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1

Vacuum plasma spray coating  

NASA Technical Reports Server (NTRS)

Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

Holmes, Richard R.; Mckechnie, Timothy N.

1989-01-01

2

Vacuum Plasma Spray Coating.  

National Technical Information Service (NTIS)

Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for...

R. R. Holmes T. N. McKechnie

1989-01-01

3

Vacuum Plasma Spraying Replaces Electrodeposition  

NASA Technical Reports Server (NTRS)

Vacuum plasma spraying used to fabricate large parts with complicated contours and inner structures, without uninspectable welds. Reduces time, and expense of fabrication. Wall of combustion chamber built up inside of outer nickel-alloy jacket by plasma spraying. Particles of metal sprayed partially melted in plasma gun and thrown at supersonic speed toward deposition surface. Vacuum plasma-spray produces stronger bond between the grooves and covering layer completing channels and wall of combustion chamber. In tests, bond withstood pressure of 20 kpsi, three times allowable limit by old method.

Holmes, Richard R.; Power, Chris; Burns, David H.; Daniel, Ron; Mckechnie, Timothy N.

1992-01-01

4

Thermal expansion of vacuum plasma sprayed coatings  

Microsoft Academic Search

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 1223K. The corrected thermal expansion, (?L\\/L0)thermal, varies with the absolute temperature, T, as?LL0thermal=A(T?293)3+B(T?293)2+C(T?293)+Dwhere A, B, C and D are regression constants. Excellent reproducibility was observed for all of the coatings except for data obtained on

S. V. Raj; A. Palczer

2010-01-01

5

Alignment Fixtures For Vacuum-Plasma-Spray Gun  

NASA Technical Reports Server (NTRS)

Fixtures for alignment of vacuum-plasma-spray guns built. Each fixture designed to fit specific gun and holds small, battery-powered laser on centerline of gun. Laser beam projects small red dot where centerline intersects surface of workpiece to be sprayed. After laser beam positioned on surface of workpiece, fixture removed from gun and spraying proceeds.

Woodford, William H.; Mckechnie, Timothy N.; Power, Christopher A.; Daniel, Ronald L., Jr.

1993-01-01

6

Thermal Expansion of Vacuum Plasma Sprayed Coatings  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

7

Microstructure of vacuum plasma-sprayed boron carbide  

Microsoft Academic Search

In the present study, boron carbide was deposited on Ti-6%Al-4%V alloy by vacuum plasma spraying. Chemical and phase compositions\\u000a of the initial starting powder and the as-sprayed deposit were characterized using hot gas extraction, x-ray photoelectron\\u000a spectroscopy, Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Mechanical properties of the deposition\\u000a were assessed by microhardness and nanohardness indentation. The microstructure consisted

H. R. Salimijazi; T. W. Coyle; J. Mostaghimi; L. Leblanc

2005-01-01

8

Preventing Clogging In A Vacuum Plasma Spray Gun  

NASA Technical Reports Server (NTRS)

Modification of powder-injection ports enables lengthy, high-temperature deposition operations. Graphite inserts prevent clogging of ports through which copper powder injected into vacuum plasma spray (VPS) gun. Graphite liners eliminate need to spend production time refurbishing VPS gun, reducing cost of production and increasing productivity. Concept also applied to other material systems used for net-shape fabrication via VPS.

Krotz, Phillip D.; Daniel, Ronald L., Jr.; Davis, William M.

1994-01-01

9

Removable Mandrels For Vacuum-Plasma-Spray Forming  

NASA Technical Reports Server (NTRS)

Improved mandrels developed for use in vacuum-plasma-spray (VPS) forming of refractory metal and ceramic furnace cartridge tubes. Designed so after tubes formed on them by VPS, mandrels shrink away from tubes upon cooling back to room temperature and simply slip out of tube.

Krotz, Phillip D.; Davis, William M.; Power, Christopher A.; Woodford, William H.; Todd, Douglas M.; Liaw, Yoon K.; Holmes, Richard R.; Zimmerman, Frank R.; Mckechnie, Timothy N.

1995-01-01

10

Vacuum plasma spray applications on liquid fuel rocket engines  

Microsoft Academic Search

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z,

T. N. McKechnie; F. R. Zimmerman; M. A. Bryant

1992-01-01

11

Vacuum-plasma-sprayed silicon coatings for biomedical application  

Microsoft Academic Search

Silicon coating was deposited on titanium alloy substrates by vacuum plasma spraying technology. The morphologies and phase composition of the coatings were analyzed by field-emission scanning electron microscopy and X-ray diffraction. The thermal expansion coefficient of silicon coating was measured to be about 3.70×10?6 K?1. The bond strength of coating was approximately 20.6 MPa. The density, open porosity, roughness and Young's

Yaran Niu; Xuanyong Liu; Chuanxian Ding

2008-01-01

12

Laser glazing of vacuum plasma spray coated NARloy-Z  

Microsoft Academic Search

A CO2 laser was used to modify the surface layer of vacuum plasma sprayed NARloy-Z (Cu-3 wt.%Ag-0.5 wt.%Zr). The laser glazing dramatically reduced voids and cavities originally present in the alloy matrix. In addition, grain boundary precipitates were eliminated. A highly refined microstructure was obtained with extended solid solubility of solute atoms (Ag and Zr) into the matrix. A theoretical

J. Singh; B. N. Bhat; R. Poorman; A. Kar; J. Mazumder

1996-01-01

13

Vacuum plasma spray applications on liquid fuel rocket engines  

NASA Technical Reports Server (NTRS)

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

Mckechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

1992-01-01

14

Vacuum plasma spray applications on liquid fuel rocket engines  

NASA Astrophysics Data System (ADS)

The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

McKechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

1992-07-01

15

Electrical characterization of vacuum plasma sprayed polycrystalline silicon  

NASA Astrophysics Data System (ADS)

Development in thin film growth techniques and understanding of transport phenomenon in polycrystalline semiconductors, has led to the development of active electronic devices using polycrystalline semiconductors, especially made of polycrystalline silicon. This dissertation is mainly concerned with understanding electrical transport in polycrystalline silicon made by Vacuum Plasma Spray, a high throughput process for making polycrystalline coatings. The essential question we ask ourselves is "Can we make an electronic device that uses plasma sprayed polycrystalline silicon as the active layer?". This general question was broken into three basic questions that have been answered to varying degrees of success. (1) What is the crystal structure, typical grain size and microstructure of VPS silicon? How do these change upon post deposition heat treatments? X-ray diffraction, Scanning Electron Microscopy and Transmission Electron Microscopy experiments have been employed to answer this question. Grain growth is shown to happen through the resolution of Cu Kalpha doublet for annealed samples. SEM and TEM micrographs show the laminar microstructure that is common for plasma sprayed coatings. (2) Does plasma sprayed polycrystaline silicon show semi-conducting behavior? If so does it retain the conductivity of the original source from which the powders were made? What is the nature of electrical conduction mechanism in VPS silicon? VPS silicon does show semi-conducting behavior and has the same type of conductivity as the starting material. Temperature dependent conductivity measurements show the presence of two activation energy for charge transport in operation in two different temperature ranges. (3) Can a model device be made using VPS silicon which can help in understanding intrinsic nature of VPS silicon and also offer possibilities for device applications? VPS polycrystalline silicon---single crystal silicon junction has been made and the nature of current transport across this interface elucidated. A critical evaluation of the plasma spray process is presented vis-a-vis the electronic properties of polycrystalline silicon and suggestions for improvement are presented.

Srinivasan, Narasimhan

16

Vacuum Plasma Spray Forming of Tungsten Lorentz Force Accelerator Components  

NASA Technical Reports Server (NTRS)

The Vacuum Plasma Spray (VPS) Laboratory at NASA's Marshall Space Flight Center, working with the Jet Propulsion Laboratory, has developed and demonstrated a fabrication technique using the VPS process to form anode and cathode sections for a Lorentz force accelerator made from tungsten. Lorentz force accelerators are an attractive form of electric propulsion that provides continuous, high-efficiency propulsion at useful power levels for such applications as orbit transfers or deep space missions. The VPS process is used to deposit refractory metals such as tungsten onto a graphite mandrel of the desired shape. Because tungsten is reactive at high temperatures, it is thermally sprayed in an inert environment where the plasma gun melts and deposits the molten metal powder onto a mandrel. A three-axis robot inside the chamber controls the motion of the plasma spray torch. A graphite mandrel acts as a male mold, forming the required contour and dimensions for the inside surface of the anode or cathode of the accelerator. This paper describes the processing techniques, design considerations, and process development associated with the VPS forming of Lorentz force accelerator components.

Zimmerman, Frank R.

2004-01-01

17

Vacuum Plasma Spray Forming of Tungsten Lorentz Force Accelerator Components  

NASA Technical Reports Server (NTRS)

The Vacuum Plasma Spray (VPS) Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using the VPS process to form anode sections for a Lorentz force accelerator from tungsten. Lorentz force accelerators are an attractive form of electric propulsion that provides continuous, high-efficiency propulsion at useful power levels for such applications as orbit transfers or deep space missions. The VPS process is used to deposit refractory metals such as tungsten onto a graphite mandrel of the desired shape. Because tungsten is reactive at high temperatures, it is thermally sprayed in an inert environment where the plasma gun melts and accelerates the metal powder onto the mandrel. A three-axis robot inside the chamber controls the motion of the plasma spray torch. A graphite mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the anode. This paper describes the processing techniques, design considerations, and process development associated with the VPS forming of the Lorentz force accelerator.

Zimmerman, Frank R.

2001-01-01

18

Effects of power level on characteristics of vacuum plasma sprayed hydroxyapatite coating  

NASA Astrophysics Data System (ADS)

In this study, hydroxyapatite coatings were obtained with a vacuum plasma spray system at different power levels that were achieved by altering the plasma current and voltage. The effects of spray power level on coating characteristics were investigated. X-ray diffraction was used to identify the crystallinities of as-sprayed coatings, Electron Probe Microanalysis was employed to detect the surface chemical composition of as-sprayed coatings and Scanning Electron Microscopy revealed the microstructure. The results indicated that spray power greatly affected the crystallinity, chemical composition, and microstructure of as-sprayed hydroxyapatite coatings, which were linked to the melting state of hydroxyapatite powder.

Chang, C.; Shi, J.; Huang, J.; Hu, Z.; Ding, C.

1998-12-01

19

Vacuum Plasma Spray (VPS) Material Applications for Thruster Components  

NASA Technical Reports Server (NTRS)

A variety of vacuum plasma spray (VPS) material systems have been successfully applied to injector and thrust chamber components. VPS offers a versatile fabrication process with relatively low costs to produce near net shape parts. The materials available with VPS increase operating margins and improve component life by providing superior thermal and oxidation protection in specific engine environments. Functional gradient materials (FGM) formed with VPS allow thrust chamber liners to be fabricated with GRCop-84 (an alloy of copper, chrome, and niobium) and a protective layer of NiCrAlY on the hot wall. A variety of thrust chamber liner designs have been fabricated to demonstrate the versatility of the process. Hot-fire test results have confined the improved durability and high temperature performance of the material systems for thrust chamber liners. Similar FGM s have been applied to provide superior thermal protection on injector faceplates with NiCrAlY and zirconia coatings. The durability of the applied materials has been demonstrated with hot-fire cycle testing on injector faceplates in high temperature environments. The material systems can benefit the components used in booster and main engine propulsion systems. More recent VPS efforts are focused on producing rhenium based material systems for high temperature applications to benefit in-space engines like reaction control system (RCS) thrusters.

Elam, Sandra; Holmes, Richard; Hickman, Robert

2006-01-01

20

Vacuum Plasma Spray (VPS) Material Applications for Thruster Components  

NASA Technical Reports Server (NTRS)

A variety of vacuum plasma spray (VPS) material systems have been successfully applied to injector and thrust chamber components. VPS offers a versatile fabrication process with relatively low costs to produce near net shape parts. The materials available with VPS increase operating margins and improve component life by providing superior thermal and oxidation protection in specific engine environments. Functional gradient materials (FGM) formed with VPS allow thrust chamber liners to be fabricated with GRCop-84 (an alloy of copper, chrome, and niobium) and a protective layer of NiCrAlY on the hot wall. A variety of thrust chamber liner designs have been fabricated to demonstrate the versatility of the process. Hot-fire test results have confirmed the improved durability and high temperature performance of the material systems for thrust chamber liners. Similar FGM s have been applied to provide superior thermal protection on injector faceplates with NiCrAlY and zirconia coatings. The durability of the applied materials has been demonstrated with hot-fire cycle testing on injector faceplates in high temperature environments. The material systems can benefit the components used in booster and main engine propulsion systems. More recent VPS efforts are focused on producing rhenium based material systems for high temperature applications to benefit in-space engines like reaction control system (RCS) thrusters.

Elam, Sandra; Holmes, Richard; Hickman, Robert

2006-01-01

21

Ductility degradation of vacuum-plasma-sprayed NARloy-Z at elevated temperatures  

Microsoft Academic Search

Vacuum plasma spray forming is being used in the near-net fabrication of aerospace components at the Marshall Space Flight Center (MSFC), Alabama. For example, vacuum-plasma-sprayed (VPS) NARloy-Z (a copper-based alloy with high thermal conductivity) is used to form the combustion chamber liner of liquid rocket engines. VPS NARloy-Z possesses properties comparable with the wrought alloy at temperatures ranging from ?259

P. S. Chen; J. H. Sanders; Y. K. Liaw; F. Zimmermann

1995-01-01

22

Transmission electron microscopy study of Ti\\/SiCf composites fabricated by vacuum plasma spraying and vacuum hot-pressing  

Microsoft Academic Search

The microstructures of Ti\\/SiCf composites fabricated by vacuum plasma spraying (VPS) of Ti onto SiC fibres with a duplex TiB2\\/C protective coating followed by subsequent vacuum hot-pressing (VHP) have been investigated by scanning and transmission electron microscopy. After VPS, the TiB2 coating consists of three different sub-layers: (1) an inner ? 0·3 ?m thick sub-layer of a few large acicular

J. H. Li; P. S. Grant; M. L. Jenkins; B. Cantor

1995-01-01

23

Development and characterization of vacuum plasma sprayed thin film solid oxide fuel cells  

Microsoft Academic Search

The vacuum plasma spraying (VPS) process allows the production of thin solid oxide fuel cells (SOFCs) with low internal resistances.\\u000a This enables the reduction of the cell operating temperature without a significant decrease in power density. Consequently,\\u000a the long-term stability of the cells can be improved and low-cost materials can be used.\\u000a \\u000a Different material combinations and spray parameter variations were

M. Lang; R. Henne; S. Schaper; G. Schiller

2001-01-01

24

Vacuum Plasma Sprayed titanium- manganese electrode layers for MnO 2 deposition  

Microsoft Academic Search

Vacuum-plasma-sprayed titanium-manganese alloy electrode layers are intended to improve the economy and efficiency of the\\u000a synthesis of electrolytic manganese dioxide, which is commercially used as cathodic material in primary batteries. Titanium\\u000a anodes with a high content of manganese offer high electrochemical activity and corrosion resistance, but poor mechanical\\u000a stability. Therefore, dense and well-bonded coatings of this brittle alloy were vacuum

H. D. Steffens; M. Brune

1995-01-01

25

A finite element model for consolidation of vacuum plasma spray-formed metal matrix composites  

Microsoft Academic Search

Monotapes consisting of Ti–6Al–4V vacuum plasma-sprayed onto SiC fibres were consolidated by uniaxial vacuum hot pressing. This consolidation process was modelled by computational analysis of a representative unit cell. To describe the initial deformation and densification behaviour of the monotape surface asperities, a yield criterion was derived using a continuum mechanics approach for porous metals and a contact mechanics approach

H. N. Han; D. L. Gilmore; B. Derby

1998-01-01

26

Vacuum Plasma Spray of Cu-8Cr-4Nb for Advanced Liquid-Fuel Combustion Chambers  

NASA Technical Reports Server (NTRS)

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.

Zimmerman, F.; Elam, S.; Ellis, D.; Miller, H.; McKechnie, T.; Hickman, R.

2001-01-01

27

Thermionic vacuum arc and plasma spray processing of high temperature resistant coatings  

Microsoft Academic Search

A combined coating technology was developed using thermionic vacuum arc (TVA) method for deposition of Re and Re-Ni-Cr films (1) followed by plasma spray of Ni-5Mo-5Al or Al2O3 powders at high velocity and high temperature. The composite multilayered films were developed in order to protect turbine blade material (Nimonic 80 super-alloy) against high-temperature oxidation. The pure TVA metal plasma was

I. Mustata; C. P. Lungu; V. Zaroschi; A. M. Lungu; A. Anghel; I. Trusca; G. Burcea; V. Bailescu; G. Dinuta; F. Din; Y. Matsumura; R. Tanaka; T. Oi; J. Hieda; M. A. Bratescu; O. Takai; T. Oishi; M. Kou; O. Fukumasa

2006-01-01

28

Development and characterization of vacuum plasma sprayed thin film solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

The vacuum plasma spraying (VPS) process allows the production of thin solid oxide fuel cells (SOFCs) with low internal resistances. This enables the reduction of the cell operating temperature without a significant decrease in power density. Consequently, the long-term stability of the cells can be improved and low-cost materials can be used. Different material combinations and spray parameter variations were applied to develop thin-film SOFCs, which were plasma sprayed in a consecutive deposition process onto different porous metallic substrates. The use of Laval nozzles, which were developed at the German Aerospace Center (DLR), and the use of conical F4V standard nozzles enable the fabrication of thin gas tight yttria- and scandia-stabilized ZrO2 (YSZ and ScSZ) electrolyte layers and of porous electrode layers with high material deposition rates. The optimization of the VPS parameters has been supported by laser doppler anemometry (LDA) investigations. The development of the plasma-sprayed cells with a total thickness of approximately 100 µm requires an overall electrical and electrochemical characterization process of the single layers and of the completely plasma-sprayed cell assembly. The plasma-sprayed cell layers reveal high electrical conductivities. The plasma-sprayed cells show very good electrochemical performance and low internal resistances. Power densities of 300 to 400 mW/cm2 at low operating temperatures of 750 to 800 °C were achieved. These cells can be assembled to high performance SOFC stacks with active cell areas up to 400 cm2, which can be operated at reduced temperatures and good long-term stability.

Lang, M.; Henne, R.; Schaper, S.; Schiller, G.

