensional scan maps that can easily be interpreted by the operator. These maps show the thermal wave response (Z axis) as a function of position (X and Y axis) on the test object's surface. Operator interpretation of the maps as well as processing of the information by the system's micro-computer are simple. A heat pulse injected into the test objects surface generates a thermal wave that propagates inward at a rate that depends upon the thermal impedances it encounters. These internal impedances are caused by coating density differences, thickness differences and nonbonds. They influence the surface thermal impedance of the test object. Measurement of the surface thermal impedance can be accomplished by forming the ratio of the temperature response to heat flow for sinusoidal waves, or for transforms of transient waves, at the test objects surface. The surface thermal impedance is a true complex quantity, having both phase and amplitude. It is also frequency dependent, and this makes it possible to distinguish between impedance differences resulting from coating density differences, thickness differences and nonbonds.

  12. Fundamental study of droplet spray characteristics in photomask cleaning for advanced lithography

    NASA Astrophysics Data System (ADS)

    Lu, C. L.; Yu, C. H.; Liu, W. H.; Hsu, Luke; Chin, Angus; Lee, S. C.; Yen, Anthony; Lee, Gaston; Dress, Peter; Singh, Sherjang; Dietze, Uwe

    2010-09-01

    The fundamentals of droplet-based cleaning of photomasks are investigated and performance regimes that enable the use of binary spray technologies in advanced mask cleaning are identified. Using phase Doppler anemometry techniques, the effect of key performance parameters such as liquid and gas flow rates and temperature, nozzle design, and surface distance on droplet size, velocity, and distributions were studied. The data are correlated to particle removal efficiency (PRE) and feature damage results obtained on advanced photomasks for 193-nm immersion lithography.

  13. Microstructural studies of thermal spray coatings for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sun, Limin

    2002-01-01

    This project aims to address two major concerns with the use of hydroxyapatite [Ca10(PO4)6(OH)2, i.e., HA] coatings; i.e., (i) the resorption of the coating, and (ii) the resorption of bone. The objective is to optimize coating design through microstructural studies of two coating systems: a HA coating and a HA/polymer composite coating. For the HA coating, the HA powders were atmospherically plasma sprayed (APS) using various process parameters. The phase, structure and microstructure of the coatings were investigated and the mechanical property and dissolution behavior measured. Both crystallinity and hydroxyl contents decreased with increasing spray power and stand-off distance (SOD), and increased from the coating interface to surface. Impurity phase contents increased with increasing spray power. Crystallinity alone cannot reflect coating quality due to the existence of various HA, i.e., unmelted, recrystallized and dehydroxylated, and the gradient structure. Coating microstructure varied from a porous structure to a smooth glassy structure or a typical lamellar structure, and some newly formed nanocrystalline regions were revealed. These effects were associated with the temperature-time experiences of particles, their cooling rates and the heat and hydroxyl accumulation during coating buildup. Different coating properties and performance resulted from the characteristic differences. The coating with highest recrystallization displayed the highest microhardness. Dissolution of all coatings reached a saturation value much lower compared to their pulverized counterparts in a fresh solution despite a higher and similar dissolution in the initial immersion stage. The coating with higher recrystallization exhibited higher saturation value. Microstructural analysis indicated the complete and preferential dissolution of amorphous and impurity phases and some precipitation of apatite observable for coatings with higher recrystallization. For the composite coating, HA

  14. Uncooled thermal imaging sensor and application advances

    NASA Astrophysics Data System (ADS)

    Norton, Peter W.; Cox, Stephen; Murphy, Bob; Grealish, Kevin; Joswick, Mike; Denley, Brian; Feda, Frank; Elmali, Loriann; Kohin, Margaret

    2006-05-01

    BAE Systems continues to advance the technology and performance of microbolometer-based thermal imaging modules and systems. 640x480 digital uncooled infrared focal plane arrays are in full production, illustrated by recent production line test data for two thousand focal plane arrays. This paper presents a snapshot of microbolometer technology at BAE Systems and an overview of two of the most important thermal imaging sensor programs currently in production: a family of thermal weapons sights for the United States Army and a thermal imager for the remote weapons station on the Stryker vehicle.

  15. A model for residual stress evolution in air-plasma-sprayed zirconia thermal barrier coatings

    SciTech Connect

    Nair, B. G.; Singh, J. P.; Grimsditch, M.

    2000-02-28

    Ruby fluorescence spectroscopy indicates that residual stress in air-plasma-sprayed zirconia thermal barrier coatings is a function of the local interface geometry. The stress profile of a simulated rough interface characterized by ``peaks'' and ``valleys'' was modeled with a finite-element approach that accounted for thermal mismatch, oxide scale growth, and top coat sintering. Dependence of the stress profile on interface geometry and microstructure was investigated, and the results were compared with measured stresses.

  16. Numerical modeling of spray combustion with an advanced VOF method

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Shang, Huan-Min; Shih, Ming-Hsin; Liaw, Paul

    1995-01-01

    This paper summarizes the technical development and validation of a multiphase computational fluid dynamics (CFD) numerical method using the volume-of-fluid (VOF) model and a Lagrangian tracking model which can be employed to analyze general multiphase flow problems with free surface mechanism. The gas-liquid interface mass, momentum and energy conservation relationships are modeled by continuum surface mechanisms. A new solution method is developed such that the present VOF model can be applied for all-speed flow regimes. The objectives of the present study are to develop and verify the fractional volume-of-fluid cell partitioning approach into a predictor-corrector algorithm and to demonstrate the effectiveness of the present approach by simulating benchmark problems including laminar impinging jets, shear coaxial jet atomization and shear coaxial spray combustion flows.

  17. Erosion-corrosion resistance of thermal sprayed coatings

    SciTech Connect

    Lee, S.W.; Wang, B.Q.

    1996-11-01

    A series of laboratory erosion-corrosion experiments at the elevated temperature, 300 C and different impact velocities (2.5 m/s, 30 m/s) were carried on AISI 1018 low carbon steel and three different sprayed coating specimens. Angular silica quartz particles of 742 um were the erodent material for testing three different impact angles of 30{degree}, 45{degree}, and 90{degree}. Material wastage rates were determined from thickness loss measurements of the specimens. The morphologies of the specimens were examined by scanning electron microscopy (SEM). The erosion-corrosion resistance of coating was found to be related to their composition and microstructure rather than to their hardness. The material wastage of the specimen was determined by weight and thickness loss measurements. The morphologies of the specimens were examined scanning electron microscopy (SEM). For the material wastage of the coating specimens, High Velocity Oxygen Fuel (HVOF) coatings (DS200) and the arc-sprayed coating at elevated temperature condition exhibited 2 to 3 times lower erosion wastage than that of AISI 1018 steel.

  18. A comparison of two laser-based diagnostics for analysis of particles in thermal spray streams

    SciTech Connect

    Smith, M.F.; O`Hern, T.J.; Brockmann, J.E.

    1995-07-01

    This paper discusses two commercially-available laser diagnostics that have been used in thermal spray research at Sandia National Laboratories: (1) a Phase Doppler Particle Analyzer (PDPA) and (2) a Laser Two-Focus (L2F) velocimeter. The PDPA provides simultaneous, correlated measurements of particle velocity and particle size distributions; but, particle sizing doesn`t work well with non-spherical particles or particles with rough surfaces. The L2F is used to collect particle velocity and number density distributions, and it can readily distinguish and separately measure particles with off-axis velocity vectors. PDPA and L2F principles of operation are presented along with potential advantages and limitations for thermal spray research. Four experiments were conducted to validate and compare measurement results with the PDPA and L2F instruments: (1) spinning wire, (2) powder in a High-Velocity Oxy-Fuel (HVOF) jet, (3) powder in a cold jet, and (4) droplets in a wire-fed HVOF jet. TWO DIFFERENT TYPES of commercially-available laser velocimeter systems, a Phase Doppler Particle Analyzer and a Laser-Two-Focus velocimeter have been used in the Thermal Spray Research Laboratory at Sandia National Laboratories. Each of these techniques has inherent advantages and limitations for thermal spray, and each involves assumptions that may not be valid for some experimental conditions. This paper describes operating principles and possible sources of measurement error for these two diagnostic systems. Some potential advantages and limitations are also presented. Four types of experiments were also conducted to validate and compare PDPA and L2F measurement results: (1) spinning wire, (2) powder in a High-Velocity Oxy-Fuel (HVOF) jet, (3) powder in a cold jet, and (4) droplets in a wire-fed HVOF jet. We also offer a few observations related to practical issues such as ease-of-use, reliability, and effects of dust and vibration in a thermal spray lab.

  19. Microstructure and thermal behaviour of plasma sprayed zirconia/alumina composite coating.

    PubMed

    Kobayashi, A; Ando, Y; Kurokawa, K; Hejwowski, T

    2011-10-01

    In thermal barrier coatings (TBC), failure occurs near or at the interface between the metallic bondcoat and topcoat. On high temperature conditions, an oxide scale which is named thermally grown oxide (TGO) occurs along the bond/topcoat interface. For diminishing the creation of TGO, a dense coating with low residual stress and thermal stress buffer layer was preferable. High hardness ceramic coatings could be obtained by gas tunnel type plasma spraying, and the deposited coating had superior property in comparison with those deposited by conventional type plasma spray method. In this study, the gas tunnel type plasma spraying system was utilized to produce a zirconia/alumina functionally graded thermal barrier coating and discussed its physical and mechanical properties, thermal behavior and high temperature oxidation resistance of the coating are discussed. Consequently, the proposed system exhibited superior mechanical properties and oxidation resistance at the expenses of a slightly lower thermal insulating effect. This interlayer is preferred in order to minimize the detrimental effect of the phase transformation of gamma-Al2O3 to alpha-Al2O3. PMID:22400271

  20. Isothermal and cyclic oxidation of an air plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.; Rigney, E.D.

    1996-08-01

    Thermogravimetric methods for evaluating bond coat oxidation in plasma-sprayed thermal barrier coating (TBC) systems were assessed by high-temperature testing of TBC systems with air plasma-sprayed (APS) Ni-22Cr-10Al-1Y bond coatings and yttria-stabilized zirconia top coatings. High-mass thermogravimetric analysis (at 1150{sup degrees}C) was used to measure bond coat oxidation kinetics. Furnace cycling was used to evaluate APS TBC durability. This paper describes the experimental methods and relative oxidation kinetics of the various specimen types. Characterization of the APS TBCs and their reaction products is discussed.

  1. Oxidation and degradation of a plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.

    1996-04-01

    The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

  2. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2 - 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of KI/KII were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma- sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  3. Combined Mode I and Mode II Fracture of Plasma-Sprayed Thermal Barrier Coatings at Ambient and Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The mode I, mode II, and combined mode I-mode II fracture behavior of ZrO2- 8wt%Y2O3 thermal barrier coatings was determined in asymmetric flexure loading at both ambient and elevated temperatures. Precracks were introduced in test specimens using the single-edge-v-notched beam (SEVNB) method incorporated with final diamond polishing to achieve sharp crack tips. A fracture envelope of KI versus KII was determined for the coating material at ambient and elevated temperatures. Propagation angles of fracture as a function of K(sub I)/K(sub II) were also determined. The mixed-mode fracture behaviors of the coating material were compared with those of monolithic advanced ceramics determined previously. The mixed-mode fracture behavior of the plasma-sprayed thermal barrier coating material was predicted in terms of fracture envelope and propagation angle using mixed-mode fracture theories.

  4. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  5. The Effect of Heat Treatment on Mechanical Properties of Thermally Sprayed Sandwich Structure Beams

    NASA Astrophysics Data System (ADS)

    Salavati, Saeid; Coyle, Thomas W.; Mostaghimi, Javad

    2016-01-01

    The application of metallic foam core sandwich structures in engineering components has been of particular interest in recent years because of their unique mechanical and thermal properties. Thermal spraying of the skin on the foam structure has recently been employed as a novel cost-efficient method for fabrication of these structures from refractory materials with complex shapes that could not otherwise be easily fabricated. The mechanical behavior of these structures under flexural loading is important in most applications. Previous studies have suggested that heat treatment of the thermally sprayed sandwich structures could improve the ductility of the skins and so affect the failure mode. In the present study, the mechanical behavior of sandwich beams prepared from arc sprayed alloy 625 skin on 40 ppi nickel foam was characterized under four point bending. The ductility of the arc sprayed alloy 625 coatings was improved after heat treatment at 1100 and 900 °C while the yield point was reduced. Heat treatment of the sandwich beams reduced the danger of catastrophic failure.

  6. Erosion resistance of cooled thermal sprayed coatings under simulated erosion conditions at waterwall in FBCs

    SciTech Connect

    Wang, B.Q.; Lee, S.W.

    1997-12-31

    The erosion-corrosion (E-C) behavior of cooled 1018 steel and several thermal sprayed coatings by bed ash, retrieved from an operating circulating fluidized bed combustor (CFBC) boiler firing biomass, was determined in laboratory tests using a nozzle type elevated temperature erosion tester. Test conditions attempted but not exactly to simulate the erosion conditions found at the refractory/bare-tube interface at the combustor waterwall of FBC boilers. The specimens were water-cooled on the backside. Material wastage rates were determined from the thickness loss measurements of specimens. Test results were compared with erosion-corrosion test results for isothermal specimens. The morphology of specimens was examined by scanning electron microscopy (SEM). It was found that the cooled specimens demonstrated higher erosion-corrosion wastage than those of the isothermal specimens. At a shallow impact angle of 30{degree} the effect of cooling specimens on the erosion wastage for thermal sprayed coatings was less than that for 1018 steel, while at a steep impact angle of 90{degree} this effect for thermal sprayed coatings was greater than that for 1018 steel. The hypersonic velocity oxygen fuel (HVOF) Cr{sub 3}C{sub 2} ceramic coating exhibited the highest E-C resistance due to its favorable composition and fine structure. The poor E-C resistance of arc-sprayed FeCrSiB coating was attributed to larger splat size, higher porosity and the presence of radial and tangential microcracks within the coating.

  7. Research On HVOF Thermal Sprays. Final Technical Report

    SciTech Connect

    Settles, G. S.

    2003-04-02

    Independent control of particle velocity and temperature in the HVOF process has been achieved in this research, allowing the variables to change by 170 m/s and 200{degree}C, respectively. The independence was achieved using a specially designed nozzel with multiple axial injection ports, and with an inert diluent added to the oxygen used for combustion. With these changes, notable changes in splat morphology, porosity, and coating oxidation are readily apparent. Increased particle velocity correlates with improved splat deformation, but appears to have little effect on porosity or oxidation. Particle temperature, however, correlates strongly with splat deformation, porosity, and oxidation. In fact, highly dense coatings that have little oxidation can be formed with relatively low velocity particles that have average temperatures in the vicinity of the melting point of the material. This surprising result suggests particle temperature control is the key to creating dense, low-oxide HVOF-sprayed coatings.

  8. Thermoelectric Devices Advance Thermal Management

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Thermoelectric (TE) devices heat, cool, and generate electricity when a temperature differential is provided between the two module faces. In cooperation with NASA, Chico, California-based United States Thermoelectric Consortium Inc. (USTC) built a gas emissions analyzer (GEA) for combustion research. The GEA precipitated hydrocarbon particles, preventing contamination that would hinder precise rocket fuel analysis. The USTC research and design team uses patent-pending dimple, pin-fin, microchannel and microjet structures to develop and design heat dissipation devices on the mini-scale level, which not only guarantee high performance of products, but also scale device size from 1 centimeter to 10 centimeters. USTC continues to integrate the benefits of TE devices in its current line of thermal management solutions and has found the accessibility of NASA technical research to be a valuable, sustainable resource that has continued to positively influence its product design and manufacturing

  9. A Numerical Study on Gas Phase Dynamics of High-Velocity Oxygen Fuel Thermal Spray

    NASA Astrophysics Data System (ADS)

    Baik, Jae-Sang; Park, Sun-Kyu; Kim, Youn-Jea

    2008-08-01

    The high-velocity oxygen fuel (HVOF) thermal spray is used for a particulate deposition process in which micro-sized particles are propelled and heated in a supersonic combusting gas stream. It is characterized by high gas velocity and high density and is being used in an increasing variety of coating applications, such as ceramic and composite coatings, to improve wear and abrasion resistance. The particle temperature and velocity are two of the most important parameters in HVOF thermal spraying, which affect the quality of the coatings. To understand the particle dynamics, it is necessary to study, first, the thermal flow characteristics in the HVOF system. In this study, a numerical analysis is performed to predict the gas dynamic behaviors, and the effect of the geometrical parameter is studied to optimize the nozzle design.

  10. Supplementary Microstructural Features Induced During Laser Surface Melting of Thermally Sprayed Inconel 625 Coatings

    NASA Astrophysics Data System (ADS)

    Ahmed, Nauman; Voisey, K. T.; McCartney, D. G.

    2014-02-01

    Laser surface melting of thermally sprayed coatings has the potential to enhance their corrosion properties by incorporating favorable microstructural changes. Besides homogenizing the as-sprayed structure, laser melting may induce certain microstructural modifications (i.e., supplementary features) in addition to those that directly improve the corrosion performance. Such features, being a direct result of the laser treatment process, are described in this paper which is part of a broader study in which high velocity oxy-fuel sprayed Inconel 625 coatings on mild-steel substrates were treated with a diode laser and the modified microstructure characterized using optical and scanning electron microscopy and x-ray diffraction. The laser treated coating features several different zones, including a region with a microstructure in which there is a continuous columnar dendritic structure through a network of retained oxide stringers.

  11. Reactive Plasma-Sprayed Aluminum Nitride-Based Coating Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Shahien, Mohammed; Yamada, Motohiro; Fukumoto, Masahiro; Egota, Kazumi; Okamoto, Kenji

    2015-12-01

    Recently, thick aluminum nitride/alumina (AlN/Al2O3) composite coatings were successfully fabricated through the reactive plasma spraying of fine Al2O3/AlN mixture in the N2/H2 atmospheric plasma. The coatings consist of AlN, Al5O6N, γ-Al2O3, and α-Al2O3 phases. This study will evaluate the thermal conductivity of these complicated plasma-sprayed coatings and optimize the controlling aspects. Furthermore, the influence of the process parameters on the coatings thermal conductivity will be investigated. The fabricated coatings showed very low thermal conductivity (2.43 W/m K) compared to the AlN sintered compacts. It is attributed to the phase composition of the fabricated coatings, oxide content, and porosity. The presence of Al2O3, Al5O6N and the high coating porosity decreased its thermal conductivity. The presence of oxygen in the AlN lattice creates Al vacancies which lead to phonon scattering and therefore suppressed the thermal conductivity. The formation of γ-Al2O3 phase in the coating leads to further decrease in its conductivity, due to its lower density compared to the α-phase. Moreover, the high porosity of the coating strongly suppressed the conductivity. This is due to the complicated microstructure of plasma spray coatings (splats, porosity, and interfaces, particularly in case of reactive spray process), which obviously lowered the conductivity. Furthermore, the measured coating density was lower than the AlN value and suppressed the coating conductivity. In addition, the spraying parameter showed a varied effect on the coating phase composition, porosity, density, and therefore on its conductivity. Although the N2 gas flow improved the nitride content, it suppressed the thermal conductivity gradually. It is attributed to the further increase in the porosity and further decrease in the density of the coatings with the N2 gas. Furthermore, increasing the arc did not show a significant change on the coating thermal conductivity. On the other hand

  12. Fluid and Thermal Dynamics of Cryogen Sprays Impinging on a Human Tissue Phantom

    PubMed Central

    Franco, Walfre; Vu, Henry; Jia, Wangcun; Nelson, J. Stuart; Aguilar, Guillermo

    2009-01-01

    Cryogen spray cooling (CSC) protects the epidermis from unintended heating during cutaneous laser surgery. The present work investigated the time-dependent flow characteristics of cryogen sprays and correspondent thermal dynamics at the surface of a human tissue phantom. First, a numerical analysis was carried out to evaluate an epoxy block substrate as a human tissue phantom. Next, the velocity and diameter of cryogen droplets were measured simultaneously and correlated with surface temperature of the human tissue phantom during CSC. Finally, velocity and diameter measurements were used to compute the spray number, mass, and kinetic energy fluxes, and temperature measurements were used to compute the surface heat flux. Numerical modeling showed that the thermal response of our phantom was qualitatively similar to that of human stratum corneum and epidermis; quantitatively, thermal responses differed. A simple transformation to map the temperature response of the phantom to that of tissue was derived. Despite the relatively short spurt durations (10 ms, 30 ms, and 50 ms), cryogen delivery is mostly a steady state process with initial and final fluid transients mainly due to the valve dynamics. Thermal transients (16 ms) are longer than fluid transients (4 ms) due to the low thermal diffusivity of human tissues; steady states are comparable in duration (≈10 ms, 30 ms, and 50 ms) although there is an inherent thermal delay (≈12 ms). Steady state temperatures are the lowest surface temperatures experienced by the substrate, independent of spurt duration; hence, longer spurt durations result in larger exposures of the tissue surface to the same lower, steady state temperature as in shorter spurts. Temperatures in human tissue during CSC for the spray system and parameters used herein are estimated to be ≈−19°C at the stratum corneum surface and >0°C across the epidermis. PMID:19045512

  13. Comparative Study of Microstructure and Properties of Thermal Sprayed MCrAlY Bond Coatings

    NASA Astrophysics Data System (ADS)

    Inglima, Michael William

    A series of experiments were performed in order to observe certain process-property trends in thermally sprayed MCrAlY bond coatings for thermal barrier coating (TBC) applications in gas-turbine engines. Firstly, the basis of gas-turbine operation and design is discussed with a focus on the Brayton cycle and basic thermodynamic properties with respect to both the thermal and fuel efficiency of the turbine. The high-temperature environment inside the gas-turbine engine creates an extremely corrosive medium in which the engineering components must operate with sufficient operating life times. These engineering constraints, both thermal/fuel efficiency and operating life, pose a serious problem during long operation as well as thermal cycling of a civil aerospace engine. The concept of a thermal barrier coating is introduced along with how these coatings protect the internal engineering components, mostly in the hot-section of the turbine, and increase both the efficiency as well as the operating life of the components. The method used to create TBC's is then introduced being thermal spray processing along with standard operating procedures (SOP) used during coating deposition. The main focus of the experiments was to quantify the process-property trends seen during thermal spray processing of TBC's with respect to the adhesion and thermally grown oxide (TGO) layer, as well as how sensitive these properties are to changing variables during coating deposition. The design of experiment (DOE) method was used in order to have sufficient statistical process control over the output as well as a standard method for quantifying the results. A total of three DOE's were performed using two main types of thermal spray processes being high-velocity oxygen fuel (HVOF) and atmospheric plasma spray (APS), with a total of five different types of torches which are categorized by liquid-fuel, gas-fuel, and single cathode plasma. The variables used in the proceeding experiments were

  14. On the gas dynamics of HVOF thermal sprays. [HVOF (High-Velocity Oxy-Fuel)

    SciTech Connect

    Hackett, C.M.; Settles, G.S.; Miller, J.D.

    1993-01-01

    An experimental study has been performed on the gas dynamic aspects of the HVOF thermal spray process. A commercially-available HVOF gun (Hobart Tafa JP-5000) is used in this study. Optical diagnostic techniques including microsecond-exposure schlieren and shadowgraph imaging are applied to visualize the hot supersonic jet produced by this equipment without any particle injection. Rapid turbulent mixing of the jet with the surrounding atmosphere is observed, which is an issue of concern in coating quality because of the possibility of oxidation of the sprayed particles. This mixing appears principally to be a function of the density ratio between the hot jet and the cold atmosphere, rather than depending upon the combustion-chamber pressure or barrel length. The supersonic core of the HVOF jet dissipates rapidly due to the, mixing, so that the jet is no longer supersonic when it impinges upon the target surface being sprayed. Secondary issues also observed in this study include strong jet-noise radiation from the HVOF plume and the entrainment and induced bulk motion of the surrounding air. All these issues have a background in the field of gas dynamics which has not been previously applied to thermal spray technology.

  15. Fast Regime Fluidized Bed Machining (FR-FBM) of Thermally Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Barletta, Massimiliano; Rubino, Gianluca; Bolelli, Giovanni; Lusvarghi, Luca

    2008-12-01

    Finishing of thermally sprayed metallic, ceramic, and cermet coatings is required to meet tolerances and requirements on surface roughness in most industrial applications. Conventional machining is a costly and time-consuming process, and is difficult to automate. Therefore, this study investigates and develops a new technique highly amenable for automation: fast regime—fluidized bed machining (FR-FBM). Atmospheric plasma sprayed TiO2, Cr2O3, and HVOF-sprayed WC-17%Co and Tribaloy-800 coatings, deposited on AISI 1040 steel substrates, were subjected to FR-FBM treatment. The effects of the leading operational parameters, namely, abrasive size, jet pressure, and processing time, were evaluated on all coatings by using a two/three-levels full factorial design of experiments. The FR-FBM treated surfaces were observed by FE-SEM and their surface finishing was evaluated by contact profilometry. Significant improvements in surface finishing of all the machined thermally sprayed coatings can always be detected, with FR-FBM being able to guarantee the precision and to ensure the closest geometrical tolerances.

  16. Optimal Substrate Preheating Model for Thermal Spray Deposition of Thermosets onto Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Tsurikov, A.; Sutter, J. K.

    2003-01-01

    High velocity oxy-fuel (HVOF) sprayed, functionally graded polyimide/WC-Co composite coatings on polymer matrix composites (PMC's) are being investigated for applications in turbine engine technologies. This requires that the polyimide, used as the matrix material, be fully crosslinked during deposition in order to maximize its engineering properties. The rapid heating and cooling nature of the HVOF spray process and the high heat flux through the coating into the substrate typically do not allow sufficient time at temperature for curing of the thermoset. It was hypothesized that external substrate preheating might enhance the deposition behavior and curing reaction during the thermal spraying of polyimide thermosets. A simple analytical process model for the deposition of thermosetting polyimide onto polymer matrix composites by HVOF thermal spray technology has been developed. The model incorporates various heat transfer mechanisms and enables surface temperature profiles of the coating to be simulated, primarily as a function of substrate preheating temperature. Four cases were modeled: (i) no substrate preheating; (ii) substrates electrically preheated from the rear; (iii) substrates preheated by hot air from the front face; and (iv) substrates electrically preheated from the rear and by hot air from the front.

  17. Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)

    NASA Astrophysics Data System (ADS)

    Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

    2015-01-01

    The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

  18. Tribological Properties of Ti(Al,O)/Al2O3 Composite Coating by Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Salman, Asma; Gabbitas, Brian; Cao, Peng; Zhang, Deliang

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti(Al,O)/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion. A feedstock of Ti(Al,O)/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  19. Embedding properties of optical fibers integrated into ceramic coatings obtained by wire flame thermal spray

    NASA Astrophysics Data System (ADS)

    Duo, Yi; Costil, Sophie; Pfeiffer, Pierre; Serio, Bruno

    2015-03-01

    The elaboration of smart materials with optical fiber sensors embedded into several dissimilar layers is capable of monitoring various system parameters inside the layered structure without damaging the host structure itself. This work mainly concentrates on the thermal elaboration process used to embed optical fibers into ceramic coating layers and their characterization. A new mechanical holder is first proposed in order to maintain the optical fiber during the thermal spray process and protect it from the strong atmospheric turbulence caused by the heat flux. Wire flame thermal spray where particles are propelled on the substrate at a temperature of more than 2000 °C is chosen as the elaboration process and the favorable elaboration conditions are evaluated. The microscopic characteristics of both the surface and cross-section of the embedding structure are evaluated, and the mechanical adhesion strength of the embedded optical fiber is then measured and discussed. The results show that the optical fiber remains undamaged after the thermal spray process and keeps perfect adhesion with the ceramic coating, making the former a competitive method to elaborate the embedded hybrid structure.

  20. Remaining Fatigue Life Assessment of Plasma Sprayed Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Robin, Philippe; Gitzhofer, François; Fauchais, Pierre; Boulos, Maher

    2010-09-01

    Ceramic functional coatings are frequently applied to structural materials, covering a wide range of thermomechanical and electrochemical applications. The main limiting feature is their reliability when subjected to cyclic transient thermal stresses. The study described in this article is a continuation of earlier research study focused on acoustic emission (AE) monitoring of the thermomechanical aging effects in ceramic coatings. Here, emphasis is placed on the usefulness of combining AE short-term monitoring with finite element modeling (FEM) to predict the performance of such coatings when subjected to cyclic thermal loads. The FEM study presented in this article is based on a three-dimensional, time-dependent approach, of the stress fields that developed within the coatings during the post-deposition cooling step and the thermal cycling. Experiments were conducted using yttrium-stabilized zirconia (YSZ) and Alumina (Al2O3) ceramic coatings combined with a NiCr-based intermetallic bond coat.

  1. Diesel engine emissions and combustion predictions using advanced mixing models applicable to fuel sprays

    NASA Astrophysics Data System (ADS)

    Abani, Neerav; Reitz, Rolf D.

    2010-09-01

    An advanced mixing model was applied to study engine emissions and combustion with different injection strategies ranging from multiple injections, early injection and grouped-hole nozzle injection in light and heavy duty diesel engines. The model was implemented in the KIVA-CHEMKIN engine combustion code and simulations were conducted at different mesh resolutions. The model was compared with the standard KIVA spray model that uses the Lagrangian-Drop and Eulerian-Fluid (LDEF) approach, and a Gas Jet spray model that improves predictions of liquid sprays. A Vapor Particle Method (VPM) is introduced that accounts for sub-grid scale mixing of fuel vapor and more accurately and predicts the mixing of fuel-vapor over a range of mesh resolutions. The fuel vapor is transported as particles until a certain distance from nozzle is reached where the local jet half-width is adequately resolved by the local mesh scale. Within this distance the vapor particle is transported while releasing fuel vapor locally, as determined by a weighting factor. The VPM model more accurately predicts fuel-vapor penetrations for early cycle injections and flame lift-off lengths for late cycle injections. Engine combustion computations show that as compared to the standard KIVA and Gas Jet spray models, the VPM spray model improves predictions of in-cylinder pressure, heat released rate and engine emissions of NOx, CO and soot with coarse mesh resolutions. The VPM spray model is thus a good tool for efficiently investigating diesel engine combustion with practical mesh resolutions, thereby saving computer time.

  2. JPL Advanced Thermal Control Technology Roadmap - 2008

    NASA Technical Reports Server (NTRS)

    Birur, Gaj

    2008-01-01

    This slide presentation reviews the status of thermal control technology at JPL and NASA.It shows the active spacecraft that are in vairous positions in the solar syatem, and beyond the solar system and the future missions that are under development. It then describes the challenges that the past missions posed with the thermal control systems. The various solutions that were implemented duirng the decades prior to 1990 are outlined. A review of hte thermal challenges of the future misions is also included. The exploration plan for Mars is then reviewed. The thermal challenges of the Mars Rovers are then outlined. Also the challenges of systems that would be able to be used in to explore Venus, and Titan are described. The future space telescope missions will also need thermal control technological advances. Included is a review of the thermal requirements for manned missions to the Moon. Both Active and passive technologies that have been used and will be used are reviewed. Those that are described are Mechanically Pumped Fluid Loops (MPFL), Loop Heat Pipes, an M3 Passive Cooler, Heat Siwtch for Space and Mars surface applications, phase change material (PCM) technology, a Gas Gap Actuateor using ZrNiH(x), the Planck Sorption Cooler (PCS), vapor compression -- Hybrid two phase loops, advanced pumps for two phase cooling loops, and heat pumps that are lightweight and energy efficient.

  3. Behavior of thermal spray aluminum coating in wet H{sub 2}S environments

    SciTech Connect

    Joia, C.; Berrera, P.; Kane, R.D.

    1999-11-01

    Sulfide stress cracking (SSC) and hydrogen induced cracking can cause severe damage in steel equipment exposed to wet H{sub 2}S environments. Metallic thermal spray coatings based on aluminum protect carbon steel from the corrosive media, when wet H{sub 2}S environments are a concern. In this program, a series of electrochemical tests were conducted. These tests involved exposure of coated samples to various environments containing H{sub 2}S, ammonia, chloride and cyanide to study the behavior of the aluminum coating associated with a stainless steel interlayer both applied by thermal spray. Results showed that the aluminum layer was corroded rapidly in solutions with pH higher than 11. In alkaline solutions with pH lower than 9 a protective aluminum layer and the corrosion rate was very low.

  4. Metallurgical characterization and determination of residual stresses of coatings formed by thermal spraying

    NASA Astrophysics Data System (ADS)

    Laribi, M.; Mesrati, N.; Vannes, A. B.; Treheux, D.

    2003-06-01

    This work presents an experimental determination of residual stresses in 35CrMo4 (Euronorm) low alloyed steel substrates with thermally sprayed coatings. Two different materials were separately deposited. The first one consisted of a blend of two superalloys: Cr-Ni steel and Cr-Mn steel, designated 55E and 65E, respectively. The second material was molybdenum. In a first part, basic characteristics of the deposited layers (metallographic analysis, hardness, and adhesion) are presented. In a second part, the determination of the residual stresses, in both substrate and thermal sprayed layers is performed using an extensometric method in combination with a simultaneous progressive electrolytic polishing. The influence of a nickel-aluminum (80:20%) bond-coat and/or a post-annealing at 850 °C in air for 1 h is studied.

  5. The effects of ultrasonic cleaning on the microstructural characteristics of thermally sprayed coatings

    SciTech Connect

    Blann, G.A.

    1995-12-31

    Accurate microstructural analysis of thermally sprayed coatings is possible only if each step of the preparation process is performed in a careful manner. Various methods are used to evaluate the characteristics of thermally sprayed coatings, but metallographic examination provides the most information about the many different coating characteristics. Any one step that is improperly performed during the metallographic preparation process can potentially produce incorrect coating characterization information. Ultrasonic cleaning of coated samples between preparation steps and after the completion of the entire process is not an accepted practice. The possibility of enlarging existing porosity is a concern due to the ultrasonic action. A study was conducted on five different coating types specifically evaluating the effects of ultrasonic cleaning on each coating. Variations in the coating porosity were quantified using image analysis and photomicrography.

  6. Vacuum Plasma Spray (VPS) Forming of Solar Thermal Propulsion Components Using Refractory Metals

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank; Gerish, Harold; Davis, William; Hissam, D. Andy

    1998-01-01

    The Thermal Spray Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using Vacuum Plasma Spray (VPS) to form structural components from a tungsten/rhenium alloy. The components were assembled into an absorption cavity for a fully-functioning, ground test unit of a solar thermal propulsion engine. The VPS process deposits refractory metal onto a graphite mandrel of the desired shape. The mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the deposit. Tungsten and tungsten/25% rhenium were used in the development and production of several absorber cavity components. These materials were selected for their high temperature (less than 2500 C) strength. Each absorber cavity comprises 3 coaxial shells with two, double-helical flow passages through which the propellant gas flows. This paper describes the processing techniques, design considerations, and process development associated with forming these engine components.

  7. Thermoelectric properties of magnesium silicide fabricated using vacuum plasma thermal spray

    NASA Astrophysics Data System (ADS)

    Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Gambino, Richard

    2013-10-01

    The thermoelectric properties of magnesium silicide samples prepared by Vacuum Plasma Spray (VPS) are compared with those made from the conventional hot press method using the same feedstock powder. Thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit are characterized from room temperature to 700 K. X-ray diffraction and scanning electron microscopy of the samples are obtained to assess how phase and microstructure influence the thermoelectric properties. Carrier concentration and Hall mobility are obtained from Hall Effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Low-temperature electrical conductivity measurements suggest a 3D variable range hopping effect in the samples. VPS samples achieved a maximum ZT = 0.16 at 700 K, which is around 30% of the hot press sample ZT = 0.55 at 700 K using the same raw powder. The results suggest that thermal spray is a potential deposition technique for thermoelectric materials.

  8. Sliding wear behavior of tungsten carbide thermal spray coatings for replacement of chromium electroplate in aircraft applications

    NASA Astrophysics Data System (ADS)

    Savarimuthu, A. C.; Taber, H. F.; Megat, I.; Shadley, J. R.; Rybicki, E. F.; Cornell, W. C.; Emery, W. A.; Somerville, D. A.; Nuse, J. D.

    2001-09-01

    Tungsten carbide (WC) thermal spray coatings have gained increased acceptance for commercial aircraft applications driven by the desire to replace chromium electroplate due to environmental and economic considerations. In order to confidently replace electroplated chrome with WC thermal spray coatings in aircraft applications, the coatings must demonstrate fatigue and wear characteristics as good as or better than those of electroplated chrome. Previous research in this area has shown that the fatigue life of the WC thermal spray coatings can be improved by inducing compressive residual stresses in the coating. This paper compares the wear characteristics of several types of WC thermal spray coatings with those of electroplated chrome in sliding wear tests using the “block-on-ring” procedures described in the ASTM G77 standard. Wear results are interpreted in terms of coating residual stresses and in terms of x-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.

  9. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-09-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  10. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  11. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    D. Trent Weaver; Matthew T. Kiser

    2003-10-01

    In the 11th quarter, further testing was performed on thermal spray coatings. A component coated and fused in the 9th quarter underwent high-stress abrasive wear testing. The test successfully showed this coating could survive in a high stress, sliding wear environment as the base layer in an FGM design coating. Work on the ferrous metal-matrix composites was completed in previous quarter and therefore no update is provided.

  12. Evaluation of thermal sprayed metallic coatings for use on the structures at Launch Complex 39

    NASA Technical Reports Server (NTRS)

    Welch, Peter J.

    1990-01-01

    The current status of the evaluation program is presented. The objective was to evaluate the applicability of Thermal Sprayed Coatings (TSC) to protect the structures in the high temperature acid environment produced by exhaust of the Solid Rocket Boosters during the launches of the Shuttle Transportation System. Only the relatively low cost aluminum TSC which provides some cathodic protection for steel appears to be a practical candidate for further investigation.

  13. Study of Substrate Preheating on Flattening Behavior of Thermal-Sprayed Copper Particles

    NASA Astrophysics Data System (ADS)

    Yang, K.; Fukumoto, M.; Yasui, T.; Yamada, M.