2001-12-01

29

Measurement of interfacial properties for aluminum and titanium matrix alloy composites manufactured by vacuum plasma spray  

SciTech Connect

Continuous fiber silicon carbide/titanium and aluminum matrix composite monolayers were tested by means of an indentation technique to measure the interfacial shear strength. Experimental results were interpreted using two analytical models and compared to results of other researches in order to evaluate the interface quality obtained with a vacuum plasma spray fabrication method. The separate contribution of chemical bond and friction to the mechanical shear strength of the fiber-matrix interface is discussed. For aluminum matrix composites, the interface strength is mainly controlled by frictional force. For titanium matrix composites, chemical bond plays a primary role. The vacuum plasma spray process used needs further optimization work, but it is a very promising fabrication method for continuous fiber reinforced metal matrix composites. 20 refs.

Valente, T. [Rome Univ `La Sapienza`, Rome (Italy)

1994-07-01

30

Vacuum Plasma Spray Forming of Copper Alloy Liners for Regeneratively Cooled Liquid Rocket Combustion Chambers  

NASA Technical Reports Server (NTRS)

Vacuum plasma spray (VPS) has been demonstrated as a method to form combustion chambers from copper alloys NARloy-Z and GRCop-84. Vacuum plasma spray forming is of particular interest in the forming of CuCrNb alloys such as GRCop-84, developed by NASA s Glenn Research Center, because the alloy cannot be formed using conventional casting and forging methods. This limitation is related to the levels of chromium and niobium in the alloy, which exceed the solubility limit in copper. Until recently, the only forming process that maintained the required microstructure of CrNb intermetallics was 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. This paper discusses the techniques used to form combustion chambers from CuCrNb and NARloy-Z, which will be used in regeneratively cooled liquid rocket combustion chambers.

Zimmerman, Frank

2003-01-01

31

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

32

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

33

Improvement of Ceramic Coatings for Electrostatic Adsorption Force Using Vacuum Plasma Spraying  

NASA Astrophysics Data System (ADS)

The purpose of this study is to improve ceramic coatings having a high stable electrostatic adsorption force. The use of the coating is for the Johnsen-Rahbek force type electrostatic chucks used to fix silicon wafers inside vacuum chambers for processes such as Etch, CVD and PVD for semiconductor manufacturers. Previously the authors developed a dielectric substance ceramic coating for electrostatic chucks using Atmospheric Plasma Spraying (APS). This ceramic coating was not suitable because of its unstable electrostatic adsorption force. In a subsequent study, Vacuum Plasma Sprayed (VPS) Al2O3-7.5mass%TiO2 coating was investigated. As a result, it was found that the VPS coating has stable electrical resistivity and adsorption force. The dielectric constant of VPS Al2O3-TiO2 coating was sufficient for application to electrostatic chuck. On the other hand, it was suggested from results with respect to residual adsorption force and duration time after power off that the residual adsorption characteristic was not adequate.

Takeuchi, Jun-Ichi; Yamasaki, Ryo; Tani, Kazumi; Takahashi, Yasuo

34

Plasma spray consolidation of materials  

Microsoft Academic Search

Plasma spray deposition, long considered a coating process for applying thin protective layers has experienced recent major advances. Technology, such as the introduction the process into vacuum, the development of higher enthalpy plasma torches and the fabrication of composite materials deposition, as well as others has enabled a wide range of structural applications for the plasma spray deposition process. Spray

R. W. Smith; D. Apelian

1990-01-01

35

Net Shaped Component Fabrication of Refractory Metal Alloys using Vacuum Plasma Spraying  

NASA Technical Reports Server (NTRS)

The vacuum plasma spraying (VPS) technique was employed to produce dense and net shaped components of a new tungsten-rhenium (W-Re) refractory metal alloy. The fine grain size obtained using this technique enhanced the mechanical properties of the alloy at elevated temperatures. The alloy development also included incorporation of thermodynamically stable dispersion phases to pin down grain boundaries at elevated temperatures and thereby circumventing the inherent problem of recrystallization of refractory alloys at elevated temperatures. Requirements for such alloys as related to high temperature space propulsion components will be discussed. Grain size distribution as a function of cooling rate and dispersion phase loading will be presented. Mechanical testing and grain growth results as a function of temperature will also be discussed.

Sen, S.; ODell, S.; Gorti, S.; Litchford, R.

2006-01-01

36

Advanced Vacuum Plasma Spray (VPS) for a Robust, Longlife and Safe Space Shuttle Main Engine (SSME)  

NASA Technical Reports Server (NTRS)

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.

Holmes, Richard R.; Elam, Sandra K.; McKechnie, Timothy N.; Power, Christopher A.

2010-01-01

37

Fabrication and Tribological Evaluation of Vacuum Plasma-Sprayed B4C Coating  

NASA Astrophysics Data System (ADS)

B4C coating was fabricated by vacuum plasma spraying and the tribological properties of the coating against WC-Co alloy were evaluated by sliding wear tests. Al2O3 coating, one of the most commonly used wear-resistant coatings, was employed as comparison in the tribological evaluation. The results obtained show that, the B4C coating is composed of a large amount of nanostructured particles along with some amorphous phases. Both of the friction coefficient and wear rate of the B4C coating are much lower than those of the Al2O3 coating, and the tribological evaluation reveals a decreasing trend for the B4C coating in friction coefficient as well as wear rate with increasing normal load, which is explained in terms of the formation of a protective transfer layer on its worn surface. Tribofilm wear is found to be the dominant wear mechanism involved in the B4C/WC-Co alloy friction pair.

Zhu, Huiying; Niu, Yaran; Lin, Chucheng; Huang, Liping; Ji, Heng; Zheng, Xuebin

2012-12-01

38

Microstructure Characteristics and Oxidation Behavior of Molybdenum Disilicide Coatings Prepared by Vacuum Plasma Spraying  

NASA Astrophysics Data System (ADS)

In this study, molybdenum disilicide (MoSi2) coatings were fabricated by vacuum plasma spraying technology. Their morphology, composition, and microstructure characteristics were intensively investigated. The oxidation behavior of MoSi2 coatings was also explored. The results show that the MoSi2 coatings are compact with porosity less than 5%. Their microstructure exhibits typical lamellar character and is mainly composed of tetragonal and hexagonal MoSi2 phases. A small amount of tetragonal Mo5Si3 phase is randomly distributed in the MoSi2 matrix. A rapid weight gain is found between 300 and 800 °C. The MoSi2 coatings exhibit excellent oxidation-resistant properties at temperatures between 1300 and 1500 °C, which results from the continuous dense glassy SiO2 film formed on their surface. A thick layer composed of Mo5Si3 is found to be present under the SiO2 film for the MoSi2 coatings treated at 1700 °C, suggesting that the phenomenon of continuous oxidation took place.

Niu, Yaran; Fei, Xiaoai; Wang, Hongyan; Zheng, Xuebin; Ding, Chuanxian

2013-03-01

39

Kinetic Study of the Solid-State Transformation of Vacuum-Plasma-Sprayed Ti-6Al-4V Alloy  

NASA Astrophysics Data System (ADS)

Because of the nature of the plasma spraying process, the physical and mechanical properties of vacuum-plasma-sprayed structures of Ti-6Al-4V alloy are completely different from those of conventionally manufactured alloys such as bulk materials from casting and forging. To obtain desired mechanical and physical properties, vacancy and internal defects must be reduced, splat boundaries must be eliminated, and optimal phase compositions should be obtained through postdeposition heat treatments. To determine appropriate heat treatment processes, one needs to study the kinetic behavior of the as-sprayed microstructure at elevated temperatures. In the current study, the kinetics of the solid transformations found in Ti-6Al-4V alloys produced during the vacuum plasma spraying process was studied based on the Johnson-Mehl-Avrami theory. For the kinetic behavior of this alloy, the nonconstant temperature dependence of the transformation rate constant exhibits an irregularity at 900 °C, marking a change in the transformation mechanism. For the lower-temperature (<900 °C) curves, the constant gradient indicates a lack of change in the transformation mechanism, including homogeneous nucleation, with growth of ? phase. For higher temperatures (>900 °C), a gradient change indicates a change in the transformation mechanism. The first mechanism was the formation of ?-phase grain boundary, and the second mechanism was ?-plate nucleation and growth from grain boundaries. The value of the transformation rate constant in the kinetics study of as-sprayed Ti-6Al-4V alloy was much higher than for material produced by the casting method. Using the results obtained from the kinetics of the phase transformation at different constant temperatures, a time-temperature-transformation (TTT) diagram for as-sprayed Ti-6Al-4V alloy was developed.

Salimijazi, H. R.; Mousavi, Z. A.; Golozar, M. A.; Mostaghimi, J.; Coyle, T.

2014-01-01

40

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

NASA Technical Reports Server (NTRS)

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 while maintaining the superior CuCrNb properties are also presented.

Zimmerman, Frank

2000-01-01

41

Reaction diffusion behaviors for interface between Ni-based super alloys and vacuum plasma sprayed MCrAlY coatings  

SciTech Connect

The object of this study is overlay coatings of MCrAlY alloy sprayed by a vacuum plasma spray (VPS) process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Reaction diffusion behaviors at the interface between the MCrAlY coatings and the substrate, which have an important effect on coating degradation, have not always been clarified. Three kinds of substrate, equiaxis IN738LC, directional solidified CM247LC and single-crystal CMSX-2, and the four kinds of vacuum plasma sprayed MCrAlY coating have been selected for these experiments. The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and aluminum depleted layer, expecting that the aluminum depleted layer could not be observed in the case of CoNiCrAlY and NiCoCrAlY coatings. It also indicated that the diffusion thickness could be observed to follow a parabolic time dependence. The order of reaction diffusion rate was NiCrAlY > CoCrAlY > CoNiCrAlY > NiCoCrAlY independent of the substrates. A convenient computer-aided system was developed for analyzing the reaction diffusion behaviors at the interface between coating and substrate. It was also clear that the estimated results of long time diffusion behaviors by simulation analysis was in good agreement with experiments.

Itoh, Y.; Tamura, M. [Toshiba Corp., Kawasaki, Kanagawa (Japan)

1999-07-01

42

Silicon-substituted hydroxyapatite composite coating by using vacuum-plasma spraying and its interaction with human serum albumin  

Microsoft Academic Search

The incorporation of silicon can improve the bioactivity of hydroxyapatite (HA). Silicon-substituted HA (Ca10(PO4)6?x\\u000a (SiO4)\\u000a x\\u000a (OH)2?x\\u000a , Si-HA) composite coatings on a bioactive titanium substrate were prepared by using a vacuum-plasma spraying method. The\\u000a surface structure was characterized by using XRD, SEM, XRF, EDS and FTIR. The bond strength of the coating was investigated\\u000a and XRD patterns showed that

Feng-juan Xiao; Lei Peng; Ying Zhang; Li-jiang Yun

2009-01-01

43

High heat loading properties of vacuum plasma spray tungsten coatings on reduced activation ferritic/martensitic steel  

NASA Astrophysics Data System (ADS)

High density W coatings on reduced activation ferritic martensitic steel (RAF/M) have been produced by Vacuum Plasma Spraying technique (VPS) and heat flux experiments on them have been carried out to evaluate their possibility as a plasma-facing armor in a fusion device. In addition, quantitative analyses of temperature profile and thermal stress have been carried out using the finite element analysis (FEA) to evaluate its thermal properties. No cracks or exfoliation has been formed by steady state and cyclic heat loading experiments under heat loading at 700 °C of surface temperature. In addition, stress distribution and maximum stress between interface of VPS-W and RAF/M have been obtained by FEA. On the other hand, exfoliation has occurred at interlayer of VPS-W coatings near the interface between VPS-W and RAF/M at 1300 °C of surface temperature by cyclic heat loading.

Tokunaga, K.; Hotta, T.; Araki, K.; Miyamoto, Y.; Fujiwara, T.; Hasegawa, M.; Nakamura, K.; Ezato, K.; Suzuki, S.; Enoeda, M.; Akiba, M.; Nagasaka, T.; Kasada, R.; Kimura, A.

2013-07-01

44

Nd-Fe-B permanent magnets (thick films) produced by a vacuum-plasma-spraying process  

NASA Astrophysics Data System (ADS)

Thick, hard-magnetic Nd-Fe-B films (~1 mm) were deposited on different substrates (Cu, steel) by a low-pressure plasma-spraying process. The properties of the applied Nd-Fe-B powders (e.g., grain size, composition) and the conditions of the spraying process were optimized with respect to the mechanical and magnetic properties of the films. Film thicknesses up to 1.2 mm were achieved with good adhesive properties (bond strength>40 MPa). Cracks at the interface or within the films during the deposition process could be suppressed by adjusting the temperature profile of the substrate and controlling the deposition rate. Depending on the maximum temperature of the substrate and the thickness of the Nd-Fe-B films, either amorphous or microcrystalline structures were obtained. In general, the magnetic properties were improved by a postdeposition annealing treatment. Coercivities HcJ up to 16 kA/cm and isotropic remanences of about 0.6 T were achieved.

Rieger, G.; Wecker, J.; Rodewald, W.; Sattler, W.; Bach, Fr.-W.; Duda, T.; Unterberg, W.

2000-05-01

45

Evaluation of vacuum plasma-sprayed boron carbide protection for the stainless steel first wall of WENDELSTEIN 7-X  

NASA Astrophysics Data System (ADS)

To minimize radiation losses of the plasma during long pulse operation, the first wall protection of WENDELSTEIN 7-X demands low-Z plasma facing materials. In addition to carbon materials on high heat flux loaded components, 300-500 ?m thick vacuum plasma-sprayed (VPS) layers of boron carbide (B 4C) are considered as coatings on large actively cooled stainless steel panels. In order to evaluate the behaviour relevant to the expected plasma wall interactions, an extensive material characterization and test programme was executed. Also included is the examination of the industrial manufacturing and the suitability of these coatings as 70 m 2 first wall plasma facing material for W7-X. To improve the adhesion of thick B 4C layers on stainless steel, different interlayers have been investigated. Based on the results, a VPS-based coating technique was identified which is suitable to manufacture the B 4C protection layers on stainless steel wall panels of W7-X.

Greuner, H.; Balden, M.; Boeswirth, B.; Bolt, H.; Gadow, R.; Grigull, P.; Hofmann, G.; Huber, T.; Kasparek, W.; Kumric, H.; Lindig, S.; Matern, G.; Mayer, M.; Neu, R.; Renner, H.; Roth, J.; Riegert-Escribano, M.; Simon-Weidner, J.; Wacker, R.

2004-08-01

46

Process Measurements in A vacuum Microplasma Spray System  

Microsoft Academic Search

Summary form only given. A system has been developed and refined for small-scale vacuum plasma spraying of metals. This system operates at arc power 1-3 kW and deposition rates below 0.1 g min-1. The plasma is an argon-hydrogen mixture expanded through a Laval nozzle into chamber pressures in the range 5.3-13 kPa (40-100 torr). The vacuum spray environment, which distinguishes

W. S. Crawford; M. A. Cappelli; F. B. Prinz

2005-01-01

47

Comparison of the Properties of Cold-Sprayed Cu-0.5Cr-0.05Zr Alloys after Various Heat Treatments Versus Forged and Vacuum Plasma-Sprayed Alloys  

NASA Astrophysics Data System (ADS)

In this work, Cu-0.5Cr-0.05Zr (wt.%) samples obtained by the cold spray process were studied regarding the microstructure and the mechanical properties versus several heat treatments. Ultimate tensile strength higher than 600 MPa, yield strength of 570 MPa and Vickers hardness HV0.2 of about 200 were obtained. Comparison of these results with those obtained by forging or vacuum plasma spraying highlighted the ability of the cold spray technique to produce dense Cu-Cr-Zr deposits with low oxygen content, low level of residual stresses and high mechanical properties.

Coddet, Pierre; Verdy, Christophe; Coddet, Christian; Lecouturier, Florence; Debray, François

2014-02-01

48

Microstructure and failure mechanism in As-deposited, vacuum plasma-sprayed Ti-6Al-4V alloy  

NASA Astrophysics Data System (ADS)

The microstructure, phase composition, and chemical composition of vacuum plasma-sprayed Ti-6Al-4V alloys were examined in detail using a variety of techniques, including x-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy. The observed chemistry and structure were related to the conditions under which the deposit was formed and the phase equilibria in the Ti alloy system. The porosity of the deposit was in the range of 3 to 5%. A slight decrease in the Al content and a slight increase in the amount of oxygen and hydrogen was found relative to the starting powder. Within individual splats, a columnar solidification structure can be seen. However, the as-deposited material is ?90% ?? martensite that is present in the form of fine lathes on the order of 500 nm in width surrounded by residual ?-phase. This herringbone structure obscures to some extent the preexisting columnar structure of the as-solidified ?-phase. The material fails at low elongations (˜1%) when tested in tension, with a macroscopic stress-strain curve, which appears to be quite brittle. Examination of the fracture surface, however, reveals a ductile failure mode within individual splats, which is consistent with the structure described above. Sections perpendicular to the fracture surface show that failure occurs at the weak splat boundaries through the development and growth of voids between splats.

Salimijazi, H. R.; Coyle, T. W.; Mostaghimi, J.; Leblanc, L.

2005-06-01

49

Porous tantalum coatings prepared by vacuum plasma spraying enhance bmscs osteogenic differentiation and bone regeneration in vitro and in vivo.  

PubMed

Tantalum, as a potential metallic implant biomaterial, is attracting more and more attention because of its excellent anticorrosion and biocompatibility. However, its significantly high elastic modulus and large mechanical incompatibility with bone tissue make it unsuitable for load-bearing implants. In this study, porous tantalum coatings were first successfully fabricated on titanium substrates by vacuum plasma spraying (VPS), which would exert the excellent biocompatibility of tantalum and alleviate the elastic modulus of tantalum for bone tissue. We evaluated cytocompatibility and osteogenesis activity of the porous tantalum coatings using human bone marrow stromal cells (hBMSCs) and its ability to repair rabbit femur bone defects. The morphology and actin cytoskeletons of hBMSCs were observed via electron microscopy and confocal, and the cell viability, proliferation and osteogenic differentiation potential of hBMSCs were examined quantitatively by PrestoBlue assay, Ki67 immunofluorescence assay, real-time PCR technology and ALP staining. For in vivo detection, the repaired femur were evaluated by histomorphology and double fluorescence labeling 3 months postoperation. Porous tantalum coating surfaces promoted hBMSCs adhesion, proliferation, osteogenesis activity and had better osseointegration and faster new bone formation rate than titanium coating control. Our observation suggested that the porous tantalum coatings had good biocompatibility and could enhance osseoinductivity in vitro and promote new bone formation in vivo. The porous tantalum coatings prepared by VPS is a promising strategy for bone regeneration. PMID:23776648

Tang, Ze; Xie, Youtao; Yang, Fei; Huang, Yan; Wang, Chuandong; Dai, Kerong; Zheng, Xuebin; Zhang, Xiaoling

2013-01-01

50

Plasma spray forming  

Microsoft Academic Search

The technology of plasma spray forming (PSF) is introduced, and the technical processes of plasma spray for fabricating parts and moulds are investigated emphatically in this paper. The technological characteristics of PSF are summarized, including original prototype fabrication and surface treatment, post-treatment of a formed workpiece and demoulding methods. Also, some important factors affecting the qualities of workpiece formed by

J. C Fang; W. J Xu

2002-01-01

51

Effect of Vacuum Annealing on the Characteristics of Plasma Sprayed Al2O3-13wt.%TiO2 Coatings  

NASA Astrophysics Data System (ADS)

Adhesion strength is one of the critical properties for plasma-sprayed coating. In this study, the plasma-sprayed Al2O3-13wt.%TiO2/NiCrAl coatings were annealed at 300-900 °C for 6 h in vacuum. The tensile bond strength and porosity of the coatings were investigated. The microstructure and the fracture were studied using optical microscopy, scanning electron spectroscopy, and x-ray diffraction. It was found that the tensile bond strength of coatings increased with the increase of annealing temperature until 500 °C, reaching the maximum value of 41.2 MPa, and then decreased as the annealing temperature continues to increase. All coatings presented a brittle fracture and the fracture occurred inside the ceramic coatings except for the coating annealed at 500 °C, which had a brittle-ductile mixed fracture and the fracture occurred at the interface of bond coating and the substrate.

Jingjing, Zhang; Zehua, Wang; Pinghua, Lin; Hongbin, Yuan; Zehua, Zhou; Shaoqun, Jiang

2012-09-01

52

The response of SiC fibres to vacuum plasma spraying and vacuum hot pressing during the fabrication of titanium matrix composites  

PubMed

Vacuum plasma spraying (VPS) and vacuum hot pressing (VHP) have been used to fabricate Ti-6Al-4V matrix composite material reinforced longitudinally with DERA Sigma C coated SiC 1140+ fibres. VPS of Ti-6Al-4V onto Sigma 1140+ SiC fibres caused no fibre/matrix interfacial reaction. During VHP a fibre/matrix reaction occurred, producing a mixture of fine (< 50 nm) TiCx (x

Baker; Grant; Jenkins

1999-11-01

53

Plasma Spray System  

NASA Technical Reports Server (NTRS)

Computer aided, fully-automatic TRW system sprays very hot plasma onto a turbine blade. Composed of gas into which metallic and ceramic powders have been injected, the plasma forms a two-layer coating which insulates the blade. Critical part of operation is controlling the thickness of the deposit which is measured in thousandths of an inch. This is accomplished by an optical detector which illuminates spots at various locations on the blade and determines thickness by measuring the light reflections. Optical sensor monitors spraying process until precise thickness is attained, then computer halts the spraying.

1980-01-01

54

Suspension and solution plasma spraying  

NASA Astrophysics Data System (ADS)

Suspension and solution plasma spraying makes it possible to achieve coatings with fine microstructural features and is becoming a common route in laboratories to elaborate coatings a few tenths to a few hundreds of micrometres thick. This paper presents the recent developments in direct current plasma spraying of suspensions or solutions. It begins with a short description of the main plasma torches used for liquid feedstock spraying as well as the techniques used to experimentally observe droplets and particles in the plasma jet and characterize the void network of nanostructured plasma-sprayed coatings. The paper then turns to the momentum and heat transfers between fine particles and the plasma jet and the interactions between the plasma jet and a liquid in the form of a jet or drops. It concludes by linking some characteristic features of coating microstructures with the liquid processing in the plasma jet.

Fauchais, P.; Joulia, A.; Goutier, S.; Chazelas, C.; Vardelle, M.; Vardelle, A.; Rossignol, S.

2013-06-01

55

A Plasma Flame Spray Handbook.  

National Technical Information Service (NTIS)

The Plasma Spraying process is a versatile fabrication technique used to apply a wide range of coatings on various workpiece materials. Coatings are applied to restore or attain desired dimensions, to provide electrical or thermal shielding or conduction,...

T. J. Roseberry F. W. Boulger

1977-01-01

56

Vapor Phase Deposition Using Plasma Spray-PVD™  

NASA Astrophysics Data System (ADS)

Plasma spray—physical vapor deposition (PS-PVD) is a low pressure plasma spray technology to deposit coatings out of the vapor phase. PS-PVD is a part of the family of new hybrid processes recently developed by Sulzer Metco AG (Switzerland) on the basis of the well-established low pressure plasma spraying (LPPS) technology. Included in this new process family are plasma spray—chemical vapor deposition (PS-CVD) and plasma spray—thin film (PS-TF) processes. In comparison to conventional vacuum plasma spraying and LPPS, these new processes use a high energy plasma gun operated at a work pressure below 2 mbar. This leads to unconventional plasma jet characteristics which can be used to obtain specific and unique coatings. An important new feature of PS-PVD is the possibility 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 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 EB-PVD coatings. This paper reports on the progress made at Sulzer Metco to develop functional coatings build up from vapor phase of oxide ceramics and metals.

von Niessen, K.; Gindrat, M.; Refke, A.

2010-01-01

57

Vacuum application of thermal barrier plasma coatings  

NASA Technical Reports Server (NTRS)

Coatings are presently applied to Space Shuttle Main Engine (SSME) turbine blades for protection against the harsh environment realized in the engine during lift off-to-orbit. High performance nickel, chromium, aluminum, and yttrium (NiCrAlY) alloy coatings, which are applied by atmospheric plasma spraying, crack and spall off because of the severe thermal shock experienced during start-up and shut-down of the engine. Ceramic coatings of yttria stabilized zirconia (ZrO2-Y2O3) were applied initially as a thermal barrier over coating to the NiCrAlY but were removed because of even greater spalling. Utilizing a vacuum plasma spraying process, bond coatings of NiCrAlY were applied in a low pressure atmosphere of argon/helium, producing significantly improved coating-to-blade bonding. The improved coatings showed no spalling after 40 MSFC burner rig thermal shock cycles, cycling between 1700 and -423 F. The current atmospheric plasma NiCrAlY coatings spalled during 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2-Y2O3 to the turbine blades of first stage high-pressure fuel turbopumps utilizing the vacuum plasma process. The improved thermal barrier coating has successfully passed 40 burner rig thermal shock cycles without spalling. Hot firing in an SSME turbine engine is scheduled for the blades. Tooling was installed in preparation for vacuum plasma spray coating other SSME hardware, e.g., the titanium main fuel valve housing (MFVH) and the fuel turbopump nozzle/stator.

Holmes, R. R.; Mckechnie, T. N.

1988-01-01

58

Plasma_sprayed components for SOFC applications  

Microsoft Academic Search

The major challenge in the development of plasma sprayed components for SOFC was the fabrication of dense electrolytes by atmospheric plasma_spraying (APS) avoiding cracks typically generated during the spraying process. Compared to conventional plasma_sprayed ceramics both the number of micro_cracks and segmentation cracks have to be reduced considerably to achieve sufficiently low leakage rates.Based on a detailed understanding of the

Detlev Stöver; Dag Hathiramani; Robert Vaßen; Rajiv J. Damani

2006-01-01

59

Recent Developments in the Field of Plasma-Sprayed Thermal Barrier Coatings  

Microsoft Academic Search

Thermal barrier coating (TBC) systems are widely used in gas turbines on thermally highly loaded parts as blades, vanes or combustion chamber to improve the performance of the engines. The standard plasma-sprayed systems consist of a vacuum plasma-sprayed (VPS) MCrAlY (M = Ni or Co) and an atmospherically plasma sprayed (APS) ceramic top layer made of yttria partially stabilised zirconia

R. Vaßen; J.-E. Döring; M. Dietrich; H. Lehmann; D. Stöver

60

DESIGN AND TUNING OF A VACUUM MICROPLASMA SPRAY SYSTEM: PARTICLE ENTRAINMENT  

Microsoft Academic Search

A vacuum microplasma spray system, operating on gross power levels of 1-3 kW, with powder feed rates below 1 g\\/min and using plasma gas mixtures of argon and hydrogen, was built and tested. In order to improve the deposition efficiency and quality of coatings, the system was analyzed and the matter of particle entrainment into the plasma jet core was

W. Scott Crawford; Mark A. Cappelli; Friedrich B. Prinz

61

Mold manufacture with plasma spraying  

NASA Astrophysics Data System (ADS)

A process has been developed to produce molds or tooling using a steel or chrome- plated steel model. The investigation examined the effect of coating and model materials, model temperature and spray angle on the coating separation from the model surface, coating delamination, and surface quality. A polished model disk was heated and then plasma sprayed with iron, nickel, Ni- Al, or Ni- Cr- B- Si. It was found that the minimum temperature to facilitate entire coating removal was lower for steel models and varied be tween 200 and 450 °C depending on the material. However, at higher temperatures the higher bond strength produced by oxidation on the steel resulted in significant coating pullout. A chrome- plated model, heated to 600 to 700 °C, is required to produce a defect- free coating. The effect of substrate angle on open porosity is most critical for the Ni- Cr- B- Si alloy and least important for Ni- Al coatings. The sur face roughness of the plasma- sprayed molds is comparable to the corresponding models, permitting good surface detail reproducibility. Several molds and tools were produced for use in the glass, rubber, and plastics industries.

Grossand, K. A.; Kovalevskis, A.

1996-12-01

62

Metallurgy and properties of plasma spray formed materials  

NASA Technical Reports Server (NTRS)

Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure.

Mckechnie, T. N.; Liaw, Y. K.; Zimmerman, F. R.; Poorman, R. M.

1992-01-01

63

The effect of heat treatment on the stiffness of zirconia top coats in plasma-sprayed TBCs  

Microsoft Academic Search

Thermal barrier coating (TBC) specimens have been prepared by plasma spraying. A vacuum plasma spray (VPS) MCrAlY bond coat and atmospheric plasma spray (APS) zirconia top coat were deposited onto a nickel superalloy substrate. The stiffness of detached top coats was measured by cantilever bending and also by nanoindentation procedures. Measurements were made on specimens in the as-sprayed state and

J. A. Thompson; T. W. Clyne

2001-01-01

64

Plasma-Spray Coating Thickness Monitoring System.  

National Technical Information Service (NTIS)

The Plasma-Spray Coating Thickness Monitoring System incorporates a unique optical transform technique that enables an image of a coupon (part) surface to be projected on a one-dimensional linear diode array (LDA). Parts to be coated with plasma spray are...

1981-01-01

65

The Testing of Plasma Spray Coatings.  

National Technical Information Service (NTIS)

This program was conducted for the purpose of providing reference data on plasma-sprayed coatings for use in the design and repair/salvage of naval ordnance hardware. Plasma-spray deposition parameters and surface finishing techniques were developed for m...

T. J. Roseberry E. J. Onesto K. F. Dufrane

1976-01-01

66

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

NASA Astrophysics Data System (ADS)

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 resistance but also the simultaneous coverage of multiple air foils.

von Niessen, Konstantin; Gindrat, Malko

2011-06-01

67

Fluid dynamic study of direct current plasma jets for plasma spraying applications  

Microsoft Academic Search

Recently, direct current (dc) plasma torches equipped with converging-diverging (Laval) nozzles, instead of standard cylindrical\\u000a ones, have been shown to present several advantages for both vacuum and atmospheric plasma spraying, such as diminishing the\\u000a gradients of temperature and velocity and reducing the turbulence intensity in the jet fringes. The present study was concerned\\u000a with the diagnostics of the plasma jets

M. Rahmane; G. Soucy; M. I. Boulos; R. Henne

1998-01-01

68

Effect of critical plasma spray parameter on properties of hollow cathode plasma sprayed alumina coatings  

Microsoft Academic Search

A 20 kW hollow cathode plasma spray torch was manufactured and its performances were examined by spraying alumina coatings on mild steel substrates with different critical plasma spray parameters (CPSP: 0.12, 0.24, 0.36, 0.48). CPSP is defined as the ratio between the torch input power and primary plasma forming gas flow rate. The effects of CPSP on the microstructure, porosity, microhardness,

S. Yugeswaran; V. Selvarajan; D. Seo; K. Ogawa

2008-01-01

69

Influence of critical plasma spraying parameter (CPSP) on plasma sprayed Alumina–Titania composite coatings  

Microsoft Academic Search

Plasma sprayed ceramic coatings are successfully used in many industrial applications, where high wear and corrosion resistance with thermal insulation are required. Critical plasma spraying parameter (CPSP) is a key factor to control the quality of coatings. In this study, Alumina–Titania composite coatings in different compositions (Alumina–3wt.% Titania, Alumina–13wt.% Titania and Alumina–40wt.% Titania) were prepared by 40kW atmospheric plasma spray

S. Yugeswaran; V. Selvarajan; M. Vijay; P. V. Ananthapadmanabhan; K. P. Sreekumar

2010-01-01

70

Plasma-Sprayed Electrically Insulating Ceramic Coatings.  

National Technical Information Service (NTIS)

The technique of plasma spraying makes possible the deposition of electrically insulating ceramic coatings on metals, graphite and other conductors. The oxide ceramic materials usable for this purpose are described and the range of possible applications i...

K. Kirner

1976-01-01

71

Spray parameters and particle behavior relationships during plasma spraying  

Microsoft Academic Search

Using laser anemometry, laser fluxmetry, and statistical two-color pyrometry, the velocity, number flux, and surface temperature\\u000a distributions of alumina and zirconia particles in dc plasma jets have been determined inflight for various spraying parameters.\\u000a The flux measurements emphasized the importance of the carrier gas flow rate, which must be adjusted to the plasma jet momentum\\u000a depending on the arc current,

M. Vardelle; A. Vardelle; P. Fauchais

1993-01-01

72

Creep of plasma sprayed zirconia  

NASA Technical Reports Server (NTRS)

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 1000, 2000, and 3500 psi and temperatures of 1100 C, 1250 C, and 1400 C. The coatings were stabilized with lime, magnesia, and two different concentrations of yttria. 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. The creep rate for 20% Y2O3-80% ZrO2 was 1/3 to 1/2 that of 8% Y2O3-92% ZrO2. Both magnesia and calcia stabilized ZrO2 crept at a rate 5 to 10 times that of the 20% Y2O3 material. A near proportionality between creep rate and applied stress was observed. The rate controlling process appeared to be thermally activated, with an activation energy of approximately 100 cal/gm mole K. Creep deformation was due to cracking and particle sliding.

Firestone, R. F.; Logan, W. R.; Adams, J. W.

1982-01-01

73

Material Spraying Using Electromagnetically Accelerated Plasma  

Microsoft Academic Search

In magneto-plasma-dynamic (MPD) arcjet generators, plasma is accelerated by electromagnetic body forces. The MPD arcjet generator can produce higher-velocity, higher-temperature, higher-density and larger-area plasmas than those of conventional thermal plasma torches. Two types of MPD arcjet generator were developed for applications to ceramic spray coatings. One generator was installed with a cathode covered with mullite or zirconia ceramics and the

Hirokazu Tahara; Tetsuji Shibata; Kazunori Mitsuo; Yasutaka Ando; Toshiaki Yasui; Yoichi Kagaya; Takao Yoshikawa

2003-01-01

74

Plasma Sprayed Hydroxyapatite Coatings: Influence of Spraying Power on Microstructure  

SciTech Connect

The plasma sprayed hydroxyapatite (HA) coatings are used on metallic implants to enhance the bonding between the implant and bone in human body. The coating process was implemented at different spraying power for each spraying condition. The coatings formed from a rapid solidification of molten and partly molten particles that impact on the surface of substrate at high velocity and high temperature. The study was concentrated on different spraying power that is between 23 to 31 kW. The effect of different power on the coatings microstructure was investigated using scanning electron microscope (SEM) and phase composition was evaluated using X-ray diffraction (XRD) analysis. The coatings surface morphology showed distribution of molten, partially melted particles and some micro-cracks. The produced coatings were found to be porous as observed from the cross-sectional morphology. The coatings XRD results indicated the presence of crystalline phase of HA and each of the patterns was similar to the initial powder. Regardless of different spraying power, all the coatings were having similar XRD patterns.

Mohd, S. M.; Abd, M. Z.; Abd, A. N. [Advanced Material Centre (AMREC), SIRIM Bhd, Lot 34, Jalan Hi-Tech 2/4, Kulim Hi-Tech Park, 09000 Kulim (Malaysia)

2010-03-11

75

Development of a micromechanical life prediction model for plasma sprayed thermal barrier coatings  

Microsoft Academic Search

A widely used method to produce thermal barrier coating (TBC) systems is the vacuum plasma spraying of a highly dense bondcoat layer with a defined surface roughness and the atmospheric plasma spraying (APS) of a porous (10–15%) Y2O3-stabilized zirconia top coat. In thermal cycling operation these systems often fail by crack initiation and propagation close to the bondcoat–top coat interface.

R. Vaßen; G. Kerkhoff; D. Stöver

2001-01-01

76

Thermomechanical processing of plasma sprayed intermetallic sheets  

DOEpatents

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

Hajaligol, Mohammad R. (Midlothian, VA); Scorey, Clive (Cheshire, CT); Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Midlothian, VA); Fleischhauer, Grier (Midlothian, VA); Lilly, Jr., A. Clifton (Chesterfield, VA); German, Randall M. (State College, PA)

2001-01-01

77

Plasma-Spray Metal Coating On Foam  

NASA Technical Reports Server (NTRS)

Molds, forms, and other substrates made of foams coated with metals by plasma spraying. Foam might be ceramic, carbon, metallic, organic, or inorganic. After coat applied by plasma spraying, foam left intact or removed by acid leaching, conventional machining, water-jet cutting, or another suitable technique. Cores or vessels made of various foam materials plasma-coated with metals according to method useful as thermally insulating containers for foods, liquids, or gases, or as mandrels for making composite-material (matrix/fiber) parts, or making thermally insulating firewalls in automobiles.

Cranston, J.