    2010-12-01

    In this study, the effect of substrate preheating on flattening behavior of thermal-sprayed particles was systematically investigated. A part of mirror-polished AISI304 substrates were preheated to 573 and 773 K for 10 min, and then exposed to an air atmosphere for different durations of up to 48 h, respectively. Contact angle of water droplet was measured on the substrate under designated conditions. It was found that the contact angle increased gradually with the increase of substrate duration after preheating. Moreover, smaller contact angle was maintained on the substrate with higher preheating temperature. Commercially available Cu powders were thermally sprayed onto the substrates with the same thermal treatment history as contact angle measurement using atmospheric plasma-spray technique. The splat shape had a transitional changing tendency from a splash splat to a disk one on the substrate with a short duration after preheating, while reappearance of splash splat with the increase of duration was confirmed. In general, wetting of substrate surface by molten particles may dominate the flattening behavior of thermal-sprayed particles. The occurrence of desorption of adsorbed gas/condensation caused by substrate preheating likely provides good wetting. On the other hand, the poor wetting may be attributed to the re-adsorption of gas/condensation on the substrate surface with the increase of duration. In addition, the shear adhesion strength of coating fabricated on blasted AISI304 substrate was enhanced on the once-heated substrate, but weakened with the increase of duration. The changing tendency of the coating adhesion strength and the wetting of substrate by droplet corresponded quite well with each other.

  14. Nuclear Thermal Propulsion for Advanced Space Exploration

    NASA Technical Reports Server (NTRS)

    Houts, M. G.; Borowski, S. K.; George, J. A.; Kim, T.; Emrich, W. J.; Hickman, R. R.; Broadway, J. W.; Gerrish, H. P.; Adams, R. B.

    2012-01-01

    The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation Nuclear Cryogenic Propulsion Stage (NCPS) based on NTP could provide high thrust at a specific impulse above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of the NCPS in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation. Progress made under the NCPS project could help enable both advanced NTP and advanced Nuclear Electric Propulsion (NEP).

  15. Compositionally Graded Thermal Barrier Coating by Hybrid Thermal Spraying Route and its Non-isothermal Oxidation Behavior

    NASA Astrophysics Data System (ADS)

    Nath, Subhasisa; Manna, Indranil; Dutta Majumdar, Jyotsna

    2013-08-01

    The present study concerns a detailed investigation of the characteristics and oxidation resistance property of a duplex and compositionally graded thermal barrier coating on Inconel 718. The duplex coating consists of a CoNiCrAlY bond coat layer sprayed on to sand-blasted Inconel 718 substrate (by high velocity oxy-fuel spraying) followed by deposition of a yttria-stabilized zirconia (YSZ) top coat by plasma spraying. The compositionally graded coating consists of several layers deposited by plasma spraying of pre-mixed CoNiCrAlY and YSZ powders in the weight ratios of 70:30, 50:50, 30:70, and 0:100 varying from the bond coat to the top surface, respectively. A detailed investigation of the microstructure, composition, and phases in the coating and its non-isothermal oxidation behavior from room temperature to 1250°C was performed. Oxidation proceeds by three stages in the as-received Inconel 718 and the compositionally graded coating, but by two stages in the duplex coating with a maximum activation energy for oxidation in the compositionally graded coating at high temperature (stage III). The kinetics and mechanism of oxidation were established.

  16. Sintering and Interface Strain Tolerance of Plasma-Sprayed Thermal and Environmental Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Leissler, George W.; Miller, Robert A.

    2003-01-01

    Ceramic thermal and environmental barrier coatings will be more aggressively designed to protect gas turbine engine hot section SiC/SiC Ceramic Matrix Composite (CMC) components in order to meet future engine higher fuel efficiency and lower emission goals. A coating system consisting of a zirconia-based oxide topcoat (thermal barrier) and a mullite/BSAS silicate inner coat (environmental barrier) is often considered a model system for the CMC applications. However, the coating sintering, and thermal expansion mismatch between the zirconia oxide layer and the silicate environmental barrier/CMC substrate will be of major concern at high temperature and under thermal cycling conditions. In this study, the sintering behavior of plasma-sprayed freestanding zirconia-yttria-based thermal barrier coatings and mullite (and/or barium-strontium-aluminosilicate, i.e., BSAS) environmental barrier coatings was determined using a dilatometer in the temperature range of 1200-1500 C. The effects of test temperature on the coating sintering kinetics were systematically investigated. The plasma-sprayed zirconia-8wt.%yttria and mullite (BSAS) two-layer composite coating systems were also prepared to quantitatively evaluate the interface strain tolerance of the coating system under thermal cycling conditions based on the dilatomentry. The cyclic response of the coating strain tolerance behavior and interface degradation as a function of cycle number will also be discussed.

  17. Surface modification of austenitic thermal-spray coatings by low-temperature nitrocarburizing

    NASA Astrophysics Data System (ADS)

    Lindner, T.; Mehner, T.; Lampke, T.

    2016-03-01

    Thermal-spray coatings of austenitic materials are mainly used under corrosive conditions. The relatively poor wear resistance strongly limits their use. In comparative studies between nitrocarburized and untreated thermal-spray coatings, the influence of the nitrogen and carbon enrichment on the properties of the coatings and the microstructure was investigated. The cross-section micrograph of the nitrocarburized coating shows the S-phase formation in the surface layer region. The depth profile of the nitrogen and carbon concentration was determined by glow discharge optical emission spectroscopy (GDOS) analysis. A selective enrichment of the surface layer region with nitrogen and carbon by means of thermochemical heat treatment increases the wear resistance. The interstitially dissolved nitrogen and carbon causes the formation of strong compressive residual stresses and high surface hardness. Increases in the service life of existing applications or new material combinations with face-centred cubic friction partners are possible. In the absence of dimensional change, uniform as well as partial nitrogen enrichment of the thermal spray coating is possible. Nitrocarburized coatings demonstrate a significant improvement in adhesive wear resistance and extremely high surface hardness.

  18. Hydrophilicity Characteristic of Thermal Sprayed Coating Produced Using Calcination Powders Recovered from Waste Dry Batteries

    NASA Astrophysics Data System (ADS)

    Futamata, Masami; Hoshino, Yasutaka; Nakanishi, Kimio; Itoh, Hidenobu; Ohnishi, Nobuhiro

    The powders called IZC(Itomuka Zinc Calcine) that are obtained from waste dry battery by roast processing mainly consist of oxides of zinc and manganese. Part of IZC is used as a raw material of the ferrite but the majority is unused. Authors considered its application to the thermal spray material. Thermal sprayed coating made by IZC powders possesses excellent light absorption, heat absorption, electromagnetic wave absorption and hydrophilicity characteristics. Hydrophilicity characteristic of IZC coating is especially remarkable, and IZC coating is expected to be applied for various heat exchangers such as evaporators. In this study, control test was done on two kinds of thermal sprayed coatings made by IZC powders decreased in zinc oxide and manganese dioxide powders without containing zinc oxide, and hydrophilicity characteristic of the IZC coatings were experimentally considered from the viewpoint of structure of coating and chemical composition. As a result of this study, the following useful findings were acquired to the clarification of the hydrophilicity appearance mechanism. Contact angle as an evaluation indicator of hydrophilicity characteristic is effected by manganese oxide stronger than zinc oxide, while not strongly effected by the roughness of the structure. The diameter of waterdrop spread is not necessarily the same even if the contact angle is the same as θ=0°.

  19. Elastoplastic analysis of process induced residual stresses in thermally sprayed coatings

    SciTech Connect

    Chen Yongxiong; Liang Xiubing; Liu Yan; Xu Binshi

    2010-07-15

    The residual stresses induced from thermal spraying process have been extensively investigated in previous studies. However, most of such works were focused on the elastic deformation range. In this paper, an elastoplastic model for predicting the residual stresses in thermally sprayed coatings was developed, in which two main contributions were considered, namely the deposition induced stress and that due to differential thermal contraction between the substrate and coating during cooling. The deposition induced stress was analyzed based on the assumption that the coating is formed layer-by-layer, and then a misfit strain is accommodated within the multilayer structure after the addition of each layer (plastic deformation is induced consequently). From a knowledge of specimen dimensions, processing temperatures, and material properties, residual stress distributions within the structure can be determined by implementing the model with a simple computer program. A case study for the plasma sprayed NiCoCrAlY on Inconel 718 system was performed finally. Besides some similar phenomena observed from the present study as compared with previous elastic model reported in literature, the elastoplastic model also provides some interesting features for prediction of the residual stresses.

  20. Real-time imaging for thermal spray process development and control

    NASA Astrophysics Data System (ADS)

    Agapakis, J.; Hoffman, T.

    1992-03-01

    Thermal spray and other high-temperature industrial processes are quite difficult to monitor with the human eye, because the luminous volume of the plasma or flame obscures the behavior of the solid or molten material in the heat-affected area. When a photographic or video camera is used, viewing is further degraded by the extreme contrast variation across the image area, making it impossible to achieve proper exposure throughout the image—except possibly for small areas of comparable brightness. Optical filtering with neutral density filters, such as those used in a welder’s helmet, are of no practical benefit. With thermal spray processes, the injection and flow of particles within the plasma flame is almost totally concealed by the extreme brightness of the plasma, flame, or arc. In addition, the particles quickly accelerate to very high speeds, making their detection even more difficult. This article discusses the development of integrated thermal spray process monitoring and analysis techniques based on two principles. The first is a unique vision sensing system that suppresses the flame, plasma, arc, or other high-luminosity phenomena in the video image. A further improvement is the use of dedicated image and analysis processing to enhance the sensor images and extract features of interest or dimensional measurements. These experimental techniques can be used as feedback for automated process monitoring and control.

  1. Effects of service condition on rolling contact fatigue failure mechanism and lifetime of thermal spray coatings—A review

    NASA Astrophysics Data System (ADS)

    Cui, Huawei; Cui, Xiufang; Wang, Haidou; Xing, Zhiguo; Jin, Guo

    2015-01-01

    The service condition determines the Rolling Contact Fatigue(RCF) failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable; it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating's resistance of RCF. The effects of service conditions(lubrication states, contact stresses, revolve speed, and slip ratio) on the changing of thermal spray coatings' contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings' contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.

  2. Advanced Multi-Component Defect Cluster Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1990-01-01

    The advantages of using ceramic thermal barrier coatings in gas turbine engine hot sections include increased fuel efficiency and improved engine reliability. However, current thermal barrier coatings will not have the low thermal conductivity and necessary sintering resistance under higher operating temperatures and thermal gradients required by future advanced ultra-efficient and low-emission aircraft engines. In this paper, a novel oxide defect cluster design approach is described for achieving low thermal conductivity and excellent thermal stability of the thermal barrier coating systems. This approach utilizes multi-component rare earth and other metal cluster oxide dopants that are incorporated in the zirconia-yttria based systems, thus significantly reducing coating thermal conductivity and sintering resistance by effectively promoting the formation of thermodynamically stable, essentially immobile defect clusters and/or nanoscale phases. The performance of selected plasma-sprayed cluster oxide thermal barrier coating systems has been evaluated. The advanced multi-component thermal barrier coating systems were found to have significantly lower initial and long-term thermal conductivities, and better high temperature stability. The effect of oxide cluster dopants on coating thermal conductivity, sintering resistance, oxide grain growth behavior and durability will be discussed.

  3. Advanced Multi-Component Defect Cluster Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The advantages of using ceramic thermal barrier coatings in gas turbine engine hot sections include increased fuel efficiency and improved engine reliability. However, current thermal barrier coatings will not have the low thermal conductivity and necessary sintering resistance under higher operating temperatures and thermal gradients required by future advanced ultra efficient and low emission aircraft engines. In this paper, a novel oxide defect cluster design approach is described for achieving low thermal conductivity and excellent thermal stability of the thermal barrier coating systems. This approach utilizes multi-component rare earth and other metal cluster oxide dopants that are incorporated in the zirconia-yttna based systems, thus significantly reducing coating thermal conductivity and sintering resistance by effectively promoting the formation of thermodynamically stable, essentially immobile defect clusters and/or nanoscale phases. The performance of selected plasma-sprayed cluster oxide thermal barrier coating systems has been evaluated. The advanced multi-component thermal barrier coating systems were found to have significantly lower initial and long-term thermal conductivities, and better high temperature stability. The effect of oxide cluster dopants on coating thermal conductivity, sintering resistance, oxide grain growth behavior and durability will be discussed.

  4. Microstructure and thermal conductivity of thermal barrier coatings processed by plasma spray and physical vapor deposition techniques

    SciTech Connect

    Ravichandran, K.S.; An, K.; Dutton, R.E.; Semiatin, S.L.

    1996-12-31

    Improvements in the efficiency of gas turbine require the highest operating temperatures possible. Because the Ni-base superalloys used as turbine materials rapidly lose strength and oxidize above 1,000 C, a reduction in service temperature is often accomplished by the use of thermal barrier coatings. The temperature dependence of the thermal conductivity of multilayer coatings made by a plasma spray technique as well as some coatings made by physical vapor deposition (PVD) was investigated. The multilayer coatings consisted of a varying number of layers of Al{sub 2}O{sub 3} and ZrO{sub 2} stabilized by 8% Y{sub 2}O{sub 3}. Plasma sprayed coatings exhibited a large reduction in thermal conductivity at all temperatures when compared to the bulk monolithic materials. This reduction was found to be due to porosity as well as thermal resistance brought about by interfaces in the coatings. A comparable reduction in thermal conductivity was achieved in monolithic ZrO{sub 2} as well as in a composite coating deposited by the PVD technique. Microstructural factors that may be responsible for this reduction are discussed.

  5. Thermally Sprayed Coatings as Effective Tool Surfaces in Sheet Metal Forming Applications

    NASA Astrophysics Data System (ADS)

    Franzen, V.; Witulski, J.; Brosius, A.; Trompeter, M.; Tekkaya, A. E.

    2011-06-01

    Two approaches to produce wear-resistant effective surfaces for deep drawing tools by thermal arc wire spraying of hard materials are presented. Arc wire spraying is a very economic coating technique due to a high deposition rate. The coated surface is very rough compared to that of conventional sheet metal forming tools. In the first approach, the coated surface is smoothed in a subsequent CNC-based incremental roller burnishing process. In this process, the surface asperities on the surface are flattened, and the roughness is significantly reduced. In the second approach, the hard material coatings are not sprayed directly on the tool but on a negative mould. Afterward, the rough "as-sprayed" side of the coating is backfilled with a polymer. The bonded hard metal shell is removed from the negative mould and acts as the surface of the hybrid sheet metal forming tool. Sheet metal forming experiments using tools based on these two approaches demonstrate that they are suitable to form high-strength steels. Owing to a conventional body of steel or cast iron, the first approach is suitable for large batch sizes. The application of the second approach lies within the range of small up to medium batch size productions.

  6. Analytical methods to characterize heterogeneous raw material for thermal spray process: cored wire Inconel 625

    NASA Astrophysics Data System (ADS)

    Lindner, T.; Bonebeau, S.; Drehmann, R.; Grund, T.; Pawlowski, L.; Lampke, T.

    2016-03-01

    In wire arc spraying, the raw material needs to exhibit sufficient formability and ductility in order to be processed. By using an electrically conductive, metallic sheath, it is also possible to handle non-conductive and/or brittle materials such as ceramics. In comparison to massive wire, a cored wire has a heterogeneous material distribution. Due to this fact and the complex thermodynamic processes during wire arc spraying, it is very difficult to predict the resulting chemical composition in the coating with sufficient accuracy. An Inconel 625 cored wire was used to investigate this issue. In a comparative study, the analytical results of the raw material were compared to arc sprayed coatings and droplets, which were remelted in an arc furnace under argon atmosphere. Energy-dispersive X-ray spectroscopy (EDX) and X-ray fluorescence (XRF) analysis were used to determine the chemical composition. The phase determination was performed by X-ray diffraction (XRD). The results were related to the manufacturer specifications and evaluated in respect to differences in the chemical composition. The comparison between the feedstock powder, the remelted droplets and the thermally sprayed coatings allows to evaluate the influence of the processing methods on the resulting chemical and phase composition.

  7. Thermally Sprayed Coatings as Interlayers for DLC-Based Thin Films

    NASA Astrophysics Data System (ADS)

    Bolelli, G.; Gualtieri, E.; Lusvarghi, L.; Pighetti Mantini, F.; Pitacco, F.; Valeri, S.; Volz, H.

    2009-06-01

    This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al2O3-13%TiO2, or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al2O3-13%TiO2 and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al2O3-13%TiO2 interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al2O3-13%TiO2 interlayer is rapidly removed because the interlayer itself is fractured. At 300 °C, by contrast, the DLC-based film on the Al2O3-13%TiO2 interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/WC-Co systems possess the lowest corrosion current density.

  8. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 2, Computational results

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1993-12-31

    The fluid dynamics inside and outside a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injected on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The details of the CFD simulation are given in a companion paper. This paper describes the general gas dynamic features of HVOF spraying and then gives a detailed discussion of the computational predictions of the present analysis. The gas velocity, temperature, pressure and Mach number distributions are presented for various locations inside and outside the torch. Characteristics of the metal spray particle velocity, temperature, Mach number, trajectory, and phase state (solid or liquid) are also presented and discussed. Extensive numerical flow visualization is provided to show flow features such as mixing layers, shock waves, and expansion waves.

  9. Thermal shock behavior of alumina/MoSi2 plasma sprayed laminated composites

    SciTech Connect

    Castro, R. G.; Petrovic, J. J.; Vaidya, R. U.; Mendoza, D.

    2001-01-01

    Alumina (Al{sub 2}O{sub 3}) is very susceptible to thermal shock, which leads to strength degradation. By reinforcing Al{sub 2}O{sub 3} with molybdenum disilicide (MoSi{sub 2}) layers, the tolerance to damage caused by thermal shock can be improved. The thermal shock resistance of plasma sprayed Al{sub 2}O{sub 3}/MoSi{sub 2} laminated composites were investigated. Three laminate microstructures having different layer thickness were fabricated by atmospheric plasma spraying while maintaining a 50/50-volume fraction. Quenching experiments done on 4-point bend bars showed a gradual decrease in the strength as the change in temperature ({Delta}T) increased. Thermal shock resistant parameters (R{prime} and R-quadruple prime) provided a representative numerical value of the thermal shock resistance for the laminated composites. The corresponding material properties for the different microstructures were determined experimentally in order to calculate the R{prime} and R quadruple prime values. The intermediate layered composite showed the highest R-quadruple prime va1ue at 1061 {micro}m, while the thin layered composite had the highest R{prime} value at 474 W/m.

  10. Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

    2015-08-01

    Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

  11. Validation of the thermal effect of roof with the Spraying and green plants in an insulated building

    SciTech Connect

    Zhou, Nan; Gao, Weijun; Nishida, Masaru; Ojima, Toshio

    2004-08-08

    In recent years, roof-spraying and rooftop lawns have proven effective on roofs with poor thermal insulation. However, the roofs of most buildings have insulating material to provide thermal insulation during the winter. The effects of insulation has not previously been quantified. In this study, the authors collected measurements of an insulated building to quantify the thermal effects of roof-spraying and rooftop lawns. Roof-spraying did not significantly reduce cooling loads and required significant amounts of water. The conclusion is that roof spraying is not suitable for buildings with well-insulated roofs. Rooftop lawns, however, significantly stabilized the indoor temperature while additionally helping to mitigate the heat island phenomenon.

  12. Validation on the thermal effect of roof with the spraying and green plants in an insulated building

    SciTech Connect

    Zhou, Nan; Gao, Weijun; Nishida, Masaru; Ojima, Toshio

    2004-03-20

    In recent years, roof-spraying and rooftop lawns has proved effective on roofs with poor thermal insulation. However, roofs of most buildings have insulating material to provide thermal insulation during the winter. The effects of such a practice have not previously been quantified. In this study, the authors conducted measurements of an insulated building to quantify the thermal effects of roof-spraying and rooftop lawns. Roof-spraying did not significantly reduce cooling loads, and required significant amounts of water. The conclusion is that roof spraying is not suitable for buildings with well-insulated roofs. Rooftop lawns, however, significantly stabilized the indoor temperature while additionally helping to mitigate the heat island phenomenon.

  13. System for NDE of thermal spray coating bonds

    SciTech Connect

    Green, D.R.; Wandling, C.R.; Gatto, F.B.; Rogers, F.S.

    1984-09-01

    A nondestructive testing system that is especially well suited to NDE of bonds between coatings and substrates has been developed. It injects heat into the test specimen surface from a hot gas pulse and detects and other coating problems by means of an emissivity independent infrared scanning method. This method is very practical and has been proven in numerous demonstrations. It is the only method known by the authors to be applicable to such a wide variety of coatings. Qualitative correlation between bond strength and scan results from the system was demonstrated on one small group of test specimens. Due to its emissivity independence, the method yields results that are, in many cases, far superior to other infrared-thermal NDE methods. It can be applied to coatings having tough surfaces, and no physical contact with the test specimen is required.

  14. Thermal Aging Behavior of Axial Suspension Plasma-Sprayed Yttria-Stabilized Zirconia (YSZ) Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Zhao, Yuexing; Wang, Liang; Yang, Jiasheng; Li, Dachuan; Zhong, Xinghua; Zhao, Huayu; Shao, Fang; Tao, Shunyan

    2015-02-01

    7.5YSZ thermal barrier coatings (TBCs) were deposited onto the stainless steel substrates using axial suspension plasma spraying (ASPS). Free-standing coatings were isothermally aged in air from 1200 to 1600 °C for 24 h and at 1550 °C for 20 to 100 h, respectively. Thermal aging behavior such as phase composition, microstructure evolutions, grain growth, and mechanical properties for thermal-aged coatings were investigated. Results show that the as-sprayed metastable tetragonal (t'-ZrO2) phase decomposes into equilibrium tetragonal (t-ZrO2) and cubic (c-ZrO2) phases during high-temperature exposures. Upon further cooling, the c-ZrO2 may be retained or transform into another metastable tetragonal (t″-ZrO2) phase, and tetragonal → monoclinic phase transformation occurred after 1550 °C/40 h aging treatment. The coating exhibits a unique structure with segmentation cracks and micro/nano-size grains, and the grains grow gradually with increasing aging temperature and time. In addition, the hardness ( H) and Young's modulus ( E) significantly increased as a function of temperature due to healing of pores or cracks and grain growth of the coating. And a nonmonotonic variation is found in the coatings thermal aged at a constant temperature (1550 °C) with prolonged time, this is a synergetic effect of coating sintering and m-ZrO2 phase formation.

  15. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

    SciTech Connect

    B.Mi; X. Zhao; R. Bayles

    2006-05-26

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with different surface preparation conditions before applying the coating, e.g., grit-blasted surface, wire-brush cleaned surface, and a dirty surface. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that the three surface preparation conditions can be successfully differentiated by looking into the impedance difference observed from the eddy current probe. The measurement is fairly robust and consistent. More specimens are also prepared with variations of process parameters, such as spray angle, stand-off distance, and application of corrosion protective sealant, etc. They are blindly tested to evaluate the reliability of the eddy current system. Quantitative relations between the coating bond strength and the eddy current response are also established with the support of destructive testing. This non-contact, non-destructive, easy to use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  16. Demands, Potentials, and Economic Aspects of Thermal Spraying with Suspensions: A Critical Review

    NASA Astrophysics Data System (ADS)

    Toma, Filofteia-Laura; Potthoff, Annegret; Berger, Lutz-Michael; Leyens, Christoph

    2015-10-01

    Research and development work for about one decade have demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Some particular advantages are direct feeding of fine nano- and submicron-scale particles avoiding special feedstock powder preparation, ability to produce coating thicknesses ranging from 10 to 50 µm, homogeneous microstructure with less anisotropy and lower surface roughness compared to conventional coatings, possibility of retention of the initial crystalline phases, and others. This paper discusses the main aspects of thermal spraying with suspensions which have been taken into account in order to produce these coatings on an economical way. The economic efficiency of the process depends on the availability of suitable additional system components (suspension feeder, injectors), on the development and handling of stable suspensions, as well as on the high process stability for acceptance at industrial scale. Special focus is made on the development and processability of highly concentrated water-based suspensions. While costs and operational safety clearly speak for use of water as a liquid media for preparing suspensions on an industrial scale, its use is often critically discussed due to the required higher heat input during spraying compared to alcoholic suspensions.

  17. Thermal conductivity of spray-on foam insulations for aerospace applications

    NASA Astrophysics Data System (ADS)

    Barrios, Matt; Vanderlaan, Mark; Van Sciver, Steven

    2012-06-01

    A guarded-hot-plate apparatus [1] has been developed to measure the thermal conductivity of spray-on foam insulations (SOFI) at temperatures ranging from 30 K to 300 K. The foam tested in the present study is NCFI 24-124, a polyisocyanurate foam used on the External Tanks of the Space Shuttle. The foam was tested first in ambient pressure air, then evacuated and tested once more. These thermal conductivities were compared to the thermal conductivity taken from a sample immediately after being subjected to conditions similar to those experienced by the foam while on the launch pad at Kennedy Space Center. To mimic the conditions experienced on the launch pad, an apparatus was built to enclose one side of the foam sample in a warm, humid environment while the other side of the sample contacts a stainless steel surface held at 77 K. The thermal conductivity data obtained is also compared to data found in the literature.

  18. Erosion Resistance of High Velocity Oxy-Fuel WC-Co-Cr Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Imeson, Chris

    Thermal spray coatings have been incorporated in oil and gas extraction efforts for many years. Recently, High Velocity Oxy-Fuel (HVOF) has become increasingly incorporated where erosive environments are present. This study investigates the microstructural and mechanical properties of HVOF WC-Co-Cr coatings deposited at SharkSkin Coatings ltd. The deposited coatings exhibited a low porosity with high adhesion strength, hardness, and superior erosion resistance. In this study, a recirculating solid particle erosion testing machine was designed and fabricated to simulate an erosive environment on a laboratory scale. This study was also aimed at improving microstructures and mechanical properties of the coatings by modifying the two coating deposition parameters e.g. standoff and pre-cycle heating. It was determined that pre-spray substrate heating negatively affected the coatings microstructures e.g. porosity, while reducing the stand-off distance positively influenced the coating microstructures and mechanical properties, e.g. erosion resistance.

  19. The first result of an optical monitoring system for optimization of thermal spray droplets

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Y.; Miyazaki, F.; Yamasaki, M.; Yamagata, Y.; Muraoka, K.

    2015-12-01

    This article describes the first experimental result of a simple but reliable optical monitoring system for optimization of thermal spray droplets. The system, which was used in the present experiment and the authors call as ``a pre-proto instrument'', consisted of a light collecting lens followed by a part for separating the light into two wavelengths, with the light of each wavelength guided into an avalanche photo-diode (APD) to be electronically detected. First, it was calibrated using a special purpose-built calibration system. Then, it was taken to a plasma spray gun for a field test, yielding a satisfactory first result. Based on this positive result, future plans of the project are discussed.

  20. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-07-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

  1. Vacuum Plasma Spray (VPS) Forming of Solar Thermal Propulsion Components Using Refractory Metals

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank R.; Hissam, David A.; Gerrish, Harold P.; Davis, William M.

    1999-01-01

    The Thermal Spray Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using Vacuum Plasma Spray (VPS) to form structural components from a tungsten/rhenium alloy. The components were assembled into an absorber cavity for a fully-functioning, ground test unit of a solar then-nal propulsion engine. The VPS process deposits refractory metal onto a graphite mandrel of the desired shape. The mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the deposit. Tungsten and tungsten/25% rhenium were used in the development and production of several absorber cavity components. These materials were selected for their high temperature (greater than 25000 C [greater than 4530 F]) strength. Each absorber cavity comprises 3 coaxial shells with two, double-helical flow passages through which the propellant gas flows. This paper describes the processing techniques, design considerations, and process development associated with forming these engine components.

  2. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-05-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

  3. Evaluation of plasma-sprayed CoS{sub 2} cathodes for thermal batteries

    SciTech Connect

    Guidotti, R.A.

    1999-12-22

    Conventional electroactive stack components in thermal batteries are constructed from pressed-powder parts. These include the anode, separator, and cathode pellets (discs). Pressing parts that are less than 0.010 inch thick is difficult. The use of plasma spray to deposit thin CoS{sub 2} cathode films onto a stainless steel substrate was examined as an alternative to pressed-powder cathodes. The plasma-sprayed electrodes were tested in single cells under isothermal conditions and constant-current discharge over a temperature range of 400 C to 550 C using standard LiSi anodes and separators based on the LiCl-KCl eutectic. Similar tests were conducted with cells built with conventional pressed-powder cathodes, which were tested under the same conditions for comparative purposes. This paper presents the results of those tests.

  4. Continuous Synthesis of Doped Pyrochlore Materials by Spray Pyrolysis for Auto-thermal Reforming Applications

    NASA Astrophysics Data System (ADS)

    Yancey, Jonathan

    The use of a spray-pyrolysis method is studied for the continuous synthesis of refractory oxide reforming catalyst for the conversion of hydrocarbon fuels to H2 and CO at 900°C. Nickel- and rhodium-doped zirconate pyrochlore materials with the formulas La1.89Ni2.81Y 0.25Ca0.11Zr1.47 and La1.89Rh 1.09Y0.25Ca0.11Zr1.641 were synthesized using the spray pyrolysis method. Both Pechini and glycine-nitrate precursor solutions were used in order to control the particle morphology, crystallinity, and surface area of the catalyst powder. Samples synthesized by the Pechini solution required post-synthesis heat treatment to 1000 °C for 2 hours to form the fully-crystalline pyrochlore phase. Both the Ni- and Rh-doped compositions formed by the spray-pyrolysis method performed as reported elsewhere for powder produced by solid-state and Pechini bulk methods. The use of the glycine-nitrate precursor solution in the spray-pyrolysis resulted in the formation of fully crystalline pyrochlore catalyst for the Ni-doped composition without any additional high temperature treatment. The Rh-doped catalysts synthesized from the glycine-nitrate precursor did not form a fully crystalline material directly from the spray-pyrolysis process, but required a further thermal treatment to 800 °C for 8 hours to transform the powder and burn-off excess carbon remaining from the synthesis process. Rapid catalyst aging tests for the Rh-doped catalysts synthesized by spray-pyrolysis (using either the Pechini and glycine-nitrate precursor solutions) produced stable and active catalysts achieving equilibrium hydrogen yield of 90% for 15 hours. To conclude, the work showed that through proper chemical design of the precursor system, a high surface area, chemically active, and stable zirconate pyrochlore catalyst could be synthesized efficiently by the spray-pyrolysis method developed.

  5. Advances in scientific balloon thermal modeling

    NASA Astrophysics Data System (ADS)

    Bohaboj, T.; Cathey, H.

    The National Aeronautics and Space Administration's Balloon Program Office has long acknowledged that the accurate modeling of balloon performance and flight prediction is dependant on how well the balloon is thermally modeled. This ongoing effort is focused on developing accurate balloon thermal models that can be used to quickly predict balloon temperatures and balloon performance. The ability to model parametric changes is also a driver for this effort. This paper will present the most recent advances made in this area. This research effort continues to utilize the ``Thermal Desktop'' addition to AUTO CAD for the modeling. Recent advances have been made by using this analytical tool. A number of analyses have been completed to test the applicability of this tool to the problem with very positive results. Progressively detailed models have been developed to explore the capabilities of the tool as well as to provide guidance in model formulation. A number of parametric studies have been completed. These studies have varied the shape of the structure, material properties, environmental inputs, and model geometry. These studies have concentrated on spherical ``proxy models'' for the initial development stages and then to transition to the natural shaped zero pressure and super pressure balloons. An assessment of required model resolution has also been determined. Model solutions have been cross checked with known solutions via hand calculations. The comparison of these cases will also be presented. One goal is to develop analysis guidelines and an approach for modeling balloons for both simple first order estimates and detailed full models. This paper presents the step by step advances made as part of this effort, capabilities, limitations, and the lessons learned. Also presented are the plans for further thermal modeling work.

  6. Advanced Devices for Cryogenic Thermal Management

    NASA Astrophysics Data System (ADS)

    Bugby, D.; Stouffer, C.; Garzon, J.; Beres, M.; Gilchrist, A.

    2006-04-01

    This paper describes six advanced cryogenic thermal management devices/subsystems developed by Swales Aerospace for ground/space-based applications of interest to NASA, DoD, and the commercial sector. The devices/subsystems described herein include the following: (a) a differential thermal expansion cryogenic thermal switch (DTE-CTSW) constructed with high purity aluminum end-pieces and an Ultem support rod for the 6 K Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) (b) a quad-redundant DTE-CTSW assembly for the 35 K science instruments (NIRCam, NIRSpec, and FGS) mounted on the JWST Integrated Science Instrument Module (ISIM) (c) a cryogenic diode heat pipe (CDHP) thermal switching system using methane as the working fluid for the 100 K CRISM hyperspectral mapping instrument on the Mars Reconnaissance Orbiter (MRO) and (d) three additional devices/subsystems developed during the AFRL-sponsored CRYOTOOL program, which include a dual DTE-CTSW/dual cryocooler test bed, a miniaturized neon cryogenic loop heat pipe (mini-CLHP), and an across gimbal cryogenic thermal transport system (GCTTS). For the first three devices/subsystems mentioned above, this paper describes key aspects of the development efforts including concept definition, design, fabrication, and testing. For the latter three, this paper provides brief overview descriptions as key details are provided in a related paper.

  7. Carbon nanotube reinforced aluminum based nanocomposite fabricated by thermal spray forming

    NASA Astrophysics Data System (ADS)

    Laha, Tapas

    The present research concentrates on the fabrication of bulk aluminum matrix nanocomposite structures with carbon nanotube reinforcement. The objective of the work was to fabricate and characterize multi-walled carbon nanotube (MWCNT) reinforced hypereutectic Al-Si (23 wt% Si, 2 wt% Ni, 1 wt% Cu, rest Al) nanocomposite bulk structure with nanocrystalline matrix through thermal spray forming techniques viz. plasma spray forming (PSF) and high velocity oxy-fuel (HVOF) spray forming. This is the first research study, which has shown that thermal spray forming can be successfully used to synthesize carbon nanotube reinforced nanocomposites. Microstructural characterization based on quantitative microscopy, scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and X ray photoelectron spectroscopy (XPS) confirms (i) retention and macro/sub-macro level homogenous distribution of multiwalled carbon nanotubes in the Al-Si matrix and (ii) evolution of nanostructured grains in the matrix. Formation of ultrathin beta-SiC layer on MWCNT surface, due to chemical reaction of Si atoms diffusing from Al-Si alloy and C atoms from the outer walls of MWCNTs has been confirmed theoretically and experimentally. The presence of SiC layer at the interface improves the wettability and the interfacial adhesion between the MWCNT reinforcement and the Al-Si matrix. Sintering of the as-sprayed nanocomposites was carried out in an inert environment for further densification. As-sprayed PSF nanocomposite showed lower microhardness compared to HVOF, due to the higher porosity content and lower residual stress. The hardness of the nanocomposites increased with sintering time due to effective pore removal. Uniaxial tensile test on CNT-bulk nanocomposite was carried out, which is the first ever study of such nature. The tensile test results showed inconsistency in the data attributed to inhomogeneous

  8. The behavior of high-purity, low-density air plasma sprayed thermal barrier coatings

    SciTech Connect

    Helminiak, Yanar NM

    2009-12-01

    Research on the behavior of high-purity, low-density (85%) air plasma sprayed (APS) thermal barrier coatings (TBC) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The microstructure of the APS topcoats is one variable in this study intended to maximize the coating thicknesses that can be applied without spallation and to minimize the thermal conduction through the YSZ layer. The specimens were evaluated using cyclic oxidation tests and important properties of the TBCs, such as resistance to sintering and phase transformation, were determined. The high purity resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The porous topcoat microstructure also resulted in significant durability during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, CTE of the superalloy substrate and the nature of the thermal exposure.

  9. Thermal stability studies of plasma sprayed yttrium oxide coatings deposited on pure tantalum substrate

    NASA Astrophysics Data System (ADS)

    Nagaraj, A.; Anupama, P.; Mukherjee, Jaya; Sreekumar, K. P.; Satpute, R. U.; Padmanabhan, P. V. A.; Gantayet, L. M.

    2010-02-01

    Plasma sprayed Yttrium oxide is used for coating of crucibles and moulds that are used at high temperature to handle highly reactive molten metals like uranium, titanium, chromium, and beryllium. The alloy bond layer is severely attacked by the molten metal. This commonly used layer contributes to the impurity addition to the pure liquid metal. Yttrium oxide was deposited on tantalum substrates (25 mm × 10mm × 1mm thk and 40 mm × 8mm × 1mm thk) by atmospheric plasma spray technique with out any bond coat using optimized coating parameters. Resistance to thermal shock was evaluated by subjecting the coated specimens, to controlled heating and cooling cycles between 300K to 1600K in an induction furnace in argon atmosphere having <= 0.1ppm of oxygen. The experiments were designed to examine the sample tokens by both destructive and non-destructive techniques, after a predetermined number of thermal cycles. The results upto 24 thermal cycles of 25 mm × 10mm × 1mm thk coupons and upto 6 cycles of 40 mm × 8mm × 1mm thk coupons are discussed. The coatings produced with the optimized parameters were found to exhibit excellent thermal shock resistance.

  10. Tribological properties of thermally sprayed TiAl-Al2O3 composite coating

    NASA Astrophysics Data System (ADS)

    Salman, A.; Gabbitas, B.; Li, J.; Zhang, D.

    2009-08-01

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity oxy fuel (HVOF) thermally sprayed wear resistant TiAl/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting. A feedstock of TiAl/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity oxy-fuel (HVOF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The results showed that the composite coating has lower wear rate at high temperature (700°C) than the uncoated H13 sample. At Room temperature without using lubricant there is no much significant difference between the wear rate of the coated and uncoated samples. The experimental results showed that the composite coating has great potential for high temperature application due to its lower wear rate at high temperature in comparison with the uncoated sample at the same temperature. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  11. Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

    2002-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

  12. Recent advances in large-eddy simulation of spray and coal combustion

    NASA Astrophysics Data System (ADS)

    Zhou, L. X.

    2013-07-01

    Large-eddy simulation (LES) is under its rapid development and is recognized as a possible second generation of CFD methods used in engineering. Spray and coal combustion is widely used in power, transportation, chemical and metallurgical, iron and steel making, aeronautical and astronautical engineering, hence LES of spray and coal two-phase combustion is particularly important for engineering application. LES of two-phase combustion attracts more and more attention; since it can give the detailed instantaneous flow and flame structures and more exact statistical results than those given by the Reynolds averaged modeling (RANS modeling). One of the key problems in LES is to develop sub-grid scale (SGS) models, including SGS stress models and combustion models. Different investigators proposed or adopted various SGS models. In this paper the present author attempts to review the advances in studies on LES of spray and coal combustion, including the studies done by the present author and his colleagues. Different SGS models adopted by different investigators are described, some of their main results are summarized, and finally some research needs are discussed.