1994-01-01

78

Plasma sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Functionally graded thermal barrier coatings of the system yttria stabilised zirconia\\/NiCoCrAlY were fabricated through plasma spraying using pre-alloyed composite powders as feedstock. Composite powders with different compositions (75% NiCoCrAlY:25% YSZ; 50% NiCoCrAly:50% YSZ and 25% NiCoCrAlY:75% YSZ) were prepared by mechanical alloying and plasma powder spheroidisation, and are subsequently sprayed successively in a single plasma torch to form the functionally

K. A. Khor; Z. L. Dong; Y. W. Gu

1999-01-01

79

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)

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.

Mcdonald, Gary H.

1990-01-01

80

Current problems in plasma spray processing  

SciTech Connect

This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of ``Plasma Spray Processing`` is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P. [State Univ. of New York, Stony Brook, NY (United States). Thermal Spray Lab.

1991-12-31

81

Current problems in plasma spray processing  

SciTech Connect

This detailed report summarizes 8 contributions from a thermal spray conference that was held in late 1991 at Brookhaven National Laboratory (Upton, Long Island, NY, USA). The subject of Plasma Spray Processing'' is presented under subject headings of Plasma-particle interactions, Deposit formation dynamics, Thermal properties of thermal barrier coatings, Mechanical properties of coatings, Feed stock materials, Porosity: An integrated approach, Manufacture of intermetallic coatings, and Synchrotron x-ray microtomographic methods for thermal spray materials. Each section is intended to present a concise statement of a specific practical and/or scientific problem, then describe current work that is being performed to investigate this area, and finally to suggest areas of research that may be fertile for future activity.

Berndt, C.C.; Brindley, W.; Goland, A.N.; Herman, H.; Houck, D.L.; Jones, K.; Miller, R.A.; Neiser, R.; Riggs, W.; Sampath, S.; Smith, M.; Spanne, P. (State Univ. of New York, Stony Brook, NY (United States). Thermal Spray Lab.)

1991-01-01

82

THE NEW PLASMA EQUIPMENT FOR SUPERSONIC SPRAYING  

Microsoft Academic Search

The new approach to building the supersonic plasma powder spraying has been developed in view of the current trends. The approach is based on using a variable-composition mixture of gas and air and a stabilized elongated electric arc that burns in a plasmatron and is adapted to meet the technology requirements. Cost effectiveness and technical expediency of using air- gas

S. V. Petrov

83

Modeling of plasma spraying of two powders  

Microsoft Academic Search

The behavior of metal and ceramic powders co-sprayed through a plasma jet was simulated using a commercial fluid dynamics\\u000a model in which the particles are considered as discrete Langrangian entities. Computations were carried out for the plasma\\u000a jet and the injected particles using (a) a steady-state three-dimensional (3-D) jet and (b) a simplified two-dimensional (2-D)\\u000a model. An analytical method was

B. Dussoubs; A. Vardelle; G. Mariaux; P. Fauchais; N. J. Themelis

2001-01-01

84

Properties of plasma sprayed boron carbide protective coatings for the first wall in fusion experiments  

Microsoft Academic Search

In this study stainless steel substrates were coated by vacuum plasma spraying with a two-layer system consisting of a bond coat of 40 ?m nickel–chromium and the top coat material B4C of 160–200 ?m thickness. The spray angle was varied from normal incidence to 60° with respect to the substrate normal. The effects of processing conditions on microstructure, mechanical properties

J.-E. Döring; R. Vaszen; J. Linke; D. Stover

2002-01-01

85

Porosity in plasma sprayed alumina coatings  

SciTech Connect

Small-angle neutron scattering (SANS) was used to study the porosity of plasma sprayed deposits of alumina in as-sprayed and heat-treated conditions. SANS results were compared with mercury intrusion porosimetry (MIP) and water immersion techniques. Multiple small-angle neutron scattering yields a volume-weighted effective pore radius (R{sub eff}), for pores with sizes between 0.08 and 10{mu}m, the pore volume in this size region, and from the Porod region, the surface area of pores of all sizes.

Ilavsky, J.; Herman, H.; Berndt, C.C. [State Univ. of New York, Stony Brook, NY (United States); Goland, A.N. [Brookhaven National Lab., Upton, NY (United States); Long, G.G.; Krueger, S.; Allen, A.J. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1994-03-01

86

Strength degradation of SiC fiber during manufacture of titanium matrix composites by plasma spraying and hot pressing  

Microsoft Academic Search

Titanium matrix composites (TMCs) reinforced with Sigma 1140+ SiC fiber have been manufactured by a combination of low pressure plasma spraying (LPPS spray\\/wind) and simultaneous fiber winding, followed by vacuum hot pressing (VHP). Fiber damage during TMC manufacture has been evaluated by measuring fiber tensile strength after fiber extraction from the TMCs at various processing stages, followed by fitting of

K. H. Baik; P. S. Grant

2001-01-01

87

Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases.

Tillmann, Wolfgang; Vogli, Evelina; Krebs, Benjamin

2008-12-01

88

Plasma instability of a vacuum arc centrifuge.  

PubMed

Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a "universal" instability, driven by the density gradient, in a plasma with finite conductivity. PMID:12006025

Hole, M J; Dallaqua, R S; Simpson, S W; Del Bosco, E

2002-04-01

89

Influence of Plasma Instabilities in Ceramic Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Direct current Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This article presents an analysis of the influence of plasma instabilities on the yttria-stabilized suspension drops fragmentation. A particular attention is paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of the arc root) and depending on the different spray parameters such as the plasma forming gas mixture composition and mass flow rate and the suspension momentum. By observing the suspension drops injection with a fast shutter camera and a laser flash sheet triggered by a defined transient voltage level of the plasma torch, the influence of plasma fluctuations on jet or drops fragmentation is studied through the deviation and dispersion trajectories of droplets within the plasma jet.

Etchart-Salas, R.; Rat, V.; Coudert, J. F.; Fauchais, P.; Caron, N.; Wittman, K.; Alexandre, S.

2007-12-01

90

Vacuum electron heating by surface plasma wave  

NASA Astrophysics Data System (ADS)

Vacuum heating of electrons by a large amplitude surface plasma wave (SPW) over a metal surface due to the Brunel effect is studied. The surface plasma wave has large normal component of electric vector. The normal field pulls the electrons away from the plasma during the half cycle. Each electron sees, besides the E? of the surface plasma wave, a static space charge field. As the electron returns back to the interface, it possesses kinetic energy that is deposited into the plasma, leading to plasma heating.

Kumar, Pawan; Tripathi, V. K.

2011-07-01

91

Behaviour of plasma spray coatings under disruption simulation  

NASA Astrophysics Data System (ADS)

The behaviour of metallic and ceramic protective coatings under disruption simulations was studied correlating the damage with their physical and structural parameters. Plasma Spray (PS) and Vacuum Plasma Spray (VPS) were the techniques used for the production of the coatings. W-5% Re was selected for divertor plates, and TiC, TiO 2, A1 2O 3, low-Z ceramic materials for the first wall protection on 316 SS, Cu and Al as substrates. An electron beam gun was used to simulate the plasma disruptions. The tests were carried out from 0.6 to 6 MJ/m 2. The thermal effects were studied by metallographic and EDXA analysis. The damage was observed comparing the degree of protection provided by each coating to discover the minimum thickness necessary to prevent the underlying material from melting. Good protective coatings must have a high melting point, great porosity and low thermal conductivity. Such coatings act as thermal barriers, increasing the surface temperature and radiating back large parts of the energy.

Brossa, F.; Rigon, G.; Looman, B.

1988-07-01

92

Fluid dynamic study of direct current plasma jets for plasma spraying applications  

NASA Astrophysics Data System (ADS)

Recently, direct current (dc) plasma torches equipped with converging-diverging (Laval) nozzles, instead of standard cylindrical ones, have been shown to present several advantages for both vacuum and atmospheric plasma spraying, such as diminishing the gradients of temperature and velocity and reducing the turbulence intensity in the jet fringes. The present study was concerned with the diagnostics of the plasma jets produced by three nozzles of various contours: a standard cylindrical anode and a Mach 2.5 and Mach 3 Laval nozzle. Emission spectroscopy (absolute intensity) and enthalpy probe techniques were used to measure temperature and velocity fields. Special attention was given to the effects of spray chamber pressure on flow regime inside the nozzles and to the distribution of the temperature and velocity fields in the plasma jet. Results showed that under the chamber pressure conditions used (vacuum), for which Laval nozzles originally were designed, the generated plasma jets had greater centerline velocities and larger high temperature zones compared to standard cylindrical nozzles. The results showed significant improvement in the deposition efficiency by using nozzles with these computed contours.

Rahmane, M.; Soucy, G.; Boulos, M. I.; Henne, R.

1998-09-01

93

Automated Plasma Spray (APS) process feasibility study  

NASA Technical Reports Server (NTRS)

An automated plasma spray (APS) process was developed to apply two layer (NiCrAlY and ZrO2-12Y2O3) thermal barrier coatings to aircraft and stationary gas turbine engine blade airfoils. The APS process hardware consists of four subsystems: a mechanical positioning subsystem incorporating two interlaced six degree of freedom assemblies (one for coating deposition and one for coating thickness monitoring); a noncoherent optical metrology subsystem (for in process gaging of the coating thickness buildup at specified points on the specimen); a microprocessor based adaptive system controller (to achieve the desired overall thickness profile on the specimen); and commerical plasma spray equipment. Over fifty JT9D first stage aircraft turbine blade specimens, ten W501B utility turbine blade specimens and dozens of cylindrical specimens were coated with the APS process in preliminary checkout and evaluation studies. The best of the preliminary turbine blade specimens achieved an overall coating thickness uniformity of 53 micrometers (2.1 mils), much better than is achievable manually. Comparative evaluations of coating thickness uniformity for manually sprayed and APS coated specimens were performed. One of the preliminary turbine blade evaluation specimens was subjected to a torch test and metallographic evaluation. Some cylindrical specimens coated with the APS process survived up to 2000 cycles in subsequent burner rig testing.

Fetheroff, C. W.; Derkacs, T.; Matay, I. M.

1981-01-01

94

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

SciTech Connect

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.

Haynes, J.A. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States)

1996-04-01

95

Effects of Feedstock and Laser Post-spray Treatment on Plasma Sprayed Bioceramic Coatings  

Microsoft Academic Search

Hydroxyapatite (HA) is a bioactive material with Ca to P ratio similar to that of natural bone. This can encourage early bonding between bony tissues and the implant surface. Plasma spraying is efficient in coating HA onto biomedical implants. However, the biocompatibility of hydroxyapatite (HA) changes after plasma spraying. This paper reports the preparation and characterization of HA coatings using

K. A. Khor; P. Cheang

1996-01-01

96

Plasma spraying of beryllium and beryllium-aluminum-silver alloys  

Microsoft Academic Search

A preliminary investigation on plasma-spraying of beryllium and a beryllium-aluminum 4% silver alloy was done at the Los Alamos National Laboratory`s Beryllium Atomization and Thermal Spray Facility (BATSF). Spherical Be and Be-Al-4%Ag powders, which were produced by centrifugal atomization, were used as feedstock material for plasma-spraying. The spherical morphology of the powders allowed for better feeding of fine (<38 μm)

R. G. Castro; P. W. Stanek; K. E. Elliott; L. A. Jacobson

1993-01-01

97

Material design of ceramic coating by plasma spray method  

Microsoft Academic Search

In the ceramic coating on substrate, cracking and peeling occur due to the difference of thermal expansion between substrate material and coating material. For evaluation of peeling property of plasma sprayed coating, it is demanded that thermal properties of plasma sprayed coating are estimated in detail. In this study, the results of comparison of thermal properties between bulk material and

Masaru Nakamichi; Takeshi Takabatake; Hiroshi Kawamura

1998-01-01

98

Molybdenum disilicide composites produced by plasma spraying  

SciTech Connect

The intermetallic compound, molybdenum disilicide (MoSi{sub 2}) is being considered for high temperature structural applications because of its high melting point and superior oxidation resistance at elevated temperatures. The lack of high temperature strength, creep resistance and low temperature ductility has hindered its progress for structural applications. Plasma spraying of coatings and structural components of MoSi{sub 2}-based composites offers an exciting processing alternative to conventional powder processing methods due to superior flexibility and the ability to tailor properties. Laminate, discontinuous and in situ reinforced composites have been produced with secondary reinforcements of Ta, Al{sub 2}O{sub 3}, SiC, Si{sub 3}N{sub 4} and Mo{sub 5}Si{sub 3}. Laminate composites, in particular, have been shown to improve the damage tolerance of MoSi{sub 2} during high temperature melting operations. A review of research which as been performed at Los Alamos National Laboratory on plasma spraying of MoSi{sub 2}-based composites to improve low temperature fracture toughness, thermal shock resistance, high temperature strength and creep resistance will be discussed.

Castro, R.G.; Hollis, K.J.; Kung, H.H.; Bartlett, A.H.

1998-05-25

99

A torch nozzle design to improve plasma spraying techniques  

NASA Astrophysics Data System (ADS)

The effects of nozzle design on the plasma characteristics of supersonic flow conditions are investigated using a D.C. plasma jet under low-pressure plasma spraying conditions. Comparison is made between a 5 mm I.D. standard nozzle and a 13 mm E.D. (exit diameter) Mach 3 Laval nozzle. Emission spectroscopy is used to study the temperature and electron density distributions in the plasma jets produced by the different nozzle configurations. The effects of the observed modifications of the temperature and electron density fields on the properties of the plasma sprayed deposits are studied using Rene 80 powders which are sprayed using both types of nozzle under similar operating conditions. The results show that the M3 Laval nozzle provides a better spraying efficiency and spraying density than a standard anode nozzle under similar conditions.

Cao, M.; Gitzhofer, F.; Gravelle, D. V.; Henne, R.; Boulos, M. I.

1997-02-01

100

Solid oxide fuel cell processing using plasma arc spray deposition techniques. Final report  

SciTech Connect

The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

Ray, E.R.; Spengler, C.J.; Herman, H.

1991-07-01

101

Solid oxide fuel cell processing using plasma arc spray deposition techniques  

SciTech Connect

The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

Ray, E.R.; Spengler, C.J.; Herman, H.

1991-07-01

102

Suspension Plasma Spraying: Process Characteristics and Applications  

NASA Astrophysics Data System (ADS)

Suspension plasma spraying (SPS) offers the manufacture of unique microstructures which are not possible with conventional powdery feedstock. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the plasma jet, the attainable microstructural features like splat and pore sizes can be downsized to the nanometer range. Our present understanding of the deposition process including injection, suspension plasma plume interaction, and deposition will be outlined. The drawn conclusions are based on analysis of the coating microstructures in combination with particle temperature and velocity measurements as well as enthalpy probe investigations. The last measurements with the water cooled stagnation probe gives valuable information on the interaction of the carrier fluid with the plasma plume. Meanwhile, different areas of application of SPS coatings are known. In this paper, the focus will be on coatings for energy systems. Thermal barrier coatings (TBCs) for modern gas turbines are one important application field. SPS coatings offer the manufacture of strain-tolerant, segmented TBCs with low thermal conductivity. In addition, highly reflective coatings, which reduce the thermal load of the parts from radiation, can be produced. Further applications of SPS coatings as cathode layers in solid oxide fuel cells (SOFC) and for photovoltaic (PV) applications will be presented.

Vaßen, Robert; Kaßner, Holger; Mauer, Georg; Stöver, Detlev

2010-01-01

103

Inelastic Deformation of Freestanding Plasma-sprayed Thermal Barrier Coatings  

NASA Astrophysics Data System (ADS)

A fundamental study for an inelastic deformation of freestanding plasma-sprayed thermal barrier coatings (TBCs) has been conducted. Cantilever-type bending tests are carried out to obtain a stress-strain curve of the freestanding ceramic coating peeled from the TBC coated sample by an electrochemical treatment. In order to investigate about an inelastic deformation and its mechanism appeared in the sample, in-situ scanning electron microscope (SEM) observation is performed by means of a small tensile testing device that can be inserted into the SEM vacuum chamber. The bending test result indicated that the coating deforms with a nonlinear behavior under a monotonic loading and with a hysteresis loop under cyclic loading, in spite of that it is ceramic material. In-flight particle velocity in the spraying parameter affected the stress-strain curve significantly. In-situ SEM observation during the bending test revealed that sliding at boundary between splats plays an important role in an inelastic deformation.

Arai, Masayuki; Wu, Xiaohong; Fujimoto, Koji

104

Spray-drying of ceramics for plasma-spray coating  

Microsoft Academic Search

The spray-drying process of ceramics which are candidate materials for thermal barrier coatings (TBCs), i.e. 3YSZ+0, 2, 4, 6 wt.% Al2O3, is discussed in this paper. The two most important properties of spray-dried powders to determine the coating quality are density and particle size. Polyethyleneimine (PEI) acts as both an organic binder and a dispersant giving low viscosity in the

X. Q Cao; R Vassen; S Schwartz; W Jungen; F Tietz; D Stöever

2000-01-01

105

Strength degradation of SiC fiber during manufacture of titanium matrix composites by plasma spraying and hot pressing  

Microsoft Academic Search

Titanium matrix composites (TMCs) reinforced with Sigma 1140+ SiC fiber have been manufactured by a combination of low pressure\\u000a plasma spraying (LPPS spray\\/wind) and simultaneous fiber winding, followed by vacuum hot pressing (VHP). Fiber damage during\\u000a TMC manufacture has been evaluated by measuring fiber tensile strength after fiber extraction from the TMCs at various processing\\u000a stages, followed by fitting of

K. H. Baik; P. S. Grant

2001-01-01

106

Plasma Electrolytic Oxidation of Arc-Sprayed Aluminum Coatings  

Microsoft Academic Search

Different posttreatment methods, such as heat treatment, mechanical processing, sealing, etc., are known to be capable to\\u000a improve microstructure and exploitation properties of thermal spray coatings. In this work, a plasma electrolytic oxidation\\u000a of aluminum coatings obtained by arc spraying on aluminum and carbon steel substrates is carried out. Microstructure and properties\\u000a of oxidized layers formed on sprayed coating as

Vasyl Pokhmurskii; Hrygorij Nykyforchyn; Mykhajlo Student; Mykhajlo Klapkiv; Hanna Pokhmurska; Bernhard Wielage; Thomas Grund; Andreas Wank

2007-01-01

107

Coanda-Assisted Spray Manipulation Collar for a Commercial Plasma Spray Gun  

Microsoft Academic Search

A Coanda-assisted Spray Manipulation (CSM) collar was retrofitted to a Praxair SG-100 plasma spray gun. The CSM device makes\\u000a it possible to change the direction of (vector) the plasma jet and powder without moving the gun. The two-piece retrofit device\\u000a replaces the standard faceplate. Two separate collars were tested: one designed for small vector angles and one for larger\\u000a vector

K. Mabey; B. L. Smith; G. Whichard; T. McKechnie

2011-01-01

108

Plasma-Sprayed Dual Density Ceramic Turbine Seal System.  