  13. Effect of Thermally Softened Bronze Matrix on the Fracturing Behavior of Diamond Particles in Hybrid Sprayed Bronze/Diamond Composite

    NASA Astrophysics Data System (ADS)

    Na, Hyuntaek; Bae, Gyuyeol; Kang, Kicheol; Kim, Hyungjun; Kim, Jay-Jung; Lee, Changhee

    2010-09-01

    In our previous study (Na et al., Compos Sci Technol 69:463-468, 2009), optimized thickness of protective nickel film was proposed for smaller diamond feedstock to obtain reduced impact stress and uniform flight behavior of particles during kinetic (or cold) spraying. However, in this study, nickel-coated diamond particles were severely fractured with increasing particle size due to high kinetic energy. Hence, an innovative hybrid spraying technique (a combination of kinetic and thermal spraying) was introduced to embed relatively large diamond particles into the bronze matrix. Size distributions of the diamond particles in the composite coatings were analyzed by scanning electron microscopy, an electron probe micro analyzer, and image analysis methods. In addition, impact behaviors of diamond particles in kinetic and hybrid gas flows were simulated through finite element analysis (ABAQUS/Explicit 6.7-2). Diamond fracturing was significantly minimized by the reduced impact energy afforded by the thermally softened bronze matrix through hybrid spraying.

  14. Thermal Shock Properties of Yttria-Stabilized Zirconia Coatings Deposited Using Low-Energy Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Zhang, Nannan; Bolot, Rodolphe; Liao, Hanlin; Coddet, Christian

    2015-08-01

    Yttria-stabilized zirconia (YSZ) coatings have been frequently used as a thermal protective layer on the metal or alloy component surfaces. In the present study, ZrO2-7%Y2O3 thermal barrier coatings (TBCs) were successfully deposited by DC (direct current) plasma spray process under very low pressure conditions (less than 1 mbar) using low-energy plasma guns F4-VB and F100. The experiments were performed to evaluate the thermal shock resistance of different TBC specimens which were heated to 1373 K at a high-temperature cycling furnace and held for 0.5 h, followed by air cooling at room temperature for 0.2 h. For comparison, a corresponding atmospheric plasma spray (APS) counterpart was also elaborated to carry out the similar experiments. The results indicated that the very low pressure plasma spray (VLPPS) coatings displayed better thermal shock resistance. Moreover, the failure mechanism of the coatings was elucidated.

  15. Adaptation of the Advanced Spray Combustion Code to Cavitating Flow Problems

    NASA Technical Reports Server (NTRS)

    Liang, Pak-Yan

    1993-01-01

    A very important consideration in turbopump design is the prediction and prevention of cavitation. Thus far conventional CFD codes have not been generally applicable to the treatment of cavitating flows. Taking advantage of its two-phase capability, the Advanced Spray Combustion Code is being modified to handle flows with transient as well as steady-state cavitation bubbles. The volume-of-fluid approach incorporated into the code is extended and augmented with a liquid phase energy equation and a simple evaporation model. The strategy adopted also successfully deals with the cavity closure issue. Simple test cases will be presented and remaining technical challenges will be discussed.

  16. Advances in Scientific Balloon Thermal Modeling

    NASA Technical Reports Server (NTRS)

    Bohaboj, T.; Cathey, H. M., Jr.

    2004-01-01

    The National Aeronautics and Space Administration's Balloon Program office has long acknowledged that the accurate modeling of balloon performance and flight prediction is dependant on how well the balloon is thermally modeled. This ongoing effort is focused on developing accurate balloon thermal models that can be used to quickly predict balloon temperatures and balloon performance. The ability to model parametric changes is also a driver for this effort. This paper will present the most recent advances made in this area. This research effort continues to utilize the "Thrmal Desktop" addition to AUTO CAD for the modeling. Recent advances have been made by using this analytical tool. A number of analyses have been completed to test the applicability of this tool to the problem with very positive results. Progressively detailed models have been developed to explore the capabilities of the tool as well as to provide guidance in model formulation. A number of parametric studies have been completed. These studies have varied the shape of the structure, material properties, environmental inputs, and model geometry. These studies have concentrated on spherical "proxy models" for the initial development stages and then to transition to the natural shaped zero pressure and super pressure balloons. An assessment of required model resolution has also been determined. Model solutions have been cross checked with known solutions via hand calculations. The comparison of these cases will also be presented. One goal is to develop analysis guidelines and an approach for modeling balloons for both simple first order estimates and detailed full models. This papa presents the step by step advances made as part of this effort, capabilities, limitations, and the lessons learned. Also presented are the plans for further thermal modeling work.

  17. Advanced materials for thermal protection system

    NASA Astrophysics Data System (ADS)

    Heng, Sangvavann; Sherman, Andrew J.

    1996-03-01

    Reticulated open-cell ceramic foams (both vitreous carbon and silicon carbide) and ceramic composites (SiC-based, both monolithic and fiber-reinforced) were evaluated as candidate materials for use in a heat shield sandwich panel design as an advanced thermal protection system (TPS) for unmanned single-use hypersonic reentry vehicles. These materials were fabricated by chemical vapor deposition/infiltration (CVD/CVI) and evaluated extensively for their mechanical, thermal, and erosion/ablation performance. In the TPS, the ceramic foams were used as a structural core providing thermal insulation and mechanical load distribution, while the ceramic composites were used as facesheets providing resistance to aerodynamic, shear, and erosive forces. Tensile, compressive, and shear strength, elastic and shear modulus, fracture toughness, Poisson's ratio, and thermal conductivity were measured for the ceramic foams, while arcjet testing was conducted on the ceramic composites at heat flux levels up to 5.90 MW/m2 (520 Btu/ft2ṡsec). Two prototype test articles were fabricated and subjected to arcjet testing at heat flux levels of 1.70-3.40 MW/m2 (150-300 Btu/ft2ṡsec) under simulated reentry trajectories.

  18. Semi-automated structural characterisation of high velocity oxy fuel thermally sprayed WC-Co based coatings

    NASA Astrophysics Data System (ADS)

    Fay, M. W.; Han, Y.; McCartney, G.; Korpiola, K.; Brown, P. D.

    2008-08-01

    The application of an automated procedure for the rapid assessment of selected area electron diffraction patterns is described. Comparison with complementary EDX spectra has enabled the thermal decomposition reactions within high velocity oxy-fuel thermally sprayed WC-Co coatings to be investigated.

  19. Mechanical Properties of Plasma-Sprayed ZrO2-8 wt% Y2O3 Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dongming; Miller, Robert A.

    2004-01-01

    Mechanical behavior of free standing, plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings, including strength, fracture toughness, fatigue, constitutive relation, elastic modulus, and directionality, has been determined under various loading-specimen configurations. This report presents and describes a summary of mechanical properties of the plasma-sprayed coating material to provide them as a design database.

  20. Thermal-sprayed zinc anodes for cathodic protection of steel-reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; McGill, Galen E.

    1996-01-01

    Thermal-sprayed zinc anodes are being used in Oregon in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges. The U.S. Department of Energy, Albany Research Center, is collaborating with the Oregon Department of Transportation (ODOT) to evaluate the long-term performance and service life of these anodes. Laboratory studies were conducted on concrete slabs coated with 0.5 mm (20 mil) thick, thermal-sprayed zinc anodes. The slabs were electrochemically aged at an accelerated rate using an anode current density of 0.032 A/m2 (3mA/ft2). Half the slabs were preheated before thermal-spraying with zinc; the other half were unheated. Electrochemical aging resulted in the formation at the zinc-concrete interface of a thin, low pH zone (relative to cement paste) consisting primarily of ZnO and Zn(OH)2, and in a second zone of calcium and zinc aluminates and silicates formed by secondary mineralization. Both zones contained elevated concentrations of sulfate and chloride ions. The original bond strength of the zinc coating decreased due to the loss of mechanical bond to the concrete with the initial passage of electrical charge (aging). Additional charge led to an increase in bond strength to a maximum as the result of secondary mineralization of zinc dissolution products with the cement paste. Further charge led to a decrease in bond strength and ultimately coating disbondment as the interfacial reaction zones continued to thicken. This occurred at an effective service life of 27 years at the 0.0022 A/m2 (0.2 mA/ft2) current density typically used by ODOT in ICCP systems for coastal bridges. Zinc coating failure under tensile stress was primarily cohesive within the thickening reaction zones at the zinc-concrete interface. There was no difference between the bond strength of zinc coatings on preheated and unheated concrete surfaces after long service times.

  1. Effect of Sintering on Mechanical and Physical Properties of Plasma-Sprayed Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    The effect of sintering on mechanical and physical properties of free-standing plasma-sprayed ZrO2-8 wt% Y2O3 thermal barrier coatings (TBCs) was determined by annealing them at 1316 C in air. Mechanical and physical properties of the TBCs, including strength, modes I and II fracture toughness, elastic modulus, Poisson s response, density, microhardness, fractography, and phase stability, were determined at ambient temperature as a function of annealing time ranging from 0 to 500 h. All mechanical and physical properties, except for the amount of monoclinic phase, increased significantly in 5 to 100 h and then reached a plateau above 100 h. Annealing resulted in healing of microcracks and pores and in grain growth, accompanying densification of the TBC s body due to the sintering effect. However, an inevitable adverse effect also occurred such that the desired lower thermal conductivity and good expansivity, which makes the TBCs unique in thermal barrier applications, were degraded upon annealing. A model was proposed to assess and quantify all the property variables in response to annealing in a normalized scheme. Directionality of as-sprayed TBCs appeared to have an insignificant effect on their properties, as determined via fracture toughness, microhardness, and elastic modulus measurements.

  2. Spray-Coated Multiwalled Carbon Nanotube Composite Electrodes for Thermal Energy Scavenging Electrochemical Cells.

    PubMed

    Holubowitch, Nicolas E; Landon, James; Lippert, Cameron A; Craddock, John D; Weisenberger, Matthew C; Liu, Kunlei

    2016-08-31

    Spray-coated multiwalled carbon nanotube/poly(vinylidene fluoride) (MWCNT/PVDF) composite electrodes, scCNTs, with varying CNT compositions (2 to 70 wt %) are presented for use in a simple thermal energy-scavenging cell (thermocell) based on the ferro/ferricyanide redox couple. Their utility for direct thermal-to-electrical energy conversion is explored at various temperature differentials and cell orientations. Performance is compared to that of buckypaper, a 100% CNT sheet material used as a benchmark electrode in thermocell research. The 30 to 70 wt % scCNT composites give the highest power output by electrode area-seven times greater than buckypaper at ΔT = 50 °C. CNT utilization is drastically enhanced in our electrodes, reaching 1 W gCNT(-1) compared to 0.036 W gCNT(-1) for buckypaper. Superior performance of our spray-coated electrodes is attributed to both wettability with better use of a large portion of electrochemically active CNTs and minimization of ohmic and thermal contact resistances. Even composites with as low as 2 wt % CNTs are still competitive with prior art. The MWCNT/PVDF composites developed herein are inexpensive, scalable, and serve a general need for CNT electrode optimization in next-generation devices. PMID:27510029

  3. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    D. Trent Weaver; Matthew T. Kiser; Frank W. Zok; Carlos G. Levi; Jeffrey Hawk

    2004-02-01

    In an effort to realize minimum of a 2x increase in wear life of ground engaging components used on mining machines, two potentially cost effective processes were explored for the production of tailored, highly abrasion resistant materials: (1) hybrid pressure casting of steel composites, and (2) arc lamp fusing of thermal spray coatings. Steel composites comprised of cermet or oxide hard particles were successfully produced using pressure casting processes, although a cost effective process has not yet been identified for oxide particles. Both composites achieved project wear targets in high stress gouging wear, but the cermet composites did not meet the targets in impact wear, due to poor matrix toughness resulting from particle dissolution. Oxide composites had superior toughness and are expected to meet impact wear goals. Arc lamp processing of thermal spray coatings was successfully demonstrated to produce a metallurgical bond at the coating interface. Functionally graded materials were developed and successfully fused to allow for the accommodation of thermal process stresses in an intermediate layer. Ultimately, three functionally graded materials were identified as having high stress, three-body abrasion resistance sufficient to exceed project goals.

  4. Ultimate Heat Sink Thermal Performance and Water Utilization: Measurements on Cooling and Spray Ponds

    SciTech Connect

    Athey, G. F.; Hadlock, R. K.; Abbey, O. B.

    1982-02-01

    A data acquisition research program, entitled "Ultimate Heat Sink Performance Field Experiments," has been brought to completion. The primary objective is to obtain the requisite data to characterize thermal performance and water utilization for cooling ponds and spray ponds at elevated temperature. Such data are useful for modeling purposes, but the work reported here does not contain modeling efforts within its scope. The water bodies which have been studied are indicative of nuclear reactor ultimate heat sinks, components of emergency core cooling systems. The data reflect thermal performance and water utilization for meteorological and solar influences which are representative of worst-case combinations of conditions. Constructed water retention ponds, provided with absolute seals against seepage, have been chosen as facilities for the measurement programs; the first pond was located at Raft River, Idaho, and the second at East Mesa, California. The data illustrate and describe, for both cooling ponds and spray ponds, thermal performance and water utilization as the ponds cool from an initially elevated temperature. To obtain the initial elevated temperature, it has been convenient to conduct the measurements at geothermal sites having large supplies and delivery rates of hot geothermal fluid. The data are described and discussed in the text, and presented in the form of data volumes as appendices.

  5. Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties

    SciTech Connect

    Van Every, Kent; Krane, Matthew; Trice, Rodney; Wang, Hsin; Porter, Wallace D; Besser, Matthew; Sordelet, Daniel; Ilavsky, Dr. Jan; Almer, Jon

    2011-01-01

    The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 {micro}m and 80 nm. The powder-ethanol suspensions made with 15-{micro}m diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k th) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k th values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k th of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k th increase was less than has been observed in APS coatings.

  6. Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties

    SciTech Connect

    VanEvery, Kent; Krane, Matthew J.M.; Trice, Rodney W; Wang, Hsin; Porter, Wallace; Besser, Matthew; Sordelet, Daniel; Ilavsky, Jan; Almer, Jonathan

    2012-03-19

    The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 {micro}m and 80 nm. The powder-ethanol suspensions made with 15-{micro}m diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k{sub th}) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k{sub th} values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k{sub th} of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k{sub th} increase was less than has been observed in APS coatings.

  7. Column formation in suspension plasma-sprayed coatings and resultant thermal properties.

    SciTech Connect

    Van Every, K.; Krane, M. J. M.; Trice, R. W.; Wang, H.; Porter, W.; Besser, M.; Sordelet, D.; Ilavsky, J.; Almer, J.

    2011-06-01

    The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with median diameters of 15 {micro}m and 80 nm. The powder-ethanol suspensions made with 15-{micro}m diameter YSZ particles formed coatings with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to variations in deposition behavior. The thermal conductivity (k th) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 C heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.% exhibited significantly different k th values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension formulations. Heat treatment increased the k th of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k th increase was less than has been observed in APS coatings.

  8. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 1, Numerical formulation

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1994-01-01

    The fluid and particle dynamics of a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injection on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. Choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The CFD simulation assumes three injection streams (solid metal particles with argon as a carrier gas, premixed oxygen/fuel, and air) inside the aircap and solves the combusting two-phase flow until the external spray stream decays to sonic conditions. The numerical formulation solves the mass, momentum, and energy transfer for both the gas and particle phase and strongly couples each phase. The combustion process is modeled using approximate equilibrium chemistry with dissociation of the gas with a total of nine species. Melting and re-solidification of the metal panicles is modeled as a lumped-mass system. Turbulent flow is modeled by a two equation k-{epsilon} turbulence model, including compressibility effects on turbulent dissipation. A time iterative, implicit, finite volume numerical method is used to solve the partial differential equations. A companion paper [10] presents the results of the numerical simulation and gives a detailed discussion of the gas and panicle dynamics.

  9. Mechanization of the Grit Blasting Process for Thermal Spray Coating Applications: A Parameter Study

    NASA Astrophysics Data System (ADS)

    Begg, Henry; Riley, Melissa; de Villiers Lovelock, Heidi

    2016-01-01

    The bond strength between a thermal spray coating and substrate is critical for many applications and is dependent on good substrate surface preparation and optimized spray parameters. While spray parameters are usually carefully monitored and controlled, most surface preparation is carried out by manual grit blasting, with little or no calibration of blast parameters. Blasting is currently highly dependent on operator skill and often surface finish is only assessed visually, meaning a consistent, reproducible surface profile cannot be guaranteed. This paper presents investigations on the effect of blast parameters (including blast pressure, standoff distance, media feed rate, blast angle, traverse speed, and media size) on surface profile for seven different metallic substrates using a mechanized, robotic blasting system and employing a brown fused alumina blast medium. Substrates were characterized using non-contact focus variation microscopy. Average surface roughness was found to be most affected by blast pressure, media size, and traverse speed, while changes to media feed rate and standoff distance had a limited effect on surface profile. Changes to blast angle resulted in limited change to average roughness, but microscopy examinations suggested a change in the mechanism of material removal.

  10. Particle melting behavior during high-velocity oxygen fuel thermal spraying

    NASA Astrophysics Data System (ADS)

    He, J.; Ice, M.; Lavernia, E.

    2001-03-01

    Particle melting behavior during high-velocity oxygen fuel (HVOF) thermal spraying was investigated using Inconel 625 powders. The powder characteristics and coating properties were investigated using scanning electron microscopy (SEM), x-ray, and microhardness studies. Results indicated that the volume fraction of unmelted particles in the coatings was dependent on the proportion of powder within a specified size range, in these experiments, 30 to 50 µm. This particle size range was primarily determined by the particle temperature, which was measured during spraying. Particle temperature significantly decreased as particle size increased. The microhardness values for the coatings containing unmelted particles were predicted by a simple rule-of-mixtures equation for the case of a low volume fraction of unmelted particles. However, for the condition of high volume fraction of unmelted particles, the measured microhardness values did not compare favorably with the calculated values, probably due to the presence of porosity, which occurred in the form of voids found among unmelted particles. The microstructure and characteristics of the feedstock powder were retained in the corresponding coating under certain spray conditions.

  11. The thermal stability of porous alumina/stainless steel catalyst support obtained by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Novaković, Tatjana; Radić, Nenad; Grbić, Boško; Dondur, Vera; Mitrić, Miodrag; Randjelović, Danijela; Stoychev, Dimitar; Stefanov, Plamen

    2008-12-01

    Active porous alumina coatings were obtained by deposition of boehmite sol on stainless steel (SS) substrate by spray pyrolysis method. The temperature and the doping of polyethylene glycol (PEG) and La 3+ in the boehmite sol effects on the textural and structural properties and surface morphology of alumina coatings on stainless steel samples are presented. It was found that the addition of polyethylene glycol combined with La 3+ to the boehmite sol before spraying improves the thermal stability of porous alumina coatings. X-ray diffraction patterns of a doped sample, even after 5 h at 1000 °C, point out to the presence only of δ-Al 2O 3, with a SBET of 74 m 2/g. XPS data and SEM photographs of coated samples show that alumina were well deposited on the metallic supports. The absence of any lanthanum compounds indicates very well homogeneous dispersion of La 3+-ions on the surface of alumina crystallites. AFM images show sphere like alumina grains and agglomerates with surface roughness from 60 to 180 nm, depending on temperature and doping. Surface roughness of doped alumina samples was higher than that of non-doped. It was pointed out that spray pyrolysis method enables preparation of alumina layers with relatively high specific surface area, suitable for applications as catalysts supports.

  12. Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

    1984-01-01

    ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

  13. Nondestructive Measurement Material Characterization of Thermal Sprayed Nickel Aluminum Coatings by using Laser Ultrasound Technique

    NASA Astrophysics Data System (ADS)

    Yeh, Cheng Hung; Wu, Tai Chieh; Yang, Che Hua

    This research focused on characterization of mechanical properties in Nickel-Aluminum coating with different thermal technique and processing parameters at high temperature environment up to 295°C. With the laser ultrasound technique (LUT), guided acoustic waves are generated to propagate on the Ni-Al sprayed coatings. By measuring dispersive phase velocity followed by SCE-UA inversion algorithm. The Young's modulus of coatings which fabricated by HVOF technique is higher than APS technique. This technique is potentially useful to probe the material characterization at high temperature environment in a remote and non-destructive way.

  14. Position Paper External Tank Thermal Protection System (TPS) Manually Sprayed fly-as-is Foam Certification

    NASA Technical Reports Server (NTRS)

    Stadler, John H.

    2009-01-01

    During manufacture of the existing External Tanks (ETs), the Thermal Protection System (TPS) foam manual spray application processes lacked the enhanced controls/procedures to ensure that defects produced were less than the critical size. Therefore the only remaining option to certify the "fly-as-is" foam is to verify ET120 tank hardware meets the new foam debris requirements. The ET project has undertaken a significant effort studying the existing "fly-as-is" TPS foam. This paper contains the findings of the study.

  15. Numerical analysis of partially molten splat during thermal spray process using the finite element method

    NASA Astrophysics Data System (ADS)

    Zirari, M.; Abdellah El-Hadj, A.; Bacha, N.

    2010-03-01

    A finite element method is used to simulate the deposition of the thermal spray coating process. A set of governing equations is solving by a volume of fluid method. For the solidification phenomenon, we use the specific heat method (SHM). We begin by comparing the present model with experimental and numerical model available in the literature. In this study, completely molten or semi-molten aluminum particle impacts a H13 tool steel substrate is considered. Next we investigate the effect of inclination of impact of a partially molten particle on flat substrate. It was found that the melting state of the particle has great effects on the morphologies of the splat.

  16. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2014-01-01

    An apparatus and method for thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such as Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air, and a spark. Metal is inserted continuously in a high volume of metal into a combustion chamber of the pulsejet. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tailpipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  17. Monitoring Delamination of Plasma-Sprayed Thermal Barrier Coatings by Reflectance-Enhanced Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.; Bencic, Timothy J.

    2006-01-01

    Highly scattering plasma-sprayed thermal barrier coatings (TBCs) present a challenge for optical diagnostic methods to monitor TBC delamination because scattering attenuates light transmitted through the TBC and usually degrades contrast between attached and delaminated regions of the TBC. This paper presents a new approach where reflectance-enhanced luminescence from a luminescent sublayer incorporated along the bottom of the TBC is used to identify regions of TBC delamination. Because of the higher survival rate of luminescence reflecting off the back surface of a delaminated TBC, the strong scattering exhibited by plasma-sprayed TBCs actually accentuates contrast between attached and delaminated regions by making it more likely that multiple reflections of luminescence off the back surface occur before exiting the top surface of the TBC. A freestanding coating containing sections designed to model an attached or delaminated TBC was prepared by depositing a luminescent Eu-doped or Er-doped yttria-stabilized zirconia (YSZ) luminescent layer below a plasma-sprayed undoped YSZ layer and utilizing a NiCr backing layer to represent an attached substrate. For specimens with a Eu-doped YSZ luminescent sublayer, luminescence intensity maps showed excellent contrast between unbacked and NiCr-backed sections even at a plasma-sprayed overlayer thickness of 300 m. Discernable contrast between unbacked and NiCr-backed sections was not observed for specimens with a Er-doped YSZ luminescent sublayer because luminescence from Er impurities in the undoped YSZ layer overwhelmed luminescence originating form the Er-doped YSZ sublayer.

  18. Design and physicochemical characterization of advanced spray-dried tacrolimus multifunctional particles for inhalation

    PubMed Central

    Wu, Xiao; Hayes, Don; Zwischenberger, Joseph B; Kuhn, Robert J; Mansour, Heidi M

    2013-01-01

    The aim of this study was to design, develop, and optimize respirable tacrolimus microparticles and nanoparticles and multifunctional tacrolimus lung surfactant mimic particles for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced at different pump rates by advanced spray-drying particle engineering design from organic solution in closed mode. In addition, multifunctional tacrolimus lung surfactant mimic dry powder particles were prepared by co-dissolving tacrolimus and lung surfactant mimic phospholipids in methanol, followed by advanced co-spray-drying particle engineering design technology in closed mode. The lung surfactant mimic phospholipids were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-1-glycerol]. Laser diffraction particle sizing indicated that the particle size distributions were suitable for pulmonary delivery, whereas scanning electron microscopy imaging indicated that these particles had both optimal particle morphology and surface morphology. Increasing the pump rate percent of tacrolimus solution resulted in a larger particle size. X-ray powder diffraction patterns and differential scanning calorimetry thermograms indicated that spray drying produced particles with higher amounts of amorphous phase. X-ray powder diffraction and differential scanning calorimetry also confirmed the preservation of the phospholipid bilayer structure in the solid state for all engineered respirable particles. Furthermore, it was observed in hot-stage micrographs that raw tacrolimus displayed a liquid crystal transition following the main phase transition, which is consistent with its interfacial properties. Water vapor uptake and lyotropic phase transitions in the solid state at varying levels of relative humidity were determined by gravimetric vapor sorption technique. Water content in the various powders was very low and well within the levels necessary

  19. Design and physicochemical characterization of advanced spray-dried tacrolimus multifunctional particles for inhalation.

    PubMed

    Wu, Xiao; Hayes, Don; Zwischenberger, Joseph B; Kuhn, Robert J; Mansour, Heidi M

    2013-01-01

    The aim of this study was to design, develop, and optimize respirable tacrolimus microparticles and nanoparticles and multifunctional tacrolimus lung surfactant mimic particles for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced at different pump rates by advanced spray-drying particle engineering design from organic solution in closed mode. In addition, multifunctional tacrolimus lung surfactant mimic dry powder particles were prepared by co-dissolving tacrolimus and lung surfactant mimic phospholipids in methanol, followed by advanced co-spray-drying particle engineering design technology in closed mode. The lung surfactant mimic phospholipids were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-1-glycerol]. Laser diffraction particle sizing indicated that the particle size distributions were suitable for pulmonary delivery, whereas scanning electron microscopy imaging indicated that these particles had both optimal particle morphology and surface morphology. Increasing the pump rate percent of tacrolimus solution resulted in a larger particle size. X-ray powder diffraction patterns and differential scanning calorimetry thermograms indicated that spray drying produced particles with higher amounts of amorphous phase. X-ray powder diffraction and differential scanning calorimetry also confirmed the preservation of the phospholipid bilayer structure in the solid state for all engineered respirable particles. Furthermore, it was observed in hot-stage micrographs that raw tacrolimus displayed a liquid crystal transition following the main phase transition, which is consistent with its interfacial properties. Water vapor uptake and lyotropic phase transitions in the solid state at varying levels of relative humidity were determined by gravimetric vapor sorption technique. Water content in the various powders was very low and well within the levels necessary

  20. Evaluation of Erosion Resistance of Advanced Turbine Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Kuczmarski, Maria A.; Miller, Robert A.; Cuy, Michael D.

    2007-01-01

    The erosion resistant turbine thermal barrier coating system is critical to aircraft engine performance and durability. By demonstrating advanced turbine material testing capabilities, we will be able to facilitate the critical turbine coating and subcomponent development and help establish advanced erosion-resistant turbine airfoil thermal barrier coatings design tools. The objective of this work is to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and/or thermal gradient environments, validating advanced turbine airfoil thermal barrier coating systems based on nano-tetragonal phase toughening design approaches.

  1. Cross-Sectional Residual Stresses in Thermal Spray Coatings Measured by Moiré Interferometry and Nanoindentation Technique

    NASA Astrophysics Data System (ADS)

    Zhu, Jianguo; Xie, Huimin; Hu, Zhenxing; Chen, Pengwan; Zhang, Qingming

    2012-09-01

    A plasma-sprayed thermal barrier coating (TBC) was deposited on a stainless steel substrate. The residual stresses were firstly measured by moiré interferometry combined with a cutting relaxation method. The fringe patterns in the cross-section of the specimen clearly demonstrate the deformation caused by the residual stress in thermal spray coatings. However, restricted by the sensitivity of moiré interferometry, there are few fringes in the top coat, and large errors may exist in evaluating the residual stress in the top coat. Then, the nanoindentation technique was used to estimate the residual stresses across the coating thickness. The stress/depth profile shows that the process-induced stresses after thermal spray are compressive in the top coat and a tendency to a more compressive state toward the interface. In addition, the stress gradient in the substrate is nonlinear, and tensile and compressive stresses appear simultaneously for self-equilibrium in the cross-section.

  2. Mathematical analysis of thermoelastic characteristics in plasma-sprayed thermal barrier coatings.

    PubMed

    Go, Jaegwi; Jungo, Yeon-Gil; Kim, Seokchan; Ali, Md Afsar; Paik, Ungyu

    2012-02-01

    The thermoelastic characteristics of plasma-sprayed thermal barrier coatings (TBCs) have been analyzed using mathematical modeling. Two types of TBC model, cylinder and circular disk which are commercial plasma-sprayed TBCs, subjecting to symmetric temperature distribution to the radial and longitudinal directions, respectively, were taken into consideration. Based on the thermoelastic theories, a second order ordinary differential equation was derived for the cylinder model and a pair of partial differential equations were set up for the circular disk model. The analytic solution was obtained from the ordinary differential equation, while a finite volume method was developed for numerical solutions to the pair of partial differential equations due to the complexity of governing equations. The thermoelastic characteristics of TBC models, such as temperature distributions, displacements, and stresses, were displayed according to the obtained solutions. The rate of heat conduction in the section of the top coat is relatively slow in comparison with the substrate, and no profound difference appears in the temperature distribution between two TBC models. The highest longitudinal tensile stress is expressed at the bond coat of both models, and the substrate is under the compressive stresses to the circumferential direction. While the cylinder expands to the positive longitudinal direction only, the expansion in the circular disk occurs to both the positive and negative longitudinal directions. Relatively large displacement and stresses exhibit in the cylinder as compared with the circular disk. In the circular disk, the stresses to the radial direction undulate at each section, and the displacement profile displays that the width of the circular disk is slightly narrowed. The results demonstrate that the mechanical and thermal properties of the top and bond coats are the crucial factors to be considered in controlling the thermoelastic characteristics of plasma-sprayed

  3. Protection of carbon steel against hot corrosion using thermal spray Si- and Cr-base coatings

    SciTech Connect

    Porcayo-Calderon, J.; Gonzalez-Rodriguez, J.G.; Martinez, L.

    1998-02-01

    A Fe75Si thermal spray coating was applied on the surface of a plain carbon steel baffle plate. Beneath this coating, a Ni20Cr coating was applied to give better adherence to the silicon coating. The baffle was installed in the high-temperature, fireside, corrosion zone of a steam generator. At the same time, an uncoated 304 stainless steel baffle was installed nearby for comparison. For 13 months the boiler burned heavy fuel oil with high contents of vanadium. The samples were studied employing scanning electron microscopy, x-ray microanalysis, and x-ray diffraction techniques. After that, it was possible to inspect the structural state of the components, and it was found that the stainless steel baffle plates were destroyed almost completely by corrosion, whereas the carbon steel coated baffle plate did not suffer a significant attack, showing that the performance of the thermal spray coating was outstanding and that the coating was not attacked by vanadium salts of the molten slag.

  4. Isothermal Oxidation Behavior of Supersonic Atmospheric Plasma-Sprayed Thermal Barrier Coating System

    NASA Astrophysics Data System (ADS)

    Bai, Yu; Ding, Chunhua; Li, Hongqiang; Han, Zhihai; Ding, Bingjun; Wang, Tiejun; Yu, Lie

    2013-10-01

    In this work, Y2O3 stabilized zirconia-based thermal barrier coatings (TBCs) were deposited by conventional atmospheric plasma spraying (APS) and high efficiency supersonic atmospheric plasma spraying (SAPS), respectively. The effect of Al2O3 layer stability on the isothermal growth behavior of thermally grown oxides (TGOs) was studied. The results revealed that the Al2O3 layer experienced a three-stage change process, i.e., (1) instantaneous growth stage, (2) steady-state growth stage, and (3) depletion stage. The thickness of Al2O3 scale was proved to be an important factor for the growth rate of TGOs. The SAPS-TBCs exhibited a higher Al2O3 stability and better oxidation resistance as compared with the APS-TBCs. Additionally, it was found that inner oxides, especially nucleated on the top of the crest, continually grew and swallowed the previously formed Al2O3 layer, leading to the granulation and disappearance of continuous Al2O3 scale, which was finally replaced by the mixed oxides and spinel.

  5. Investigation of thermal spray coatings on austenitic stainless steel substrate to enhance corrosion protection

    NASA Astrophysics Data System (ADS)

    Rogers, Daniel M.

    The research is aimed to evaluate thermal spray coatings to address material issues in supercritical and ultra-supercritical Rankine cycles. The primary purpose of the research is to test, evaluate, and eventually implement a coating to improve corrosion resistance and increase efficiency of coal fired power plants. The research is performed as part of a comprehensive project to evaluate the ability of titanium, titanium carbide, or titanium diboride powders to provide fireside corrosion resistance in supercritical and ultra-supercritical steam boilers, specifically, coal driven boilers in Illinois that must utilize high sulfur and high chlorine content coal. [1] The powder coatings that were tested are nano-sized titanium carbide (TiC) and titanium di-boride (TiB2) powders that were synthesized by a patented process at Southern Illinois University. The powders were then sent to Gas Technology Institute in Chicago to coat steel coupons by HVOF (High Velocity Oxy-Fuel) thermal spray technique. The powders were coated on an austenitic 304H stainless steel substrate which is commonly found in high temperature boilers, pipelines, and heat exchangers. The samples then went through various tests for various lengths of time under subcritical, supercritical, and ultra-supercritical conditions. The samples were examined using a scanning electron microscope and x-ray diffraction techniques to study microstructural changes and then determined which coating performed best.

  6. Effect of Residual Stress on the Wear Resistance of Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Luo, W.; Selvadurai, U.; Tillmann, W.

    2016-01-01

    The wear resistance of thermal spray coatings mainly depends on coating properties such as the microstructure, hardness, and porosity, as well as on the residual stress in the coating. The residual stress is induced by a variety of influences e.g., temperature gradients, difference of the thermal expansion coefficient of the coating/substrate materials, and the geometry of the components. To investigate the residual stress, the impulse excitation technique was employed to measure the Young's and shear moduli. The residual stress was determined by the hole-drilling method and x-ray diffraction. Pin-on-Disk and Pin-on-Tube tests were used to investigate the wear behavior. After the wear tests, the wear volume was measured by means of a 3D-profilometer. The results show that the value of the residual stress can be modified by varying the coating thickness and the substrate geometry. The compressive stress in the HVOF-sprayed WC-Co coatings has a significant positive influence on the wear resistance whereas the tensile stress has a negative effect.

  7. Thermal interaction between WC-Co coating and steel substrate in process of HVOF spraying

    SciTech Connect

    Guilemany, J.M.; Sobolev, V.V.; Nutting, J.; Dong, Z.; Calero, J.A. . Metalurgia Fisica-Ciencia de Materials)

    1994-10-01

    The WC-Co powders can be used to produce good adhesive and wear resistant HVOF thermal spray coatings on steel and light alloys substrates. In order to understand the properties of this kind of coating, the phases which are present in the coatings and structure changes during post heat treatments have been investigated. Although the coating properties depend very much on the structure developed in the substrate-coating interfacial region it has not been yet investigated in detail. The present study is devoted to the experimental and theoretical analysis of this interfacial region. The structure characterization has been performed mainly through the use of transmission electron microscopy. To provide a theoretical investigation a realistic prediction model of the process has been developed and on its base the mathematical simulation of the substrate-coating thermal interaction has been undertaken.

  8. Finite Element Modeling of the Different Failure Mechanisms of a Plasma Sprayed Thermal Barrier Coatings System

    NASA Astrophysics Data System (ADS)

    Ranjbar-Far, M.; Absi, J.; Mariaux, G.

    2012-12-01

    A new finite element model is used to investigate catastrophic failures of a thermal barrier coatings system due to crack propagation along the interfaces between the ceramic top-coat, thermally grown oxide, and bond-coat layers, as well as between the lamellas structure of the ceramic layer. The thermo-mechanical model is designed to take into account a non-homogenous temperature distribution and the effects of the residual stresses generated during the coating process. Crack propagation is simulated using the contact tool "Debond" present in the ABAQUS finite element code. Simulations are performed with a geometry corresponding to similar or dissimilar amplitudes of asperity, and for different thicknesses of the oxide layer. The numerical results have shown that crack evolution depends crucially on the ratio of the loading rate caused by growth and swelling of the oxide layer and also on the interface roughness obtained during the spraying of coatings.

  9. Microstructure and Sliding Wear Behavior of Fe-Based Coatings Manufactured with HVOF and HVAF Thermal Spray Processes

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Matikainen, V.; Bolelli, G.; Koivuluoto, H.; Lusvarghi, L.; Vuoristo, P.

    2016-04-01

    The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate.

  10. Microstructure and Sliding Wear Behavior of Fe-Based Coatings Manufactured with HVOF and HVAF Thermal Spray Processes

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Matikainen, V.; Bolelli, G.; Koivuluoto, H.; Lusvarghi, L.; Vuoristo, P.

    2016-06-01

    The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate.

  11. Adapting of the Background-Oriented Schlieren (BOS) Technique in the Characterization of the Flow Regimes in Thermal Spraying Processes

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Rademacher, H. G.; Anjami, N.; Hagen, L.

    2014-01-01

    In thermal spraying technique, the changes in the in-flight particle velocities are considered to be only a function of the drag forces caused by the dominating flow regimes in the spray jet. Therefore, the correct understanding of the aerodynamic phenomena occurred at nozzle out let and at the substrate interface is an important task in the targeted improvement in the nozzle and air-cap design as well as in the spraying process in total. The presented work deals with the adapting of an innovative technique for the flow characterization called background-oriented Schlieren. The flow regimes in twin wire arc spraying (TWAS) and high velocity oxygen fuel (HVOF) were analyzed with this technique. The interfering of the atomization gas flow with the intersected wires causes in case of TWAS process a deformation of the jet shape. It leads also to areas with different aero dynamic forces. The configurations of the outlet air-caps in TWAS effect predominantly the outlet flow characteristics. The ratio between fuel and oxygen determine the dominating flow regimes in the HVOF spraying jet. Enhanced understanding of the aerodynamics at outlet and at the substrate interface could lead to a targeted improvement in thermal spraying processes.

  12. Resistance of thermal-sprayed duplex coating composed of aluminum and 80Ni-20Cr alloy against aqueous corrosion

    NASA Astrophysics Data System (ADS)

    Ishikawa, K.; Suzuki, T.; Tobe, S.; Kitamura, Y.

    2001-09-01

    The development of corrosion-resistant sprayed coatings without sealing is required to increase the reliability of the thermal spray coating method and to expand the field of application for wet corrosion environments. The conventional wire flame-sprayed aluminum coating on steel without sealing has poor resistance against aqueous corrosion and has restricted practical use. A duplex coating composed of sprayed aluminum on an 80Ni-20Cr alloy undercoat exhibited sufficient resistance in a hot, near-neutral aqueous environment through a trial use in a vegetable oil process. In this paper, the mechanism of corrosion resistance of the duplex coating is investigated by electrochemical polarization measurements and electron probe microchemical analysis (EPMA) to examine the individual role of each layer and the change of the microstructure with time.

  13. Thermal fatigue durability for advanced propulsion materials

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.

    1989-01-01

    A review is presented of thermal and thermomechanical fatigue (TMF) crack initiation life prediction and cyclic constitutive modeling efforts sponsored recently by the NASA Lewis Research Center in support of advanced aeronautical propulsion research. A brief description is provided of the more significant material durability models that were created to describe TMF fatigue resistance of both isotropic and anisotropic superalloys, with and without oxidation resistant coatings. The two most significant crack initiation models are the cyclic damage accumulation model and the total strain version of strainrange partitioning. Unified viscoplastic cyclic constitutive models are also described. A troika of industry, university, and government research organizations contributed to the generation of these analytic models. Based upon current capabilities and established requirements, an attempt is made to project which TMF research activities most likely will impact future generation propulsion systems.

  14. Damage Accumulation and Failure of Plasma-Sprayed Thermal Barrier Coatings under Thermal Gradient Cyclic Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Choi, Sung R.; Ghosn, Louis J.; Miller, rober A.

    2005-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. A fundamental understanding of the sintering and thermal cycling induced delamination of thermal barrier coating systems under engine-like heat flux conditions will potentially help to improve the coating temperature capability. In this study, a test approach is established to emphasize the real-time monitoring and assessment of the coating thermal conductivity, which can initially increase under the steady-state high temperature thermal gradient test due to coating sintering, and later decrease under the thermal gradient cyclic test due to coating cracking and delamination. Thermal conductivity prediction models have been established for a ZrO2-(7- 8wt%)Y2O3 model coating system in terms of heat flux, time, and testing temperatures. The coating delamination accumulation is then assessed based on the observed thermal conductivity response under the combined steady-state and cyclic thermal gradient tests. The coating thermal gradient cycling associated delaminations and failure mechanisms under simulated engine heat-flux conditions will be discussed in conjunction with the coating sintering and fracture testing results.

  15. Mechanical and tribological properties of thermally sprayed tungsten carbide-cobalt coatings

    NASA Astrophysics Data System (ADS)

    Qiao, Yunfei

    Since previous work in our laboratory has shown that very fine microstructures increase the hardness and the resistance to sliding and abrasive wear of bulk, sintered, WC/Co composites, it was decided to explore whether similar benefits can be obtained in coatings of this material deposited by the Thermal Spray Method. The research was a collaborative effort in which a number of companies and universities prepared feedstock powders by a number of methods and deposited coatings by Plasma Spray and High Velocity Oxy Fuel spray techniques. Our role was to study the resistance of these coatings to abrasion and to wear in unlubricated sliding, to relate our findings to the microstructure of the coatings and to the properties of the powder and the parameters of deposition. The results were then used by our partners in the program to modify their processes in order to obtain the best possible performance. The thesis consists of four parts. In the first, we review the literature on WC/Co coatings and present the results of our survey of 45 coatings. This shows that the details of the thermal spray technique determine the tribological performance of the coatings much more than the size of the WC grains in the starting powder. It also shows that abrasive and sliding wear respond differently to the material properties. The remainder of the thesis describes a systematic variation of powders and deposition techniques, based on our earlier findings. In the second part, we describe the microstructures, hardness and toughness of nine coatings deposited by A. Dent at SUNY Stony Brook, with three different powders and three different flame chemistries. We find that the hardness is determined mainly by the flame temperature; hardness is decreased by porosity on the 50-nm size range, and this porosity is produced by insufficient melting of the Co binder. High temperatures and certain powder morphologies cause extensive decarburization, and the latter reduces the adhesion between the

  16. Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)

    SciTech Connect

    Not Available

    2010-08-01

    Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.

  17. Analysis of Plasma-Sprayed Thermal Barrier Coatings With Homogeneous and Heterogeneous Bond Coats Under Spatially Uniform Cyclic Thermal Loading

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Pindera, Marek-Jerzy; Aboudi, Jacob

    2003-01-01

    This report summarizes the results of a numerical investigation into the spallation mechanism in plasma-sprayed thermal barrier coatings observed under spatially-uniform cyclic thermal loading. The analysis focuses on the evolution of local stress and inelastic strain fields in the vicinity of the rough top/bond coat interface during thermal cycling, and how these fields are influenced by the presence of an oxide film and spatially uniform and graded distributions of alumina particles in the metallic bond coat aimed at reducing the top/bond coat thermal expansion mismatch. The impact of these factors on the potential growth of a local horizontal delamination at the rough interface's crest is included. The analysis is conducted using the Higher-Order Theory for Functionally Graded Materials with creep/relaxation constituent modeling capabilities. For two-phase bond coat microstructures, both the actual and homogenized properties are employed in the analysis. The results reveal the important contributions of both the normal and shear stress components to the delamination growth potential in the presence of an oxide film, and suggest mixed-mode crack propagation. The use of bond coats with uniform or graded microstructures is shown to increase the potential for delamination growth by increasing the magnitude of the crack-tip shear stress component.

  18. Microstructure and mechanical properties of ceramic and metallic thermal spray coatings

    NASA Astrophysics Data System (ADS)

    Racek, Ondrej

    Within the present work microstructure and mechanical properties of thermal spray coatings will be discussed with an emphasis on thermal barrier coating applications. Yttria stabilized zirconia is a commonly used material for thermal barrier coatings. The potential of a novel nanostructured feedstock material was investigated and the properties compared to a conventional feedstock material. Thermal spray coatings consist of a complex structure of interlocked particles, pores and cracks and the coating microstructure directly influences the mechanical properties. It is necessary for the coating to be tolerant to strain that is evolving, for example, from thermal expansion mismatch. Porous microstructures lower coating stiffness and also increase the ability to endure irreversible deformation by microcracking. The novel nanostructured feedstock microstructure consists of partially molten particles that form agglomerates where a large fraction of the pores are of size less than 1 mum in diameter. The effect of the deposition process and its parameters on the microstructure and hardness was studied. The porosity was determined by image analysis and correlated to the measured hardness. Selected samples were extensively studied using a depth sensitive indentation technique. Elastic modulus and hardness were primarily investigated; however, also fracture behavior is reported and discussed. Coating mechanical properties are directly associated with the resistance to damage caused by mechanical forces. The processes that primarily damage the coating surface include abrasion, erosion, and sliding wear as well as cavitation. However, mechanical interaction with the surface also affects the material to a depth that is related to the extent of the stress field. Mechanical processes, such as plastic deformation associated with Hertzian spherical contact, may initiate failure under the surface. Mechanical stresses that act within the coating originate from external mechanical

  19. High-temperature sulfidation of Fe{sub 3}Al thermal spray coatings at 600 C

    SciTech Connect

    Luer, K.R.; DuPont, J.N.; Marder, A.R.

    2000-02-01

    Sulfidation behavior of Fe{sub 3}Al thermal spray coatings was studied in Ar-3.5% H{sub 2}-0.1{degree} hydrogen sulfide (H{sub 2}S) at 600 C for 500 h. Coatings were processed from the same lot of gas atomized Fe{sub 3}Al powder using a high-velocity oxygen fuel (HVOF) process and an air plasma spray (APS) process. In general, the Fe{sub 3}Al-type composition displayed excellent resistance to sulfidation corrosion at 600 C, which correlated with the reported literature on wrought Fe{sub 3}Al alloys. However, the method of processing affected the corrosion response. Particle degradation and porosity were two important factors that affected corrosion resistance. HVOF processing did not degrade significantly the composition of the powder and produced coatings with low porosity, low oxide content, high sulfidation resistance, and high resistance to sulfur penetration. HVOF coatings produced from finer sized powders exhibited slightly more corrosion damage because a greater percentage of the consumable was degraded. In contrast, APS processing caused significant degradation to the consumable and created coatings with a significant quantity of alloy-depleted regions, high oxide content, and high porosity. As a result, sulfur attached alloy-depleted regions within the splats and permeated through the porous splat boundaries to the coating-substrate interface.

  20. Development of Thermal Spraying and Coating Techniques by Using Thixotropic Slurries Including Metals and Ceramics Particles

    NASA Astrophysics Data System (ADS)

    Kirihara, S.; Itakura, Y.; Tasaki, S.

    2013-03-01

    Thermal nanoparticles coating and microlines patterning were newly developed as novel technologies to fabricate fine ceramics layers and geometrical intermetallics patterns for mechanical properties modulations of practical alloys substrates. Nanometer sized alumina particles were dispersed into acrylic liquid resins, and the obtained slurries were sputtered by using compressed air jet. The slurry mists could blow into the arc plasma with argon gas spraying. On stainless steels substrates, the fine surface layers with high wear resistance were formed. In cross sectional microstructures of the coated layers, micromater sized cracks or pores were not observed. Subsequently, pure aluminum particles were dispersed into photo solidified acrylic resins, and the slurry was spread on the stainless steel substrates by using a mechanical knife blade. On the substrates, microline patterns with self similar fractal structures were drawn and fixed by using scanning of an ultra violet laser beam. The patterned pure metal particles were heated by the argon arc plasma spray assisting, and the intermetallics or alloys phases with high hardness were created through reaction diffusions. Microstructures in the coated layers and the patterned lines were observed by using a scanning electron microscopy.

  1. Silicate-Based Thermal Spray Coatings for Environmental Protection of Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Sagiv, Ari Isaac

    Environmental barrier coatings are a key technology for implementing ceramics in high-temperature, high-moisture environments. One such ceramic, silicon carbide, is a material that can be used in gas turbines. However, silicon carbide oxidizes into silicon dioxide with exposure to oxygen, carbon dioxide, and water vapor and would normally provide protection for the silicon carbide. However, silicon dioxide volatilizes in a gas turbine environment, which leads to the degradation of its mechanical properties, making it unfit for use in a gas turbine. Materials like yttria-monosilicate and barium-strontium doped aluminosilicate (BSAS) both have good environmental coating properties. However, sintered yttria-monosilicate does not bond well to silicon carbide, and thermally sprayed BSAS transforms very slowly from a metastable hexacelsian phase to the desired celsian phase that is necessary for it to bond well to silicon carbide. Coatings of these materials have been produced by plasma spray with some additional work using HVOF. Phase identification has been done by x-ray diffraction, and microstructural analysis has been done using scanning electron microscopy.

  2. Nonlinear Behavior in Compression and Tension of Thermally Sprayed Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Kroupa, F.

    2007-03-01

    Mechanical properties of thermally sprayed coatings, especially of ceramics, are strongly influenced by a high density of mesoscopic defects, microcracks of dimensions between fractions of μm up to tens of μm. The anisotropic linear elastic stress-strain relations are valid only at very low deformations, e.g., | e| < 0.05%, with small values of Young’s moduli due to elastic openings and elastic partial closings of microcracks. At higher deformations, e.g., 0.05% < | e| < 0.4%, the stress-strain relations are strongly nonlinear. Under compressive stresses, elastic closing of microcracks leads to a gradual decrease of the microcrack density and to an increase of Young’s modulus in compression. Under tensile stresses, the microcracks slightly grow by inelastic processes; the microcrack density gradually increases and effective Young’s modulus in tension decreases. A two-parametric equation containing linear and quadratic terms is used to describe the nonlinear stress-strain curves of plasma-sprayed ceramic coatings. The effect of nonlinearity on the bending of beams with coatings and the nonlinear combination of external and residual stresses are discussed. The fracture of coatings at higher tensile stresses due to coalescence of the microcracks is mentioned.

  3. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    Matthew T. Kiser

    2002-01-01

    In the fourth quarter, more pressure casting trials on steel/WC-Co composite were carried out. In addition, initial trials on steel/Al{sub 2}O{sub 3} composite were started. The effects of processing parameters on infiltration process were investigated. It was found the quality of infiltration was determined by wettability of the liquid steel on hard particles, preheating temperature of the die, pouring temperature, and applied pressure. From the preliminary study on pressure casting of steel/Al{sub 2}O{sub 3} composites, little infiltration was observed because of poor wetting and rapid solidification of liquid steel. UC Santa Barbara was able to make a steel/Al{sub 2}O{sub 3} composite in a hot isostatic press which will be used to evaluate the viability of this composite system. For thermal spray coatings, another round of coupons were sprayed for arc-lamp processing trials at Oak Ridge National Lab. Low stress scratching wear measurements at Albany Research Center on coupons from the previous arc-lamp trial demonstrated that the coatings had 3-10X higher abrasive wear resistance than Brinell 500 abrasion resistant plate. An overview of the progress during the 4th quarter of this project is given below. Research details are provided in the limited rights appendix to this report.

  4. Characterization of Thermal Sprayed Aluminum and Stainless Steel Coatings for Clean Laser Enclosures

    SciTech Connect

    Chow, R; Decker, T A; Gansert, R V; Gansert, D

    2000-04-06

    Surfaces of steel structures that enclose high-fluence, large-beam lasers have conventional and unconventional requirements. Aside from rust prevention, the surfaces must resist laser-induced degradation and the contamination of the optical components. The latter requires a surface that can be precision cleaned to low levels of particulate and organic residue. In addition, the surface treatment for the walls should be economical to apply because of the large surface areas involved, and accommodating with intricate joint geometries. Thermal sprayed coatings of aluminum (Al) and stainless steel are candidate surface materials. Coatings are produced and characterized for porosity, smoothness, and hardness. These properties have a bearing on the cleanliness of the coating. The laser resistance of Al and 3 16L coatings are given. The paper summarizes the characterization of twin-wire-arc deposited Al, high-velocity-oxygen-fueled (HVOF) deposited Al, flame-sprayed 316L, and HVOF deposited316L. The most promising candidate coating is that of HVOF Al. This Al coating has the lowest porosity (8%) compared the other three coatings and relatively low hardness (100 VHN). The as-deposited roughness (Ra) is 433 pinches, but after a quick sanding by hand, the roughness decreased to 166 pinches. Other post-coat treatments are discussed. HVOF aluminum coatings are demonstrated. Al coatings are corrosion barriers for steel, and this work shows promising resistance to laser damage and low particulation rates.

  5. Computational fluid dynamic analysis of a High-Velocity Oxygen-Fuel (HVOF) thermal spray torch

    SciTech Connect

    Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1995-09-01

    The gas dynamics of a High-Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamics (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is assumed to be axisymmetric with premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. The aircap, a cronically converging nozzle, achieves choked flow conditions at the exit and a supersonic, under-expanded jet develops externally. Finite difference equations for mass, momentum, and energy conservation are solved for the gas dynamics. The combustion process is modeled using a single-step and a 12-step quasi-global finite-rate chemistry model with dissociation of the gas and a total of nine species. Turbulent flow inside the aircap and in the free-jet decay is modeled using a two-equation k-{epsilon} model. An iterative, implicit, finite volume numerical method is used to solve the gas dynamic equations inside and outside the torch . The CFD results are compared with recent experimental measurements of pressure inside the HVOF aircap. Comparisons are made for two flow rates of premixed fuel and oxygen and air cooling. This paper presents the first published comparisons of CFD predictions and experimental measurements for HVOF tbermal spraying.

  6. Study of thermal and electrical parameters of workpieces during spray coating by electrolytic plasma jet

    NASA Astrophysics Data System (ADS)

    Khafizov, A. A.; Shakirov, Yu I.; Valiev, R. A.; Valiev, R. I.; Khafizova, G. M.

    2016-01-01

    In this paper the results are presented of thermal and electrical parameters of products in the system bottom layer - intermediate layer when applying protective coatings of ferromagnetic powder by plasma spray produced in an electric discharge with a liquid cathode, on steel samples. Temperature distribution and gradients in coating and intermediate coating were examined. Detailed descriptions of spray coating with ferromagnetic powder by plasma jet obtained in electrical discharge with liquid cathode and the apparatus for obtaining thereof is provided. Problem has been solved by using of Fourier analysis. Initial data for calculations is provided. Results of numerical analysis are provided as temporal functions of temperature in contiguity between coating and intermediate coating as well as temporal function of the value Q=q-φ where q is density of heat current directed to the free surface of intermediate coating, φ is density of heat current in contiguity between coating and intermediate coating. The analysis of data given shows that in the systems of contact heat exchange bottom layer-intermediate layer with close values of the thermophysical characteristics of constituting materials is observed a slow increase of the temperature of the contact as a function of time.

  7. Evaluation of excipients for enhanced thermal stabilization of a human type 5 adenoviral vector through spray drying.

    PubMed

    LeClair, Daniel A; Cranston, Emily D; Xing, Zhou; Thompson, Michael R

    2016-06-15

    We have produced a thermally stable recombinant human type 5 adenoviral vector (AdHu5) through spray drying with three excipient formulations (l-leucine, lactose/trehalose and mannitol/dextran). Spray drying leads to immobilization of the viral vector which is believed to prevent viral protein unfolding, aggregation and inactivation. The spray dried powders were characterized by scanning electron microscopy, differential scanning calorimetry, Karl Fischer titrations, and X-ray diffraction to identify the effects of temperature and atmospheric moisture on the immobilizing matrix. Thermal stability of the viral vector was confirmed in vitro by infection of A549 lung epithelial cells. Mannitol/dextran powders showed the greatest improvement in thermal stability with almost no viral activity loss after storage at 20°C for 90days (0.7±0.3 log TCID50) which is a significant improvement over the current -80°C storage protocol. Furthermore, viral activity was retained over short term exposure (72h) to temperatures as high as 55°C. Conversely, all powders exhibited activity loss when subjected to moisture due to amplified molecular motion of the matrix. Overall, a straightforward method ideal for the production of thermally stable vaccines has been demonstrated through spray drying AdHu5 with a blend of mannitol and dextran and storing the powder under low humidity conditions. PMID:27130366

  8. A particle temperature sensor for monitoring and control of the thermal spray process

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.

    1995-12-01

    The temperature and velocity of thermally sprayed particles prior to their impact on the substrate are two of the predominant determinants of coating quality and characteristics. This paper describes an instrument developed for real time monitoring of in-flight particle temperature in an industrial environment. The instrument is designed to operate as a stand alone device for verifying that a desired particle temperature is attained or for developing process settings to yield a particular temperature. The device is also suitable for incorporation into a closed loop process controller. Data showing the relationship between torch parameters and average particle temperature are presented. There is good agreement between previous measurements using laboratory instrumentation and the simpler, industrially hardened technique described here. The assumption of gray body behavior is evaluated and for known emissivities corrections are developed.

  9. Application of thermal spray coatings for 304 SS SCC mitigation in high temperature water

    SciTech Connect

    Kim, Y.J.; Andresen, P.L.

    1998-12-31

    The thermal spray coating technique was applied to produce the catalytic or insulated protective coatings on 304 stainless steel (SS) surface. The electrochemical corrosion potential (ECP) response of such coatings in high temperature water under various water chemistry conditions were evaluated. The ECP results clearly demonstrated that the catalytic coatings (CC) produced with various alloy powders containing small amounts of Pd responded fully catalytically in the presence of the stoichiometric excess hydrogen, showing a ECP value well below the intergranular stress corrosion cracking (IGSCC) protection potential ({minus}230 mV{sub she}). Furthermore, the insulated protective coating (IPC) layer created with a powder of yttria-stabilized zirconia (YSZ) restricted the oxidant transport rate to the metal surface, and the ECP remained at <{minus}300 mV{sub she} in 288 C water containing to 200--300 ppb oxygen (O{sub 2}) and no hydrogen (H{sub 2}).

  10. Characterization of Thermal Spray Coatings for Cylinder Running Surfaces of Diesel Engines

    NASA Astrophysics Data System (ADS)

    Hahn, Mareike; Fischer, Alfons

    2010-09-01

    Future demands of diesel engines are about low-friction and wear-resistant materials in order to increase the efficiency and achieve environmentally sound solutions. Thus, thermally sprayed Fe-base coatings are investigated for application as cylinder running surfaces in cast aluminum crankcases. They should allow the desired combination of structural, productional, and topographical properties required in Diesel engines. To understand the influence of the characteristic microstructures on the integrity of the composites the coatings have to be examined in laboratory tests in terms of different loading situations. Cavitation tests were carried out where the tribological stability of these coatings and their ability to resist high-frequency cyclic impact stresses are revealed. Composite samples (base material and coating) were investigated in terms of crack initiation in a scanning electron microscope with an in situ 3-point-bending test. The endurance under cyclic mechanical stresses was tested with a 4-point-bending stress controlled test.

  11. Analysis of gas flow evolution and shock wave decay in detonation thermal spraying systems

    NASA Astrophysics Data System (ADS)

    Ramadan, K.; Butler, P. Barry

    2004-06-01

    The reactive Euler equations with variable gas properties are solved in both axisymmetric and plane two-dimensional flows to analyze the gas flow evolution, shock wave decay, and shock reflections in pulsed detonation thermal spraying (PDTS) systems. The gas phase governing equations are numerically solved using a high-resolution shock capturing numerical method. Expansion-compression waves are formed upon external gas expansion and persist for a long time (on the time scale of a PDTS cycle) with wide fluctuations in the gas velocity and temperature. The results show that the reflected shock wave from the substrate dies out extremely fast that micron-sized particles used in PDTS do not encounter these transients. The external shock wave decay is also analyzed for different reactive mixtures and flow geometries and is related to the truncation of the computational domain and the implementation of numerical boundary conditions at the open end boundaries.

  12. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2010-01-01

    An apparatus and method [or thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such a Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air. and a spark. Metal is inserted continuously in a high volume of meta1 into a combustion chamber of the pulsejet. The combustion is thereafter. controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tail pipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  13. Creep of plasma-sprayed-ZrO2 thermal-barrier coatings

    NASA Technical Reports Server (NTRS)

    Firestone, R. F.; Logan, W. R.; Adams, J. W.; Bill, R. C., Jr.

    1982-01-01

    Specimens of plasma-sprayed-zirconia thermal-barrier coatings with three different porosities and different initial particle sizes were deformed in compression at initial loads of 6900, 13,800, and 24,100 kPa (1000, 2000, and 3500 psi) and temperatures of 1100, 1250, and 1400 C. The coatings were stabilized with lime, MgO, and two different concentrations of Y2O3. Creep began as soon as the load was applied and continued at a constantly decreasing rate until the load was removed. Temperature and stabilization had a pronounced effect on creep rate while the stress, particle size, and porosity had a lesser effect. Creep deformation was due to cracking and particle sliding.

  14. Aerodynamic study on supersonic flows in high-velocity oxy-fuel thermal spray process

    NASA Astrophysics Data System (ADS)

    Katanoda, Hiroshi; Matsuoka, Takeshi; Kuroda, Seiji; Kawakita, Jin; Fukanuma, Hirotaka; Matsuo, Kazuyasu

    2005-06-01

    To clarify the characteristics of gas flow in high velocity oxy-fuel (HVOF) thermal spray gun, aerodynamic research is performed using a special gun. The gun has rectangular cross-sectional area and sidewalls of optical glass to visualize the internal flow. The gun consists of a supersonic nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. Compressed dry air up to 0.78 MPa is used as a process gas instead of combustion gas which is used in a commercial HVOF gun. The high-speed gas flows with shock waves in the gun and jets are visualized by schlieren technique. Complicated internal and external flow-fields containing various types of shock wave as well as expansion wave are visualized.

  15. Hydrophilicity Characteristics of Thermal Sprayed Coating Produced Using Calcination Powders Recovered from Waste Dry Batteries

    NASA Astrophysics Data System (ADS)

    Futamata, Masami; Nakanishi, Kimio; Itoh, Hidenobu; Ohnishi, Nobuhiro

    A ceramic coating with super hydrophilicity characteristics (the contact angle θ=0°) was prepared by the thermal spraying technique using calcinations powders recovered from the waste dry batteries (IZC). Evaporation behavior and evaporation time of a water droplet for the IZC coatings on a mild steel substrate were examined. It was found that the water droplet did not show the Leidenfrost phenomenon on the IZC coatings surface, and the evaporation time remarkably shortened compared with those on the grinding or blasted surfaces of the mild steel substrate. On the other hand, the cooling speed in soaking the heated test piece in boiling water was examined. The cooling speed of the IZC coated substrate remarkably increases in the initial stage, since it changes from film boiling to nucleate boiling. These facts suggest that the IZC coatings are effective for improvement in the evaporation and cooling speed.

  16. Bond strength of thermal-sprayed zinc on concrete during early electrochemical aging

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S. Jr.; Holcomb, Gordon R.; Cramer, Stephen D.; McGill, G.E.

    1997-01-01

    The Albany Research Center, in collaboration with the Oregon Department of Transportation, is studying changes in the bond strength of thermal-sprayed zinc anodes on reinforced concrete during the early stages of electrochemical aging in impressed current cathodic protection (CP) systems where the zinc surface was not wetted. The bond strength of the zinc to the concrete decreased more rapidly with electrochemical aging when the zinc surface was not wetted than when wetted. The zinc-concrete interfacial chemistry for samples not wetted showed a greater buildup of chlorides and only weak evidence of secondary mineralization. pH at the zinc-concrete interface was around 7, which was similar to that measured for wetted surfaces. pH at the steel-concrete interface did not change on aging, remained strongly basic, and was similar to that for wetted samples.

  17. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    D. Trent Weaver; Matthew T. Kiser

    2003-07-01

    In the 10th quarter no further work was conducted on the steel matrix composite element of this project. For this element work is effectively complete and all that remains is the composition of the final report. For the thermal spray coating effort, components coated and fused in the previous quarter were subject to high stress abrasive wear testing. Some complications were encountered with the wear testing, but the tests which were completed successfully showed that the coatings provided wear resistance 5x that of the baseline material. Further wear testing is planned for the 11th and final quarter. An overview of the progress during the 10th quarter of this project is given below. Additional research details are provided in the limited rights appendix to this report.

  18. Anisotropic Mechanical Properties of Plasma-Sprayed Thermal Barrier Coatings at High Temperature Determined by Ultrasonic Method

    NASA Astrophysics Data System (ADS)

    Wei, Qin; Zhu, Jianguo; Chen, Wei

    2016-02-01

    The mechanical properties of plasma-sprayed thermal barrier coatings (TBC) are of great scientific and technological significance for the design and fabrication of TBC systems. The ultrasonic method combined with a sing-around method for mechanical properties measurement of TBC is deduced and the elastic modulus can be determined in the spray, or longitudinal, direction, and the transverse direction. Tested specimens of plasma-sprayed TBC are detached from the substrate and treated with thermal exposure at 1400 °C. The elastic moduli along the longitudinal and transverse directions of the TBCs are measured by different types of ultrasonic waves combined with a sing-around method, while the Poisson's ratio is also obtained simultaneously. The experimental results indicate that the magnitude of longitudinal elastic modulus is larger than that of the transverse one, and thus the plasma-sprayed TBC has an anisotropic mechanical property. Moreover, the elastic moduli along both longitudinal and transverse directions change with high-temperature exposure time, which consists of a rapid increasing stage followed by a slow decreasing stage. In addition, the magnitude of Poisson's ratio increases slightly from 0.05 to 0.2 with the high-temperature exposure time. Generally, the microstructures in the plasma-sprayed coatings and their evolution in a high-temperature environment are the main causes of the varying anisotropic mechanical properties.

  19. Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Schmitt, Michael P.; Rai, Amarendra K.; Zhu, Dongming; Dorfman, Mitchell R.; Wolfe, Douglas E.

    2015-01-01

    To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability.

  20. Improved Oxidation Life of Segmented Plasma Sprayed 8YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Smialek, James L.

    2004-03-01

    Unconventional plasma sprayed thermal barrier coating (TBC) systems were produced and evaluated by interrupted or cyclic furnace oxidation life testing. First, approximately 250 µm thick 8YSZ coatings were directly sprayed onto grit blasted surfaces of PWA 1484, without a bond coat, to take advantage of the excellent oxidation resistance of this superalloy. For nominal sulfur (S) contents of 1 ppmw, total coating separation took place at relatively short times (200 h at 1100°C). Reductions in the S content, by melt desulfurization commercially (0.3 ppmw) or by hydrogen (H2) annealing in the laboratory (0.01 ppmw), improved scale adhesion and extended life appreciably, by factors of 5-10. However, edge-initiated failure persisted, producing massive delamination as one sheet of coating. Secondly, surfaces of melt desulfurized PWA 1484 were machined with a grid of grooves or ribs (˜250 µm wide and high), resulting in a segmented TBC surface macrostructure, for the purpose of subverting this failure mechanism. In this case, failure occurred only as independent, single-segment events. For grooved samples, 1100 °C segment life was extended to ˜1000h for 5 mm wide segments, with no failure observed out to 2000 h for segments ≤2.5 mm wide. Ribbed samples were even more durable, and segments ≤6 mm remained intact for 2000 h. Larger segments failed by buckling at times inversely related to the segment width and decreased by oxidation effects at higher temperatures. This critical buckling size was consistent with that predicted for elastic buckling of a TBC plate subject to thermal expansion mismatch stresses. Thus, low S substrates demonstrate appreciable coating lives without a bond coat, while rib segmenting extends life considerably.

  1. Microstructures and Thermal Properties of Cold-Sprayed Cu-Cr Composite Coatings

    NASA Astrophysics Data System (ADS)

    Kikuchi, S.; Yoshino, S.; Yamada, M.; Fukumoto, M.; Okamoto, K.

    2013-08-01

    Copper-based composites for thermal conductive components were prepared via the cold spray process, and the deposition efficiency and adhesion morphology of feedstock powders on Cu substrate were evaluated. Cu-based composites were fabricated using Cu-Cr mixed powders with their mixture ratio of 20, 35, 50, and 65 mass% Cr onto oxygen-free copper substrate with N2 carrier gas. Cu-Cr composite coatings were investigated for their Cr content ratio, microstructures, and thermal conductivity. The Cr content ratio in the coating was approximately 50-60% of feedstock mixture ratio due to the low formability of the hard particles. Transmission electron microscopy characterizations revealed that an oxygen-rich layer exists at the Cr particle/Cu substrate interface, which contributes to the deposition of the Cr particles. After the heat treatment at 1093 K, the coatings showed denser cross-sectional structures than those before the heat treatment, and the thermal conductivity was improved as a result of the recrystallization of Cu matrix.

  2. Plasma-Sprayed Thermal Barrier Coatings with Enhanced Splat Bonding for CMAS and Corrosion Protection

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Yao, Shu-Wei; Wang, Li-Shuang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2016-01-01

    The infiltration of molten CMAS in thermal barrier coatings (TBCs) at high temperature is significantly affected by the microstructure of the ceramic coating. Enhancing the bonding ratio between splats can reduce the interconnected pores and suppress the infiltration of the molten CMAS into the coating. In this study, a dual-layered (DL) TBC with the dense 8YSZ on the top of the conventional porous 8YSZ was proposed to enhance CMAS corrosion of atmospheric plasma-sprayed YSZ. The dense YSZ coating with improved lamellar bonding was deposited at a higher deposition temperature. The microstructure of the coatings before and after CMAS attack test was characterized by scanning electron microscopy. It was clearly revealed that by adjusting the microstructure and applying a dense ceramic layer with the improved interface bonding on the top of porous TBC, the infiltration of CMAS into porous YSZ coating can be effectively suppressed. Moreover, by designing DL TBCs, the thermal conductivity of the TBC system exhibits a limited increase. Thus with the design of DL structure, the TBCs with high CMAS corrosion resistance and low thermal conductivity can be achieved.

  3. In-flight particle pyrometer for thermal spray processes. Final report, October 1, 1992--December 31, 1994

    SciTech Connect

    1995-02-20

    The objective of the project was to produce an industrial hardened particle temperature sensor. In general the thermal spray community believes that the particle temperature and velocity prior to impact on the substrate are two of the predominant parameters which effect coating quality. Prior to the full scale prototyping of such an instrument it was necessary to firmly establish the relationship between operating parameters, particle temperature and coating characteristics. It was shown in the first year of this project that the characteristics and consistency of the coatings formed are directly determined by particle velocity and temperature at impact. For the HVOF spray process the authors have also shown that the particle velocity is determined primarily by chamber pressure, while stoichiometry (the ratio of oxygen to fuel) has a minor influence. Hence, particle velocity can be controlled by maintaining the chamber pressure at a set point. Particle temperature, on the other hand is primarily a function of stoichiometry. Therefore particle velocity and temperature can be independently controlled. In the second year (FY-94), an industrial hardened prototype particle temperature sensor (In-flight Particle Pyrometer) was produced. The IPP is a two-color radiation pyrometer incorporating improvements which make the device applicable to the measurement of in-flight temperature of particles over a wide range of operating conditions in thermal spray processes. The device is insensitive to particulate loading (particle feed rate), particle composition, particle size distribution, and provides an ensemble average particle temperature. The sensor head is compact and coupled to the electronics via a fiber optic cable. Fiber optic coupling allows maximum flexibility of deployment while providing isolation of the electronics from electromagnetic interference and the hot, particulate laden environment of a typical spray booth. The device is applicable to all thermal spray

  4. Plasma-Spraying Ceramics Onto Smooth Metallic Substrates

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Brindley, William J.; Rouge, Carl J.; Leissler, George

    1992-01-01

    In fabrication process, plasma-sprayed ceramic coats bonded strongly to smooth metallic surfaces. Principal use of such coats in protecting metal parts in hot-gas paths of advanced gas turbine engines. Process consists of application of initial thin layer of ceramic on smooth surface by low-pressure-plasma spraying followed by application of layer of conventional, low-thermal-conductivity atmospheric-pressure plasma-sprayed ceramic.

  5. X-ray photoelectron spectroscopy study of the passive films formed on thermally sprayed and wrought Inconel 625

    NASA Astrophysics Data System (ADS)

    Bakare, M. S.; Voisey, K. T.; Roe, M. J.; McCartney, D. G.

    2010-11-01

    There is a well known performance gap in corrosion resistance between thermally sprayed corrosion resistant coatings and the equivalent bulk materials. Interconnected porosity has an important and well known effect, however there are additional relevant microstructural effects. Previous work has shown that a compositional difference exists between the regions of resolidified and non-melted material that exist in the as-sprayed coatings. The resolidified regions are depleted in oxide forming elements due to formation of oxides during coating deposition. Formation of galvanic cells between these different regions is believed to decrease the corrosion resistance of the coating. In order to increase understanding of the details of this effect, this work uses X-ray photoelectron spectroscopy (XPS) to study the passive films formed on thermally sprayed coatings (HVOF) and bulk Inconel 625, a commercially available corrosion resistant Ni-Cr-Mo-Nb alloy. Passive films produced by potentiodynamic scanning to 400 mV in 0.5 M sulphuric acid were compared with air-formed films. The poorer corrosion performance of the thermally sprayed coatings was attributed to Ni(OH) 2, which forms a loose, non-adherent and therefore non-protective film. The good corrosion resistance of wrought Inconel 625 is due to formation of Cr, Mo and Nb oxides.

  6. Advanced Vacuum Plasma Spray (VPS) for a Robust, Longlife and Safe Space Shuttle Main Engine (SSME)

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Elam, Sandra K.; McKechnie, Timothy N.; Power, Christopher A.

    2010-01-01

    In 1984, the Vacuum Plasma Spray Lab was built at NASA/Marshall Space Flight Center for applying durable, protective coatings to turbine blades for the space shuttle main engine (SSME) high pressure fuel turbopump. Existing turbine blades were cracking and breaking off after five hot fire tests while VPS coated turbine blades showed no wear or cracking after 40 hot fire tests. Following that, a major manufacturing problem of copper coatings peeling off the SSME Titanium Main Fuel Valve Housing was corrected with a tenacious VPS copper coating. A patented VPS process utilizing Functional Gradient Material (FGM) application was developed to build ceramic lined metallic cartridges for space furnace experiments, safely containing gallium arsenide at 1260 degrees centigrade. The VPS/FGM process was then translated to build robust, long life, liquid rocket combustion chambers for the space shuttle main engine. A 5K (5,000 Lb. thrust) thruster with the VPS/FGM protective coating experienced 220 hot firing tests in pristine condition with no wear compared to the SSME which showed blanching (surface pulverization) and cooling channel cracks in less than 30 of the same hot firing tests. After 35 of the hot firing tests, the injector face plates disintegrated. The VPS/FGM process was then applied to spraying protective thermal barrier coatings on the face plates which showed 50% cooler operating temperature, with no wear after 50 hot fire tests. Cooling channels were closed out in two weeks, compared to one year for the SSME. Working up the TRL (Technology Readiness Level) to establish the VPS/FGM process as viable technology, a 40K thruster was built and is currently being tested. Proposed is to build a J-2X size liquid rocket engine as the final step in establishing the VPS/FGM process TRL for space flight.

  7. Preliminary study of cyclic thermal shock resistance of plasma-sprayed zirconium oxide turbine outer air seal shrouds

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Wisander, D. W.

    1977-01-01

    Several experimental concepts representing potential high pressure turbine seal material systems were subjected to cyclic thermal shock exposures similar to those that might be encountered under severe engine start-up and shut-down sequences. All of the experimental concepts consisted of plasma-sprayed yttria stabilized ZrO2 on the high temperature side of the blade tip seal shroud. Between the ZrO2 and a cooled, dense metal backing, various intermediate layer concepts intended to mitigate thermal stresses were incorporated. Performance was judged on the basis of the number of thermal shock cycles required to cause loss of seal material through spallation. The most effective approach was to include a low modulus, sintered metal pad between the ZrO2 and the metallic backing. It was also found that reducing the density of the ZrO2 layer significantly improved the performance of specimens with plasma-sprayed metal/ceramic composite intermediate layers.

  8. Advances in hypersonic vehicle synthesis with application to studies of advanced thermal protection system

    NASA Technical Reports Server (NTRS)

    Ardema, Mark D.

    1995-01-01

    This report summarizes the work entitled 'Advances in Hypersonic Vehicle Synthesis with Application to Studies of Advanced Thermal Protection Systems.' The effort was in two areas: (1) development of advanced methods of trajectory and propulsion system optimization; and (2) development of advanced methods of structural weight estimation. The majority of the effort was spent in the trajectory area.

  9. Effects of coating spray speed and convective heat transfer on transient thermal stress in thermal barrier coating system during the cooling process of fabrication

    NASA Astrophysics Data System (ADS)

    Song, Yan; Lv, Zhichao; Liu, Yilun; Zhuan, Xin; Wang, T. J.