National Technical Information Service (NTIS)

Dual density, plasma sprayed ceramic coating systems were investigated for possible application as abradable turbine tip seal systems in small gas turbine engines. Abradability, erosion resistance, internal leakage, and microstructural characterization we...

D. L. Clingman B. Schechter K. R. Cross J. R. Cavanagh

1979-01-01

109

Superior thermal barrier coatings using solution precursor plasma spray  

Microsoft Academic Search

A novel process, solution precursor plasma spray (SPPS), is presented for depositing thermal barrier coatings (TBCs), in which\\u000a aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting coatings microstructure\\u000a has three unique features: (1) ultra fine splats (1 µm), (2) nanometer and micron-sized interconnected porosity, and (3) closely\\u000a spaced, through-thickness cracks. Coatings over 3

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

2004-01-01

110

Numerical Investigation of a Hybrid HVOF-Plasma Spraying Process  

Microsoft Academic Search

This study deals with the numerical investigation of a hybrid thermal spray process that combines HVOF and thermal plasma\\u000a technologies. In this process, a thermal plasma is used to assist the combustion process that proceeds in a quasi-conventional\\u000a HVOF system. It is expected that this coupling makes the HVOF system more flexible in terms of working parameters and sprayed\\u000a materials.

B. Martinez; G. Mariaux; A. Vardelle; G. Barykin; M. Parco

2009-01-01

111

Plasma spray deposition of ultra high temperature ceramics  

Microsoft Academic Search

An innovative, proprietary methodology was developed to produce, by plasma spraying deposition, a ceramic composite containing SiC particles dispersed in a ZrB2 matrix. With such a technique both coatings and free standing parts were fabricated. In spite of the well known difficulty to obtain plasma sprayed coatings containing SiC, characterisation results evidenced that the used process did not affect the

Mario Tului; Giuliano Marino; Teodoro Valente

2006-01-01

112

Plasma spray synthesis of nanomaterial powders and deposits  

Microsoft Academic Search

Conventional plasma spraying was used to process atomized liquid droplets of precursor solutions to produce alumina, zirconia and yttria stabilized zirconia nanoparticles and deposits. An electrostatic precipitator collected the plasma synthesized ceramic particles at a rate of ~0.2 mg s?1, with ~5–20% collection efficiency. Spray processing produced 1–50 nm size ceramic particles. The size, shape and phase composition of the

J. Karthikeyan; C. C. Berndt; J. Tikkanen; S. Reddy; H. Herman

1997-01-01

113

Partial Evaporation of Strontium Zirconate During Atmospheric Plasma Spraying  

NASA Astrophysics Data System (ADS)

Perovskite-type SrZrO3 has been investigated as a candidate material for thermal barrier coating application. During plasma spraying of SrZrO3, SrO volatilized more than ZrO2 and the coating composition deviates from initial stoichiometry. In this investigation, partial evaporation was investigated by spraying SrZrO3 powders into water. The influences of spraying current, distance and particle size of the powder on the partial evaporation were also investigated in a quantitative way. With optimized spraying parameters, stoichiometric SrZrO3 coating was produced by adding an excess amount of Sr in the precursors before plasma spraying to compensate for the volatilized component.

Zhang, Yanfei; Mack, Daniel Emil; Jarligo, Maria Ophelia; Cao, Xueqiang; Vaßen, Robert; Stöver, Detlev

2009-12-01

114

Self-consistent modeling of plasma spraying processes  

SciTech Connect

A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of the melting of alumina particles injected into an axisymmetric pure argon plasma jet. 13 refs., 5 figs.

Chang, C.H.; Ramshaw, J.D.

1991-01-01

115

Electromagnetic Acceleration Plasma Spraying Applied to Ceramic Coating  

Microsoft Academic Search

Electromagnetic acceleration plasma generators, which are called Magneto-Plasma-Dynamic (MPD) arcjet generators, can produce higher-velocity, higher-temperature and higher-density plasmas than those of conventional thermal plasma torches, because MPD arcjet plasma is efficiently accelerated by electromagnetic body forces in MW-class input power operation. For applications of MPD arcjet generators to ceramic spray coatings, an MPD arcjet generator that has a continuous supply

Tetsuji Shibata; Hirokazu Tahara; Toshiaki Yasui; Yoichi Kagaya; Takao Yoshikawa

1998-01-01

116

Spray dried plasma for pigs weaned at different ages.  

PubMed

A review was done with 25 scientific papers published in the past fifteen years with the objective to verify the effects of spray dried plasma added to diets for pigs weaned at different ages on the feed intake, weight gain, intestinal structure, and number of E. coli colonies. Beneficial effects of spray dried plasma were observed during the first week after weaning for weight gain and feed intake of piglets weaned at 14, 21, and 28 days old. The beneficial effects of spray dried plasma decreased with the increase in weaning age. Positive effects of spray dried plasma were observed on the morph-physiological conditions of the small intestine, with higher villi height and crypt depth, when substituted completely for the powdered skim milk in diets for weaned pigs. Also, pigs fed diets with the inclusion of spray dried plasma had decreased E. coli colonies in the small intestine of pigs weaned at 21, 28, and 35 days old. The research also indicated that spray dried plasma can replace antibiotic in diets to pigs weaned at 28 and 35 days old. The article presents some promising patents on feed intake for pigs weaned at different ages. PMID:20653544

Ferreira, Aloízio S; Barbosa, Fellipe F; Tokach, Mike D; Santos, Marilu

2009-11-01

117

Properties of plasma sprayed boron carbide protective coatings for the first wall in fusion experiments  

NASA Astrophysics Data System (ADS)

In this study stainless steel substrates were coated by vacuum plasma spraying with a two-layer system consisting of a bond coat of 40 ?m nickel-chromium and the top coat material B 4C of 160-200 ?m thickness. The spray angle was varied from normal incidence to 60° with respect to the substrate normal. The effects of processing conditions on microstructure, mechanical properties and thermal load resistance were investigated by use of X-ray diffraction, optical microscopy, SEM, optical porosimetry, roughness- and adhesion-tests and thermal shock experiments in the electron beam test facility JUDITH. The thickness of the deposited B 4C-coatings decrease to a minimum of 40 ?m with increasing spray angle. Simultaneously the average roughness increases at a constant value of porosity. It could be stated, that the coatings, deposited at a larger angle, tend to exhibit a larger erosive attack pattern at slightly lower energy.

Döring, J.-E.; Vaßen, R.; Linke, J.; Stöver, D.

2002-12-01

118

Influence of spray angle on the pore and crack microstructure of plasma-sprayed deposits  

SciTech Connect

To understand the influence of processing parameters on the microstructure of plasma-sprayed deposits, small-angle neutron scattering measurements were made of the processing-parameter-dependent specific surface area of the voids in gray alumina deposits. These studies indicate that the voids are in the form of pores between the splats and around inclusions or unmelted particles, and are also in the form of cracks within the splats which may develop during cooling. The porous volume increases as the angle between the spray gun and the substrate (the spray angle) decreases. This study also indicates that the cracks are preferentially oriented, and that the crack orientation also depends on the spray angle. The interlamellar pores, however, are preferentially oriented parallel to the substrate surface, and the orientation of the pore is independent of the spray angle.

Ilavsky, J.; Allen, A.J.; Long, G.G.; Krueger, S. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Berndt, C.C.; Herman, H. [State Univ. of New York, Stony Brook, NY (United States)

1997-03-01

119

Boron carbide coating by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

A new system of electromagnetically accelerated plasma spraying (EMAPS) consisting of a pulsed high-current arc-plasma gun\\u000a and a large flow rate pulsed powder injector has been developed to synthesize a hard and dense coating of boron carbide (B4C) with a high adhesion. The plasma gun with a co-axial cylindrical electrode configuration generates electromagnetically\\u000a accelerated arc plasma with a typical velocity

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

120

Characterization of YSZ solid oxide fuel cells electrolyte deposited by atmospheric plasma spraying and low pressure plasma spraying  

NASA Astrophysics Data System (ADS)

Yttria doped zirconia has been widely used as electrolyte materials for solid oxide fuel cells (SOFC). Plasma spraying is a cost-effective process to deposit YSZ electrolyte. In this study, the 8 mol% Y2O3 stabilized ZrO2 (YSZ) layer was deposited by low pressure plasma spraying (LPPS) and atmospheric plasma spraying (APS) with fused-crushed and agglomerated powders to examine the effect of spray method and particle size on the electrical conductivity and gas permeability of YSZ coating. The microstructure of YSZ coating was characterized by scanning electron microscopy and x-ray diffraction analysis. The results showed that the gas permeability was significantly influenced by powder structure. The gas permeability of YSZ coating deposited by fused-crushed powder is one order lower in magnitude than that by agglomerated powder. Moreover, the gas permeability of YSZ deposited by LPPS is lower than that of APS YSZ. The electrical conductivity of the deposits through thickness direction was measured by potentiostat/galvanostat based on three-electrode assembly approach. The electrical conductivity of YSZ coating deposited by low pressure plasma spraying with fused-crushed powder of small particle size was 0.043 S cm-1 at 100 °C, which is about 20% higher than that of atmospheric plasma spraying YSZ with the same powder.

Zhang, C.; Liao, H. L.; Li, W. Y.; Zhang, G.; Coddet, C.; Zhang, C.; Li, C. J.; Li, C. X.; Ning, X. J.

2006-12-01

121

Slurry and Plasma-spray Coating of Selective Emitting Rare-earth Oxides on High Temperature Resistant Substrates  

NASA Astrophysics Data System (ADS)

Selective emitting coatings of the rare-earth oxides Yb2O3 and Yb-doped garnet have been applied on SiC by slurry coating and on the high refractory intermetallic compound MoSi2 by vacuum plasma-spraying. The TPV emitters produced are fully operable in oxygen atmosphere at high temperatures > 1500 °C. The novel technique of pairing MoSi2 substrate with plasma-sprayed rare-earth oxide results in highly thermal shock stable emitters due to an ideal match of the thermal expansion coefficients of intermetallic compound and ceramics.

Tobler, W. J.; Durisch, W.

2007-02-01

122

Development of porous anode layers for the solid oxide fuel cell by plasma spraying  

NASA Astrophysics Data System (ADS)

This article focuses on the development of the anode layer for solid oxide fuel cells by plasma spraying. The composite (cermet) anode, developed by thermal spraying, consisted of nickel and yttria-stabilized zirconia (YSZ). The effect of different plasma-spraying technologies on the microstructure characteristics and the electrochemical behavior of the anode layer were investigated. Coatings were fabricated by spraying nickel-coated graphite or nickel oxide with YSZ using a Triplex II plasma torch under atmospheric conditions as well as a standard F4 torch under atmospheric or soft-vacuum conditions. The investigations were directed to have an open microporous structure, higher electrical conductivity, and catalytic activity of anode deposits. Porosity was investigated by measuring the gas permeability. Scanning electron microscopy and x-ray diffraction technologies were applied to examine the morphology, microstructure, and composition of the layers. Electrical conductivity measurements were carried out to determine the ohmic losses within the anode layer. The most promising layers were analyzed by measuring the electrochemical behavior to obtain information about catalytic activity and performance.

Weckmann, H.; Syed, A.; Ilhan, Z.; Arnold, J.

2006-12-01

123

Process Design and Monitoring for Plasma Sprayed Abradable Coatings  

Microsoft Academic Search

Abradable coatings in compressor and high-pressure stages of gas turbines must provide specific hardness and porosity values\\u000a to achieve an optimal cut-in of the blade tips. A fractional factorial experimental plan was designed to investigate the influence\\u000a of the plasma spraying parameters argon flow rate, current, spraying distance and powder feed rate on these properties of\\u000a magnesia spinel. Based on

Tanja Steinke; Georg Mauer; Robert Vaßen; Detlev Stöver; Dan Roth-Fagaraseanu; Matthew Hancock

2010-01-01

124

Thermal shock characteristics of plasma sprayed mullite coatings  

Microsoft Academic Search

Commercially available mullite (3Al2O3·2SiO2) powders containing oxides of calcium and iron as impurities, have been made suitable for plasma spraying by using an organic binder. Stainless steel substrates covered with Ni-22Cr-10Al-1.0Y bond coat were spray coated with mullite. The 425 µm thick coatings were subjected to thermal shock cycling under burner rig conditions between 1000 and 1200 °C and less

P. Ramaswamy; S. Seetharamu; K. J. Rao; K. B. R. Varma

1998-01-01

125

Characterization of microstructure of Nano-TiO2 coating deposited by vacuum cold spraying  

NASA Astrophysics Data System (ADS)

Control of the microstructure of TiO2 coatings through preparation methods significantly influences the coating performance. In this study, a vacuum cold-spray process, as a new coating technology, is used to deposit nanocrystalline TiO2 coatings on conducting glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders with mean particle diameters of 200 and 25 nm. Coating microstructures were characterized by scanning electron microscopy and x-ray diffraction analysis. Results demonstrate that a thick nanocrystalline TiO2 coating can be deposited by the vacuum cold-spray process. The coating was found to consist of particles stacked as agglomerates that build up to several hundred nanometers. The coating also presents a mesoporous microstructure that could be effective in such applications as photocatalytic degradation and dye-sensitized solar cells.

Fan, S. Q.; Yang, G. J.; Li, C. J.; Liu, G. J.; Li, C. X.; Zhang, L. Z.

2006-12-01

126

Coanda-Assisted Spray Manipulation Collar for a Commercial Plasma Spray Gun  

NASA Astrophysics Data System (ADS)

A Coanda-assisted Spray Manipulation (CSM) collar was retrofitted to a Praxair SG-100 plasma spray gun. The CSM device makes it possible to change the direction of (vector) the plasma jet and powder without moving the gun. The two-piece retrofit device replaces the standard faceplate. Two separate collars were tested: one designed for small vector angles and one for larger vector angles. It was demonstrated that the small-angle device could modify the trajectory of zirconia powder up to several degrees. Doing so could realign the plasma with the powder resulting in increased powder temperature and velocity. The large-angle device was capable of vectoring the plasma jet up to 45°. However, the powder did not vector as much. Under large-angle vectoring, the powder velocity and temperature decreased steadily with vector angle. Both devices were tested using a supersonic configuration to demonstrate that CSM is capable of vectoring supersonic plasmas.

Mabey, K.; Smith, B. L.; Whichard, G.; McKechnie, T.

2011-06-01

127

Characterization of microstructure of Nano-TiO2 coating deposited by vacuum cold spraying  

Microsoft Academic Search

Control of the microstructure of TiO2 coatings through preparation methods significantly influences the coating performance. In this study, a vacuum cold-spray process, as a new coating technology, is used to deposit nanocrystalline TiO2 coatings on conducting glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders with mean particle diameters of 200 and 25

S. Q. Fan; G. J. Yang; C. J. Li; G. J. Liu; C. X. Li; L. Z. Zhang

2006-01-01

128

Characterization of microstructure of Nano-TiO 2 coating deposited by vacuum cold spraying  

Microsoft Academic Search

Control of the microstructure of TiO2 coatings through preparation methods significantly influences the coating performance. In this study, a vacuum cold-spray\\u000a process, as a new coating technology, is used to deposit nanocrystalline TiO2 coatings on conducting glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders with mean particle diameters of 200 and 25

S.-Q. Fan; G.-J. Yang; C.-J. Li; G.-J. Liu; C.-X. Li; L.-Z. Zhang

2006-01-01

129

Quantum electrodynamics vacuum polarization modification of photon acceleration in plasma  

SciTech Connect

The modification of photon frequency shifting based on taking into account the nonlinear quantum electrodynamics vacuum properties in plasma is studied. Motion equations of a laser field propagating in a plasma are derived from the Heisenberg-Euler Lagrangian density. It is found that besides the classical density perturbation of the plasma electrons, the energy density perturbation of the laser field will induce the frequency shifting via the ponderomotive force of the laser field on the vacuum. In addition it is shown that the electron density will be suppressed, which is attributed to a screening effect on the plasma electrons via the quantum vacuum polarization.

Bu Zhigang [Department of Physics, Shanghai University, Shanghai 200444 (China); Ji Peiyong [Department of Physics, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of Astrophysics, Shanghai 200234 (China)

2010-07-15

130

Thermal sprayed zirconium coatings for corrosion resistance  

Microsoft Academic Search

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

Bamola

1992-01-01

131

A torch nozzle design to improve plasma spraying techniques  

Microsoft Academic Search

The effects of nozzle design on the plasma characteristics of supersonic flow conditions are investigated using a D.C. plasma jet under low-pressure plasma spraying conditions. Comparison is made between a 5 mm I.D. standard nozzle and a 13 mm E.D. (exit diameter) Mach 3 Laval nozzle. Emission spectroscopy is used to study the temperature and electron density distributions in the

M. Cao; F. Gitzhofer; D. V. Gravelle; R. Henne; M. I. Boulos

1997-01-01

132

Characterization of plasma sprayed and explosively consolidated simulated lunar soil  

SciTech Connect

Two methods for the use of lunar materials for the construction of shelters on the Moon are being proposed: explosive consolidation of the soil into structural components and plasma spraying of the soil to join components. The plasma-sprayed coating would also provide protection from the intense radiation. In this work, a mare simulant was plasma-sprayed onto a stainless steel substrate. Deposition of a 0.020 inch coating using power inputs of 23, 25, 27 and 29 kW were compared. Hardness of the coatings increased with each increase of power to the system, while porosity at the interface decreased. All coatings exhibited good adhesion. Simultaneously, an explosively consolidated sample was similarly characterized to afford a comparison of structural features associated with each mode of proposed use.