    2015-01-01

    The coating spray speed and the convective heat transfer have significant effects on transient thermal stress in TBCs (Thermal Barrier Coating system) during the cooling process of fabrication. In this work, a simplified analytical model is developed firstly, to predict the transient thermal stress in YSZ (ZrO2-8%Y2O3) coating and shear stress at the coating-substrate interface during the cooling process of fabrication. Then, based on this simplified model, the effects of coating spray speed which determines the initial temperature field of YSZ coating, and the convective heat transfer coefficient between YSZ coating and the environment on transient thermal stress in TBCs during the cooling process have been studied. The results indicate that the YSZ coating spray speed has a significant effect on the transient thermal stress in YSZ coating and the shear stress near the edge of YSZ-substrate interface; effect of convective heat transfer on the thermal stress is more significant when convective heat transfer coefficient is bigger enough, and for a given convective heat transfer the effect becomes smaller as the cooling down process going on.

  10. Failure of thick, low density air plasma sprayed thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Helminiak, Michael Aaron

    This research was directed at developing fundamental understandings of the variables that influence the performance of air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC). Focus was placed on understanding how and why each variable influenced the performance of the TBC system along with how the individual variables interacted with one another. It includes research on the effect of surface roughness of NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying, the interdiffusion behavior of bond coats coupled to commercial superalloys, and the microstructural and compositional control of APS topcoats to maximize the coating thicknesses that can be applied without spallation. The specimens used for this research were prepared by Praxair Surface Technologies and have been evaluated using cyclic oxidation and thermal shock tests. TBC performance was sensitive to bond coat roughness with the rougher bond coats having improved cyclic performance than the smoother bond coats. The explanation being the rough bond coat surface hindered the propagation of the delamination cracks. The failure mechanisms of the APS coatings were found to depend on a combination of the topcoat thickness, topcoat microstructure and the coefficient of thermal expansion (CTE) mismatch between the superalloy and topcoat. Thinner topcoats tended to fail at the topcoat/TGO interface due to bond coat oxidation whereas thicker topcoats failed within the topcoat due to the strain energy release rate of the thicker coating exceeding the fracture strength of the topcoat. Properties of free-standing high and conventional purity YSZ topcoats of both a lowdensity (LD) and dense-vertically fissure (DVF) microstructures were evaluated. The densification rate and phase evolution were sensitive to the YSZ purity and the starting microstructure. Increasing the impurity content resulted in enhanced sintering and phase decomposition rates, with the exception of the

  11. A New Type of Self-lubricated Thermal Spray Coatings: Liquid Lubricants Embedded in a Metal Matrix

    NASA Astrophysics Data System (ADS)

    Espallargas, N.; Armada, S.

    2015-01-01

    Oils and greases are commonly used for lubricating, rotating and sliding systems such as bearings, gears, connectors, etc. The maintenance of such lubricated systems in some applications where access is difficult (e.g., offshore wind farms and subsea equipment) increases the operational costs. In some cases, it can be thought that the use of solid lubricants (MoS2, PTFE, graphite, etc.) embedded in coatings could be a solution for such applications; however, the mechanical and dynamic conditions of most of the systems are not appropriate for solid lubricants. Despite this, solid lubricants such as PTFE and MoS2 have been largely employed in different industries, especially in those applications where liquid lubricants cannot be used and when the dynamic conditions allow for it. Self-lubricated coatings have been a major topic of interest in thermal spray in the last decades. Although the use of liquid lubricants is desirable whenever it is possible, limited research has been addressed toward the development of self-lubricated coatings containing liquid lubricants. One of the main reasons for this is due to the complexity of embedding liquid lubricant reservoirs inside the coating matrix. In the present work, a new type of liquid-solid self-lubricated coatings is presented, being the matrix a metal alloy. Three thermal spray techniques used were as follows: arc-spray, plasma spray, and HVOAF. The metal matrices were two stainless steel types and liquid lubricant-filled capsules with different liquid contents were used. No degradation of the capsules during spraying was observed and the coatings containing capsules were able to keep a low coefficient of friction. The optimal performance is found for the coatings obtained at the lowest spraying temperature and velocity.

  12. A New Type of Self-lubricated Thermal Spray Coatings: Liquid Lubricants Embedded in a Metal Matrix

    NASA Astrophysics Data System (ADS)

    Espallargas, N.; Armada, S.

    2014-09-01

    Oils and greases are commonly used for lubricating, rotating and sliding systems such as bearings, gears, connectors, etc. The maintenance of such lubricated systems in some applications where access is difficult (e.g., offshore wind farms and subsea equipment) increases the operational costs. In some cases, it can be thought that the use of solid lubricants (MoS2, PTFE, graphite, etc.) embedded in coatings could be a solution for such applications; however, the mechanical and dynamic conditions of most of the systems are not appropriate for solid lubricants. Despite this, solid lubricants such as PTFE and MoS2 have been largely employed in different industries, especially in those applications where liquid lubricants cannot be used and when the dynamic conditions allow for it. Self-lubricated coatings have been a major topic of interest in thermal spray in the last decades. Although the use of liquid lubricants is desirable whenever it is possible, limited research has been addressed toward the development of self-lubricated coatings containing liquid lubricants. One of the main reasons for this is due to the complexity of embedding liquid lubricant reservoirs inside the coating matrix. In the present work, a new type of liquid-solid self-lubricated coatings is presented, being the matrix a metal alloy. Three thermal spray techniques used were as follows: arc-spray, plasma spray, and HVOAF. The metal matrices were two stainless steel types and liquid lubricant-filled capsules with different liquid contents were used. No degradation of the capsules during spraying was observed and the coatings containing capsules were able to keep a low coefficient of friction. The optimal performance is found for the coatings obtained at the lowest spraying temperature and velocity.

  13. Microstructure and Wear Resistance of Fe-Based Amorphous Metallic Coatings Prepared by HVOF Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Wang, L.; He, D. Y.; Wang, F. C.; Liu, Y. B.

    2010-12-01

    Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were fabricated by means of high velocity oxygen fuel (HVOF) thermal spraying process. The microstructure and wear performance of the coatings were characterized simultaneously in this article. It is found that the coatings present a dense layered structure with the porosity below 1.5%. The coatings primarily consist of amorphous matrix and some precipitated nanocrystals, though a fraction of Fe-rich phases and oxide stringers also formed during deposited process. High thermal stability enables the amorphous coatings to work below 920 K temperature without crystallization. Depending on the structural advantage, the amorphous coatings exhibit high average microhardness of 997.3 HV0.2, and excellent wear resistance during dry frictional wear process. The dominant wear mechanism of amorphous coating under this condition is fatigue wear, leading to partial or entire flaking off of the lamellae. In addition, the appearance of oxidative wear accelerates the failure of fatigue wear.

  14. Characterization of thermally sprayed coatings for high-temperature wear-protection applications

    SciTech Connect

    Li, C.C.

    1980-03-01

    Under normal high-temperature gas-cooled reactor (HTGR) operating conditions, faying surfaces of metallic components under high contact pressure are prone to friction, wear, and self-welding damage. Component design calls for coatings for the protection of the mating surfaces. Anticipated operating temperatures up to 850 to 950/sup 0/C (1562 to 1742/sup 0/F) and a 40-y design life require coatings with excellent thermal stability and adequate wear and spallation resistance, and they must be compatible with the HTGR coolant helium environment. Plasma and detonation-gun (D-gun) deposited chromium carbide-base and stabilized zirconia coatings are under consideration for wear protection of reactor components such as the thermal barrier, heat exchangers, control rods, and turbomachinery. Programs are under way to address the structural integrity, helium compatibility, and tribological behavior of relevant sprayed coatings. In this paper, the need for protection of critical metallic components and the criteria for selection of coatings are discussed. The technical background to coating development and the experience with the steam cycle HTGR (HTGR-SC) are commented upon. Coating characterization techniques employed at General Atomic Company (GA) are presented, and the progress of the experimental programs is briefly reviewed. In characterizing the coatings for HTGR applications, it is concluded that a systems approach to establish correlation between coating process parameters and coating microstructural and tribological properties for design consideration is required.

  15. Sintering and Creep Behavior of Plasma-Sprayed Zirconia and Hafnia Based Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1998-01-01

    The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO2-8wt%y2O3, ZrO2-25wt%CeO2-2.5wt%Y2O3, ZrO2-6w%NiO- 9wt%Y2O3, ZrO2-6wt%Sc2O3-2wt%y2O3 and HfO2-27wt%y2O3 coating materials were investigated using dilatometry. It was found that the HfO2-Y2O3 and baseline ZrO2-Y2O3 exhibited the best sintering resistance, while the NiO-doped ZrO2-Y2O3 showed the highest shrinkage strain rates during the tests. Higher shrinkage strain rates of the coating materials were also observed when the specimens were tested in Ar+5%H2 as compared to in air. This phenomenon was attributed to an enhanced metal cation interstitial diffusion mechanism under the reducing conditions. It is proposed that increased chemical stability of coating materials will improve the material sintering resistance.

  16. Characterization and High-Temperature Erosion Behaviour of HVOF Thermal Spray Cermet Coatings

    NASA Astrophysics Data System (ADS)

    Kumar, Pardeep; Sidhu, Buta Singh

    2016-01-01

    High-velocity oxygen fuel (HVOF) thermal spray, carbide-cermet-based coatings are usually employed in high-temperature erosive and erosive-corrosive environments. Extensive literature is available on high-temperature erosion performance of HVOF coatings under moderate to low particle flux and velocities for application in boiler tubes. This research work presents the characterization and high-temperature erosion behaviour of Cr3C2-25NiCr and WC-10Co-4Cr HVOF-sprayed coatings. Coatings were formulated on the substrate steel of type AISI 304, commonly used for the fabrication of pulverized coal burner nozzles (PCBN). Erosion testing was carried out in high-temperature air-jet erosion tester after simulating the conditions akin to that prevailing in PCBN in the boiler furnace. The coatings were tested for erosion behaviour at different angles and temperatures by freezing other test parameters. Brittle erosion behaviour was depicted in erosion testing, and the coatings couldn't restrain the erodent attacks to protect the substrate. High particle velocity and high particle flux were attributed to be the reasons of extensive erosive weight loss of the coatings. The surface morphology of the eroded specimens was analysed from back-scattered electron images to depict the probable mechanism of material removal. The coatings were characterized with optical microscopy, SEM-EDS analysis, XRD analysis, micro-hardness testing, porosity measurements, surface roughness testing and bond strength testing. The work was undertaken to investigate the performance of the selected coatings in highly erosive environment, so as to envisage their application in PCBNs for protection against material degradation. The coatings could only sustain in oblique impact erosion at room temperature and depleted fully under all other conditions.

  17. Thermal Spray Using a High-Frequency Pulse Detonation Combustor Operated in the Liquid-Purge Mode

    NASA Astrophysics Data System (ADS)

    Endo, T.; Obayashi, R.; Tajiri, T.; Kimura, K.; Morohashi, Y.; Johzaki, T.; Matsuoka, K.; Hanafusa, T.; Mizunari, S.

    2016-02-01

    Experiments on thermal spray by pulsed detonations at 150 Hz were conducted. Two types of pulse detonation combustors were used, one operated in the inert gas purge (GAP) mode and the other in the liquid-purge (LIP) mode. In both modes, all gases were supplied in the valveless mode. The GAP mode is free of moving components, although the explosive mixture is unavoidably diluted with the inert gas used for the purge of the hot burned gas. In the LIP mode, pure fuel-oxygen combustion can be realized, although a liquid-droplet injector must be actuated cyclically. The objective of this work was to demonstrate a higher spraying temperature in the LIP mode. First, the temperature of CoNiCrAlY particles heated by pulsed detonations was measured. As a result, the spraying temperature in the LIP mode was higher than that in the GAP mode by about 1000 K. Second, the temperature of yttria-stabilized zirconia (YSZ) particles, whose melting point was almost 2800 °C, heated by pulsed detonations in the LIP mode was measured. As a result, the YSZ particles were heated up to about 2500 °C. Finally, a thermal spray experiment using YSZ particles was conducted, and a coating with low porosity was successfully deposited.

  18. Development of a Thermal Transport Database for Air Plasma Sprayed ZrO2 ? Y2O3 Thermal Barrier Coatings

    SciTech Connect

    Wang, Hsin; Dinwiddie, Ralph Barton; Porter, Wallace D

    2010-01-01

    Thermal Diffusivities of Air Plasma Sprayed (APS) thermal barrier coatings (TBCs) are measured by the laser flash method. The data are used to calculate thermal conductivity of TBCs when provided with density and specific heat data. Due to the complicated microstructure and other processing related parameters, thermal diffusivity of TBCs can vary as much as three to four fold. Data collected from over 200 free-standing ZrO2 7-8 wt%Y2O3 TBCs are presented. The large database gives a clear picture of the expected band of thermal diffusivity values. When this band is used as reference for thermal diffusivity of a specific TBC, the thermal transport property of TBC can be more precisely described. The database is intended to serve researchers and manufacturers of TBCs as a valuable source for evaluating their coatings.

  19. Minimizing Superficial Thermal Injury Using Bilateral Cryogen Spray Cooling During Laser Reshaping of Composite Cartilage Grafts

    PubMed Central

    Chang, Cheng-Jen; Cheng, Sally M.H.; Chiu, Lynn L.; Wong, Brian J.F.; Ting, Keen

    2014-01-01

    Composite cartilage grafts were excised from New Zealand rabbit ears. Flat composite grafts (of cartilage and overlying skin graft on both surfaces) were obtained from each ear and cut into a rectangle measuring 50 mm by 25 mm (x by y) with an average thickness of approximately 1.3 mm (z), skin included. Specimens were manually deformed with a jig and maintained in this new position during laser illumination. The composite cartilage grafts were illuminated on the concave surface with an Nd:YAG laser (1,064 nm, 3 mm spot) at 10 W, 20 W, 30 W, 40 W, 50 W. Cryogen spray cooling (CSC) was applied to both exterior (convex) and interior (concave) surfaces of the tissue to reduce thermal injury to the grafts. CSC was delivered: (1) in controlled applications (cryogen released when surface reached 40°C, and (2) receiving only laser at above wattage, no CSC [representing the control group]. The specimens were maintained in a deformation for 15 minutes after illumination and serially examined for 14 days. The control group with no CSC caused injury to all specimens, ranging from minor to full thickness epidermal thermal injury. Although most levels of laser and CSC yielded a high degree of reshaping over an acute time period, after 14 days specimens exposed to 30 W, 40 W, 50 W retained shape better than those treated at 10 W and 20 W. The specimens exposed to 50 W with controlled CSC retained its new shape to the highest degree over all others, and thermal injury was minimal. In conclusion, combinations of laser and CSC parameters were effective and practical for the reshaping of composite cartilage grafts. Lasers Surg. PMID:18727025

  20. Review on the Oxidation of Metallic Thermal Sprayed Coatings: A Case Study with Reference to Rare-Earth Permanent Magnetic Coatings

    NASA Astrophysics Data System (ADS)

    Gan, Jo Ann; Berndt, Christopher C.

    2013-10-01

    Thermal spray fabrication of rare-earth permanent magnetic coatings (PMCs) presents potential manufacturing routes for micro-magnetic devices. Despite this potential, thermal spray of PMCs is still not widely explored due to oxidation concerns. It was established that oxidation leads to the loss of ferromagnetic phases in these materials and results in deterioration of magnetic performance. Although this review focuses on a specific class of material, i.e., magnetic materials, there is significant technical crossover to all classes of feedstocks that are employed in thermal spray processing. The oxidation mechanisms and the associated influencing factors are explored in this work to implement effective processing techniques during the deposition process. This paper reviews the various stages and mechanisms of oxidation in thermal spray processes. The factors that influence the extent of oxidation depend on the type of oxidation that is dominant and rely on the type of spray system, powder injection position, and the particle size of feedstock. Among the aspects that are reviewed include the oxygen-fuel ratio for high velocity oxygen-fuel (HVOF), current intensity, gas flow rate, particle size, spray distance, and substrate temperature. Protection strategies to minimize oxidation in thermal spray processes, such as gas shrouding and shielding, are presented.

  1. Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen J.; Fabanich, William Anthony; Schmitz, Paul C.

    2014-01-01

    This presentation describes the capabilities of three-dimensional thermal power model of advanced stirling radioisotope generator (ASRG). The performance of the ASRG is presented for different scenario, such as Venus flyby with or without the auxiliary cooling system.

  2. Thermal spray removal of lead-based paint from the viaduct bridge at Rock Island Arsenal, IL. Final report

    SciTech Connect

    Boy, J.H.; Weber, R.A.; Kumar, A.

    1998-06-01

    This report documents a field demonstration at the Rock Island Arsenal, IL, that validated the thermal spray vitrification (TSV) process as a safe and effective technique for removing lead-based paint from a steel bridge. Specially formulated glass was applied in a molten state to painted steel using a conventional thermal spray application system. The molten glass reacts with the paint, and encapsulates the lead. The cooled glass readily cracks and falls off, removing the paint. After onsite remelting of the glass waste to complete the encapsulation process, the final waste product is chemically inert and may be disposed of in a regular landfill. The Illinois Environmental Protection Agency, Division of Air Pollution Control determined that the glass remelt process could be considered a paint-removal operation for which no air quality permit was required.

  3. Preparation of the Wire of ZChSnSb11-6 Used for Remanufacturing Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Yang, Z. Y.; Fu, D. X.; Li, X. F.; Chen, W.

    Tin base Babbitt alloy widely used in bearing bush production and repair, the performance of ZChSnSb11-6 is better than ZChSnSb8-4.But as a result of as-cast structure of ZChSnSb11-6 is rich in big hard phase, its processing performance is bad, in this paper, through the optimization of smelting, casting, extrusion, drawing and other processes we have been successfully prepared ZChSnSb11-6 wire suitable for thermal spraying. Through metallographic examination, micro hardness, bond strength and porosity testing, it was proved that the wire meet the requirements of bearing manufacturing thermal spraying.

  4. Advances in photonics thermal management and packaging materials

    NASA Astrophysics Data System (ADS)

    Zweben, Carl

    2008-02-01

    Heat dissipation, thermal stresses, and cost are key packaging design issues for virtually all semiconductors, including photonic applications such as diode lasers, light-emitting diodes (LEDs), solid state lighting, photovoltaics, displays, projectors, detectors, sensors and laser weapons. Heat dissipation and thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20 th century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. There are an increasing number of low-CTE materials with thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other new low-CTE materials with lower thermal conductivities. An important benefit of low-CTE materials is that they allow use of hard solders. Some advanced materials are low cost. Others have the potential to be low cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing the number of required devices. Advanced thermal materials can constrain PCB CTE and greatly increase thermal conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status, applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites reinforced with carbon nanotubes and other thermally conductive materials.

  5. Advanced thermal barrier coatings for operation in high hydrogen content fueled gas turbines.

    SciTech Connect

    Sampath, Sanjay

    2015-04-02

    The Center for Thermal Spray Research (CTSR) at Stony Brook University in partnership with its industrial Consortium for Thermal Spray Technology is investigating science and technology related to advanced metallic alloy bond coats and ceramic thermal barrier coatings for applications in the hot section of gasified coal-based high hydrogen turbine power systems. In conjunction with our OEM partners (GE and Siemens) and through strategic partnership with Oak Ridge National Laboratory (ORNL) (materials degradation group and high temperature materials laboratory), a systems approach, considering all components of the TBC (multilayer ceramic top coat, metallic bond coat & superalloy substrate) is being taken during multi-layered coating design, process development and subsequent environmental testing. Recent advances in process science and advanced in situ thermal spray coating property measurement enabled within CTSR has been incorporated for full-field enhancement of coating and process reliability. The development of bond coat processing during this program explored various aspects of processing and microstructure and linked them to performance. The determination of the bond coat material was carried out during the initial stages of the program. Based on tests conducted both at Stony Brook University as well as those carried out at ORNL it was determined that the NiCoCrAlYHfSi (Amdry) bond coats had considerable benefits over NiCoCrAlY bond coats. Since the studies were also conducted at different cycling frequencies, thereby addressing an associated need for performance under different loading conditions, the Amdry bond coat was selected as the material of choice going forward in the program. With initial investigations focused on the fabrication of HVOF bond coats and the performance of TBC under furnace cycle tests , several processing strategies were developed. Two-layered HVOF bond coats were developed to render optimal balance of density and surface roughness

  6. Manual for the thermal and hdyraulic design of direct contract spray columns for use in extracting heat from geothermal brines

    NASA Astrophysics Data System (ADS)

    Jacobs, H. R.

    1985-06-01

    This report outlines the current methods being used in the thermal and hydraulic design of spray column type, direct contact heat exchangers. It provides appropriate referenced equations for both preliminary design and detailed performance. The design methods are primarily empirical and are applicable for use in the design of such units for geothermal application and for application with solar ponds. Methods for design, for both preheater and boiler sections of the primary heat exchangers, for direct contact binary powers plants are included.

  7. Advanced X-ray Astrophysics Facility thermal control

    NASA Technical Reports Server (NTRS)

    Fritz, C. G.

    1983-01-01

    A conceptual active/passive thermal control system design is presented for the Advanced X-ray Astrophysics Facility (AXAF), where the design variables considered in system optimization were vehicle orientation for environmental extremes, thermal coating properties, and insulation materials. Because power and weight are at a premium, the design was limited to one power module, resulting in a thermal control limit of 441 W of regulated power. The present study has determined that all thermal control objectives for AXAF's instruments can be met by the design considered. The thermal resistance schematics employed in this conceptual study are presented, together with simulated performance characteristics.

  8. High temperature sulfidation of Fe{sub 3}Al and NiCr thermal spray coatings at 600 C

    SciTech Connect

    Luer, K.; DuPont, J.; Marder, A.

    1999-11-01

    Three Fe{sub 3}Al and two Ni45Cr thermal spray coatings were tested in Ar-3.5H{sub 2}-0.1H{sub 2}S for 500h at 600 C and compared to AISI 1008 steel. The three Fe{sub 3}Al-type coatings were processed from the same lot of gas atomized Fe{sub 3}Al powder using a high velocity oxygen fuel (HVOF) thermal spray process and an air plasma spray (APS) process. In general, the Fe{sub 3}Al-type composition displayed excellent resistance to sulfidation corrosion at 600 C which correlated with the reported literature on wrought Fe{sub 3}Al alloys. HVOF processing did not significantly degrade the composition of the consumable and produced coatings with low porosity, low oxide content, high sulfidation resistance, and high resistance to sulfur penetration. In contrast, APS processing caused significant degradation to the particles which reduced the sulfidation resistance of the coating and enabled local sulfidation attack at alloy depleted regions. The APS processed Fe{sub 3}Al coating also contained high porosity which enabled sulfur to fully penetrate the splat boundaries of the coating to the substrate. The two Ni45Cr-type coatings were produced using different processes and different consumables. One of the Ni45Cr coatings was processed using a proprietary wire combustion arc-spray (CAS) process. The second Ni45Cr coating was processed using a HVOF spray process. Both NiCr-type coatings reacted moderately with the sulfidizing gas at 600 C to form a mixed chromium oxide-sulfide scale despite marked differences in coating structure and composition. CAS processing caused significant degradation of the Ni45Cr consumable and produced a coating with low porosity and high oxide content. In contrast, HVOF processing caused negligible degradation of the Ni45Cr consumable and produced a coating with low porosity and moderate oxide content.

  9. In vitro characterisation of terbutaline sulphate particles prepared by thermal ink-jet spray freeze drying.

    PubMed

    Sharma, Garima; Mueannoom, Wunlapa; Buanz, Asma B M; Taylor, Kevin M G; Gaisford, Simon

    2013-04-15

    Thermal ink-jet spray freeze-drying (TIJ-SFD) was used to produce inhalable particles of terbutaline sulphate, the aerosolisation properties of which were compared to the commercial Bricanyl formulation. Scanning electron micrograph images showed the particles to be spherical, highly porous and suitable for aerosolisation from a simple, capsule-based dry-powder device (Cyclohaler) without the need for additional excipients. Particle size was dependent upon the concentration of solution jetted, as well as the distance between the print head and the surface of the liquid nitrogen. Starting with a 5% (w/v) solution and maintaining this distance at 3cm produced spherical, porous particles of volume median diameter (VMD) 14.1 ± 0.8 μm and mass median aerodynamic diameter (MMAD) 4.0 ± 0.6 μm. The fine particle fraction (proportion of aerosol with MMAD ≤ 4.46 μm) was 22.9 ± 3.3%, which compared favourably with that of the marketed dry powder inhaler formulation of terbutaline (Bricanyl Turbohaler; 25.7 ± 3.8%), tested under the same conditions. These findings show that TIJ-SFD is a useful tool to predict the viability of a DPI formulation during preformulation physicochemical characterisation. PMID:23454848

  10. Role of Powder Granulometry and Substrate Topography in Adhesion Strength of Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Kromer, R.; Cormier, J.; Costil, S.

    2016-06-01

    APS coating is deposited with different treated surfaces to understand the effects of surface topography and particle sizes on adhesion bond strength. Grit blasting and laser surface texturing have been used to create a controlled roughness and controlled surface topography, respectively. Coating adhesion is mainly controlled by a mechanical interlocking mechanism. Fully melted Ni-Al powder fills the respected target surface with high-speed radial flow. Pores around central flattening splat are usually seen due to splash effects. Laser surface texturing has been used to study near interface coating depending on the target shape and in-contact area. Pull-off test results have revealed predominant correlation with powder, surface topography, and adhesion bond strength. Adhesion bond strength is linked to the in-contact area. So, coating adhesion might be optimized with powder granulometry. Pores near the interface would be localized zones for crack initiations and propagations. A mixed-mode failure has been reported for sharp interface (interface and inter-splats cracks) due to crack kicking out phenomena. Coating toughness near the interface is a key issue to maximize adhesion bond strength. Volume particles and topography parameters have been proposed to enhance adhesion bond strength for thermal spray process for small and large in-contact area.

  11. Quasistatic vs. Dynamic Modulus Measurements Of Plasma-Sprayed Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Morscher, G. N.; Choi, S. R.

    2002-01-01

    Plasma-sprayed 8wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) have been demonstrated to exhibit nonlinear hysteretic elastic behavior by quasistatic cyclic compression and cylindrical punch indentation measurements. In particular, the instantaneous (tangential) elastic modulus increases with applied stress and exhibits significant hysteresis during cycling. Sound velocity (dynamic) measurements also show an increase in TBC modulus with applied compressive stress, but in contrast show no significant hysteresis for the modulus during cycling. The nonlinear elastic behavior of the TBCs evidenced by these tests is attributed to coating compaction and internal sliding. The differences between the quasistatic and dynamic measurements are explained by the relative absence of the effect of internal sliding in the dynamic modulus measurements. By incorporating short load reversals into the larger loading cycle and measuring the instantaneous modulus at the start of each load reversal, the effects of internal sliding can be substantially reduced in the quasistatic measurements, and the resulting modulus values show good agreement with the modulus values determined by dynamic sound velocity measurements.

  12. Mitigating Localized Corrosion Using Thermally Sprayed Aluminum (TSA) Coatings on Welded 25% Cr Superduplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Paul, S.; Lu, Q.; Harvey, M. D. F.

    2015-04-01

    Thermally sprayed aluminum (TSA) coating has been increasingly used for the protection of carbon steel offshore structures, topside equipment, and flowlines/pipelines exposed to both marine atmospheres and seawater immersion conditions. In this paper, the effectiveness of TSA coatings in preventing localized corrosion, such as pitting and crevice corrosion of 25% Cr superduplex stainless steel (SDSS) in subsea applications, has been investigated. Welded 25% Cr SDSS (coated and uncoated) with and without defects, and surfaces coated with epoxy paint were also examined. Pitting and crevice corrosion tests, on welded 25% Cr SDSS specimens with and without TSA/epoxy coatings, were conducted in recirculated, aerated, and synthetic seawater at 90 °C for 90 days. The tests were carried out at both the free corrosion potentials and an applied cathodic potential of -1100 mV saturated calomel electrode. The acidity (pH) of the test solution was monitored daily and adjusted to between pH 7.5 and 8.1, using dilute HCl solution or dilute NaOH, depending on the pH of the solution measured during the test. The test results demonstrated that TSA prevented pitting and crevice corrosion of 25% Cr SDSS in artificial seawater at 90 °C, even when 10-mm-diameter coating defect exposing the underlying steel was present.

  13. Preparing Al-Mg Substrate for Thermal Spraying: Evaluation of Surface State After Different Pretreatments

    NASA Astrophysics Data System (ADS)

    Lukauskaitė, R.; Valiulis, A. V.; Černašėjus, O.; Škamat, J.; Rębiś, J. A.

    2016-06-01

    The article deals with the pretreatment technique for preparing the surface of aluminum alloy EN AW 5754 before thermal spray. The surface after different pretreatments, including degreasing with acetone, chemical etching with acidic and alkali solutions, grit-blasting, cathodic cleaning, and some combinations of these techniques, has been studied. The investigation of pre-treated surfaces covered the topographical study (using scanning electron microscopy, atomic force microscopy, and 3D profilometry), the chemical analysis by x-ray photoelectron spectroscopy, the evaluation of surface wettability (sessile drop method), and the assessment of surface free energy. Compared with all the techniques used in present work, the cathodic cleaning and its combination with grit-blasting provide the most preferable chemistry of the surface. Due to the absence of hydroxides at the surface and, possible, due to the diffusion of magnesium to the surface of substrate, the surface wettability and the surface free energy have been significantly improved. No direct correlation between the surface topography and the surface wettability has been established.

  14. Flow Characteristics in Compact Thermal Spray Coating Systems with Minimum Length Nozzle

    NASA Astrophysics Data System (ADS)

    Seung-Hyun, Kim; Youn-Jea, Kim

    2009-10-01

    In this study, numerical analysis is performed to adopt the equivalence ratio on the high velocity oxygen fuel (HVOF) thermal spray coating systems equipped with a minimum length nozzle. The analysis is applied to investigate the axisymmetric, steady-state, turbulent, and chemically combusting flow both within the torch and in a free jet region between the torch and the substrate to be coated. The combustion is modeled using a single-step and eddy-dissipation model which assumes that the reaction rate is limited by the turbulent mixing rate of the fuel and oxidant. As the diameter of the nozzle throat is increased, the location of the Mach shock disc moves backward from the nozzle exit. As the throat diameter and the divergent portion are 6 mm and 8 mm, respectively, the pressure in the HVOF system is the lowest at the chamber and the expanding gas is steadily maintained with both high velocity and high temperature for different equivalence ratios. Thus, relatively minor amendments of the equivalence ratio and the geometry of HVOF can lead to improved control over coating characteristics.

  15. The surface cracking behavior in air plasma sprayed thermal barrier coating system incorporating interface roughness effect

    NASA Astrophysics Data System (ADS)

    Zhang, W. X.; Fan, X. L.; Wang, T. J.

    2011-11-01

    The objective of this work is to understand the effect of interface roughness on the strain energy release rate and surface cracking behavior in air plasma sprayed thermal barrier coating system. This is achieved by a parameter investigation of the interfacial shapes, in which the extended finite element method (XFEM) and periodic boundary condition are used. Predictions for the stress field and driving force of multiple surface cracks in the film/substrate system are presented. It is seen that the interface roughness has significant effects on the strain energy release rate, the interfacial stress distribution, and the crack propagation patterns. One can see the completely different distributions of stress and strain energy release rate in the regions of convex and concave asperities of the substrate. Variation of the interface asperity is responsible for the oscillatory characteristics of strain energy release rate, which can cause the local arrest of surface cracks. It is concluded that artificially created rough interface can enhance the durability of film/substrate system with multiple cracks.

  16. Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

    SciTech Connect

    Blink, J; Choi, J; Farmer, J

    2007-07-09

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials.

  17. Criticality-Control Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

    SciTech Connect

    Farmer, J; Choi, J

    2007-07-18

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. The high boron content of Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} (SAM2X5) makes it an effective neutron absorber, and suitable for criticality control applications. Average measured values of the neutron absorption cross section in transmission ({Sigma}{sub t}) for Type 316L stainless steel, Alloy C-22, borated stainless steel, a Ni-Cr-Mo-Gd alloy, and SAM2X5 have been determined to be approximately 1.1, 1.3, 2.3, 3.8 and 7.1 cm{sup -1}, respectively.

  18. Applications in the Nuclear Industry for Corrosion-Resistant Amorphous-Metal Thermal-Spray Coatings

    SciTech Connect

    Farmer, J; Choi, J

    2007-07-18

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Fe-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials.

  19. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    D. Trent Weaver; Matthew T. Kiser; Jeffrey Hawk

    2003-01-01

    In the eighth quarter, investigations in both thrusts focused on abrasive wear characterization. For the steel matrix composites, various systems were tested at DOE Albany Research Center using wear tests which produced low stress scratching, high stress gouging, and gouging and impact wear. Based on the wear results, it is uncertain as to whether the composites created have sufficient wear resistance to provide a 2x life increase in a selectively reinforced component in all applications. High stress component abrasive wear tests were conducted at Caterpillar on arc lamp processed, thermal sprayed components. Testing showed that in many cases, arc lamp processing parameters and resulting fusion were insufficient to prevent coating spallation. Of those coatings which experienced only limited spallation, wear life improvements approached 2x and it is expected that project goals can be met with additional process modifications. An overview of the progress during the 8th quarter of this project is given below. Additional research details are provided in the limited rights appendix to this report.

  20. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    Li Liu; Trent Weaver; F.W. Zok; C.G. Levi; Matthew T. Kiser

    2002-04-01

    In the fifth quarter, tooling for the steel MMC effort was redesigned based on the findings from the pressure casting trials of the previous quarter. While awaiting the arrival of that tooling, gravity casting trials were performed to assess modified performing technology and new hard particle systems. Steel-boride composite systems demonstrated good wetting and infiltration behavior, and fully infiltrated steel-boride composites were obtained under certain conditions. However, preform floating and particle dissolution are challenges which must be overcome. Ceramic oxide composites successfully pressure cast in a hot isostatic press at UC Santa Barbara were characterized and subject to fracture toughness testing. Resulting differences in fracture toughness are believed to be due to differences in matrix hardness, potentially imparted through reaction of the molten steel with the particles. Some evidence of bonding between the steel and oxide particles was noted on fracture surfaces. Arc lamp processing trials at Oak Ridge National Laboratory demonstrated that thermal spray coatings were successfully designed to facilitate fusion. All coatings investigated developed some degree of metallurgical bond after lamp fusion and for most coatings lamp fusion also further increased coating hardness. An overview of the progress during the 1st quarter of this project is given below. Research details are provided in the limited rights appendix to this report.

  1. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    D. Trent Weaver; Frank W. Zok; Carlos G. Levi; Matthew T. Kiser

    2003-04-01

    In the ninth quarter, investigations in steel matrix composites focused on characterization of abrasive wear and fracture test coupons in order to gain a better understanding of the material attributes contributing to the observed behavior in each test. Both the wear and fracture work found that the performance of the carbide cermet based composites was significantly affected by the dissolution of the hard particles and the elements added in hopes of discouraging dissolution. both thrusts focused on abrasive wear characterization. In abrasive wear this led to increase matrix hardness which increased wear resistance, however the fracture toughness of the composites were significantly reduced. In contrast, the oxide based composites demonstrated good fracture characteristics and the oxide particles provided superior protection to the high stress gouging wear imparted by pin-abrasion testing. For the thermal spray coating effort, modified coatings and fusing parameters were explored on simulated components. Significant improvements appear to have been achieved, and are demonstrated in the lack of observable cracking in the coatings. The abrasive wear characteristics of these components will be explored in the 10th quarter. An overview of the progress during the 9th quarter of this project is given below. Additional research details are provided in the limited rights appendix to this report.

  2. Influence of Process Parameter on Grit Blasting as a Pretreatment Process for Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Linke, T. F.; Sommer, J.; Liao, X.

    2016-01-01

    In thermal spraying, uncoated substrates usually require roughening. As the most common roughening method, grit blasting increases the surface area and produces undercuts in almost all cases, which facilitate mechanical interlocking and thus promote the bonding between the substrate and coating. The effects of grit blasting parameters, i.e., the particle size, the blasting angle, the stand-off distance, and the pressure, on the resulting surface topography are investigated. Furthermore, the efficiency and wear behavior of the blasting media are analyzed. Influences of three different blasting media, corundum, alumina zirconia, and steel shot, on the surface roughening, are compared. By varying adjusted blasting parameters, different initial conditions (surface topography) are created. Subsequently, the substrate is coated, and the coating bond strength is measured. One of the main results of this publication is that alumina zirconia and steel grit show a longer lifetime than pure alumina as a blasting media. Moreover, it has been shown that the blasting parameters such as grain size, working pressure, and history (wear status) of the abrasive particles have a significant effect on the resulting surface topography. Additionally, systematical analysis in this study shows that the blasting parameters such as stand-off distance and blasting angle have a small influence on the results of the blasting process. Another important conclusion of this study is that the conventional surface parameters that have been analyzed in this study did not turn out to be suitable for describing the relationship between the surface topography of the substrate and resulting bond strength.

  3. Quantification and Taxonomy of Pores in Thermal Spray Coatings by Image Analysis and Stereology Approach

    NASA Astrophysics Data System (ADS)

    Gan, Jo Ann; Berndt, Christopher C.

    2013-10-01

    Porosity is one of the most important microstructural features in thermal spray coatings and has been actively studied and measured by many methods. Image analysis techniques have become popular techniques in determining porosity in coatings because of simplicity, accessibility, and an ability to measure both open and closed porosities as well as pore characteristics such as size, shape, orientation, and spatial distribution. In the current study, an image analysis technique has been complemented by several stereology procedures to determine the porosity level and characteristics of pores within coatings. Stereology protocols such as Delesse, DeHoff, and Cruz-Orive analyses were used to derive the porosity level, pore size, and shape distributions, and the effectiveness of each stereology protocol was compared. Standoff distance (SOD) and annealing process did not alter the distribution trend of number of pores but influenced the distribution of pore volume fractions significantly. The bivariate size-shape distribution of the pores was used to predict the dominant pore type and fractions of pores that arose from different formation mechanisms. It was found that nearly spherical pores that originated from gas bubbles and entrapped gas pockets dominate at shorter SOD, while the different types of pores become more evenly distributed when the SOD was increased.

  4. Role of Powder Granulometry and Substrate Topography in Adhesion Strength of Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Kromer, R.; Cormier, J.; Costil, S.