Powell, S.J.; Inal, O.T. [New Mexico Tech, Socorro, NM (United States); Smith, M.F. [Sandia National Labs., Albuquerque, NM (United States)

1997-06-01

133

Plasma spray synthesis from precursors: Progress, issues, and considerations  

NASA Astrophysics Data System (ADS)

Precursor plasma spray synthesis is an innovative and rapid method for making functional oxide ceramic coatings by starting from solution precursors and directly producing inorganic films. This emerging method utilizes molecularly mixed precursor liquids, which essentially avoids the handling and selection of powders, opening up new avenues for developing compositionally complex functional oxide coatings. Precursor plasma spray also offers excellent opportunities for exploring the nonequilibrium phase evolution during plasma spraying of multicomponent oxides from inorganic precursors. Although there have been efforts in this area since the 1980s and early 1990s with the goal of synthesizing nanoparticles, only recently has the work progressed in the area of functional systems. At the Center for Thermal Spray Research an integrated investigative strategy has been used to explore the benefits and limits of this synthesis strategy. Water- and alcohol-based sol/solution precursors derived from various chemical synthesis methods were used as feedstocks to deposit thin/thick films of spherical and nanostructured coatings of yttrium aluminum garnet (YAG), yttrium iron garnet, lanthanum strontium manganate and Zr-substituted yttrium titanates, and compositions of Y2O3-Al2O3 and their microstructural space centered around stoichiometric YAG. A detailed discussion of the salient features of the radiofrequency induction plasma spraying approach, the results obtained in the investigations to develop various functional oxide coatings, and process issues and challenges are presented.

Ravi, B. G.; Sampath, S.; Gambino, R.; Parise, J. B.; Devi, P. S.

2006-12-01

134

Phase analysis of plasma-sprayed zirconia-yttria coatings  

NASA Technical Reports Server (NTRS)

Phase analysis of plasma-sprayed 8 wt pct-yttria-stabilized zirconia (YSZ) thermal barrier coatings and powders was carried out by X-ray diffraction. Step scanning was used for increased peak resolution. Plasma spraying of the YSZ powder into water or onto a steel substrate to form a coating reduced the cubic and monoclinic phases with a simultaneous increase in the tetragonal phase. Heat treatment of the coating at 1150 C for 10 h in an Ar atmosphere increased the amount of cubic and monoclinic phases. The implications of these transformations on coating performance and integrity are discussed.

Shankar, N. R.; Berndt, C. C.; Herman, H.

1983-01-01

135

The solution precursor plasma spray processing of nanomaterials  

NASA Astrophysics Data System (ADS)

Solution precursor plasma spray (SPPS) synthesis is a simple, single-step, and rapid technique for synthesizing nano-ceramic materials from solution precursors. This innovative method uses molecularly mixed precursors as liquids, avoiding a separate processing method for the preparation of powders and enabling the synthesis of a wide range of metal oxide powders and coatings. Also, this technique is considered to be promising for the formation of non-equilibrium phases in multi-component oxide systems. This short review provides an insight into the important aspects of SPPS, the properties obtained in comparison to conventional plasma spray, and the potential applications of the SPPS process.

Brinley, E.; Babu, K. S.; Seal, S.

2007-07-01

136

The Role of Spraying Parameters and Inert Gas Shrouding in Hybrid Water-Argon Plasma Spraying of Tungsten and Copper for Nuclear Fusion Applications  

NASA Astrophysics Data System (ADS)

Tungsten-based coatings have potential application in the plasma-facing components in future nuclear fusion reactors. By the combination of refractory tungsten with highly thermal conducting copper, or steel as a construction material, functionally graded coatings can be easily obtained by plasma spraying, and may result in the development of a material with favorable properties. During plasma spraying of these materials in the open atmosphere, oxidation is an important issue, which could have adverse effects on their properties. Among the means to control it is the application of inert gas shrouding, which forms the subject of this study and represents a lower-cost alternative to vacuum or low-pressure plasma spraying, potentially applicable also for spraying of large surfaces or spacious components. It is a continuation of recent studies focused on the effects of various parameters of the hybrid water-argon torch on the in-flight behavior of copper and tungsten powders and the resultant coatings. In the current study, argon shrouding with various configurations of the shroud was applied. The effects of torch parameters, such as power and argon flow rate, and powder morphology were also investigated. Their influence on the particle in-flight behavior as well as the structure, composition and properties of the coatings were quantified. With the help of auxiliary calculations, the mass changes of the powder particles, associated with oxidation and evaporation, were assessed.

Mat?jí?ek, J.; Kavka, T.; Bertolissi, G.; Ctibor, P.; Vilémová, M.; Mušálek, R.; Nevrlá, B.

2013-06-01

137

Development of amorphous and CNT-reinforced amorhpous 3eramic coatings fabricated by plasma spraying process  

Microsoft Academic Search

The plasma-sprayed amorphous ceramic coating and CNT-reinforced amorphous ceramic coating were successfully developed by plasma spraying process. Also, the microstructure, mechanical, and chemical properties of the plasma-sprayed amorphous ceramic coating and CNT-reinforced amorphous ceramic coating were systematically investigated. The formation mechanism of plasma-sprayed amorphous ceramic coating was involved with rapid quenching of the fully melted ceramic splats via ultra-high-temperature of

Eun Young Choi; Hoon Jeong; Kwang Ho Kim; Hyun Kwang Seok

2011-01-01

138

Effect of Spraying Parameters on Deposition Efficiency and Wear Behavior of Plasma Sprayed Alumina-Titania Composite Coatings  

NASA Astrophysics Data System (ADS)

The effects of parameters, in the process of plasma-sprayed ceramic coating, upon the deposition efficiency of alumina-13 wt.% titania composite coatings are reported. The coatings were prepared by the atmospheric plasma spray process. The plasma torch input power, flow rates of primary, secondary and carrier gas, powder feed rate and spraying distance were considered as variables. The results show that the variations in all the selected spraying parameters strongly affect the deposition efficiency. The micro-hardness, as well as erosive and sliding wear rates of the coating are also affected by these parameters. Especially the input power strongly affects the phase and microstructure of the coatings.

Vijay, M.; Selvarajan, V.; Yugeswaran, S.; V. Ananthapadmanabhan, P.; P. Sreekumar, K.

2009-12-01

139

Atmospheric plasma sprayed thermal barrier coatings with high segmentation crack densities: Spraying process, microstructure and thermal cycling behavior  

Microsoft Academic Search

Thermal barrier coatings (TBCs) with high strain tolerance are favorable for application in hot gas sections of aircraft turbines. To improve the strain tolerance of atmospheric plasma sprayed (APS) TBCs, 400?m–500?m thick coatings with very high segmentation crack densities produced with fused and crushed yttria stabilized zirconia (YSZ) were developed. Using a Triplex II plasma gun and an optimized spraying

M. Karger; R. Vaßen; D. Stöver

2011-01-01

140

Improved Small-Particle Powders for Plasma Spraying  

NASA Technical Reports Server (NTRS)

Improved small-particle powders and powder-processing conditions have been developed for use in plasma spray deposition of thermal-barrier and environmental barrier coatings. Heretofore, plasma-sprayed coatings have typically ranged in thickness from 125 to 1,800 micrometers. As explained below, the improved powders make it possible to ensure complete coverage of substrates at unprecedently small thicknesses of the order of 25 micrometers. Plasma spraying involves feeding a powder into a hot, high-velocity plasma jet. The individual powder particles melt in the plasma jet as they are propelled towards a substrate, upon which they splat to build up a coating. In some cases, multiple coating layers are required. The size range of the powder particles necessarily dictates the minimum thickness of a coating layer needed to obtain uniform or complete coverage. Heretofore, powder particle sizes have typically ranged from 40 to 70 micrometers; as a result, the minimum thickness of a coating layer for complete coverage has been about 75 micrometers. In some applications, thinner coatings or thinner coating layers are desirable. In principle, one can reduce the minimum complete-coverage thickness of a layer by using smaller powder particles. However, until now, when powder particle sizes have been reduced, the powders have exhibited a tendency to cake, clogging powder feeder mechanisms and feed lines. Hence, the main problem is one of synthesizing smaller-particle powders having desirable flow properties. The problem is solved by use of a process that begins with a spray-drying subprocess to produce spherical powder particles having diameters of less than 30 micrometers. (Spherical-particle powders have the best flow properties.) The powder is then passed several times through a commercial sifter with a mesh to separate particles having diameters less than 15 micrometers. The resulting fine, flowable powder is passed through a commercial fluidized bed powder feeder into a plasma spray jet.

Nguyen, QuynhGiao, N.; Miller, Robert A.; Leissler, George W.

2005-01-01

141

Parameters Controlling Liquid Plasma Spraying: Solutions, Sols, or Suspensions  

NASA Astrophysics Data System (ADS)

This article presents what is our present knowledge in plasma spraying of suspension, sol, and solution in order to achieve finely or nano-structured coatings. First, it describes the different plasma torches used, the way liquid jet is injected, and the different measurements techniques. Then, drops or jet fragmentation is discussed with especially the influence of arc root fluctuations for direct current plasma jets. The heat treatment of drops and droplets is described successively for suspensions, sols, and solutions both in direct current or radio-frequency plasmas, with a special emphasize on the heat treatment, during spraying, of beads and passes deposited. The resulting coating morphologies are commented and finally examples of applications presented: Solid Oxide Fuel Cells, Thermal Barrier coatings, photocatalytic titania, hydroxyapatite, WC-Co, complex oxides or metastable phases, and functional materials coatings.

Fauchais, P.; Etchart-Salas, R.; Rat, V.; Coudert, J. F.; Caron, N.; Wittmann-Ténèze, K.

2008-03-01

142

Novel high-temperature reliable heaters in plasma spray technology  

NASA Astrophysics Data System (ADS)

Novel high-temperature (600°C) self-regulated heaters have been developed with air plasma spray technology on metal supports, according to the design and processes disclosed in the U.S. patent that was recently published. In the present article, the essential steps of this development are delineated together with the results achieved.

Prudenziati, Maria; Cirri, Gianfranco; Dal Bo, Peter

2006-09-01

143

Plasma-sprayed ceramics and ceramic-matrix composites  

Microsoft Academic Search

The versatility of plasma spray technology enables the formation of a broad range of metal and ceramic matrix composites, both as coatings and as free-standing bulk forms. The concept is simple, while the details are rather complex: a primary feedstock material destined to be the matrix, is melted and propelled to a substrate where rapid solidification occurs. The powder reinforcing

H. Herman; K. Lapierre

1992-01-01

144

Thermal Plasma Spraying Applied on Solid Oxide Fuel Cells  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

145

Mechanical and physical properties of plasma-sprayed stabilized zirconia  

SciTech Connect

Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

Siemers, P.A.; Mehan, R.L.

1983-09-01

146

Pulsed laser processing of plasma sprayed thermal barrier coatings  

Microsoft Academic Search

The requirements for thermal barrier coatings on turbine blades in jet engines and gas turbines are stringent due to the extreme temperatures and constant thermal cycling that demand a material with excellent thermal shock resistant and thermal insulation properties. Plasma sprayed zirconia alloys have been found to fit this role with some degrees of success. However, the presence of surface

K. A. Khor; S. Jana

1997-01-01

147

Failure analysis of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings have been subjected to thermal cycling tests with simultaneous acoustic emission (AE) monitoring. Process variables and their effect on coating integrity were evaluated in terms of cracking behavior. Failure of the thermal protection is progressive since cracking and crack growth were observed prior to ultimate failure. Catastrophic failure occurs when microcracks are transformed to macrocracks.

C. C. Berndt; R. A. Miller

1984-01-01

148

Mechanical and physical properties of plasma-sprayed stabilized zirconia  

NASA Technical Reports Server (NTRS)

Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

Siemers, P. A.; Mehan, R. L.

1983-01-01

149

Multilayer refractory nozzles produced by plasma-spray process  

NASA Technical Reports Server (NTRS)

Multilayer rocket nozzles formed by plasma spraying have good thermal shock resistance and can be reheated in an oxidizing environment without loss of coating adherence. Suggested application of this process are for the production of refractory components, which can be formed as surfaces of revolution.

Bliton, J. L.; Rausch, J. L.

1966-01-01

150

Plasma tests of sprayed coatings for rocket thrust chambers  

NASA Technical Reports Server (NTRS)

Several plasma-sprayed coating systems were evaluated for structural stability in hydrogen plasma and in oxygen plasma mixed with hydrogen plasma. The principal test heat flux was 15 Btu per inch squared seconds. The system consisted of a number of thin 0.002 to 0.020 in. layers of metal oxides and/or metals. The principal materials included are molybdenum nichrome, alumina, and zirconia. The study identifies important factors in coating system fabrication and describes the durability of the coating systems in the test environments. Values of effective thermal conductivity for some of the systems are indicated.

Curren, A. N.; Love, W. K.

1974-01-01

151

Influence of Glass Content on Damping Properties of Plasma-Sprayed Mixtures of Zirconia and Glass  

NASA Astrophysics Data System (ADS)

The addition by vacuum infiltration of small quantities of a polymer has been found to increase significantly the ability of a plasma-sprayed coating to dissipate vibratory energy at temperatures in the glassy-rubbery transition range of the polymer. As vitreous enamels and glasses undergo a glassy transition, but at much higher temperatures, the addition of a small amount of glass to a ceramic has the potential of providing high damping at such temperatures. Mixtures of yttria-stabilized zirconia (YSZ) and a glass frit were plasma sprayed on specimens with bond coats. Measures of system response (resonant frequencies and loss factors) were extracted from frequency responses to excitations of cantilever beam specimens over a range of excitation amplitudes. Comparisons of values determined before and after coating were used to determine the damping properties of the coatings alone as functions of strain, at temperatures of special interest. Emphasis was given to identifying the lowest level of glass giving significantly more damping than that of the plasma-sprayed ceramic alone. Coatings with weight fractions of 5, 2, 1, ½, and 0% glass were tested. The inclusion of glass at all weight fractions considered was found to yield significant increases in both the stiffness and dissipation of the coatings.

Torvik, P. J.; Henderson, J. P.

2012-07-01

152

Formation of boron carbide coating by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

Boron carbide (B4C) coating formation is investigated using an electromagnetically accelerated plasma spraying, which can generate a dense and a high velocity plasma jet of 1 MPa and 2.0–2.5 km\\/s by applying a pulsed high-current arc-discharge to accelerate and heat powders. Highly crystalline B4C coatings with roughened coating-substrate interfaces were formed on mirror-polished stainless (SUS304) substrates without a binder material.

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

153

Electroform/Plasma-Spray Laminates for X-Ray Optics  

NASA Technical Reports Server (NTRS)

Electroform/plasma-spray laminates have shown promise as lightweight, strong, low-thermal-expansion components for xray optics. The basic idea is to exploit both (1) the well-established art of fabrication of optical components by replication and (2) plasma spraying as a means of reinforcing a thin replica optic with one or more backing layer(s) having tailorable thermomechanical properties. In x-ray optics as in other applications, replication reduces the time and cost of fabrication because grinding and polishing can be limited to a few thick masters, from which many lightweight replicas can thereafter be made. The first step in the fabrication of a component of the type in question is to make a replica optic by electroforming a thin layer of nickel on a master. Through proper control of the electroforming process conditions, it is possible to minimize residual stress and, hence, to minimize distortion in the replica. Next, a powder comprising ceramic particles coated with a metal compatible with the electroformed nickel is plasma-sprayed onto the backside of the nickel replica. Then through several repetitions and variations of the preceding steps or perhaps a small compressive stress, alternating layers of electroformed nickel and plasma-sprayed metal-coated ceramic powder are deposited. The thicknesses of the layers and the composition of the metal-coated ceramic powder are chosen to optimize the strength, areal mass density, and toughness of the finished component. An important benefit of using both electroforming and plasma spraying is the possibility of balancing stresses to a minimum level, which could be zero or perhaps a small net compressive stress designed to enhance the function of the component in its intended application.

Ulmer, Melville P.; Graham, Michael; Vaynman, Semyon

2007-01-01

154

Continuous spray forming of functionally gradient materials.  

National Technical Information Service (NTIS)

Researchers at Plasma Processes Inc. have produced a Functional Gradient Material (FGM) through advanced vacuum plasma spray processing for high heat flux applications. Outlined in this paper are the manufacturing methods used to develop a four component ...

T. N. McKechnie E. H. Richardson

1995-01-01

155

Thermal shock characteristics of plasma sprayed mullite coatings  

Microsoft Academic Search

Commercially available mullite (3Al2O3·2SiO2) powders containing oxides of calcium and iron as impurities, have been made suitable for plasma spraying by using an organic\\u000a binder. Stainless steel substrates covered with Ni-22Cr-10Al-1.0Y bond coat were spray coated with mullite. The 425 µm thick\\u000a coatings were subjected to thermal shock cycling under burner rig conditions between 1000 and 1200 °C and less

P. Ramaswamy; S. Seetharamu; K. J. Rao; K. B. R. Varma

1998-01-01

156

Functionally Graded Materials using Plasma Spray with Nano Structured Ceramic  

NASA Astrophysics Data System (ADS)

In this paper, nano structured FGM was fabricated using DC plasma spray technique. Nano structured and micro structured powder were used as the feeding powder with steel substrate. The spray parameters was optimized and characterisation of nano-ceramic FGM and micro-ceramic FGM were done using bending test and micro-hardness test. Experimental results have shown that the nano-structured FGM exhibit 20% improvement flexure strength and 10% in hardness. A comparison was made between sintered micro ceramic tile and nano ceramic FGM using simple drop test method.

Sioh, E. L.; Tok, A. I. Y.

2013-03-01

157

Plasma spray deposited superconducting Y-Ba-Cu-oxide coatings  

SciTech Connect

The properties of YBa{sub 2}Cu{sub 3}O{sub 6+x} thick films, deposited by plasma spraying of reacted powders in Ar atmosphere, are determined as a function of powder properties, conditions of post-annealing process and substrate materials. The relations between the electrical resistivity near critical temperature, the chemical composition and structure of the films in their as-sprayed and annealed states are investigated by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and metallography.

Rohr, S.; Bacher, I.; Schlafer, U.; Schneider, L.; Muller, R.; Teresiak, A.; Verges, P. (Central Institute of Solid State Physics and Materials Research of the Academy of Sciences of the GDR, Dresden 8027 (DD)); Eckart, G. (Technical Univ. Dresden, Dresden 8027 (DD))

1990-06-01

158

Plasma cleaning device. [designed for high vacuum environments  

NASA Technical Reports Server (NTRS)

High vacuum cleaning of contaminated surfaces such as hydrocarbon containment films can be accomplished by a plasma cleaning device which includes a plasma discharge housing to permit generation of a plasma in an environment having a higher pressure than the surface which is to be cleaned. A ground electrode and a radio frequency electrode partially surround a quartz plasma tube, for the introduction of an ionizable gas. These electrodes ionize the gas and help generate the plasma. This plasma flows through a non-constrictive aperture, through the plasma discharge housing and then on to the contaminated surface.