    2016-05-01

    APS coating is deposited with different treated surfaces to understand the effects of surface topography and particle sizes on adhesion bond strength. Grit blasting and laser surface texturing have been used to create a controlled roughness and controlled surface topography, respectively. Coating adhesion is mainly controlled by a mechanical interlocking mechanism. Fully melted Ni-Al powder fills the respected target surface with high-speed radial flow. Pores around central flattening splat are usually seen due to splash effects. Laser surface texturing has been used to study near interface coating depending on the target shape and in-contact area. Pull-off test results have revealed predominant correlation with powder, surface topography, and adhesion bond strength. Adhesion bond strength is linked to the in-contact area. So, coating adhesion might be optimized with powder granulometry. Pores near the interface would be localized zones for crack initiations and propagations. A mixed-mode failure has been reported for sharp interface (interface and inter-splats cracks) due to crack kicking out phenomena. Coating toughness near the interface is a key issue to maximize adhesion bond strength. Volume particles and topography parameters have been proposed to enhance adhesion bond strength for thermal spray process for small and large in-contact area.

  5. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    SciTech Connect

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-21

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the potential development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a liquid metal cooled reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  6. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-01

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  7. Impact formation and microstructure characterization of thermal sprayed hydroxyapatite/titania composite coatings.

    PubMed

    Li, H; Khor, K A; Cheang, P

    2003-03-01

    Formation mechanism of hydroxyapatite (HA)/titania (TiO(2)) composite coating deposited by high velocity oxy-fuel (HVOF) thermal spray process was studied, and its structural characterization was conducted and elaborated in this paper. The impact theory was employed to analyze the formation procedure of the HA/titania composite coatings. Results revealed that the crater caused by the impact of entirely unmelted TiO(2) particles on the HA matrix during coating formation was of smaller dimensions than the original size of the reinforcements. It was found that chemical reaction between the mechanically blended HA and TiO(2) powder took place exclusively during the impingement stage, and calcium titanate, CaTiO(3), was one notable by-product. The bonding between the HA matrix and TiO(2) reinforcement might have been achieved predominantly through a chemical bond that resulted from the mutual chemical reactions among the components. Differential scanning calorimetry analyses showed that the chemical reaction between HA and TiO(2) was at approximately 1410 degrees C. The TiO(2) addition was found to exert particular effects on the thermal behavior of HA at elevated temperatures, during both heating and cooling cycles. Transmission electron microscopy observation identified the chemical reaction zone between HA and TiO(2), which revealed an improved splats' interface. The reaction zone demonstrated some influence on the grain size of HA nearby during resolidification of the melted portion. A structural model was proposed to illustrate the location of the different phases in the HA/titania composite coating. PMID:12504516

  8. Method for Thermal Spraying of Coatings Using Resonant-Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2008-01-01

    A method has been devised for high-volume, high-velocity surface deposition of protective metallic coatings on otherwise vulnerable surfaces. Thermal spraying is used whereby the material to be deposited is heated to the melting point by passing through a flame. Rather than the usual method of deposition from the jet formed from the combustion products, this innovation uses non-steady combustion (i.e. high-frequency, periodic, confined bursts), which generates not only higher temperatures and heat transfer rates, but exceedingly high impingement velocities an order of magnitude higher than conventional thermal systems. Higher impingement rates make for better adhesion. The high heat transfer rates developed here allow the deposition material to be introduced, not as an expensive powder with high surface-area-to-volume, but in convenient rod form, which is also easier and simpler to feed into the system. The nonsteady, resonant combustion process is self-aspirating and requires no external actuation or control and no high-pressure supply of fuel or air. The innovation has been demonstrated using a commercially available resonant combustor shown in the figure. Fuel is naturally aspirated from the tank through the lower Tygon tube and into the pulsejet. Air for starting is ported through the upper Tygon tube line. Once operation commences, this air is no longer needed as additional air is naturally aspirated through the inlet. A spark plug on the device is needed for starting, but the process carries on automatically as the operational device is resonant and reignites itself with each 220-Hz pulse.

  9. Microstructure and Properties of Thermally Sprayed Functionally Graded Coatings for Polymeric Substrates

    NASA Technical Reports Server (NTRS)

    Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Sutter, J. K.

    2003-01-01

    The use of polymer matrix composites (PMCs) in the gas flow path of advanced turbine engines offers significant benefits for aircraft engine performance but their useful lifetime is limited by their poor erosion resistance. High velocity oxy-fuel (HVOF) sprayed polymer/cermet functionally graded (FGM) coatings are being investigated as a method to address this technology gap by providing erosion and oxidation protection to polymer matrix composites. The FGM coating structures are based on a polyimide matrix filled with varying volume fractions of WC-Co. The graded coating architecture was produced using a combination of internal and external feedstock injection, via two computer-controlled powder feeders and controlled substrate preheating. Porosity, coating thickness and volume fraction of the WC-Co filler retained in the coatings were determined using standard metallographic techniques and computer image analysis. The pull-off strength (often referred to as the adhesive strength) of the coatings was evaluated according to the ASTM D 4541 standard test method, which measured the greatest normal tensile force that the coating could withstand. Adhesive/cohesive strengths were determined for three different types of coating structures and compared based on the maximum indicated load and the surface area loaded. The nature and locus of the fractures were characterized according to the percent of adhesive and/or cohesive failure, and the tested interfaces and layers involved were analyzed by Scanning Electron Microscopy.

  10. Advanced Fuel Cell System Thermal Management for NASA Exploration Missions

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth A.

    2009-01-01

    The NASA Glenn Research Center is developing advanced passive thermal management technology to reduce the mass and improve the reliability of space fuel cell systems for the NASA exploration program. An analysis of a state-of-the-art fuel cell cooling systems was done to benchmark the portion of a fuel cell system s mass that is dedicated to thermal management. Additional analysis was done to determine the key performance targets of the advanced passive thermal management technology that would substantially reduce fuel cell system mass.

  11. Residual Stress Determination in Thermally Sprayed Coatings – A Comparison of Curvature Models and X-Ray Techniques

    SciTech Connect

    T.C. Totemeier; J.K. Wright

    2006-03-01

    Residual stresses were calculated from the curvature of coating-substrate coupons using three different models: a simple two-beam elastic model; the Tsui-Clyne progressive deposition model; and the Tsui-Clyne progressive deposition model with substrate plasticity. The coatings studied were metallic and prepared by high-velocity oxy-fuel (HVOF) thermal spraying. The calculated stresses were compared to those measured on the same coupons using x-ray diffraction (XRD) techniques. Coating surface stresses calculated using the two-beam elastic model disagreed with those measured using XRD for coupons with significant curvature. Trends in residual stresses (with varying coating and substrate thickness, substrate material, and HVOF spray particle velocity) predicted by the elastic and elastic-plastic versions of the Tsui-Clyne progressive deposition model agreed with the trends measured by XRD. The magnitudes of stresses calculated using the Tsui-Clyne model agreed with the XRD measurements for coatings sprayed at low particle velocities but were significantly more compressive for coatings sprayed at higher velocities. Accounting for substrate plasticity in the Tsui-Clyne model improved the agreement with the XRD results, but only slightly.

  12. In situ spray deposition of cell-loaded, thermally and chemically gelling hydrogel coatings for tissue regeneration.

    PubMed

    Pehlivaner Kara, Meryem O; Ekenseair, Adam K

    2016-10-01

    In this study, the efficacy of creating cellular hydrogel coatings on warm tissue surfaces through the minimally invasive, sprayable delivery of thermoresponsive liquid solutions was investigated. Poly(N-isopropylacrylamide)-based (pNiPAAm) thermogelling macromers with or without addition of crosslinking polyamidoamine (PAMAM) macromers were synthesized and used to produce in situ forming thermally and chemically gelling hydrogel systems. The effect of solution and process parameters on hydrogel physical properties and morphology was evaluated and compared to poly(ethylene glycol) and injection controls. Smooth, fast, and conformal hydrogel coatings were obtained when pNiPAAm thermogelling macromers were sprayed with high PAMAM concentration at low pressure. Cellular hydrogel coatings were further fabricated by different spraying techniques: single-stream, layer-by-layer, and dual stream methods. The impact of spray technique, solution formulation, pressure, and spray solution viscosity on the viability of fibroblast and osteoblast cells encapsulated in hydrogels was elucidated. In particular, the early formation of chemically crosslinked micronetworks during bulk liquid flow was shown to significantly affect cell viability under turbulent conditions compared to injectable controls. The results demonstrated that sprayable, in situ forming hydrogels capable of delivering cell populations in a homogeneous therapeutic coating on diseased tissue surfaces offer promise as novel therapies for applications in regenerative medicine. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2383-2393, 2016. PMID:27153299

  13. Improving Tribological Properties of Cast Al-Si Alloys through Application of Wear-Resistant Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Culliton, David; Betts, Anthony; Carvalho, Sandra; Kennedy, David

    2013-04-01

    Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity.

  14. Advanced Heat Transfer and Thermal Storage Fluids

    SciTech Connect

    Moens, L.; Blake, D.

    2005-01-01

    The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.

  15. Recent advances in thermal conductivity of nanofluids.

    PubMed

    Witharana, Sanjeeva; Weliwita, Jinendrika Anushi; Chen, Haisheng; Wang, Liang

    2013-11-01

    This paper presents the most recent review of research articles and patents on thermal conductivity on nanofluids. Larger portion of literature accounts for experimental investigations, which is a sign of the preference for hands-on work by experimentalists. Metallic, non-metallic as well as ceramic nanoparticles of different sizes and shapes were suspended in common heat transfer liquids and their thermal conductivities were measured. In contrast to previous belief, it has now been proven that when the nanoparticle concentration is kept low the degree of enhancement falls reasonably within the boundaries predicted by the effective medium theories. There are strong evidences to suggest that the main mechanisms driving the thermal conductivity behavior are nanoparticle aggregation and the particle Brownian motion in suspension. PMID:24330042

  16. Advanced Technologies for the Improvement of Spray Application Techniques in Spanish Viticulture: An Overview

    PubMed Central

    Gil, Emilio; Arnó, Jaume; Llorens, Jordi; Sanz, Ricardo; Llop, Jordi; Rosell-Polo, Joan R.; Gallart, Montserrat; Escolà, Alexandre

    2014-01-01

    Spraying techniques have been undergoing continuous evolution in recent decades. This paper presents part of the research work carried out in Spain in the field of sensors for characterizing vineyard canopies and monitoring spray drift in order to improve vineyard spraying and make it more sustainable. Some methods and geostatistical procedures for mapping vineyard parameters are proposed, and the development of a variable rate sprayer is described. All these technologies are interesting in terms of adjusting the amount of pesticides applied to the target canopy. PMID:24451462

  17. Advanced cryogenic thermal switches for JWST

    NASA Astrophysics Data System (ADS)

    Bugby, David; Beres, Matthew; Stouffer, Charles; Rodriguez, Jose

    2005-08-01

    This paper describes two cryogenic thermal switches (CTSWs) under development for instruments on the James Webb Space Telescope (JWST). The first thermal switch was designed to extend the life of the solid H2 dewar for the 6 K Mid Infrared Instrument (MIRI) while the second thermal switch is needed for contamination and over-temperature control of three 35 K instruments on the Integrated Science Instrument Module (ISIM). In both cases, differential thermal expansion (DTE) between two materials having differing CTE values is the process that underpins the thermal switching. The patented DTE-CTSW design utilizes two metallic end-pieces, one cup-shaped and the other disc-shaped (both MIRI end-pieces are Al while ISIM uses an Al/Invar cup and an Al disc), joined by an axially centered Ultem rod, which creates a narrow, flat gap between the cup (rim) and disc. A heater is bonded to the rod center. Upon cooling one or both end-pieces, the rod contracts relative to the end-pieces and the gap closes, turning the CTSW ON. When the rod heater is turned on, the rod expands relative to the end-pieces and the gap opens, turning the CTSW OFF. During testing from 6-35 K, ON conductances of 0.3-12 W/K and OFF resistances greater than 2500 K/W were measured. Of particular importance at 6 K was the Al oxide layer, which was found to significantly decrease DTE-CTSW ON conductance when the mating surfaces were bare Al. When the mating surfaces were gold-plated, the adverse impact of the oxide layer was mitigated. This paper will describe both efforts from design through model correlation.

  18. Computer-Controlled Detonation Spraying: From Process Fundamentals Toward Advanced Applications

    NASA Astrophysics Data System (ADS)

    Ulianitsky, V.; Shtertser, A.; Zlobin, S.; Smurov, I.

    2011-06-01

    Detonation spraying is a well-known technology which is applied for deposition of diverse powders, in particular cermets, to form various protective coatings. Actual progress is related to a recently developed technique of computer-controlled detonation spraying and its application in non-traditional domains as development of composite and graded coatings or metallization of plastics. The gas detonation parameters are analyzed to estimate the efficiency of different fuels to vary particle-in-flight velocity and temperature over a broad range thus providing conditions to spray diverse powders. A particle of a given nature and fixed size could be sprayed in a solid state or being strongly overheated above the melting point by variation of the quantity of the explosive gas mixture which is computer-controlled. Particle-in-flight velocity and temperature are calculated and compared with jet monitoring by a CCD-camera-based diagnostic tool and experimental data on splats formation.

  19. Plasma Spraying of Ceramics with Particular Difficulties in Processing

    NASA Astrophysics Data System (ADS)

    Mauer, G.; Schlegel, N.; Guignard, A.; Jarligo, M. O.; Rezanka, S.; Hospach, A.; Vaßen, R.

    2015-01-01

    Emerging new applications and growing demands of plasma-sprayed coatings initiate the development of new materials. Regarding ceramics, often complex compositions are employed to achieve advanced material properties, e.g., high thermal stability, low thermal conductivity, high electronic and ionic conductivity as well as specific thermo-mechanical properties and microstructures. Such materials however, often involve particular difficulties in processing by plasma spraying. The inhomogeneous dissociation and evaporation behavior of individual constituents can lead to changes of the chemical composition and the formation of secondary phases in the deposited coatings. Hence, undesired effects on the coating characteristics are encountered. In this work, examples of such challenging materials are investigated, namely pyrochlores applied for thermal barrier coatings as well as perovskites for gas separation membranes. In particular, new plasma spray processes like suspension plasma spraying and plasma spray-physical vapor deposition are considered. In some cases, plasma diagnostics are applied to analyze the processing conditions.

  20. Plasma Spraying of Ceramics with Particular Difficulties in Processing

    NASA Astrophysics Data System (ADS)

    Mauer, G.; Schlegel, N.; Guignard, A.; Jarligo, M. O.; Rezanka, S.; Hospach, A.; Vaßen, R.

    2014-09-01

    Emerging new applications and growing demands of plasma-sprayed coatings initiate the development of new materials. Regarding ceramics, often complex compositions are employed to achieve advanced material properties, e.g., high thermal stability, low thermal conductivity, high electronic and ionic conductivity as well as specific thermo-mechanical properties and microstructures. Such materials however, often involve particular difficulties in processing by plasma spraying. The inhomogeneous dissociation and evaporation behavior of individual constituents can lead to changes of the chemical composition and the formation of secondary phases in the deposited coatings. Hence, undesired effects on the coating characteristics are encountered. In this work, examples of such challenging materials are investigated, namely pyrochlores applied for thermal barrier coatings as well as perovskites for gas separation membranes. In particular, new plasma spray processes like suspension plasma spraying and plasma spray-physical vapor deposition are considered. In some cases, plasma diagnostics are applied to analyze the processing conditions.

  1. Visualization of Flow in Pressurizer Spray Line Piping and Estimation of Thermal Stress Fluctuation Caused by Swaying of Water Surface

    NASA Astrophysics Data System (ADS)

    Oumaya, Toru; Nakamura, Akira; Onojima, Daisuke; Takenaka, Nobuyuki

    The pressurizer spray line of PWR plants cools reactor coolant by injecting water into pressurizer. Since the continuous spray flow rate during commercial operation of the plant is considered insufficient to fill the pipe completely, there is a concern that a water surface exists in the pipe and may periodically sway. In order to identify the flow regimes in spray line piping and assess their impact on pipe structure, a flow visualization experiment was conducted. In the experiment, air was used substituted for steam to simulate the gas phase of the pressurizer, and the flow instability causing swaying without condensation was investigated. With a full-scale mock-up made of acrylic, flow under room temperature and atmospheric pressure conditions was visualized, and possible flow regimes were identified based on the results of the experiment. Three representative patterns of swaying of water surface were assumed, and the range of thermal stress fluctuation, when the surface swayed instantaneously, was calculated. With the three patterns of swaying assumed based on the visualization experiment, it was confirmed that the thermal stress amplitude would not exceed the fatigue endurance limit prescribed in the Japanese Design and Construction Code.

  2. Thermal characteristics of air-water spray impingement cooling of hot metallic surface under controlled parametric conditions

    NASA Astrophysics Data System (ADS)

    Nayak, Santosh Kumar; Mishra, Purna Chandra

    2016-06-01

    Experimental results on the thermal characteristics of air-water spray impingement cooling of hot metallic surface are presented and discussed in this paper. The controlling input parameters investigated were the combined air and water pressures, plate thickness, water flow rate, nozzle height from the target surface and initial temperature of the hot surface. The effects of these input parameters on the important thermal characteristics such as heat transfer rate, heat transfer coefficient and wetting front movement were measured and examined. Hot flat plate samples of mild steel with dimension 120 mm in length, 120 mm breadth and thickness of 4 mm, 6 mm, and 8 mm respectively were tested. The air assisted water spray was found to be an effective cooling media and method to achieve very high heat transfer rate from the surface. Higher heat transfer rate and heat transfer coefficients were obtained for the lesser i.e, 4 mm thick plates. Increase in the nozzle height reduced the heat transfer efficiency of spray cooling. At an inlet water pressure of 4 bar and air pressure of 3 bar, maximum cooling rates 670°C/s and average cooling rate of 305.23°C/s were achieved for a temperature of 850°C of the steel plate.

  3. Exploring thermal spray gray alumina coating pore network architecture by combining stereological protocols and impedance electrochemical spectroscopy

    NASA Astrophysics Data System (ADS)

    Antou, G.; Montavon, G.; Hlawka, F.; Cornet, A.; Coddet, C.

    2006-12-01

    Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional (3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al2O3-13TiO2 coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined. Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related formation mechanisms.

  4. Advanced Metallic Thermal Protection System Development

    NASA Technical Reports Server (NTRS)

    Blosser, M. L.; Chen, R. R.; Schmidt, I. H.; Dorsey, J. T.; Poteet, C. C.; Bird, R. K.

    2002-01-01

    A new Adaptable, Robust, Metallic, Operable, Reusable (ARMOR) thermal protection system (TPS) concept has been designed, analyzed, and fabricated. In addition to the inherent tailorable robustness of metallic TPS, ARMOR TPS offers improved features based on lessons learned from previous metallic TPS development efforts. A specific location on a single-stage-to-orbit reusable launch vehicle was selected to develop loads and requirements needed to design prototype ARMOR TPS panels. The design loads include ascent and entry heating rate histories, pressures, acoustics, and accelerations. Additional TPS design issues were identified and discussed. An iterative sizing procedure was used to size the ARMOR TPS panels for thermal and structural loads as part of an integrated TPS/cryogenic tank structural wall. The TPS panels were sized to maintain acceptable temperatures on the underlying structure and to operate under the design structural loading. Detailed creep analyses were also performed on critical components of the ARMOR TPS panels. A lightweight, thermally compliant TPS support system (TPSS) was designed to connect the TPS to the cryogenic tank structure. Four 18-inch-square ARMOR TPS panels were fabricated. Details of the fabrication process are presented. Details of the TPSS for connecting the ARMOR TPS panels to the externally stiffened cryogenic tank structure are also described. Test plans for the fabricated hardware are presented.

  5. Structurally Integrated, Damage Tolerant Thermal Spray Coatings: Processing Effects on Surface and System Functionalities

    NASA Astrophysics Data System (ADS)

    Vackel, Andrew

    Thermal Spray (TS) coatings have seen extensive application as protective surfaces to enhance the service life of substrates prone to damage in their operating environment (wear, corrosion, heat etc.). With the advent of high velocity TS processes, the ability to deposit highly dense (>99%) metallic and cermet coatings has further enhanced the protective ability of these coatings. In addition to surface functionality, the influence of the coating application on the mechanical performance of a coated component is of great concern when such a component will experience either static or cyclic loading during service. Using a process mapping methodology, the processing-property interplay between coating materials meant to provide damage tolerant surface or for structural restoration are explored in terms of relevant mechanical properties. Most importantly, the residual stresses inherent in TS deposited coatings are shown to play a significant role in the integrated mechanical performance of these coatings. Unique to high velocity TS processes is the ability to produce compressive stresses within the deposit from the cold working induced by the high kinetic energy particles upon impact. The extent of these formation stresses are explored with different coating materials, as well as processing influence. The ability of dense TS coatings to carry significant structural load and synergistically strengthen coated tensile specimens is demonstrated as a function of coating material, processing, and thickness. The sharing of load between the substrate and otherwise brittle coating enables higher loads before yield for the bi-material specimens, offering a methodology to improve the tensile performance of coated components for structural repair or multi-functionality (surface and structure). The concern of cyclic fatigue damage in coated components is explored, since the majority of service application are designed for loading to be well below the yield point. The role of

  6. Therma1 Conductivity and Durability of Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2003-01-01

    Thermal barrier coatings (TBCs) will play a crucial role in advanced gas turbine engines because of their ability to further increase engine operating temperature and reduce cooling, thus helping to achieve engine emission and efficiency goals. Future TBCs must be designed with increased phase stability, lower thermal conductivity, and improved sintering and thermal stress resistance in order to effectively protect engine hot-section components. Advanced low conductivity TBCs are being developed at NASA by incorporating multi-component oxide dopants into zirconia-yttria or hafnia-yttria to promote the formation of thermodynamically stable defect clusters within the coating structures. This presentation will primarily focus on thermal conductivity and durability of the novel defect cluster thermal barrier coatings for turbine airfoil and combustor applications, determined by a unique CO2 laser heat-flux approach. The laser heat-flux testing approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity under simulated engine temperature and thermal gradient conditions. The conductivity increase due to coating sintering (and/or phase change) and the conductivity decrease due to coating delamination have been determined under steady-state, cyclic, uniform or non-uniform heat-flux conditions. The coating radiation flux resistance has been evaluated by varying coating thermal gradients, and also by using a laser-heated radiative-flux source. Advanced multi-component TBC systems have been shown to have significantly reduced thermal conductivity and improved high temperature stability due to the nano-sized, low mobility defect clusters associated with the paired rare earth dopant additions. The effect of oxide defect cluster dopants on coating thermal conductivity, thermal stability and furnace cyclic durability will also be discussed. The current low conductivity TBC systems have demonstrated long-term cyclic durability at very high

  7. Corrosion potential behavior in high-temperature water of noble metal-doped alloy coatings deposited by underwater thermal spraying

    SciTech Connect

    Kim, Y.J.; Andresen, P.L.; Gray, D.M.; Lau, Y.C.; Offer, H.P.

    1996-06-01

    Intergranular stress corrosion cracking (IGSCC) of sensitized stainless steel (SS) components in boiling water reactors (BWR) is a major concern. The SCC susceptibility of structural materials in high-temperature water is affected by the electrochemical corrosion potential (ECP). The ECP of type 304 stainless steel coated under water by hyper-velocity oxy-fuel (HVOF) and plasma-spray (PS) techniques using noble metal-doped powders was measured to evaluate the catalytic behavior in high-temperature water under various water chemistry conditions. Thermal-spray coatings of noble metal-doped powders exhibited catalytic behavior for the recombination of oxygen and hydrogen in high-temperature water, which caused ECP to decrease well below a critical value of {minus}230 mV{sub SHE} for intergranular stress corrosion cracking protection in water. This was observed in water containing various amounts of oxygen and hydrogen peroxide when stoichiometric excess hydrogen was present.

  8. Corrosion performance of bi-layer Ni/Cr2C3-NiCr HVAF thermal spray coating

    NASA Astrophysics Data System (ADS)

    Sadeghimeresht, E.; Markocsan, N.; Nylén, P.; Björklund, S.

    2016-04-01

    The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3-NiCr coatings, and C: bi-layer Ni/Cr2C3-NiCr coating) was comparatively studied using immersion, salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3-NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3-NiCr and single-layer Cr2C3-NiCr coatings were around 194 and 38 kΩ cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.

  9. Microstructure and properties of in-flight rare-earth doped thermal barrier coatings prepared by suspension plasma spray

    NASA Astrophysics Data System (ADS)

    Gong, Stephanie

    Thermal barrier coatings with lower thermal conductivity improve the efficiency of gas turbine engines by allowing higher operating temperatures. Recent studies were shown that coatings containing a pair of rare-earth oxides with equal molar ratio have lower thermal conductivity and improved sintering resistance compared to the undoped 4-4.5 mol.% yttria-stabilized zirconia (YSZ). In the present work, rare-earth doped coatings were fabricated via suspension plasma spray by spraying YSZ powder-ethanol suspensions that contained dissolved rare-earth nitrates. The compositions of the coatings determined by inductively coupled plasma mass spectroscopy verified that 68 +/- 8% of the rare-earth nitrates added into the suspension was incorporated into the coatings. Two coatings containing different concentrations of the same dopant pair (Nd2O3/Yb2O3), and three coatings having similar concentrations of different dopant pairs (Nd 2O3/Yb2O3, Nd2O3/Gd 2O3, and Gd2O3/Yb2O 3) were produced and compared. The effect of dopant concentration and dopant pair type on the microstructure and properties of the coatings in the as-sprayed and heat treated conditions were investigated using XRD, SEM, TEM, STEM-EDX, and the laser flash method. The cross-sectional morphology of all coatings displayed columnar structure. The porosity content of the coating was found to increase with increasing dopant concentration, but did not significantly change with dopant pairs. Similarly, increasing the Nd2O3/Yb2O 3 concentration lowered the thermal conductivity of the as-sprayed coatings. Although the effect of changing dopant pair type is not as significant as increasing the dopant concentration, the coating that contained Gd2O 3/Yb2O3 exhibited the lowest conductivity compared to coatings that had other dopant pairs. Thermal conductivity measurement performed on the heat treated coatings indicated a larger conductivity increase for the rare-earth doped coatings. A detailed study on the

  10. Microstructure and Thermal Characterization of Plasma-Sprayed Nanostructured La2Ce2O7-Doped YSZ Coatings

    NASA Astrophysics Data System (ADS)

    Mantry, S.; Mandal, A.; Mishra, D. K.; Jha, B. B.; Mishra, B. K.; Chakraborty, M.

    2014-10-01

    Nanostructured La2Ce2O7-doped YSZ coatings were developed using atmospheric plasma-spraying technique by optimizing various process parameters. To ensure the retention of nanostructure, the molten state of nanoagglomerates was monitored using plasma and particle diagnostic tools. It was observed that the morphology of the coating exhibits a bimodal microstructure consisting of nanozones reinforced in a matrix of fully-molten particles. The thermal diffusivity of nano-LaCeYSZ coatings is lower than that of nano and bulk YSZ. The reason for this change in thermal diffusivity may be attributed to scattering of phonons at grain boundaries, point defect scattering and higher inter-splat porosity. Also, the thermal conductivity of the nanocomposite coatings was lower than those of nanostructured and bulk YSZ coatings. XRD results show cubic zirconia with a small amount of tetragonal zirconia. The average grain size of the as-sprayed La2Ce2O7-YSZ nanocomposite coatings is ~150-200 nm. The improved thermal behavior is mainly due to a dense, packed, and more compact structure of the coatings.

  11. Effect of High-Velocity Oxy-Fuel (HVOF) Thermal Spraying on Physical and Mechanical Properties of Type 316 Stainless Steel

    SciTech Connect

    Terry C. Totemeier

    2005-09-01

    Data on the microstructural, physical, and mechanical characteristics of high-velocity oxygen-fuel (HVOF)-sprayed type 316 stainless steel coatings are presented and compared with properties of wrought 316 stainless steel. Coatings were prepared at three different spray particle velocities; coating characteristics are presented as a function of velocity. The coatings had relatively low porosity and oxide contents and were significantly harder than annealed, wrought 316 stainless steel. The hardness difference is primarily attributed to high dislocation densities resulting from peening imparted by high-velocity spray particles. The coating hardness increased with increasing spray particle velocity, reflecting increased peening effects. The elastic modulus of the coatings was essentially identical to wrought material. The mean coefficient of thermal expansion of as-sprayed coatings was lower than wrought material, but the expansion of annealed coatings matched the wrought behavior.

  12. An investigation of the electrical behavior of thermally-sprayed aluminum oxide

    SciTech Connect

    Swindeman, C.J.; Seals, R.D.; White, R.L.; Murray, W.P.; Cooper, M.H.

    1996-09-01

    Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 C. High purity (> 99.5 wt% pure Al{sub 2}O{sub 3}) alumina powders were plasma-sprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the important of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.

  13. Microstructural and Tribological Properties of Al2O3-13pctTiO2 Thermal Spray Coatings Deposited by Flame Spraying

    NASA Astrophysics Data System (ADS)

    Younes, Rassim; Bradai, Mohand Amokrane; Sadeddine, Abdelhamid; Mouadji, Youcef; Bilek, Ali; Benabbas, Abderrahim

    2015-10-01

    T He present investigation has been conducted to study the tribological properties of Al2O3-13pctTiO2 (AT-13) ceramic coatings deposited on a low carbon steel type E335 by using a thermal flame spray technique. The microstructure and phase composition of wire and coatings were analyzed by scanning electron microscope, energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Measurements of micro hardness were also performed on the surface of the coatings. The tribological tests were carried out using a pin-on-disk tribometer at different loads. All tests were performed using two disks as counter body, namely Al2O3-ZrO2 (AZ-25) and Al2O3-TiO2 (AT-3) which formed couple 1 and couple 2, respectively, in order to work out the wear rate and friction coefficient. Roughness profiles were also evaluated before and after each test. The SEM showed that the dense microstructure of Al2O3-TiO2 (AT-13) coatings have a homogenous lamellar morphology and complex of several phases with the presence of porosities and unmelted particles. The XRD analysis of the wire before the spray showed a majority phase of α-Al2O3 rhombohedral structure and a secondary phase of Al2TiO5 orthorhombic structure with little traces of TiO2 (rutile) tetragonal structure, whereas the XRD of the coating revealed the disappearance of TiO2 replaced by the formation of a new metastable phase γ-Al2O3 cubic structure. The tribological results showed that the applied contact pressure affects the variation of the friction coefficient with time and that it decreases with the rise of the normal force of contact. It was found also that the couple 2 with nearly chemical compositions of spray-coated (AT-13) and disk (AT-3) exhibited much higher wear resistance than the couple 1 although they have sliding coefficient of friction nearly.

  14. Influence of the HVOF Gas Composition on the Thermal Spraying of WC-Co Submicron Powders (-8 + 1 μm) to Produce Superfine Structured Cermet Coatings

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Vogli, E.; Baumann, I.; Matthaeus, G.; Ostrowski, T.

    2008-12-01

    Thermal spraying technology represents a novel and promising approach to protect forming tools with complex surfaces and highest shape accuracy against abrasive wear and galling. However, due to high or nonuniform layer thicknesses or inappropriate surface roughness conventional coarse-structured coatings are not suitable to achieve this aim. The application of novel submicron or nanoscaled feedstock materials in the thermal spray process can provide the deposition of cermet coatings with significantly improved characteristics and is recently of great interest in science and industry. In this collaborative study, the feeding and HVOF spraying of WC-Co submicron powders (-8 + 1 μm) have been investigated to manufacture superfine structured, wear resistant, near-net-shape coatings with improved macroscopic properties and smooth surfaces. The influences of varying HVOF gas compositions on the spray process and the coating properties have been analyzed.

  15. Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2008-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

  16. Thermal Properties of Oxides With Magnetoplumbite Structure for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

    2007-01-01

    Oxides having magnetoplumbite structure are promising candidate materials for applications as high temperature thermal barrier coatings because of their high thermal stability, high thermal expansion, and low thermal conductivity. In this study, powders of LaMgAl11O19, GdMgAl11O19, SmMgAl11O19, and Gd0.7Yb0.3MgAl11O19 magnetoplumbite oxides were synthesized by citric acid sol-gel method and hot pressed into disk specimens. The thermal expansion coefficients (CTE) of these oxide materials were measured from room temperature to 1500 C. The average CTE value was found to be approx.9.6x10(exp -6)/C. Thermal conductivity of these magnetoplumbite-based oxide materials was also evaluated using steady-state laser heat flux test method. The effects of doping on thermal properties were also examined. Thermal conductivity of the doped Gd0.7Yb0.3MgAl11O19 composition was found to be lower than that of the undoped GdMgAl11O19. In contrast, thermal expansion coefficient was found to be independent of the oxide composition and appears to be controlled by the magnetoplumbite crystal structure. Thermal conductivity testing of LaMgAl11O19 and LaMnAl11O19 magnetoplumbite oxide coatings plasma sprayed on NiCrAlY/Rene N5 superalloy substrates indicated resistance of these coatings to sintering even at temperatures as high as 1600 C.

  17. Anisotropic thermal expansion effects in plasma-sprayed ZrO2-8 percent Y2O3 coatings

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Herman, H.

    1983-01-01

    The thermal expansion properties of plasma-sprayed ZrO2-8-wt pct Y2O3 coatings, detached from the substrate, have been examined. Coatings were heat-treated in air or in argon. Anisotropic effects in the longitudinal (planar to the substrate surface) and transverse (perpendicular to the substrate surface) directions were measured and related to the coating structure. The thermal expansion coefficient of the coating is discussed in terms of the material's properties, such as the crack network and interlamellar boundary distribution. A precise model for the expansion behavior of coatings still needs attention, since no description of all of the contributing variables exists. A quantitative analysis of thermal properties of coatings will aid in future design and modeling of coating systems.

  18. Effect of Microstructure on the Thermal Conductivity of Plasma-Sprayed Al2O3-YSZ Coatings

    NASA Astrophysics Data System (ADS)

    Song, Xuemei; Liu, Ziwei; Kong, Mingguang; Wang, Yongzhe; Huang, Liping; Zheng, Xuebin; Zeng, Yi

    2016-04-01

    The microstructures of three atmospheric plasma-sprayed (APS) Al2O3-ZrO2 coatings were investigated using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The differences in the microstructures of the three Al2O3-ZrO2 coatings, including their phase compositions, cracks, pores, grain sizes, and solid solutions, were analyzed in detail. A close relationship was observed between the thermal conductivities of the coatings and the microstructures, and the Al2O3-YSZ coatings with more spherical pores, fewer vertical cracks, and finer grains exhibited the lowest thermal conductivity of 0.91 W/m·K. Compared with YSZ coatings, Al2O3-YSZ coatings can exhibit lower thermal conductivity, which may be attributed to the formation of an amorphous phase, smaller grains, and Al2O3-YSZ solid solution.

  19. SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

    NASA Astrophysics Data System (ADS)

    Ma, Rongbin; Cheng, Xudong; Ye, Weiping

    2015-12-01

    Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

  20. Advanced thermal-sensor-system development via shuttle sortie missions

    SciTech Connect

    Angelo, J.A. Jr.; Ginsberg, I.W.

    1981-01-01

    The use of the Space Shuttle in various sortie mission modes to evaluate advanced thermal sensor system concepts, prior to a design commitment for automated spacecraft application, is described. Selected terrestrial energy sources of civilian and/or military interest are examined with respect to: (1) thermal source location and characterization and (2) temperature and emissivity measurements. Of particular interest is the application of on-orbit sensor testing to demonstrate the location and characterization of potential geothermal energy resources. The role of the payload specialist in thermal source location, sensor operation and real time evaluation of mission performance is discussed.

  1. Structural thermal tests on Advanced Neutron Source reactor fuel plates

    SciTech Connect

    Swinson, W.F.; Battiste, R.L.; Yahr, G.T.

    1995-08-01

    The thin aluminum-clad fuel plates proposed for the Advanced Neutron Source reactor are stressed by the high-velocity coolant flowing on each side of the plates and by the thermal gradients in the plates. The total stress, composed of the sum of the flow stress and the thermal stress at a point, could be reduced if the thermal loads tend to relax when the stress magnitude approaches the yield stress of the material. The potential of this occurring would be very significant in assessing the structural reliability of the fuel plates and has been investigated through experiment. The results of this investigation are given in this report.

  2. Advanced Filter Technology For Nuclear Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Castillon, Erick

    2015-01-01

    The Scrubber System focuses on using HEPA filters and carbon filtration to purify the exhaust of a Nuclear Thermal Propulsion engine of its aerosols and radioactive particles; however, new technology may lend itself to alternate filtration options, which may lead to reduction in cost while at the same time have the same filtering, if not greater, filtering capabilities, as its predecessors. Extensive research on various types of filtration methods was conducted with only four showing real promise: ionization, cyclonic separation, classic filtration, and host molecules. With the four methods defined, more research was needed to find the devices suitable for each method. Each filtration option was matched with a device: cyclonic separators for the method of the same name, electrostatic separators for ionization, HEGA filters, and carcerands for the host molecule method. Through many hours of research, the best alternative for aerosol filtration was determined to be the electrostatic precipitator because of its high durability against flow rate and its ability to cleanse up to 99.99% of contaminants as small as 0.001 micron. Carcerands, which are the only alternative to filtering radioactive particles, were found to be non-existent commercially because of their status as a "work in progress" at research institutions. Nevertheless, the conclusions after the research were that HEPA filters is recommended as the best option for filtering aerosols and carbon filtration is best for filtering radioactive particles.

  3. Thermal Spray Coatings for High-Temperature Corrosion Protection in Biomass Co-Fired Boilers

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.; Kärki, J.

    2015-01-01

    There are over 1000 biomass boilers and about 500 plants using waste as fuel in Europe, and the numbers are increasing. Many of them encounter serious problems with high-temperature corrosion due to detrimental elements such as chlorides, alkali metals, and heavy metals. By HVOF spraying, it is possible to produce very dense and well-adhered coatings, which can be applied for corrosion protection of heat exchanger surfaces in biomass and waste-to-energy power plant boilers. Four HVOF coatings and one arc sprayed coating were exposed to actual biomass co-fired boiler conditions in superheater area with a probe measurement installation for 5900 h at 550 and 750 °C. The coating materials were Ni-Cr, IN625, Fe-Cr-W-Nb-Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for HVOF spraying to compare the corrosion resistance of Ni-Cr coating structures. Reference materials were ferritic steel T92 and nickel super alloy A263. The circulating fluidized bed boiler burnt a mixture of wood, peat and coal. The coatings showed excellent corrosion resistance at 550 °C compared to the ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during the exposure at 750 °C.

  4. Spray characterization of thermal fogging equipment typically used in vector control.

    PubMed

    Hoffmann, W C; Walker, T W; Fritz, B K; Gwinn, T; Smith, V L; Szumlas, D; Quinn, B; Lan, Y; Huang, Y; Sykes, D

    2008-12-01

    Droplet size spectra from different sprayers used to generate insecticide-laden fogs for controlling flying insects were measured by a laser diffraction instrument and Teflon-coated slides. The objectives of this work were to present not only information on spray-system droplet size generated by different sprayers, but to compare methodologies by which other similar systems can be evaluated and give applicators sprayer-system performance data. Data from 45 replicated spray tests, comprising 11 sprayers and 5 pesticides, showed a wide range in the droplet size spectra produced. The volume median diameter measurements ranged from 2.6 to 75.5 microm for diesel-diluted sprays and from 27.9 to 59.9 microm for water-diluted sprays. Similarly, the percent volume <20 microm ranged between 12.0-100% and 8.5-30.7%, for diesel- and water-diluted sprays, respectively. The droplet sizes measured by the swinging slide and laser diffraction methods were not consistent. The information presented aids users in sprayer selection and operation to produce the specific droplet size spectra required for a particular application. PMID:19181064

  5. Thermal Spray Coatings for High-Temperature Corrosion Protection in Biomass Co-Fired Boilers

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.; Kärki, J.

    2014-09-01

    There are over 1000 biomass boilers and about 500 plants using waste as fuel in Europe, and the numbers are increasing. Many of them encounter serious problems with high-temperature corrosion due to detrimental elements such as chlorides, alkali metals, and heavy metals. By HVOF spraying, it is possible to produce very dense and well-adhered coatings, which can be applied for corrosion protection of heat exchanger surfaces in biomass and waste-to-energy power plant boilers. Four HVOF coatings and one arc sprayed coating were exposed to actual biomass co-fired boiler conditions in superheater area with a probe measurement installation for 5900 h at 550 and 750 °C. The coating materials were Ni-Cr, IN625, Fe-Cr-W-Nb-Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for HVOF spraying to compare the corrosion resistance of Ni-Cr coating structures. Reference materials were ferritic steel T92 and nickel super alloy A263. The circulating fluidized bed boiler burnt a mixture of wood, peat and coal. The coatings showed excellent corrosion resistance at 550 °C compared to the ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during the exposure at 750 °C.

  6. Cracking and Spalling Behavior of HVOF Thermally Sprayed WC-Co-Cr Coating in Bend and Axial Fatigue Tests

    NASA Astrophysics Data System (ADS)

    Gui, M.; Eybel, R.; Asselin, B.; Monerie-Moulin, F.

    2015-03-01

    In this work, WC-10Co-4Cr coating was sprayed by high-velocity oxygen fuel (HVOF) process on Almen strip and axial fatigue coupon. Three-point bend test was used to bend Almen strip coating specimens with tensile and compressive stress applied to the coating. Axial fatigue coating specimens were tested at a load stress of 1250 MPa and a stress ratio of R = -1. Process condition of Thermal spraying was found to have an effect on spalling performance of the coating in the fatigue test. The mechanism of cracking and spalling process in the coating was studied in bend and fatigue conditions. Based on deformation difference between the coating and the substrate, the factors, especially coating thickness, to impact the coating spalling behavior in axial fatigue test are discussed. HVOF-sprayed WC-10Co-4Cr coating matches the deformation of base substrate by cracking when tensile stress is applied in bend and fatigue tests because the coating has very limit deformation capability. In axial fatigue test of WC-10Co-4Cr coating specimen, the substrate works in a stress-to-strain manner; however the coating works in a strain-to-stress manner and is stressed due to the substrate deformation.

  7. Oxidation Behavior of In-Flight Molten Aluminum Droplets in the Twin-Wire Electric Arc Thermal Spray Process

    SciTech Connect

    Donna Post Guillen; Brian G. Williams

    2005-05-01

    This paper examines the in-flight oxidation of molten aluminum sprayed in air using the twin-wire electric arc (TWEA) thermal spray process. The oxidation reaction of aluminum in air is highly exothermic and is represented by a heat generation term in the energy balance. Aerodynamic shear at the droplet surface enhances the amount of in-flight oxidation by: (1) promoting entrainment and mixing of the surface oxides within the droplet, and (2) causing a continuous heat generation effect that increases droplet temperature over that of a droplet without internal circulation. This continual source of heat input keeps the droplets in a liquid state during flight. A linear rate law based on the Mott-Cabrera theory was used to estimate the growth of the surface oxide layer formed during droplet flight. The calculated oxide volume fraction of an average droplet at impact agrees well with the experimentally determined oxide content for a typical TWEA-sprayed aluminum coating, which ranges from 3.3 to 12.7%. An explanation is provided for the elevated, nearly constant surface temperature (~ 2000 oC) of the droplets during flight to the substrate and shows that the majority of oxide content in the coating is produced during flight, rather than after deposition.

  8. Manual for the thermal and hydraulic design of direct contact spray columns for use in extracting heat from geothermal brines

    SciTech Connect

    Jacobs, H.R.

    1985-06-01

    This report outlines the current methods being used in the thermal and hydraulic design of spray column type, direct contact heat exchangers. It provides appropriate referenced equations for both preliminary design and detailed performance. The design methods are primarily empirical and are applicable for us in the design of such units for geothermal application and for application with solar ponds. Methods for design, for both preheater and boiler sections of the primary heat exchangers, for direct contact binary powers plants are included. 23 refs., 8 figs.

  9. High Temperature Damping Behavior of Plasma-Sprayed Thermal Barrier and Protective Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.; Duffy, Kirsten P.; Ghosn, Louis J.

    2010-01-01

    A high temperature damping test apparatus has been developed using a high heat flux CO 2 laser rig in conjunction with a TIRA S540 25 kHz Shaker and Polytec OFV 5000 Vibrometer system. The test rig has been successfully used to determine the damping performance of metallic and ceramic protective coating systems at high temperature for turbine engine applications. The initial work has been primarily focused on the microstructure and processing effects on the coating temperature-dependence damping behavior. Advanced ceramic coatings, including multicomponent tetragonal and cubic phase thermal barrier coatings, along with composite bond coats, have also been investigated. The coating high temperature damping mechanisms will also be discussed.

  10. Property evaluation of thermal sprayed metallic coating by acoustic emission analysis

    SciTech Connect

    Ishida, Asako; Mizutani, Yoshihiro; Takemoto, Mikio; Ono, Kanji

    2000-03-01

    The authors analyzed acoustic emission signals from plasma sprayed sheets by first obtaining the Young's modulus, Poisson's ratio, and density. The sheets of a high Cr-Ni alloy (55Cr-41Ni-Mo, Si, B) were made by low pressure plasma spraying (LPPS) and heat treated. Utilizing laser induced surface acoustic waves (SAWs), the group velocity dispersion data of Rayleigh waves was obtained and matched to that computed by Adler's matrix transfer method. They monitored the acoustic emissions (Lamb waves) produced by microfractures in free standing as sprayed coating subjected to bending. Fast cleavage type microfracture with source rise time of around 2 {micro}s occurred as precursors to the final brittle fracture. The velocity and time-frequency amplitude spectrograms (wavelet contour maps) of the Lamb waves were utilized for the source location and fracture kinetic analyses.

  11. Vacuum Plasma Spray of Cu-8Cr-4Nb for Advanced Liquid-Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, F.; Elam, S.; Ellis, D.; Miller, H.; McKechnie, T.; Hickman, R.

    2001-01-01

    Vacuum plasma spray (VPS) formed Cu-8Cr-4Nb alloy, with low oxygen, exhibits higher strength at room and elevated temperature than material formed by extrusion. The VPS formed material exhibits slightly lower ductility than the extruded material. VPS forming of Cu-8Cr-4Nb can be used to produce near net structures with mechanical properties comparable to current extruded material.

  12. Thermal Characterization of Nanostructures and Advanced Engineered Materials

    NASA Astrophysics Data System (ADS)

    Goyal, Vivek Kumar

    to heat-sinking units. This dissertation presents results of the experimental investigation and theoretical interpretation of thermal transport in the advanced engineered materials, which include thin films for thermal management of nanoscale devices, nanostructured superlattices as promising candidates for high-efficiency thermoelectric materials, and improved TIMs with graphene and metal particles as fillers providing enhanced thermal conductivity. The advanced engineered materials studied include chemical vapor deposition (CVD) grown ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on Si substrates, directly integrated nanocrystalline diamond (NCD) films on GaN, free-standing polycrystalline graphene (PCG) films, graphene oxide (GOx) films, and "pseudo-superlattices" of the mechanically exfoliated Bi2Te3 topological insulator films, and thermal interface materials (TIMs) with graphene fillers.

  13. Thermal Barrier Coatings for Advanced Gas Turbine and Diesel Engines

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1999-01-01

    Ceramic thermal barrier coatings (TBCS) have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, durability issues of these thermal barrier coatings under high temperature cyclic conditions are still of major concern. The coating failure depends not only on the coating, but also on the ceramic sintering/creep and bond coat oxidation under the operating conditions. Novel test approaches have been established to obtain critical thermomechanical and thermophysical properties of the coating systems under near-realistic transient and steady state temperature and stress gradients encountered in advanced engine systems. This paper presents detailed experimental and modeling results describing processes occurring in the ZrO2-Y2O3 thermal barrier coating systems, thus providing a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.

  14. Thermal and Environmental Barrier Coatings for Advanced Propulsion Engine Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. For future high performance engines, the development of advanced ceramic barrier coating systems will allow these coatings to be used to simultaneously increase engine operating temperature and reduce cooling requirements, thereby leading to significant improvements in engine power density and efficiency. In order to meet future engine performance and reliability requirements, the coating systems must be designed with increased high temperature stability, lower thermal conductivity, and improved thermal stress and erosion resistance. In this paper, ceramic coating design and testing considerations will be described for high temperature and high-heat-flux engine applications in hot corrosion and oxidation, erosion, and combustion water vapor environments. Further coating performance and life improvements will be expected by utilizing advanced coating architecture design, composition optimization, and improved processing techniques, in conjunction with modeling and design tools.

  15. Design, Characterization, and Aerosol Dispersion Performance Modeling of Advanced Spray-Dried Microparticulate/Nanoparticulate Mannitol Powders for Targeted Pulmonary Delivery as Dry Powder Inhalers

    PubMed Central

    Li, Xiaojian; Vogt, Frederick G.; Hayes, Don

    2014-01-01

    Abstract Background: The purpose was to design and characterize inhalable microparticulate/nanoparticulate dry powders of mannitol with essential particle properties for targeted dry powder delivery for cystic fibrosis mucolytic treatment by dilute organic solution spray drying, and, in addition, to tailor and correlate aerosol dispersion performance delivered as dry powder inhalers based on spray-drying conditions and solid-state physicochemical properties. Methods: Organic solution advanced spray drying from dilute solution followed by comprehensive solid-state physicochemical characterization and in vitro dry powder aerosolization were used. Results: The particle size distribution of the spray-dried (SD) powders was narrow, unimodal, and in the range of ∼500 nm to 2.0 μm. The particles possessed spherical particle morphology, relatively smooth surface morphology, low water content and vapor sorption (crystallization occurred at exposure above 65% relative humidity), and retention of crystallinity by polymorphic interconversion. The emitted dose, fine particle fraction (FPF), and respirable fraction (RF) were all relatively high. The mass median aerodynamic diameters were below 4 μm for all SD mannitol aerosols. Conclusion: The in vitro aerosol deposition stage patterns could be tailored based on spray-drying pump rate. Positive linear correlation was observed between both FPF and RF values with spray-drying pump rates. The interplay between various spray-drying conditions, particle physicochemical properties, and aerosol dispersion performance was observed and examined, which enabled tailoring and modeling of high aerosol deposition patterns. PMID:24502451

  16. Review of Thermal Spray Coating Applications in the Steel Industry: Part 2—Zinc Pot Hardware in the Continuous Galvanizing Line

    NASA Astrophysics Data System (ADS)

    Matthews, S.; James, B.

    2010-12-01

    This two-part article series reviews the application of thermal spray coating technology in the production of steel and steel sheet products. Part 2 of this article series is dedicated to coating solutions in the continuous galvanizing line. The corrosion mechanisms of Fe- and Co-based bulk materials are briefly reviewed as a basis for the development of thermal spray coating solutions. WC-Co thermal spray coatings are commonly applied to low Al-content galvanizing hardware due to their superior corrosion resistance compared to Fe and Co alloys. The effect of phase degradation, carbon content, and WC grain size are discussed. At high Al concentrations, the properties of WC-Co coatings degrade significantly, leading to the application of oxide-based coatings and corrosion-resistant boride containing coatings. The latest results of testing are summarized, highlighting the critical coating parameters.

  17. METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

    SciTech Connect

    Matthew T. Kiser

    2001-07-01

    First quarter activities were limited to initial project discussions, laboratory preparation, and some initial coupon preparation. Technical discussion were held with the subcontractors to clearly define their roll in the project. Detailed preparation of the pressure casting lab were started. Initial test coupons were sprayed and provided to Oak Ridge National Lab for infrared lamp fusion trials.

  18. Experimental and numerical evaluation of the performance of supersonic two-stage high-velocity oxy-fuel thermal spray (Warm Spray) gun

    NASA Astrophysics Data System (ADS)

    Katanoda, H.; Morita, H.; Komatsu, M.; Kuroda, S.

    2011-03-01

    The water-cooled supersonic two-stage high-velocity oxy-fuel (HVOF) thermal spray gun was developed to make a coating of temperature-sensitive material, such as titanium, on a substrate. The gun has a combustion chamber (CC) followed by a mixing chamber (MC), in which the combustion gas is mixed with the nitrogen gas at room temperature. The mixed gas is accelerated to supersonic speed through a converging-diverging (C-D) nozzle followed by a straight passage called the barrel. This paper proposes an experimental procedure to estimate the cooling rate of CC, MC and barrel separately. Then, the mathematical model is presented to predict the pressure and temperature in the MC for the specific mass flow rates of fuel, oxygen and nitrogen by assuming chemical equilibrium with water-cooling in the CC and MC, and frozen flow with constant specific heat from stagnant condition to the throat in the CC and MC. Finally, the present mathematical model was validated by comparing the calculated and measured stagnant pressures of the CC of the two-stage HVOF gun.

  19. Numerical Investigation of Combustion and Flow Dynamics in a High Velocity Oxygen-Fuel Thermal Spray Gun

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

    The combustion and flow behavior within a high velocity oxygen-fuel (HVOF) thermal spray gun is very complex and involves multiphase flow, heat transfer, chemical reactions, and supersonic/subsonic transitions. Additionally, this behavior has a significant effect on the formation of a coating. Non-premixed combustion models have been developed and are able to provide insight into the underlying physics of the process. Therefore, this investigation employs a non-premixed combustion model and the SST k - ω turbulence model to simulate the flow field of the JP5000 (Praxair-TAFA, US) HVOF thermal spray gun. The predicted temperature and velocity have a high level of agreement with experimental data when using the non-premixed combustion model. The results are focused on the fuel combustion, the subsequent gas dynamics within the HVOF gun, and the development of a supersonic free jet outside the gun. Furthermore, the oxygen/fuel inlet turbulence intensity, the fuel droplet size, and the oxygen/fuel ratio are investigated to determine their effect on the supersonic flow characteristics of the combustion gas.

  20. The influence of WC-Co HVOF thermal spraying on the microstructure of an Al-4 Cu alloy substrate

    SciTech Connect

    Guilemany, J.M.; Nutting, J.; Dong, Z.; Paco, J.M. de

    1995-10-01

    The High Velocity Oxy-Fuel (HVOF) thermal spraying process can be used to produce a dense hard coating onto a metallic surface with a good bond between the coating and the substrate. Having developed techniques for the examination of the coating substrate interfacial regions with steel it was thought appropriate to examine the interfacial structure with other substrates. An aluminium copper alloy was chosen for this study for the following reasons: (1) There had been little earlier work on substrate reactions when using aluminium alloys, the published data was chiefly concerned with characterizing the coatings. (2) Aluminium alloys have a much lower melting point than steel, hence the substrate melted zone was likely to be much greater than that found in steel. (3) The structural characteristics of aged aluminium copper alloys have been well described and hence the structural changes produced in the alloy by thermal spraying could be compared with clearly established structural data so giving markers for the temperature profile well below the immediate interface region. As in the previous investigation the transmission electron microscope was used to examine thin foils prepared from the interface region and at various depths below the interface into the substrate.

  1. Electrochemical Corrosion Behavior of Thermal-Sprayed Stainless Steel-Coated Q235 Steel in Simulated Soil Solutions

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Wu, Xin-qiang; Ke, Wei; Xu, Song; Feng, Bing; Hu, Bo-tao

    2016-02-01

    The corrosion behavior of a thermal-sprayed stainless steel (SS)-coated Q235 steel has been investigated in simulated soil solutions using electrochemical measurements, x-ray photoelectron spectroscopy analysis, and scanning electron microscope. The as-received Q235 steel and galvanized steel for grounding grids were also examined for the purpose of comparison. The effects of pH value of testing solutions have been examined. The thermal-sprayed SS-coated steel showed the best corrosion resistance among the three kinds of materials. With increasing pH value, the corrosion resistance of SS-coated Q235 steel increased. In weak alkaline solutions, the SS-coated Q235 steel showed the largest polarization resistance (3.2 × 105 Ω cm2), the lowest anodic current density (1.4 × 10-2 μA/cm2), and the largest film resistance (4.5 × 106 Ω cm2), suggesting that the coated steel has the best corrosion resistance in weak alkaline environment. Related corrosion mechanisms are also discussed.

  2. Computational analysis of a three-dimensional High-Velocity Oxygen-Fuel (HVOF) Thermal Spray torch

    SciTech Connect

    Hassan, B.; Lopez, A.R.; Oberkampf, W.L.

    1995-07-01

    An analysis of a High-Velocity Oxygen-Fuel Thermal Spray torch is presented using computational fluid dynamics (CFD). Three-dimensional CFD results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire torch, but wire feed is not simulated. To the authors` knowledge, these are the first published 3-D results of a thermal spray device. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Argon is injected through the center of the nozzle. Pre-mixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled assuming instantaneous chemistry. A standard, two-equation, K-{var_epsilon} turbulence model is employed for the turbulent flow field. An implicit, iterative, finite volume numerical technique is used to solve the coupled conservation of mass, momentum, and energy equations for the gas in a sequential manner. Flow fields inside and outside the aircap are presented and discussed.

  3. Coating Bores of Light Metal Engine Blocks with a Nanocomposite Material using the Plasma Transferred Wire Arc Thermal Spray Process

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Ernst, F.; Zwick, J.; Schlaefer, T.; Cook, D.; Nassenstein, K.; Schwenk, A.; Schreiber, F.; Wenz, T.; Flores, G.; Hahn, M.

    2008-09-01

    Engine blocks of modern passenger car engines are generally made of light metal alloys, mostly hypoeutectic AlSi-alloys. Due to their low hardness, these alloys do not meet the tribological requirements of the system cylinder running surface—piston rings—lubricating oil. In order to provide a suitable cylinder running surface, nowadays cylinder liners made of gray cast iron are pressed in or cast into the engine block. A newer approach is to apply thermal spray coatings onto the cylinder bore walls. Due to the geometric conditions, the coatings are applied with specifically designed internal diameter thermal spray systems. With these processes a broad variety of feedstock can be applied, whereas mostly low-alloyed carbon steel feedstock is being used for this application. In the context of this work, an iron-based wire feedstock has been developed, which leads to a nanocrystalline coating. The application of this material was carried out with the Plasma Transferred Wire Arc system. AlMgSi0.5 liners were used as substrates. The coating microstructure and the properties of the coatings were analyzed.

  4. Influence of surface character change of substrate due to heating on flattening behavior of thermal sprayed particles

    NASA Astrophysics Data System (ADS)

    Fukumoto, M.; Nagai, H.; Yasui, T.

    2006-12-01

    The authors have confirmed that in the thermal spraying of practical powder materials, the splat shape changes with increasing substrate temperature to a circular disk shape from a fringe shape with splashing at a critical substrate temperature, T t. The increase of the substrate temperature may accompany a kind of essential change on the substrate surface, because the effect is maintained until the substrate is cooled down to room temperature. However, the nature of the substrate surface change due to the heating has not been clearly understood yet. In this study, AISI 304 stainless steel was used as a substrate material, and the substrate was heated in an air at mosphere or laser treated as a pretreatment. Substrate surface topography in nanometer scale was analyzed precisely by atomic force microscope (AFM). The relationship between surface topography in nanometer scale and splat morphology was discussed. Moreover, to evaluate the effect of chemical composition of the substrate surface, gold was coated onto the substrate surface by physical vapor deposition (PVD) after the heat treatment. The effect of adsorbate/condensate on the substrate surface on the flattening behavior of thermal sprayed particles was also verified.

  5. Development of Porous YSZ Coatings with Modified Thermal and Optical Properties by Plasma Spray Physical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Kambara, Makoto; Shinozawa, Akihiro; Aoshika, Kiyoshi; Eguchi, Keisuke; Yoshida, Toyonobu

    Porous and feather-like yttria-stabilized zirconia coatings have been deposited by plasma spray physical vapor deposition (PS-PVD) at the deposition rate of around 200 µm/min. The porosity of the coating reached > 50% and the overall thermal conductivity was reduced less than 0.5 W/mK, both of which were fundamentally independent of the coating thickness up to 120 µm. Such coating structures were characterized by their high scattering coefficients at light wavelength from 2 to 6 µm, and thus the transmittance to infrared was reduced significantly compared to the splat structure coating with the identical thickness. The thermal properties of these coatings were retained even after annealing at temperature ˜1500°C for 130 hours.

  6. Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen J.; Fabanich, William Anthony; Schmitz, Paul C.

    2014-01-01

    This paper presents recent thermal model results of the Advanced Stirling Radioisotope Generator (ASRG). The three-dimensional (3D) ASRG thermal power model was built using the Thermal Desktop(trademark) thermal analyzer. The model was correlated with ASRG engineering unit test data and ASRG flight unit predictions from Lockheed Martin's (LM's) I-deas(trademark) TMG thermal model. The auxiliary cooling system (ACS) of the ASRG is also included in the ASRG thermal model. The ACS is designed to remove waste heat from the ASRG so that it can be used to heat spacecraft components. The performance of the ACS is reported under nominal conditions and during a Venus flyby scenario. The results for the nominal case are validated with data from Lockheed Martin. Transient thermal analysis results of ASRG for a Venus flyby with a representative trajectory are also presented. In addition, model results of an ASRG mounted on a Cassini-like spacecraft with a sunshade are presented to show a way to mitigate the high temperatures of a Venus flyby. It was predicted that the sunshade can lower the temperature of the ASRG alternator by 20 C for the representative Venus flyby trajectory. The 3D model also was modified to predict generator performance after a single Advanced Stirling Convertor failure. The geometry of the Microtherm HT insulation block on the outboard side was modified to match deformation and shrinkage observed during testing of a prototypic ASRG test fixture by LM. Test conditions and test data were used to correlate the model by adjusting the thermal conductivity of the deformed insulation to match the post-heat-dump steady state temperatures. Results for these conditions showed that the performance of the still-functioning inboard ACS was unaffected.

  7. Advanced Reactors Thermal Energy Transport for Process Industries

    SciTech Connect

    P. Sabharwall; S.J. Yoon; M.G. McKellar; C. Stoots; George Griffith

    2014-07-01

    The operation temperature of advanced nuclear reactors is generally higher than commercial light water reactors and thermal energy from advanced nuclear reactor can be used for various purposes such as liquid fuel production, district heating, desalination, hydrogen production, and other process heat applications, etc. Some of the major technology challenges that must be overcome before the advanced reactors could be licensed on the reactor side are qualification of next generation of nuclear fuel, materials that can withstand higher temperature, improvement in power cycle thermal efficiency by going to combined cycles, SCO2 cycles, successful demonstration of advanced compact heat exchangers in the prototypical conditions, and from the process side application the challenge is to transport the thermal energy from the reactor to the process plant with maximum efficiency (i.e., with minimum temperature drop). The main focus of this study is on doing a parametric study of efficient heat transport system, with different coolants (mainly, water, He, and molten salts) to determine maximum possible distance that can be achieved.

  8. LSPRAY-II: A Lagrangian Spray Module

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2004-01-01

    LSPRAY-II is a Lagrangian spray solver developed for application with parallel computing and unstructured grids. It is designed to be massively parallel and could easily be coupled with any existing gas-phase flow and/or Monte Carlo Probability Density Function (PDF) solvers. The solver accommodates the use of an unstructured mesh with mixed elements of either triangular, quadrilateral, and/or tetrahedral type for the gas flow grid representation. It is mainly designed to predict the flow, thermal and transport properties of a rapidly vaporizing spray because of its importance in aerospace application. The manual provides the user with an understanding of various models involved in the spray formulation, its code structure and solution algorithm, and various other issues related to parallelization and its coupling with other solvers. With the development of LSPRAY-II, we have advanced the state-of-the-art in spray computations in several important ways.

  9. LSPRAY-V: A Lagrangian Spray Module

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2015-01-01

    LSPRAY-V is a Lagrangian spray solver developed for application with unstructured grids and massively parallel computers. It is mainly designed to predict the flow, thermal and transport properties of a rapidly vaporizing spray encountered over a wide range of operating conditions in modern aircraft engine development. It could easily be coupled with any existing gas-phase flow and/or Monte Carlo Probability Density Function (PDF) solvers. The manual provides the user with an understanding of various models involved in the spray formulation, its code structure and solution algorithm, and various other issues related to parallelization and its coupling with other solvers. With the development of LSPRAY-V, we have advanced the state-of-the-art in spray computations in several important ways.

  10. LSPRAY-III: A Lagrangian Spray Module

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2008-01-01

    LSPRAY-III is a Lagrangian spray solver developed for application with parallel computing and unstructured grids. It is designed to be massively parallel and could easily be coupled with any existing gas-phase flow and/or Monte Carlo Probability Density Function (PDF) solvers. The solver accommodates the use of an unstructured mesh with mixed elements of either triangular, quadrilateral, and/or tetrahedral type for the gas flow grid representation. It is mainly designed to predict the flow, thermal and transport properties of a rapidly vaporizing spray because of its importance in aerospace application. The manual provides the user with an understanding of various models involved in the spray formulation, its code structure and solution algorithm, and various other issues related to parallelization and its coupling with other solvers. With the development of LSPRAY-III, we have advanced the state-of-the-art in spray computations in several important ways.

  11. Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2005-01-01

    When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

  12. Deposition and characterization of plasma sprayed Ni-5A1/ magnesia stabilized zirconia based functionally graded thermal barrier coating

    NASA Astrophysics Data System (ADS)

    Baig, M. N.; Khalid, F. A.

    2014-06-01

    Thermal barrier coatings (TBCs) are employed to protect hot section components in industrial and aerospace gas turbine engines. Conventional TBCs frequently fail due to high residual stresses and difference between coefficient of thermal expansion (CTE) of the substrate & coatings. Functionally graded thermal barrier coatings (FG-TBCs) with gradual variation in composition have been proposed to minimize the problem. In this work, a five layered functionally graded thermal barrier coating system was deposited by atmospheric plasma spray (APS) technique on Nimonic 90 substrates using Ni-5Al as bond coat (BC) and magnesia stabilized zirconia as top coat (TC). The coatings were characterized by SEM, EDS, XRD & optical profilometer. Microhardness and coefficient of thermal expansion of the five layers deposited as individual coatings were also measured. The deposited coating system was oxidized at 800°C. SEM analysis showed that five layers were successfully deposited by APS to produce a FG-TBC. The results also showed that roughness (Ra) of the individual layers decreased with an increase in TC content in the coatings. It was found that microhardness and CTE values gradually changed from bond coat to cermet layers to top coat. The oxidized coated sample revealed parabolic behavior and changes in the surface morphology and composition of coating.

  13. Thermal-Cycling Behavior of Plasma-Sprayed Partially Stabilized Zirconia Coatings on High-Density Graphite Substrate

    NASA Astrophysics Data System (ADS)

    Sure, Jagadeesh; Thyagarajan, K.; Mallika, C.; Mudali, U. Kamachi

    2015-08-01

    The thermal cycling behavior of partially stabilized zirconia (PSZ)-coated by plasma-spray process on NiCrAlY bond-coated high-density (HD) graphite substrate was investigated. Thermal cycling was carried out at 600 and 750 °C under vacuum, up to 200 cycles. Each cycle comprised a 10-min heating followed by forced air cooling for 10 min down to room temperature. Characterization of the microstructure and the phase analysis of thermal-cycled PSZ coatings by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction (XRD), and Raman spectroscopy revealed the correlation between the microstructural/crystallographic phases and the mechanical integrity of the coating up to 200 cycles. Segmented and vertical cracks generated on the coating during thermal cycling were observed to propagate with increase in the number of cycles. Macrocracks and variations in elemental compositions were not observed until 200 cycles at 600 and 750 °C. XRD and Raman spectroscopic analysis confirmed the presence of nontransformable tetragonal phase only in all the thermal-cycled PSZ coatings, irrespective of temperature up to 200 cycles.

  14. Advanced thermally stable jet fuels. Technical progress report, 1995

    SciTech Connect

    Schobert, H.H.; Eser, S.; Song, C.

    1996-04-01

    The Penn State program in advanced thermally stable jet fuels has five components:(1) development of mechanisms of degradation and solids formation; (2) quantitative measurement of growth of sub- micrometer and micrometer sized particles suspended in fuels during thermal stressing; (3) characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) elucidation of the role of additives in retarding the formation of carbonaceous solids; and (5) assessment of the potential of producing high yields of cycloalkanes and hydroaromatics by direct liquefaction of coal. Progress reports for these tasks are presented.

  15. The NASA Advanced Exploration Systems Nuclear Thermal Propulsion Project

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Mitchell, Doyce P.; Kim, Tony; Emrich, William J.; Hickman, Robert R.; Gerrish, Harold P.; Doughty, Glen; Belvin, Anthony; Clement, Steven; Borowski, Stanley K.; Scott, John; Power, Kevin P.

    2015-01-01

    The fundamental capability of Nuclear Thermal Propulsion (NTP) is game changing for space exploration. A first generation NTP system could provide high thrust at a specific impulse (Isp) above 900 s, roughly double that of state of the art chemical engines. Characteristics of fission and NTP indicate that useful first generation systems will provide a foundation for future systems with extremely high performance. The role of a first generation NTP in the development of advanced nuclear propulsion systems could be analogous to the role of the DC-3 in the development of advanced aviation systems.

  16. Advanced Metal-Hydrides-Based Thermal Battery: A New Generation of High Density Thermal Battery Based on Advanced Metal Hydrides

    SciTech Connect

    2011-12-01

    HEATS Project: The University of Utah is developing a compact hot-and-cold thermal battery using advanced metal hydrides that could offer efficient climate control system for EVs. The team’s innovative designs of heating and cooling systems for EVs with high energy density, low-cost thermal batteries could significantly reduce the weight and eliminate the space constraint in automobiles. The thermal battery can be charged by plugging it into an electrical outlet while charging the electric battery and it produces heat and cold through a heat exchanger when discharging. The ultimate goal of the project is a climate-controlling thermal battery that can last up to 5,000 charge and discharge cycles while substantially increasing the driving range of EVs, thus reducing the drain on electric batteries.

  17. Measurement of thermal characteristics of spray-dried milk and juice blend.

    PubMed

    Afifi, Hanan S; Abu Shelaibi, A A; Laleye, L C; Ismail, I A

    2009-01-01

    Blended concentrated grape/peach (G/P) juice 60% total soluble solids (TSS) with condensed whole cow milk 40% TSS (1.5:8.5) was spray dried using a pilot-scale spray drier FT 80 at feeding pressure 7,000 Pa, at chamber temperature 180 degrees C and at chamber pressure -110 Pa. The glass transition state of blended G/P juice-milk powder, three pure sugars (glucose, sucrose and lactose) and casein were studied using differential scanning calorimetry. The calorimetry showed that G/P juice-milk powder is a glassy material. The glass transition temperature of blended G/P juice-milk powder at 0.248 water activity was 42 degrees C, compared with commercial full milk powder (control) of 29 degrees C at 0.334 at water activity (a(w)). PMID:19468952

  18. Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy

    SciTech Connect

    Tan, Yang; Shyam, Amit; Choi, Wanhuk Brian; Lara-Curzio, Edgar; Sampath, Sanjay

    2010-01-01

    The determination of elastic properties of plasma-sprayed ceramic and metallic coatings is difficult due to their complex microstructure, which involves a myriad array of pores, interfaces and other defects. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. In this paper, we report on the anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy (RUS). This approach along with the analysis presented enables, for the first time, the determination of elastic properties as a function of direction and temperature for these complex systems with concomitant implications for design. The coating systems investigated included plasma-sprayed yttria-stabilized zirconia (YSZ) and nickel. An additional nickel coating deposited by high-velocity oxygen-fuel process was investigated and its elastic properties were compared to those of plasma-sprayed nickel. Average Young s moduli of the coatings were independently measured by using the instrumented indentation method. The elastic properties determined from the RUS and indentation methodologies allowed description of the microstructure elastic property relationships in the coatings.

  19. Sliding and abrasive wear resistance of thermal-sprayed WC-CO coatings

    NASA Astrophysics Data System (ADS)

    Qiao, Yunfei; Liu, Yourong; Fischer, Traugott E.

    2001-03-01

    We studied the resistance of the coatings to abrasive and unlubricated sliding wear of 40 WC/Co coatings applied by high velocity oxygen fuel (HVOF), high-energy plasma spray (HEPS), and high velocity plasma spray (HVPS), using commercial and nanostructured experimental powders. The hardness of the coatings varies from 3 to 13 GPA, which is much lower than that of sintered samples (10 to 23 GPA) because of the porosity of the coatings. Phase analysis by x-ray diffraction revealed various amounts of decarburization in the coatings, some of which contain WC, W2C, W, and η phase. The abrasive and sliding wear resistance is limited by the hardness of the samples. For a given hardness, the wear resistance is lowered by decarburization, which produces a hard but brittle phase. Nanocarb powders have the shape of thin-walled hollow spheres that heat up rapidly in the gun and are more prone to decarburization than commercial materials. The work shows that, in order to obtain the performance of nanostructured coatings, the powder and spray techniques must be modified.

  20. Thermal Storage Advanced Thruster System (TSATS) Experimental Program

    NASA Technical Reports Server (NTRS)

    Rose, M. Frank; Lisano, Michael E., II

    1991-01-01

    The Thermal Storage Advanced Thruster System (TSATS) rocket test stand is completely assembled and operational. The first trial experimental runs of a low-energy TSATS prototype rocket was made using the test stand. The features of the rocket test stand and the calibration of the associated diagnostics are described and discussed. Design and construction of the TSATS prototype are discussed, and experimental objectives, procedures, and results are detailed.

  1. Characterization and durability testing of plasma-sprayed zirconia-yttria and hafnia-yttria thermal barrier coatings. Part 1: Effect of spray parameters on the performance of several lots of partially stabilized zirconia-yttria powder

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Leissler, George W.; Jobe, J. Marcus

    1993-01-01

    Initial experiments conducted on thermal barrier coatings prepared in the newly upgraded research plasma spray facility and the burner rig test facilities are discussed. Part 1 discusses experiments which establish the spray parameters for three baseline zirconia-yttria coatings. The quality of five similar coating lots was judged primarily by their response to burner rig exposure supplemented by data from other sources such as specimen characterizations and thermal diffusivity measurements. After allowing for burner rig variability, although there appears to be an optimum density (i.e., optimum microstructure) for maximum burner rig life, the distribution tends to be rather broad about the maximum. In Part 2, new hafnia-yttria-based coatings were evaluated against both baseline and alternate zirconia-yttria coatings. The hafnia-yttria coatings and the zirconia-yttria coatings that were prepared by an alternate powder vendor were very sensitive to plasma spray parameters, in that high-quality coatings were only obtained when certain parameters were employed. The reasons for this important observation are not understood. Also not understood is that the first of two replicate specimens sprayed for Part 1 consistently performed better than the second specimen. Subsequent experiments did not display this spray order affect, possibly because a chiller was installed in the torch cooling water circuit. Also, large changes in coating density were observed after switching to a new lot of electrodes. Analyses of these findings were made possible, in part, because of the development of a sensitive density measurement technique described herein in detail. The measured thermal diffusivities did not display the expected strong relationship with porosity. This surprising result was believed to have been caused by increased microcracking of the denser coatings on the stainless steel substrates.

  2. Advanced Thermal Energy Storage: Novel Tuning of Critical Fluctuations for Advanced Thermal Energy Storage

    SciTech Connect

    2011-12-01

    HEATS Project: NAVITASMAX is developing a novel thermal energy storage solution. This innovative technology is based on simple and complex supercritical fluids— substances where distinct liquid and gas phases do not exist, and tuning the properties of these fluid systems to increase their ability to store more heat. In solar thermal storage systems, heat can be stored in NAVITASMAX’s system during the day and released at night—when the sun is not shining—to drive a turbine and produce electricity. In nuclear storage systems, heat can be stored in NAVITASMAX’s system at night and released to produce electricity during daytime peak-demand hours.

  3. IMPULSE---an advanced, high performance nuclear thermal propulsion system

    SciTech Connect

    Petrosky, L.J.; Disney, R.K.; Mangus, J.D. ); Gunn, S.A.; Zweig, H.R. )

    1993-01-10

    IMPULSE is an advanced nuclear propulsion engine for future space missions based on a novel conical fuel. Fuel assemblies are formed by stacking a series of truncated (U, Zr)C cones with non-fueled lips. Hydrogen flows radially inward between the cones to a central plenum connected to a high performance bell nozzle. The reference IMPULSE engine rated at 75,000 lb thrust and 1800 MWt weighs 1360 kg and is 3.65 meters in height and 81 cm in diameter. Specific impulse is estimated to be 1000 for a 15 minute life at full power. If longer life times are required, the operating temperature can be reduced with a concomitant decrease in specific impulse. Advantages of this concept include: well defined coolant paths without outlet flow restrictions; redundant orificing; very low thermal gradients and hence, thermal stresses, across the fuel elements; and reduced thermal stresses because of the truncated conical shape of the fuel elements.

  4. Cryogenic Thermal Management Advances during the CRYOTOOL Program

    NASA Astrophysics Data System (ADS)

    Bugby, D.; Stouffer, C.; Garzon, J.; Beres, M.; Gilchrist, A.; Roberts, T.; Davis, T.