Shannon, R. L.; Gillette, R. B. (inventors)

1978-01-01

159

Electrochemical corrosion and metal ion release from Co-Cr-Mo prosthesis with titanium plasma spray coating  

Microsoft Academic Search

The corrosion behavior of CoCrMo implants with rough titanium coatings, applied by different suppliers by either sintering or vacuum plasma spraying, has been evaluated and compared with uncoated material. The open-circuit potential, corrosion current and polarization resistance were determined by electrochemical techniques. The Co, Cr and Ti ions released from the samples into the electrolyte during a potentiostatic extraction technique

Lucien Reclaru; Pierre-Yves Eschler; Reto Lerf; Andreas Blatter

2005-01-01

160

Plasma-sprayed nanocrystalline Ti–Ru–Fe–O coatings for the electrocatalysis of hydrogen evolution reaction  

Microsoft Academic Search

Nanocrystalline Ti–Ru–Fe–O (2-1-1-2) was prepared by mechanical alloying in a ZOZ attritor. Vacuum plasma spray (VPS) was then used to deposit coatings of this material on a substrate. Energy dispersive X-ray fluorescence and X-ray diffraction analysis was used to follow the change in the chemical composition and crystalline structure of the powder upon deposition by VPS. Nanocrystalline Ti–Ru–Fe–O (2-1-1-2) prepared

E Irissou; M Blouin; L Roué; J Huot; R Schulz; D Guay

2002-01-01

161

Phase evolution of hydroxapatite coatings suspension plasma sprayed using variable parameters in simulated body fluid  

Microsoft Academic Search

Fine, hydroxyapatite (HA) powder, synthesized using calcium nitrate and diammonium nitrate was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto titanium substrates. The deposition process was optimized using statistical design of 2n experiments with two variables: spray distance and electric power input to arc plasma. The sprayed coatings were soaked in simulated body

Romain d'Haese; Lech Pawlowski; Muriel Bigan; Roman Jaworski; Marc Martel

2010-01-01

162

Synchronization of Suspension Plasma Spray Injection with the Arc Fluctuations  

NASA Astrophysics Data System (ADS)

Poorly controlled heat and momentum transfers between plasma and material, plasma instabilities are some of the difficulties encountered in suspension plasma spraying. The improvement of this method is usually attempted by means of the reduction of arc fluctuations. This paper presents a new approach to the injection of reactive material in an arc jet. The principle is to produce a pulsed laminar plasma jet combined with phased injection of liquid droplets. This is achieved by the particular design of the plasma torch that works at moderate power and following a resonant mode. The droplets are injected using a piezoelectric device, based on drop-on-demand method, triggered by the voltage signal sampled at the torch connections. The results are evaluated by time-resolved imaging technique that shows how the trajectories are influenced by the moment at which the droplets penetrate the plasma jet.

Krowka, J.; Rat, V.; Goutier, S.; Coudert, J. F.

2014-06-01

163

Steam chemical reactivity of plasma-sprayed beryllium  

SciTech Connect

Plasma-spraying with the potential for in-situ repair makes beryllium a primary candidate for plasma facing and structural components in experimental magnetic fusion machines. Deposits with good thermal conductivity and resistance to thermal cycling have been produced with low pressure plasma-spraying (LPPS). A concern during a potential accident with steam ingress is the amount of hydrogen produced by the reactions of steam with hot components. In this study the authors measure the reaction rates of various deposits produced by LPPS with steam from 350 C to above 1,000 C. They correlate these reaction rates with measurements of density, open porosity and BET surface areas. They find the reactivity to be largely dependent upon effective surface area. Promising results were obtained below 600 C from a 94% theoretical dense (TD) deposit with a BET specific surface area of 0.085 m{sup 2}/g. Although reaction rates were higher than those for dense consolidated beryllium they were substantially lower, i.e., about two orders of magnitude, than those obtained from previously tested lower density plasma-sprayed deposits.

Anderl, R.A.; Pawelko, R.J.; Smolik, G.R. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States). Idaho National Engineering and Environmental Lab.; Castro, R.G. [Los Alamos National Lab., NM (United States)

1998-07-01

164

Effects of plasma spray parameters on two layer thermal barrier  

NASA Technical Reports Server (NTRS)

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.

Stecura, S.

1981-01-01

165

Laser remelting of plasma-sprayed coatings on nuclear valves  

NASA Astrophysics Data System (ADS)

Three kinds of plasma sprayed coatings on nuclear valves of FRAMATOME, which are the cobalt-based Stellite, the nickel-based Eutroloy, and the iron-based Cenium, were remelted with a 5 kW CO2 laser. The aim is to build-up a fine homogeneous metallurgical structure onto the hardface, with a uniform thickness and free of cracks in order to improve the wear and galling properties of the coatings. It was concluded from the experimental results that for plasma sprayed Stellite coating, satisfactory results can be obtained by carefully selecting the process parameters, preheating of the substrate is not needed; and for the Eutroloy coating, preheating of the substrate is necessary to get rid of cracking during laser remelting. Laser remelting is not an adequate process for Cerium coating because it is very difficult to avoid cracks on the remelted layer.

Li, Yanxiang; Steen, William M.; Sharkey, Sarah J.

1993-05-01

166

Plasma-sprayed ceramic coatings for molten metal environments.  

SciTech Connect

Coating porosity is an important parameter to optimize for plasma-sprayed ceramics which are intended for service in molten metal environments. Too much porosity and the coatings may be infiltrated by the molten metal causing corrosive attack of the substrate or destruction of the coating upon solidification of the metal. Too little porosity and the coating may fail due to its inability to absorb thermal strains. This study describes the testing and analysis of tungsten rods coated with aluminum oxide, yttria-stabilized zirconia, yttrium oxide, and erbium oxide deposited by atmospheric plasma spraying. The samples were immersed in molten aluminum and analyzed after immersion. One of the ceramic materials used, yttrium oxide, was heat treated at 1000 C and 2000 C and analyzed by X-ray diffractography and mercury intrusion porosimetry. Slight changes in crysl nl structure and significant changes in porosity were observed after heat treatments.

Hollis, K. J. (Kendall J.); Peters, M. I. (Maria I.); Bartram, B. D. (Brian D.)

2002-01-01

167

Electrochemical Evaluation of Pyrite Films Prepared by Plasma Spraying  

SciTech Connect

Thermally activated batteries use electrodes that are typically fabricated by cold pressing of powder. In the LiSi/FeS2 system, natural (mineral) pyrite is used for the cathode. In an effort to increase the energy density and specific energy of these batteries, flame and plasma spraying to form thin films of pyrite cathodes were evaluated. The films were deposited on a 304 stainless steel substrate (current collector) and were characterized by scanning electron microscopy and x-ray dlfllaction. The films were electrochemically tested in single cells at 5000C and the petiormance compared to that of standard cells made with cold-pressed powders. The best results were obtained with material deposited by de-arc plasma spraying with a proprietq additive to suppress thermal decomposion of the pyrite.

Guidotti, R.A.; Reinhardt, F.W.

1998-10-30

168

Phase distributions in plasma-sprayed zirconia-yttria  

NASA Technical Reports Server (NTRS)

The distribution of phases in plasma-sprayed zirconia-yttria has been determined over a range of yttria levels from 0 to 26.1 molpct YO(1.5) using room temperature X-ray diffractometry. Pure, plasma-sprayed zirconia is composed almost entirely of the monoclinic phase. At levels of yttria between 4 and 10 percent, a quenched-in tetragonal phase predominates, and at higher levels the cubic phase predominates. The phase distributions are compared with previously reported test lives of thermal barrier coatings formed from these materials. Regions of optimal lives were found to correlate with regions having high amounts of the tetragonal phase, small but nonzero amounts of the monoclinic phase, and little or none of the cubic phase. Possible relationships between phase composition and coating performance are discussed.

Miller, R. A.; Garlick, R. G.; Smialek, J. L.

1983-01-01

169

Residual stress in plasma sprayed Y 2O 3?PSZ coatings on piston heads  

Microsoft Academic Search

Yttria—partially-stabilized zirconia (Y—PSZ) thermal barrier coatings (TBCs) were deposited on Al alloy disks under different plasma spraying conditions, using both air plasma spraying (APS) and atmosphere and temperature controlled spraying (ATCS) processes. X-ray diffraction (XRD) was used to make a non-destructive residual stress analysis (RSA) on the surface of coatings, either as-sprayed and after a burner rig test. Regardless of

P. Scardi; M. Leoni; L. Bertamini; M. Marchese

1996-01-01

170

dc-plasma-sprayed electronic-tube device  

DOEpatents

An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

Meek, T.T.

1982-01-29

171

Response surface methodology for optimization of plasma spraying  

Microsoft Academic Search

Response surface methodology was used to describe empirical relationships among three principal independent variables that\\u000a control the plasma spraying process. The torch-substrate distance, the amount of hydrogen in the primary gas (argon), and\\u000a the powder feed rate were studied. A number of dependent variables (responses) were determined, including the deposited layer\\u000a roughness, density, hardness, chemical composition, and erosion rate. The

T. Troczynski; M. Plamondon

1992-01-01

172

In situ characterization of small-particle plasma sprayed powders  

Microsoft Academic Search

The effect of various small-particle plasma spray powder injection parameters on the in situ particle position, velocity,\\u000a and temperature is measured for yttria-stabilized zirconia and yttrium-aluminum-garnet powder. Using full-factorial experiments\\u000a and multiple regression analysis, carrier gas flow, injector angle, and powder feeder disc speed were found to significantly\\u000a affect the particle properties. Temperature and velocity were inversely related; on average,

Y. J. Su; K. T. Faber; T. F. Bernecki

2002-01-01

173

Electrochemical Evaluation of Pyrite Films Prepared by Plasma Spraying  

Microsoft Academic Search

Thermally activated batteries use electrodes that are typically fabricated by cold pressing of powder. In the LiSi\\/FeS2 system, natural (mineral) pyrite is used for the cathode. In an effort to increase the energy density and specific energy of these batteries, flame and plasma spraying to form thin films of pyrite cathodes were evaluated. The films were deposited on a 304

R. A. Guidotti; F. W. Reinhardt

1998-01-01

174

Air plasma sprayed thermal barrier coatings on titanium alloy substrates  

Microsoft Academic Search

Titanium alloys as lightweight structure materials have been shown more interest in the use at moderately elevated temperatures. However, their poor oxidation resistance at temperature above 600 °C limits a wide application. Consequently, thermal protection becomes a concern. 8 wt.% yttria partially stabilized zirconia thermal barrier coatings (TBCs) were air plasma sprayed on titanium alloy substrates (Ti–6.6Al–3.61Mo–1.69Zr–0.28Si in wt.%). The microstructures and

Hong Zhou; Fei Li; Bo He; Jun Wang; Bao-de Sun

2007-01-01

175

Microlaminate composite structures by low pressure plasma spray deposition  

SciTech Connect

The low pressure plasma spray (LPPS) process has been utilized in the development and fabrication of metal/metal, metal/carbide, and metal/oxide composite structures; including particulate dispersion and both continuous and discontinuous laminates. This report describes the LPPS process and the development of copper/tungsten microlaminate structures utilizing this processing method. Microstructures and mechanical properties of the Cu/W composites are compared to conventionally produced constituent material properties. 4 refs., 6 figs., 2 tabs.

Castro, R.G.; Stanek, P.W.

1988-01-01

176

Failure modes in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Commercial plasma-sprayed thermal barrier coatings (TBCs) were investigated in an effort to elucidate the failure modes during thermal-cycling. Residual stresses in the thermally grown oxide (TGO) was measured using the Cr3+ photoluminescence piezo-spectroscopy (PLPS) method and the microstructures of the TBCs were characterized as a function of thermal cycles. The average residual stress in the TGO was found to be

K. W Schlichting; N. P Padture; E. H Jordan; M Gell

2003-01-01

177

Well-posedness of the plasma-vacuum interface problem  

NASA Astrophysics Data System (ADS)

We consider the free-boundary problem for the plasma-vacuum interface in ideal compressible magnetohydrodynamics (MHD). In the plasma region the flow is governed by the usual compressible MHD equations, while in the vacuum region we consider the pre-Maxwell dynamics for the magnetic field. At the free interface, driven by the plasma velocity, the total pressure is continuous and the magnetic field on both sides is tangent to the boundary. The plasma-vacuum system is not isolated from the outside world, because of a given surface current on the fixed boundary that forces oscillations. Under a suitable stability condition satisfied at each point of the initial interface, stating that the magnetic fields on either side of the interface are not collinear, we show the existence and uniqueness of the solution to the nonlinear plasma-vacuum interface problem in suitable anisotropic Sobolev spaces. The proof is based on the results proved in the companion paper (Secchi and Trakhinin 2013 Interfaces Free Boundaries 15 323-57), about the well-posedness of the homogeneous linearized problem and the proof of a basic a priori energy estimate. The proof of the resolution of the nonlinear problem given in the present paper follows from the analysis of the elliptic system for the vacuum magnetic field, a suitable tame estimate in Sobolev spaces for the full linearized equations, and a Nash-Moser iteration.

Secchi, Paolo; Trakhinin, Yuri

2014-01-01

178

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings  

NASA Astrophysics Data System (ADS)

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.

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

2010-03-01

179

Suspension Plasma Spraying of YPSZ Coatings: Suspension Atomization and Injection  

NASA Astrophysics Data System (ADS)

Among processes evaluated to produce some parts of or the whole solid-oxide fuel cell, Suspension Plasma Spraying (SPS) is of prime interest. Aqueous suspensions of yttria partially stabilized zirconia atomized into a spray by an internal-mixing co-axial twin-fluid atomizer were injected into a DC plasma jet. The dispersion and stability of the suspensions were enhanced by adjusting the amount of dispersant (ammonium salt of polyacrylic acid, PAA). A polyvinyl alcohol (PVA) was further added to the suspension to tailor its viscosity. The PVA also improved the dispersion and stability of the suspensions. The atomization of optimized formulations is described implementing Weber and Ohnesorge dimensionless numbers as well as gas-to-liquid mass ratio (ALR) value. Drop size distributions changed from monomodal distributions at low We to multimodal distributions when We number increases. The viscosity of the suspensions has a clear influence on the drop size distribution and suspension spray pattern. The secondary fragmentation of the drops due to the plasma jet was evidenced and the final size of the sheared drops was shown to depend on the characteristics of the suspension. Rather dense zirconia coatings have been prepared, which is a promising way to produce electrolyte.

Rampon, Régine; Filiatre, Claudine; Bertrand, Ghislaine

2008-03-01

180

Vacuum arc plasma thrusters with inductive energy storage driver  

NASA Technical Reports Server (NTRS)

An apparatus for producing a vacuum arc plasma source device using a low mass, compact inductive energy storage circuit powered by a low voltage DC supply acts as a vacuum arc plasma thruster. An inductor is charged through a switch, subsequently the switch is opened and a voltage spike of Ldi/dt is produced initiating plasma across a resistive path separating anode and cathode. The plasma is subsequently maintained by energy stored in the inductor. Plasma is produced from cathode material, which allows for any electrically conductive material to be used. A planar structure, a tubular structure, and a coaxial structure allow for consumption of cathode material feed and thereby long lifetime of the thruster for long durations of time.

Schein, Jochen (Inventor); Gerhan, Andrew N. (Inventor); Woo, Robyn L. (Inventor); Au, Michael Y. (Inventor); Krishnan, Mahadevan (Inventor)

2004-01-01

181

Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings  

Microsoft Academic Search

The crystalline phases and degree of crystallinity in plasma sprayed calcium phosphate coatings on Ti substrates are crucial factors that influence the biological interactions of the materials in vivo. In this study, plasma sprayed hydroxyapatite (HA) coatings underwent post-spray treatment by the spark plasma sintering (SPS) technique at 500°C, 600°C, and 700°C for duration of 5 and 30min. The activity

L.-G Yu; K. A Khor; H Li; P Cheang

2003-01-01

182

Thermoelectric Properties of Magnesium Silicide Deposited by Use of an Atmospheric Plasma Thermal Spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide (Mg2Si) samples prepared by use of an atmospheric plasma spray (APS) were compared with those of samples prepared from the same feedstock powder by use of the conventional hot-pressing method. The characterization performed included measurement of thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit, ZT. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX) were used to assess how phase and microstructure affected the thermoelectric properties of the samples. Hall effect measurements furnished carrier concentration, and measurement of Hall mobility provided further insight into electrical conductivity and Seebeck coefficient. Low temperature and high velocity APS using an internal-powder distribution system achieved a phase of composition similar to that of the feedstock powder. Thermal spraying was demonstrated in this work to be an effective means of reducing the thermal conductivity of Mg2Si; this may be because of pores and cracks in the sprayed sample. Vacuum-annealed APS samples were found to have very high Seebeck coefficients. To further improve the figure of merit, carrier concentration must be adjusted and carrier mobility must be enhanced.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Chen, Yikai; Tewolde, Mahder; Sampath, Sanjay

2014-07-01

183

Thermoelectric Properties of Magnesium Silicide Deposited by Use of an Atmospheric Plasma Thermal Spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide (Mg2Si) samples prepared by use of an atmospheric plasma spray (APS) were compared with those of samples prepared from the same feedstock powder by use of the conventional hot-pressing method. The characterization performed included measurement of thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit, ZT. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX) were used to assess how phase and microstructure affected the thermoelectric properties of the samples. Hall effect measurements furnished carrier concentration, and measurement of Hall mobility provided further insight into electrical conductivity and Seebeck coefficient. Low temperature and high velocity APS using an internal-powder distribution system achieved a phase of composition similar to that of the feedstock powder. Thermal spraying was demonstrated in this work to be an effective means of reducing the thermal conductivity of Mg2Si; this may be because of pores and cracks in the sprayed sample. Vacuum-annealed APS samples were found to have very high Seebeck coefficients. To further improve the figure of merit, carrier concentration must be adjusted and carrier mobility must be enhanced.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Chen, Yikai; Tewolde, Mahder; Sampath, Sanjay

2014-04-01

184

Optimization of Plasma Spray Process Using Statistical Methods  

NASA Astrophysics Data System (ADS)

The microstructure features of coatings produced by a plasma spray process are affected significantly by the process parameters such as powder size, spray gun nozzle size, total plasma gas flow, ratio of H2 + N2 over total gas flow, and so on. This article presents a study of the effects of these parameters on the microstructure (porosity, formation of crack, unmelted particle and oxide phase) of NiCrAlY coatings deposited by the Mettech Axial III™ System. A Taguchi array is used to design the spraying process parameters. The results of the microstructure evaluation are used to generate regression equations for the prediction of coating microstructure based on process parameters. The results predicted from the regression equations are in good agreement with the experimental results according to a confidence level of 0.95. Among the parameters examined, the powder size and the ratio of H2 + N2 over total gas flow rate are the most significant parameters affecting the occurrence of crack, porosity, unmelted particle and oxide. Within the range of the designed process parameters, lower powder size and higher ratio of H2 + N2 over total gas flow rate lead to less cracks, pores, unmelted particles but more oxides. Nozzle size has marginal influence on oxides which increase with nozzle size. Gas flow rate has no direct influence on any coating feature evaluated with the range of variation.