    2006-04-01

    This paper describes the cryogenic thermal management advances made during the AFRL-sponsored CRYOTOOL program. Advances occurred as a result of conducting four technology development tasks: (1) development of a differential thermal expansion cryogenic thermal switch (DTE-CTSW) made with high purity Al end-pieces and an Ultem support rod; (2) carrying out of a dual DTE-CTSW/dual cryocooler performance test to quantify CTSW benefits in a redundant cryocooler system; (3) development of a miniaturized cryogenic loop heat pipe (mini-CLHP) that combines flex link, conduction bar, and CTSW functionalities; and (4) development of an across-gimbal cryogenic thermal transport system (GCTTS) with large diameter transport line coils for optics cooling. The results are as follows. The DTE-CTSW achieved an ON conductance of 2-3.6 W/K (from 35-90 K) and an OFF resistance of 1100-2300 K/W (300-230 K warm end). The redundant cryocooler test showed modest parasitic heat leak savings when dual DTE-CTSWs were used versus when they were not used. The mini-CLHP, using neon as the working fluid, transported 2.5 W at 35 K, achieved an OFF resistance of 1555 K/W, and had cross/axial flexibilities of 100-450 N/m. Lastly, GCTTS, using nitrogen as the working fluid, transported 20 W at 100 K in a flat configuration. Additional work is needed to verify GCTTS operation in an elevated orientation.

  5. Advanced thermal energy management: A thermal test bed and heat pipe simulation

    NASA Technical Reports Server (NTRS)

    Barile, Ronald G.

    1986-01-01

    Work initiated on a common-module thermal test simulation was continued, and a second project on heat pipe simulation was begun. The test bed, constructed from surplus Skylab equipment, was modeled and solved for various thermal load and flow conditions. Low thermal load caused the radiator fluid, Coolanol 25, to thicken due to its temperature avoided by using a regenerator-heat-exchanger. Other possible solutions modeled include a radiator heater and shunting heat from the central thermal bus to the radiator. Also, module air temperature can become excessive with high avionics load. A second preoject concerning advanced heat pipe concepts was initiated. A program was written which calculates fluid physical properties, liquid and vapor pressure in the evaporator and condenser, fluid flow rates, and thermal flux. The program is directed to evaluating newer heat pipe wicks and geometries, especially water in an artery surrounded by six vapor channels. Effects of temperature, groove and slot dimensions, and wick properties are reported.

  6. Advanced Stirling Radioisotope Generator Thermal Power Model in Thermal Desktop SINDA/FLUINT Analyzer

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen; Fabanich, William A.; Schmitz, Paul C.

    2012-01-01

    This paper presents a three-dimensional Advanced Stirling Radioisotope Generator (ASRG) thermal power model that was built using the Thermal Desktop SINDA/FLUINT thermal analyzer. The model was correlated with ASRG engineering unit (EU) test data and ASRG flight unit predictions from Lockheed Martin's Ideas TMG thermal model. ASRG performance under (1) ASC hot-end temperatures, (2) ambient temperatures, and (3) years of mission for the general purpose heat source fuel decay was predicted using this model for the flight unit. The results were compared with those reported by Lockheed Martin and showed good agreement. In addition, the model was used to study the performance of the ASRG flight unit for operations on the ground and on the surface of Titan, and the concept of using gold film to reduce thermal loss through insulation was investigated.

  7. Y2O3-MgO Nano-Composite Synthesized by Plasma Spraying and Thermal Decomposition of Solution Precursors

    NASA Astrophysics Data System (ADS)

    Muoto, Chigozie Kenechukwu

    This research aims to identify the key feedstock characteristics and processing conditions to produce Y2O3-MgO composite coatings with high density and hardness using solution precursor plasma spray (SPPS) and suspension plasma spray (SPS) processes, and also, to explore the phenomena involved in the production of homogenized nano-composite powders of this material system by thermal decomposition of solution precursor mixtures. The material system would find potential application in the fabrication of components for optical applications such as transparent windows. It was shown that a lack of major endothermic events during precursor decomposition and the resultant formation of highly dense particles upon pyrolysis are critical precursor characteristics for the deposition of dense and hard Y2O3-MgO coatings by SPPS. Using these principles, a new Y2O3-MgO precursor solution was developed, which yielded a coating with Vickers hardness of 560 Hv. This was a considerable improvement over the hardness of the coatings obtained using conventional solution precursors, which was as low as 110 Hv. In the thermal decomposition synthesis process, binary solution precursor mixtures of: yttrium nitrate (Y[n]) or yttrium acetate (Y[a]), with magnesium nitrate (Mg[n]) or magnesium acetate (Mg[a]) were used in order to study the effects of precursor chemistry on the structural characteristics of the resultant Y2O3-MgO powders. The phase domains were coarse and distributed rather inhomogeneously in the materials obtained from the Y[n]Mg[n] and Y[a]Mg[a] mixtures; finer and more homogeneously-distributed phase domains were obtained for ceramics produced from the Y[a]Mg[n] and Y[n]Mg[a] mixtures. It was established that these phenomena were related to the thermal characteristics for the decomposition of the precursors and their effect on phase separation during oxide crystallization. Addition of ammonium acetate to the Y[n[Mg[n] mixture changed the endothermic process to exothermic

  8. Intelligent Engine Systems: Thermal Management and Advanced Cooling

    NASA Technical Reports Server (NTRS)

    Bergholz, Robert

    2008-01-01

    The objective is to provide turbine-cooling technologies to meet Propulsion 21 goals related to engine fuel burn, emissions, safety, and reliability. Specifically, the GE Aviation (GEA) Advanced Turbine Cooling and Thermal Management program seeks to develop advanced cooling and flow distribution methods for HP turbines, while achieving a substantial reduction in total cooling flow and assuring acceptable turbine component safety and reliability. Enhanced cooling techniques, such as fluidic devices, controlled-vortex cooling, and directed impingement jets, offer the opportunity to incorporate both active and passive schemes. Coolant heat transfer enhancement also can be achieved from advanced designs that incorporate multi-disciplinary optimization of external film and internal cooling passage geometry.

  9. Results of field application and laboratory testing of thermal spray UNS N10276 coating for sour amine vessels

    SciTech Connect

    Baron, J.J.; Hay, M.G.; Goerz, K.G.; Schubert, R.W.; Easterly, F.B.

    1998-12-31

    The Caroline sour gas processing plant pressure vessels were constructed of bare carbon-manganese steel. Early detection of internal surface corrosion and hydrogen blistering led to a decision to field-apply a UNS N10276 coating. The dual-wire arc-spray technique was chosen following a careful review of the technical merits and costs of the alternatives. It was used to coat portions of eight vessels during a planned plant turnaround in 1995. A laboratory program was subsequently initiated in order to define the coating`s corrosion resistance and its effectiveness in preventing corrosion of, and hydrogen damage to, the steel substrate. This program examined the effect of variations in coating thickness and coverage, and steel substrate surface topography on coating performance in simulated rich amine (plant) and standard NACE International sour environments. In addition, an effective field repair procedure was qualified. The results of the inspection of the coating in three vessels after eighteen months` service justified the selection of the coating material and application technique. Only minor repairs to the coating in one vessel were required. This paper gives the results of the laboratory program and plant inspections, and provides guidelines for the application of thermal spray coatings in the field.

  10. High-Velocity Oxygen Fuel Thermal Spray of Fe-Based Amorphous Alloy: a Numerical and Experimental Study

    NASA Astrophysics Data System (ADS)

    Ajdelsztajn, L.; Dannenberg, J.; Lopez, J.; Yang, N.; Farmer, J.; Lavernia, E. J.

    2009-09-01

    The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (<16 μm) and to the fact that the crystallization temperature was not reached in the case of the large particles (16 to 53 μm).

  11. Metal Matrix Composite Coatings Manufactured by Thermal Spraying: Influence of the Powder Preparation on the Coating Properties

    NASA Astrophysics Data System (ADS)

    Aussavy, D.; Costil, S.; El Kedim, O.; Montavon, G.; Bonnot, A.-F.

    2014-01-01

    The purpose of this study is to manufacture metal matrix composite coatings by thermal spraying. In order to improve coating's mechanical properties, it is necessary to increase homogeneity. To meet this objective, the chosen approach was to optimize the powder morphology by mechanical alloying. Indeed, the mechanical alloying method (ball milling) was implemented to synthesize NiCr-Cr3C2 and NiCrBSi-WC composite powders by using cold spraying and high-velocity oxygen fuel process, respectively. After optimizing the process parameters on powder grain size, the composite coatings were compared with standard coatings manufactured from mixed powders. SEM observations, hardness measurements, and XRD analyses were the first technologies implemented to characterize the metal matrix composite coatings. Different characteristics were then observed. When mechanical alloying process is employed to synthesize composite powders strengthened by particle dispersion, the powders tend to fracture into small segments, especially when high content of hard particles is added. Powder microstructures were then refined, which induced thinner coating morphologies and reduced porosity rate. Once an improved microstructure is obtained, manufacturing of coating using milled powders was found suitable in comparison with coatings manufactured only with mixed powders.

  12. Effect of Liquid Feed-Stock Composition on the Morphology of Titanium Dioxide Films Deposited by Thermal Plasma Spray.

    PubMed

    Adán, C; Marugán, J; van Grieken, R; Chien, K; Pershin, L; Coyle, T; Mostaghimi, J

    2015-09-01

    Titanium dioxide coatings were deposited on the surface of titanium foils by Thermal Plasma Spray (TPS) process. Three different TiO2 coatings were prepared using the commercial TiO2-P25 nanopowder and titanium isopropoxide precursor solution as feed-stocks. Structure and morphology of the TiO2-P25 powder and the plasma sprayed coatings were analyzed by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption isotherms, UV-visible spectroscopy and Scanning Electron Microscopy (SEM). XRD and Raman results indicate that the TiO2 coatings were composed of an anatase/rutile mixture that is conditioned by the suspension composition used to be sprayed. Coatings prepared from TiO2-P25 nanoparticles in water suspension (NW-P25) and titanium isopropoxide solution suspension (NSP-P25) are incorporated into the coatings without phase transformation and their anatase/rutile ratio percentage remains very similar to the starting TiO2-P25 powder. On the contrary, when titanium isopropoxide solution is used for spraying (SP), the amount of rutile increases in the final TiO2 coating. SEM analysis also reveals different microstructure morphology, coating thickness, density and porosity of the three TiO2 films that depend significantly on the type of feed-stock employed. Interestingly, we have observed the role of titanium isopropoxide in the formation of more porous and cohesive layers of TiO2. The NSP-P25 coating, prepared with a mix of titanium isopropoxide solution based on TiO2 nanoparticles, presents higher deposition efficiencies and higher coating thickness than the film prepared with nanoparticles suspended in water (NW-P25) or with titanium isopropoxide solutions (SP). This is due to the precursor solution is acting as the cement between TiO2 nanoparticles, improving the cohesive strength of the coating. In sum, NSP-P25 and NW-P25 coatings display a good photocatalytic potential, based on their light absorption properties and mechanical stability. Band gap of

  13. Design, characterization, and aerosolization of organic solution advanced spray-dried moxifloxacin and ofloxacin dipalmitoylphosphatidylcholine (DPPC) microparticulate/nanoparticulate powders for pulmonary inhalation aerosol delivery

    PubMed Central

    Duan, Jinghua; Vogt, Frederick G; Li, Xiaojian; Hayes, Don; Mansour, Heidi M

    2013-01-01

    The aim of this study was to design and develop respirable antibiotics moxifloxacin (MOXI) hydrochloride and ofloxacin (OFLX) microparticles and nanoparticles, and multifunctional antibiotics particles with or without lung surfactant 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced by advanced spray-drying particle engineering from an organic solution in closed mode (no water) from dilute solution. Scanning electron microscopy indicated that these particles had both optimal particle morphology and surface morphology, and the particle size distributions were suitable for pulmonary delivery. Comprehensive and systematic physicochemical characterization and in vitro aerosol dispersion performance revealed significant differences between these two fluoroquinolone antibiotics following spray drying as drug aerosols and as cospray-dried antibiotic drug: DPPC aerosols. Fourier transform infrared spectroscopy and confocal Raman microspectroscopy were employed to probe composition and interactions in the solid state. Spray-dried MOXI was rendered noncrystalline (amorphous) following organic solution advanced spray drying. This was in contrast to spray-dried OFLX, which retained partial crystallinity, as did OFLX:DPPC powders at certain compositions. Aerosol dispersion performance was conducted using inertial impaction with a dry powder inhaler device approved for human use. The present study demonstrates that the use of DPPC offers improved aerosol delivery of MOXI as cospray-dried microparticulate/nanoparticulate powders, whereas residual partial crystallinity influenced aerosol dispersion of OFLX and most of the compositions of OFLX:DPPC inhalation powders. PMID:24092972

  14. Surface preparation and thermal spray in a single step: The PROTAL process—Example of application for an aluminum-base substrate

    NASA Astrophysics Data System (ADS)

    Coddet, C.; Montavon, G.; Ayrault-Costil, S.; Freneaux, O.; Rigolet, F.; Barbezat, G.; Folio, F.; Diard, A.; Wazen, P.

    1999-06-01

    Thermal spray techniques can fulfill numerous industrial applications. Coatings are thus applied to resist wear and corrosion or to modify the surface characteristics of the substrate (e.g., thermal conductivity/thermal insulation). However, many of these applications remain inhibited by some deposit characteristics, such as a limited coating adhesion or pores or by industrial costs because several nonsynchronized and sequential steps (that is, degreasing, sand blasting, and spraying) are needed to manufacture a deposit. The PROTAL process was designed to reduce the aforementioned difficulties by implementing simultaneously a Q-switched laser and a thermal spray torch. The laser irradiation is primarily aimed to eliminate the contamination films and oxide layers, to generate a surface state enhancing the deposit adhesion, and to limit the contamination of the deposited layers by condensed vapors. From PROTAL arises the possibility to reduce, indeed suppress, the preliminary steps of degreasing and grit blasting. In this study, the benefits of the PROTAL process were investigated, comparing adhesion of different atmospheric plasma spray coatings (e.g., metallic and ceramic coatings) on an aluminum-base substrate. Substrates were coated rough from the machine shop, for example, manipulated barehanded and without any prior surface preparation. Results obtained this way were compared with those obtained using a classical procedure; that is, degreasing and grit blasting prior to the coating deposition.

  15. solar thermal power systems advanced solar thermal technology project, advanced subsystems development

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The preliminary design for a prototype small (20 kWe) solar thermal electric generating unit was completed, consisting of several subsystems. The concentrator and the receiver collect solar energy and a thermal buffer storage with a transport system is used to provide a partially smoothed heat input to the Stirling engine. A fossil-fuel combustor is included in the receiver designs to permit operation with partial or no solar insolation (hybrid). The engine converts the heat input into mechanical action that powers a generator. To obtain electric power on a large scale, multiple solar modules will be required to operate in parallel. The small solar electric power plant used as a baseline design will provide electricity at remote sites and small communities.

  16. Iron-Based Amorphous Coatings Produced by HVOF Thermal Spray Processing-Coating Structure and Properties

    SciTech Connect

    Beardsley, M B

    2008-03-26

    The feasibility to coat large SNF/HLW containers with a structurally amorphous material (SAM) was demonstrated on sub-scale models fabricated from Type 316L stainless steel. The sub-scale model were coated with SAM 1651 material using kerosene high velocity oxygen fuel (HVOF) torch to thicknesses ranging from 1 mm to 2 mm. The process parameters such as standoff distance, oxygen flow, and kerosene flow, were optimized in order to improve the corrosion properties of the coatings. Testing in an electrochemical cell and long-term exposure to a salt spray environment were used to guide the selection of process parameters.

  17. Compositions of corrosion-resistant Fe-based amorphous metals suitable for producing thermal spray coatings

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M. G.; Haslam, Jeffery J.; Ji, Xiaoyan; Day, Sumner D.; Blue, Craig A.; Rivard, John D. K.; Aprigliano, Louis F.; Kohler, Leslie K.; Bayles, Robert; Lemieux, Edward J.; Yang, Nancy; Perepezko, John H.; Kaufman, Larry; Heuer, Arthur; Lavernia, Enrique J.

    2013-07-09

    A method of coating a surface comprising providing a source of amorphous metal that contains manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron; and applying said amorphous metal to the surface by a spray.

  18. Compositions of corrosion-resistant Fe-based amorphous metals suitable for producing thermal spray coatings

    DOEpatents

    Farmer, Joseph C; Wong, Frank M.G.; Haslam, Jeffery J; Ji, Xiaoyan; Day, Sumner D; Blue, Craig A; Rivard, John D.K.; Aprigliano, Louis F; Kohler, Leslie K; Bayles, Robert; Lemieux, Edward J; Yang, Nancy; Perepezko, John H; Kaufman, Larry; Heuer, Arthur; Lavernia, Enrique J

    2013-09-03

    A method of coating a surface comprising providing a source of amorphous metal that contains manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron; and applying said amorphous metal to the surface by a spray.

  19. Advanced thermal management needs for Lunar and Mars missions

    SciTech Connect

    Klein, A.C. ); Webb, B.J. )

    1993-01-15

    Significant improvements in thermal management technologies will be required to support NASA's planned Lunar and Mars missions. The developments needed include the application of advanced materials to reduce radiator system masses, enhanced survivability, and the use of alternative working fluids. Current thermal management systems utilize one of two heat rejection alternatives; either single phase pumped loops, or two phase heat pipes constructed with thick walled metal casings. These two technologies have proven themselves to be reliable performers in the transport and rejection of waste heat from spacecraft. As thermal management needs increase with increased power consumption and activity required on spacecraft, these metal based thermal management systems will become mission limiting. Investigations into the use of light weight ceramic materials for high temperature thermal management systems have been conducted by NASA, the Department of Energy, and the Department of Defense since the early 1980s, with results showing that significant mass savings can be obtained by replacing some of the metallic functions with ceramic materials.

  20. Advanced Mirror Technology Development (AMTD) Thermal Trade Studies

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas

    2015-01-01

    Advanced Mirror Technology Development (AMTD) is being done at Marshall Space Flight Center (MSFC) in preparation for the next large aperture UVOIR space observatory. A key science mission of that observatory is the detection and characterization of 'Earth-like' exoplanets. Direct exoplanet observation requires a telescope to see a planet which will be 10(exp -10) times dimmer than its host star. To accomplish this using an internal coronagraph requires a telescope with an ultra-stable wavefront error (WFE). This paper investigates parametric relationships between primary mirror physical parameters and thermal WFE stability. Candidate mirrors are designed as a mesh and placed into a thermal analysis model to determine the temperature distribution in the mirror when it is placed inside of an actively controlled cylindrical shroud at Lagrange point 2. Thermal strains resulting from the temperature distribution are found and an estimation of WFE is found to characterize the effect that thermal inputs have on the optical quality of the mirror. This process is repeated for several mirror material properties, material types, and mirror designs to determine how to design a mirror for thermal stability.

  1. High temperature oxidation of HFPD thermal-sprayed MCrAlY coatings in simulated gas turbine environments

    NASA Astrophysics Data System (ADS)

    Belzunce, F. J.; Higuera, V.; Poveda, S.; Carriles, A.

    2002-12-01

    NiCrAlY and CoNiCrAlY powders were thermal-sprayed using the high frequency pulse detonation method (HFPD) onto AISI 310 austenitic stainless steel samples to obtain dense, adherent, high temperature oxidation resistant coatings. The oxidation behavior of both types of coatings in a 1000°C simulated gas turbine environment was experimentally determined. The porosity, hardness, coating thickness, and microstructure were not significantly modified by the high temperature oxidation cycles, but the internal oxidation increases significantly after a very low oxidation time. Surface phase composition was evaluated using x-ray diffraction (XRD) and scanning electron microscope (SEM) techniques, revealing the formation of a continuous and highly protective alumina layer. The oxidation kinetics of both coatings can be characterized by parabolic rate constants, which are very close to those for the formation of aluminum oxide on nickel or cobalt based alloys at similar conditions.

  2. Heat Treatment of Thermal Spray Duplex Coating System of Aluminum-Nickel Chromium Alloy on Carbon Steel

    NASA Astrophysics Data System (ADS)

    Quoc Ly, Cuong; Thu Le, Quy; Van Nguyen, Tuan; Thi To Phung, Hang; The Ngo, Dien

    2013-12-01

    This paper presents our study on the influence of heat treatment at 550 °C on microstructure and microhardness of an Al-NiCr20 duplex coating prepared on low carbon steel CT38 by electric-arc thermal spray. The annealing duration was in a range of 2-8 h. It was found that after annealing, metallic grains inside the coatings became flatter and the coating's porosity decreased considerably. The phase analysis by SEM-EDS in combination with microstructural observation using an optical microscope showed a formation of two diffusion layers at the interfaces "NiCr20-Al" and "Al-steel" with very high microhardness > 900 HV. Based on chemical analysis by SEM-EDS, the chemical formulas of the formed intermetallic compounds are proposed.

  3. One-dimensional and quasi-one-dimensional ZnO nanostructures prepared by spray-pyrolysis-assisted thermal evaporation

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Cheng; Cai, Wei

    2008-03-01

    One-dimensional (1D) and quasi-1D ZnO nanostructures have been fabricated by a kind of new spray-pyrolysis-assisted thermal evaporation method. Pure ZnO powder serves as an evaporation source. Thus-obtained products have been characterized by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM). The room temperature photoluminescence spectrum of these ZnO nanostructures is presented. The results show that as-grown ZnO nanomaterials have a hexagonal wurtzite crystalline structure. Besides nanosaws, nanobelts and nanowires, complex ZnO nanotrees have also been observed in synthesized products. The study provides a new simple route to construct 1D and quasi-1D ZnO nanomaterials, which can probably be extended to fabricate other oxide nanomaterials with high melting point and doped oxide nanomaterials.

  4. Advanced concepts in ground thermal energy storage systems

    NASA Astrophysics Data System (ADS)

    Woods, Kevin David

    In recent years, ground thermal energy storage has become a topic of interest in the energy community for solar thermal energy storage systems, ground sourced heat pump systems, and data center thermal management systems due to an increase in the energy efficiency of such systems utilizing the ground as a thermal reservoir. The most common method for transferring thermal energy to the ground formation is the geothermal borehole. This dissertation presents the state of the art in geothermal borehole modeling and derives novel analytical functions to model advanced concepts concerning their operation. The novel solutions derived allow a geothermal borehole designer to better understand and design ground energy storage systems. The state of the art in geothermal borehole modeling is the stationary line source solution which is limited to boreholes operating without groundwater flow. Novel solutions for modeling a geothermal borehole with groundwater advection are presented through derivation of a transient moving line source solution as well as a transient moving cylindrical surface source solution. These solutions are applied to model a specific type of open loop geothermal borehole called a standing column well with groundwater advection and are compared to empirical and numerical data for validation. The dissertation then moves into derivation of a property determination method for geothermal boreholes with groundwater advection. The traditional property determination method used to obtain ground formation properties is based on the stationary transient line source method and fails in the presence of groundwater flow. The proposed novel property determination method calculates the thermal conductivity, thermal diffusivity, and superficial flow velocity of groundwater within a ground formation. These methods and solutions are novel tools allowing for geothermal borehole designers to grasp a better understanding of the systems they are designing as well as open other

  5. In Situ Wear Test on Thermal Spray Coatings in a Large Chamber Scanning Electron Microscope

    NASA Astrophysics Data System (ADS)

    Luo, Weifeng; Tillmann, Wolfgang; Selvadurai, Ursula

    2015-01-01

    Currently, the determination of the mass loss is usually used for a quantitative evaluation of wear tests, while the analysis of wear tracks is utilized for a qualitative evaluation of wear. Both evaluation methods can only be used after the wear testing process and their results only present the final outcome of the wear test. However, the changes during the wear test and the time-dependent wear mechanisms are of great interest as well. A running wear test in a large chamber scanning electron microscope (SEM) offers the first opportunity to observe the wear process in situ. Different wear mechanisms, such as the adhesive, abrasive wear, surface fatigue and tribochemical reaction, can be recorded with high magnification. Within this research, a special pin-on-disk testing device is designed for a vacuum environment. Using this device, arc-sprayed NiCrBSi coatings and high-velocity-oxygen-fuel-sprayed WC-12Co coatings were tested in a large chamber SEM with Al2O3 ceramic balls as wear counterparts. During the wear testing, different wear mechanisms were determined and the processes were recorded in short video streams.

  6. Development of Advanced LED Phosphors by Spray-based Processes for Solid State Lighting

    SciTech Connect

    Cabot Corporation

    2007-09-30

    The overarching goal of the project was to develop luminescent materials using aerosol processes for making improved LED devices for solid state lighting. In essence this means improving white light emitting phosphor based LEDs by improvement of the phosphor and phosphor layer. The structure of these types of light sources, displayed in Figure 1, comprises of a blue or UV LED under a phosphor layer that converts the blue or UV light to a broad visible (white) light. Traditionally, this is done with a blue emitting diode combined with a blue absorbing, broadly yellow emitting phosphor such as Y{sub 3}Al{sub 5}O{sub 12}:Ce (YAG). A similar result may be achieved by combining a UV emitting diode and at least three different UV absorbing phosphors: red, green, and blue emitting. These emitted colors mix to make white light. The efficiency of these LEDs is based on the combined efficiency of the LED, phosphor, and the interaction between the two. The Cabot SSL project attempted to improve the over all efficiency of the LED light source be improving the efficiency of the phosphor and the interaction between the LED light and the phosphor. Cabot's spray based process for producing phosphor powders is able to improve the brightness of the powder itself by increasing the activator (the species that emits the light) concentration without adverse quenching effects compared to conventional synthesis. This will allow less phosphor powder to be used, and will decrease the cost of the light source; thus lowering the barrier of entry to the lighting market. Cabot's process also allows for chemical flexibility of the phosphor particles, which may result in tunable emission spectra and so light sources with improved color rendering. Another benefit of Cabot's process is the resulting spherical morphology of the particles. Less light scattering results when spherical particles are used in the phosphor layer (Figure 1) compared to when conventional, irregular shaped phosphor particles

  7. Advancing Model Systems for Fundamental Laboratory Studies of Sea Spray Aerosol Using the Microbial Loop.

    PubMed

    Lee, Christopher; Sultana, Camille M; Collins, Douglas B; Santander, Mitchell V; Axson, Jessica L; Malfatti, Francesca; Cornwell, Gavin C; Grandquist, Joshua R; Deane, Grant B; Stokes, M Dale; Azam, Farooq; Grassian, Vicki H; Prather, Kimberly A

    2015-08-20

    Sea spray aerosol (SSA) particles represent one of the most abundant surfaces available for heterogeneous reactions to occur upon and thus profoundly alter the composition of the troposphere. In an effort to better understand tropospheric heterogeneous reaction processes, fundamental laboratory studies must be able to accurately reproduce the chemical complexity of SSA. Here we describe a new approach that uses microbial processes to control the composition of seawater and SSA particle composition. By inducing a phytoplankton bloom, we are able to create dynamic ecosystem interactions between marine microorganisms, which serve to alter the organic mixtures present in seawater. Using this controlled approach, changes in seawater composition become reflected in the chemical composition of SSA particles 4 to 10 d after the peak in chlorophyll-a. This approach for producing and varying the chemical complexity of a dominant tropospheric aerosol provides the foundation for further investigations of the physical and chemical properties of realistic SSA particles under controlled conditions. PMID:26196268

  8. Validation Database Based Thermal Analysis of an Advanced RPS Concept

    NASA Technical Reports Server (NTRS)

    Balint, Tibor S.; Emis, Nickolas D.

    2006-01-01

    Advanced RPS concepts can be conceived, designed and assessed using high-end computational analysis tools. These predictions may provide an initial insight into the potential performance of these models, but verification and validation are necessary and required steps to gain confidence in the numerical analysis results. This paper discusses the findings from a numerical validation exercise for a small advanced RPS concept, based on a thermal analysis methodology developed at JPL and on a validation database obtained from experiments performed at Oregon State University. Both the numerical and experimental configurations utilized a single GPHS module enabled design, resembling a Mod-RTG concept. The analysis focused on operating and environmental conditions during the storage phase only. This validation exercise helped to refine key thermal analysis and modeling parameters, such as heat transfer coefficients, and conductivity and radiation heat transfer values. Improved understanding of the Mod-RTG concept through validation of the thermal model allows for future improvements to this power system concept.

  9. Intelligent Engine Systems: Thermal Management and Advanced Cooling

    NASA Technical Reports Server (NTRS)

    Bergholz, Robert

    2008-01-01

    The objective of the Advanced Turbine Cooling and Thermal Management program is to develop intelligent control and distribution methods for turbine cooling, while achieving a reduction in total cooling flow and assuring acceptable turbine component safety and reliability. The program also will develop embedded sensor technologies and cooling system models for real-time engine diagnostics and health management. Both active and passive control strategies will be investigated that include the capability of intelligent modulation of flow quantities, pressures, and temperatures both within the supply system and at the turbine component level. Thermal management system concepts were studied, with a goal of reducing HPT blade cooling air supply temperature. An assessment will be made of the use of this air by the active clearance control system as well. Turbine component cooling designs incorporating advanced, high-effectiveness cooling features, will be evaluated. Turbine cooling flow control concepts will be studied at the cooling system level and the component level. Specific cooling features or sub-elements of an advanced HPT blade cooling design will be downselected for core fabrication and casting demonstrations.

  10. Deposition of Workability-Enhancing Disposable Thick Fe Deposits on Fe-Si Alloy Sheets Using Thermal and Kinetic Spray Processes

    NASA Astrophysics Data System (ADS)

    Kim, Jaeick; Lee, Changhee; Kim, Sanghoon

    2015-02-01

    Fe-Si alloys are widely applied materials in industrial fields due to their magnetic properties. However, these alloys are difficult to manufacture due to the high oxidation affinity of Fe-Si alloys at high temperature; further, the permanence of the formed oxides (i.e., Fe2SiO4) degrade their workability. In order to solve this problem, disposable workability-improving `thick' coating layers were deposited on Fe-Si alloy substrates in this study using plain carbon steel wire and pure Fe powder via thermal and kinetic spraying processes. The resulting deposits were compared in terms of microstructure and mechanical properties. In thermal sprayed deposit, the oxides degraded mechanical properties, but were helpful for the deposition of a thick layer by restraining bending by thermally induced tensile residual stress. On the other hand, kinetic sprayed deposit showed better adhesive bond strength owing to the compressive residual stress. After a post heating, it was observed that the type of oxides was not affected by diffusion of Si elements from the substrate due to the limited diffusion length of Si elements. Imperfect chemical/metallurgical bonding between the deposit and substrate was also observed. Further, mechanical properties of post heat-treated specimens were enhanced relative to the as-sprayed state.

  11. Development of processing techniques for advanced thermal protection materials

    NASA Technical Reports Server (NTRS)

    Selvaduray, Guna S.

    1994-01-01

    The effort, which was focused on the research and development of advanced materials for use in Thermal Protection Systems (TPS), has involved chemical and physical testing of refractory ceramic tiles, fabrics, threads and fibers. This testing has included determination of the optical properties, thermal shock resistance, high temperature dimensional stability, and tolerance to environmental stresses. Materials have also been tested in the Arc Jet 2 x 9 Turbulent Duct Facility (TDF), the 1 atmosphere Radiant Heat Cycler, and the Mini-Wind Tunnel Facility (MWTF). A significant part of the effort hitherto has gone towards modifying and upgrading the test facilities so that meaningful tests can be carried out. Another important effort during this period has been the creation of a materials database. Computer systems administration and support have also been provided. These are described in greater detail below.

  12. Advanced optical and thermal technologies for aperture control

    SciTech Connect

    Selkowitz, S.E.; Lampert, C.M.; Rubin, M.

    1982-09-01

    Control of heat transfer and radiant energy flow through building apertures is essential for maximizing thermal and daylighting benefits and minimizing undesired heating and cooling loads. Architectural solutions based on current technology generally add devices such as louvers, shutters, shades, or blinds to the glazing system. The objectives and initial accomplishments of a research program the goal of which is to identify and evaluate advanced optical and thermal technologies for controlling aperture energy flows, thus reducing building energy requirements are outlined. Activities are described in four program areas: (1) low-conductance, high-transmittance glazing materials (e.g., heat mirrors, aerogels); (2) optical switching materials (e.g., electrochromic, photochromic); (3) selective transmitters; and (4) daylight enhancement techniques.

  13. Advanced optical and thermal technologies for aperture control

    SciTech Connect

    Selkowitz, S.E.; Lampert, C.M.; Rubin, M.

    1983-11-01

    Control of heat transfer and radiant energy flow through building apertures is essential for maximizing thermal and daylighting benefits and minimizing undesired heating and cooling loads. Architectural solutions based on current technology generally add devices such as louvers, shutters, shades, or blinds to the glazing system. The objectives and initial accomplishments of a research program are outlined, the goal of which is to identify and evaluate advanced optical and thermal technologies for controlling aperture energy flows, thus reducing building energy requirements. Activities in four program areas are described: (1) low-conductance, high-transmittance glazing materials (e.g., heat mirrors, aerogels) (2) optical switching materials (e.g., electrochromic, photochromic) (3) selective transmitters and (4) daylight enhancement techniques.

  14. Advanced NDE research in electromagnetic, thermal, and coherent optics

    NASA Technical Reports Server (NTRS)

    Skinner, S. Ballou

    1992-01-01

    A new inspection technology called magneto-optic/eddy current imaging was investigated. The magneto-optic imager makes readily visible irregularities and inconsistencies in airframe components. Other research observed in electromagnetics included (1) disbond detection via resonant modal analysis; (2) AC magnetic field frequency dependence of magnetoacoustic emission; and (3) multi-view magneto-optic imaging. Research observed in the thermal group included (1) thermographic detection and characterization of corrosion in aircraft aluminum; (2) a multipurpose infrared imaging system for thermoelastic stress detection; (3) thermal diffusivity imaging of stress induced damage in composites; and (4) detection and measurement of ice formation on the space shuttle main fuel tank. Research observed in the optics group included advancements in optical nondestructive evaluation (NDE).

  15. Limiting factors to advancing thermal battery technology for naval applications

    NASA Astrophysics Data System (ADS)

    Davis, Patrick B.; Winchester, Clinton S.

    1991-10-01

    Thermal batteries are primary reserve electrochemical power sources using molten salt electrolyte which experience little effective aging while in storage or dormant deployment. Thermal batteries are primarily used in military applications, and are currently used in a wide variety of Navy devices such as missiles, torpedoes, decays, and training targets, usually as power supplies in guidance, propulsion, and Safe/Arm applications. Technology developments have increased the available energy and power density ratings by an order of magnitude in the last ten years. Present thermal batteries, using lithium anodes and metal sulfide cathodes, are capable of performing applications where only less rugged and more expensive silver oxide/zinc or silver/magnesium chloride seawater batteries could serve previously. Additionally, these batteries are capable of supplanting lithium/thionyl chloride reserve batteries in a variety of specifically optimized designs. Increases in thermal battery energy and power density capabilities are not projected to continue with the current available technology. Several battery designs are now at the edge of feasibility and safety. Since future naval systems are likely to require continued growth of battery energy and power densities, there must be significant advances in battery technology. Specifically, anode alloy composition and new cathode materials must be investigated to allow for safe development and deployment of these high power, higher energy density batteries.

  16. Advanced solar thermal technologies for the 21st century

    NASA Technical Reports Server (NTRS)

    Kohout, L. L.; Perez-Davis, M. E.

    1986-01-01

    The paper considers the present status of solar thermal dynamic space power technologies and projects the various attributes of these systems into the future, to the years 2000 and 2010. By the year 2000, collector weights should decrease from 1.25 kg/sq m (1985 value) to about 1.0 kg/sq m. The specific weight is also expected to decrease from 6.0 kg/kw. By the year 2010, slight improvements in the free piston Stirling energy conversion system are postulated with efficiencies reaching 32 percent. In addition, advanced concentrator concepts should be operational.

  17. Standard specification for spray-applied rigid cellular polyurethane thermal insulation. ASTM standard

    SciTech Connect

    Not Available

    1996-11-01

    DoD adopted. This practice is under the jurisdiction of ASTM Committee C-16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.22 on Organic and Nonhomogeneous Inorganic Thermal Insulations. Current edition approved Sep. 10, 1996. Published November 1996. Originally published as C 1029-85. Last previous edition was C 1029-90.

  18. Accumulated damage process of thermal sprayed coating under rolling contact by acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Xu, Jia; Zhou, Zhen-yu; Piao, Zhong-yu

    2016-07-01

    The accumulated damage process of rolling contact fatigue (RCF) of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-ondisc machine was employed to conduct RCF experiments. Acoustic emission (AE) technique was introduced to monitor the RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.

  19. Sliding Wear Properties of HVOF Thermally Sprayed Nylon-11 and Nylon-11/Ceramic Composites on Steel

    NASA Astrophysics Data System (ADS)

    Jackson, L.; Ivosevic, M.; Knight, R.; Cairncross, R. A.

    2007-12-01

    Polymer and polymer/ceramic composite coatings were produced by ball-milling 60 μm Nylon-11 together with nominal 10 vol.% of nano and multiscale ceramic reinforcements and by HVOF spraying these composite feedstocks onto steel substrates to produce semicrystalline micron and nanoscale reinforced polymer matrix composites. Room temperature dry sliding wear performance of pure Nylon-11, Nylon-11 reinforced with 7 nm silica, and multiscale Nylon-11/silica composite coatings incorporating 7-40 nm and 10 μm ceramic particles were characterized using a pin-on-disk tribometer. Coefficient of friction and wear rate were determined as a function of applied load and coating composition. Surface profilometry and scanning electron microscopy were used to characterize and analyze the coatings and wear scars. The pure Nylon-11 coating experienced less wear than the composites due to the occurrence of two additional wear mechanisms: abrasive and fatigue wear.

  20. Analytical investigation of thermal barrier coatings for advanced power generation combustion turbines

    NASA Technical Reports Server (NTRS)

    Amos, D. J.

    1977-01-01

    An analytical evaluation was conducted to determine quantitatively the improvement potential in cycle efficiency and cost of electricity made possible by the introduction of thermal barrier coatings to power generation combustion turbine systems. The thermal barrier system, a metallic bond coat and yttria stabilized zirconia outer layer applied by plasma spray techniques, acts as a heat insulator to provide substantial metal temperature reductions below that of the exposed thermal barrier surface. The study results show the thermal barrier to be a potentially attractive means for improving performance and reducing cost of electricity for the simple, recuperated, and combined cycles evaluated.