Gao, F.; Huang, X.; Liu, R.; Yang, Q.

2012-01-01

185

Suspension plasma spraying of nanostructured WC-12Co coatings  

NASA Astrophysics Data System (ADS)

Nanostructured WC-12% Co coatings were deposited by suspension plasma spraying of submicron feedstock powders, using an internal injection plasma torch. The liquid carrier used in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a fine surface finish. A polyethylene-imine (PEI) dispersant was used to stabilize the colloidal suspension in an ethanol carrier. In-flight particle states were measured for a number of operating conditions of varying plasma gas flow rates, feed rates, and standoff distances and were related to the resulting microstructure, phase composition (EDS, SEM, XRD), and Vickers hardness. High in-flight particle velocities (>800 m/s) were generated, leading to dense coatings. It was observed that the coating quality was generally compromised by the high temperature and reactivity of the small particles. To compensate for this shortcoming, the suspension feed rate was adjusted, thereby varying the thermal load on the plasma. Results showed that a slightly larger agglomerate size, in conjunction with low particle jet temperatures, could somewhat limit the decomposition of WC into brittle W2C/W3C and amorphous cobalt containing binder phases.

Berghaus, J. Oberste; Marple, B.; Moreau, C.

2006-12-01

186

Plasma-sprayed ceramic coatings for protection against molten metal.  

SciTech Connect

Molten metal environments pose a special demand on materials due to the high temperature corrosion effects and thermal expansion mismatch induced stress effects. A solution that has been successfully employed is the use of a base material for the mechanical strength and a coating material for the chemical compatibility with the molten metal. The work described here used such an approach coating tungsten rods with aluminum oxide, yttria-stabilized zirconia, yttrium oxide, and erbium oxide deposited by atmospheric plasma spraying. The ceramic materials were deposited under varying conditions to produce different structures. Measurement of particle characteristics was performed to correlate to material properties. The coatings were tested in a thermal cycling environment to simulate the metal melting cycle expected in service. Results of the testing indicate the effect of material composition and spray conditions on the thermal cycle crack resistance of the coatings.

Hollis, K. J. (Kendall J.); Peters, M. I. (Maria I.); Bartram, B. D. (Brian D.)

2002-01-01

187

Microstructural evaluation of monolithic and continuous fibre reinforced Al12wt.%Si produced by low pressure plasma spraying  

Microsoft Academic Search

The spray\\/wind process is a concurrent fibre winding and plasma spraying technique and may be used for the manufacture of continuous fibre reinforced composites in a single spraying operation. The microstructure of low pressure plasma sprayed (LPPS) Al-12wt.%Si coatings and spray\\/wind Al-12Si composites reinforced with continuous fibres has been investigated. The LPPS monolithic Al-12Si deposit sprayed in a single-pass was

Kyeong Ho Baik; Patrick S. Grant

1999-01-01

188

Deposition Behavior and Microstructural Features of Vacuum Kinetic Sprayed Aluminum Nitride  

NASA Astrophysics Data System (ADS)

The vacuum kinetic spray (VKS) method is a relatively advanced technology by which thin and dense ceramic coatings can be fabricated via the high-speed impact of submicron-sized particles at room temperature. However, the actual bonding mechanism associated with the VKS process has not yet been elucidated. In this study, AlN powders were pretreated through ball-milling and heat-treatment processes in order to investigate the effects of microstructural changes on the deposition behavior. It was found that ball-milled and heat-treated powder with polycrystals formed by partially aligned dislocations showed considerably higher deposition rates when compared to only ball-milled powder with tangled dislocations. Therefore, in the VKS process, the deposition behavior is shown to be affected by not only the particle size and defect density, but also the microstructure of the feedstock powder.

Park, Hyungkwon; Heo, Jeeae; Cao, Fei; Kwon, Juhyuk; Kang, Kicheol; Bae, Gyuyeol; Lee, Changhee

2013-08-01

189

Evaluation of corrosion on plasma sprayed and anodized titanium implants, both with and without bone cement.  

PubMed

The corrosion behavior of titanium with vacuum plasma sprayed titanium coatings and with anodized surfaces, both with and without polymeric bone cement were evaluated. Electrochemical extraction tests were carried out with subsequent analysis of the electrolyte by ICP-MS in order to verify our hypothesis of the ionic permeability of the polymer cement. The complexity of the situation resides in the existence of two interfaces: electrolyte-polymer and polymer-metal. The surface preparation (treatment of the surface) plays an important role in the corrosion resistance of titanium. The electrochemical magnitudes that were examined reveal that the plasma spray surfaces have the lowest corrosion resistance. The cement, in spite of having reduced electrical conductivity in comparison to metal, is an ionic transporter, and therefore capable of participating in the corrosion process. In the present study, we observed in fact crevice corrosion at the metal-cement interface. In the case of plasma spray surfaces, a process of diffusion of titanium particles in the electrolyte could accompany the crevice corrosion. In this study, we have shown that there is a corrosion process at the surface of the titanium through the cement which has as a consequence on the one hand the formation of titanium cations and on the other hand the growth of a passive layer on the titanium. In conclusion, we identified two principal factors that influence the corrosion process: [1] the type of surface treatment for the titanium, and [2] the ionic conductivity of the cement. There is indeed ionic transport through the cement; as evidenced by the presence of titanium in the electrolyte solution (ICP-MS analysis) and chloride at the surface of the titanium sample (EDX analysis). We show that the polymer cement is an ionic conductor and participates in the corrosion of the embedded titanium. We cannot deduce from our results, however, whether the polymer itself possesses corrosive properties. Long-term experiments will be necessary to study the degradation behavior of the polymer cement. PMID:12895575

Reclaru, L; Lerf, R; Eschler, P-Y; Blatter, A; Meyer, J-M

2003-08-01

190

Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.  

PubMed

Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites. PMID:17450788

Laha, T; Liu, Y; Agarwal, A

2007-02-01

191

Vacuum arc plasma jet interaction with neutral ambient gas  

Microsoft Academic Search

Vacuum arc plasma jet (VAPJ) propagation in a neutral nitrogen atmosphere has been calculated numerically on the basis of a hydrodynamic description. It was assumed that the VAPJ was emitted isotropically from a point source located z0 = 20 mm in front of the entrance of a straight duct 100 mm in diameter in which an axial magnetic field of

E. Gidalevich; S. Goldsmith; R. L. Boxman

2000-01-01

192

Plasma spray nozzle with low overspray and collimated flow  

NASA Technical Reports Server (NTRS)

An improved nozzle for reducing overspray in high temperature supersonic plasma spray devices comprises a body defining an internal passageway having an upstream end and a downstream end through which a selected plasma gas is directed. The nozzle passageway has a generally converging/diverging Laval shape with its upstream end converging to a throat section and its downstream end diverging from the throat section. The upstream end of the passageway is configured to accommodate a high current cathode for producing an electrical arc in the passageway to heat and ionize the gas flow to plasma form as it moves along the passageway. The downstream end of the nozzle is uniquely configured through the methodology of this invention to have a contoured bell-shape that diverges from the throat to the exit of the nozzle. Coating material in powder form is injected into the plasma flow in the region of the bell-shaped downstream end of the nozzle and the powder particles become entrained in the flow. The unique bell shape of the nozzle downstream end produces a plasma spray that is ideally expanded at the nozzle exit and thus virtually free of shock phenomena, and that is highly collimated so as to exhibit significantly reduced fanning and diffusion between the nozzle and the target. The overall result is a significant reduction in the amount of material escaping from the plasma stream in the form of overspray and a corresponding improvement in the cost of the coating operation and in the quality and integrity of the coating itself.

Beason, Jr., George P. (Inventor); McKechnie, Timothy N. (Inventor); Power, Christopher A. (Inventor)

1996-01-01

193

Optimization of Atmospheric Plasma Spray Process Parameters using a Design of Experiment for Alloy 625 coatings  

Microsoft Academic Search

Alloy 625 is a Ni-based superalloy which is often a good solution to surface engineering problems involving high temperature\\u000a corrosion, wear, and thermal degradation. Coatings of alloy 625 can be efficiently deposited by thermal spray methods such\\u000a as Air Plasma Spraying. As in all thermal spray processes, the final properties of the coatings are determined by the spraying\\u000a parameters. In

F. Azarmi; T. W. Coyle; J. Mostaghimi

2008-01-01

194

Modeling of the APS plasma spray process using artificial neural networks: basis, requirements and an example  

Microsoft Academic Search

Thermal spraying is a versatile technique to manufacture coatings which offers a large choice of processes (i.e., plasma spraying, flame spraying, electric arc spraying, etc.) and materials (i.e., metallic, ceramic, polymer and composite materials). To obtain functional coatings exhibiting selected in-service properties, combinations of processing parameters have to be planned. These combinations differ by their cost and by their influence

Sofiane Guessasma; Ghislain Montavon; Christian Coddet

2004-01-01

195

Study of plasma- and detonation gun-sprayed alumina coatings using taguchi experimental design  

Microsoft Academic Search

Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al2O3) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with\\u000a extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al2O3 coatings deposited using the above techniques by using Taguchi experimental design.\\u000a \\u000a Alumina coating

P. Saravanan; V. Selvarajan; M. P. Srivastava; D. S. Rao; S. V. Joshi; G. Sundararajan

2000-01-01

196

Thermomechanical behavior of nanostructured plasma sprayed zirconia coatings  

NASA Astrophysics Data System (ADS)

Retaining nonmelted nanoparticles of zirconia in nanostructured coatings has been a challenge in the past. Recently an air plasma spray process was developed to produce coatings that retain up to 30-35% by volume nonmelted particles, resulting in a unique structure. The creep/sintering behavior of such thermal barrier coatings deposited from nanostructured feedstock has been measured and compared with deposits produced from hot oven spherical particles (HOSP). Both feedstocks contain 6-8 wt.% Y2O3 as a stabilizer. Flexure and compression creep testing were conducted under several different loads and temperatures to obtain creep exponents and parameters.

Soltani, R.; Garcia, E.; Coyle, T. W.; Mostaghimi, J.; Lima, R. S.; Marple, B. R.; Moreau, C.

2006-12-01

197

Plasma-sprayed lead zirconate titanate-glass composites  

SciTech Connect

A plasma-spray process was used to produce piezoelectric lead zirconate titanate (PZT)-glass composite thick films. The films were found to have the same crystal structure as the PZT (Navy-type V) and lead-based glass starting powder mixture. The films showed good adhesion to stainless steel and silver-coated glass slides and poor adhesion to aluminum substrates. The dielectric constant of the films varied between 58 and 20 with dissipations between 0.019 and 0.032. The films were poled, and their piezoelectric charge coefficient, d[sub 33], was 1.1 pC/N.

Sherrit, S.; Savin, C.R.; Wiederick, H.D.; Mukherjee, B.K. (Royal Military Coll. of Canada, Kingston, Ontario (Canada). Dept. of Physics); Prasad, S.E. (Sensor Technology, Ltd., Collingwood, Ontario (Canada))

1994-07-01

198

Producing titanium aluminide foil from plasma-sprayed preforms  

SciTech Connect

A new method was used to fabricate foils of Ti-6Al-4V (Ti-6-4) alloy and Ti-14Al-21Nb(Ti-14-21) titanium aluminide, starting from a plasma-sprayed (PS) preform. The foils were 100 percent dense, with microstructures similar to those of wrought (IM) foil material. The foil made from PS preforms were characterized by the mechanical properties equivalent to their IM-processed counterparts. It is concluded that the method of roll consolidation of a PS preform is well suited for alloys and intermetallics that do not possess extensive hot and cold workability. 6 refs.

Jha, S.C.; Forster, J.A. (Texas Instruments, Inc., Attleboro, MA (United States))

1993-07-01

199

Plasma-sprayed coatings as adherend surface pretreatments  

NASA Astrophysics Data System (ADS)

Automatable and environmentally acceptable surface preparation techniques were evaluated for selected metals and composites, with particular attention given to plasma-sprayed microporous thin coatings as surface pretreatments for metals and resin-based composites. The metal adherends were Ti-6Al-4V titanium, 2024 aluminum, and cold-rolled (CR) steel, while the resin-based composite systems used as adherends included G10 glass/epoxy, SP-500 graphite/epoxy, and a commercially available sheet molding. The results of mechanical tests demonstrated the viability of this approach for achieving acceptable joint strength with these adherends.

Pike, R. A.; Patarini, V. M.; Zatorski, R.; Lamm, F. P.

1992-10-01

200

Instrumented adhesion tests on plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

The failure mechanisms of plasma-sprayed two-layer coatings consisting of an NiCrAlY or NiCrAlZr bond coat with an yttria-stabilized zirconia overlay are presently examined by tensile adhesion tests. It has been found that adhesive failure within the bond coat exhibits greater failure strain than the cohesive failure of the ceramic overlay, supporting the view of the intermediate coatings being highly compliant. The absolute extension exhibited by failures occurring only through the ceramic coating is greater than that of adhesive failure, since the ceramic coating is much thicker than the bond coat.

Berndt, Christopher C.

1989-01-01

201

Front surface thermal property measurements of air plasma spray coatings  

SciTech Connect

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.

Bennett, Ted; Kakuda, Tyler [University of California, Santa Barbara, California 93106-5070 (United States); Kulkarni, Anand [Siemens Energy, Orlando, Florida 32826-2399 (United States)

2009-04-15

202

Adhesion of plasma sprayed zirconia splats on stainless steel  

NASA Astrophysics Data System (ADS)

Thermal spray technology is an alternative material fabrication technique to the traditional solidification and powder processing methods for producing thick coatings and bulk free-forms. Extensive research has enabled the extension of this technique to a wider range of material classes including polymers, bioceramics and functionally gradient materials. A key area of application of thermal spraying is the formation of thermal barrier coatings for turbine components used in power generation and propulsion. Continuing research intends to improve the quality of coatings produced by this technique to compete with other technologies like physical vapor deposition to make use of some of the advantages like higher throughput that thermal spraying affords. Understanding the adhesion of plasma sprayed coatings is essential to improving the service life of coated components. Progressively research has focussed on the nature of the unique building blocks of plasma sprayed coatings called splats. The current research intends to characterize the microadhesion at the splat substrate interface using nondestructive methods based on the analysis of images obtained using the scanning electron microscope (SEM). A model system of yttria stabilized zirconia, a traditional thermal barrier material, on steel substrate is chosen for the study. Two techniques are developed based on the analysis of through thickness crack distribution and fragmentation of thin brittle films on ductile substrates and that based on the analysis of interface cracking. A novel imaging technique is used to determine the extent of interface cracking from the contrast observed in SEM images. Based on the understanding of ceramic splat formation on metal substrates a shear lag theory of tensile residual stress generation is used to explain the fragmentation observed in splats. An earlier analysis of cracking in brittle films due to uniaxial stress is extended to the present case of equibiaxial thermal residual stress. Three geometric features are identified to analyze the observed fragment geometries and correlated with local interfacial adhesion in splats. The measurements are extracted from secondary and back-scattered electron images using image segmentation software. Measurement of cracked interfacial areas was accomplished using charging contrast in the secondary and specimen current images of splats. Based on these measurements it was found that micro adhesion decreases within splats from center to the periphery. This variation in adhesion was attributed to the temperature and pressure distribution in the splat-substrate interface during formation.

Rangarajan, Srinivasan

2000-10-01

203

Characterization of Plasma-Sprayed Pyrite\\/Electrolyte Composite Cathodes for Thermal Batteries  

Microsoft Academic Search

A number of electrolytes were evaluated as co-spray additives for plasma spraying of pyrite powder to form composite cathodes for use in thermally activated batteries. Initial work showed that the LiCl-KCl eutectic electrolyte was effective for this purpose. In this paper, the use of alternative electrolytes is described and the effects on performance of the plasma-sprayed cathodes in Li(Si)\\/FeS 2

Ronald A. Guidotti; Frederick W. Reinhardt; Jinxiang Dai; Jeff Roth; David E. Reisner

204

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

Microsoft Academic Search

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 micron thick deposited by Low Pressure Plasma Spraying (LPPS) and a 300 micron thick ZrO2-7 wt pct Y2O3 top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying using internal air cooling through the

T. Cosack; L. Pawlowski; S. Schneiderbanger; S. Sturlese

1992-01-01

205

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

Microsoft Academic Search

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 [mu]m thick deposited by Low-Pressure Plasma Spraying (LPPS) and a 300 [mu]m thick ZrO[sub 2]-7 wt.% Y[sub 2]O[sub 3] top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying (APS) using internal air cooling

T. Cosack; S. Schneiderbanger; L. Pawlowski; S. Sturlese

1994-01-01

206

Net shape nanostructured aluminum oxide structures fabricated by plasma spray forming  

Microsoft Academic Search

The plasma spray technique has been used by several researchers to deposit nanostructured ceramic coatings, but there is no\\u000a available literature discussing how to fabricate a bulk, freestanding nanostructured component by such a technique. In the\\u000a current study, net shape nanostructured Al2O3 structures have been fabricated using the plasma spray technique. A detailed characterization of the spray-formed Al2O3 structure has

Arvind Agarwal; Tim McKechnie; Sudipta Seal

2003-01-01

207

New generation of plasma-sprayed mullite coatings on silicon carbide  

Microsoft Academic Search

Mullite is promising as a protective coating for silicon-based aggressive high-temperature environments. Conventionally plasma-sprayed mullite on SiC tends to crack and debond on thermal cycling. It is shown that this behavior is due to the presence of amorphous mullite in the conventionally sprayed mullite. Heating the SiC substrate during the plasma spraying eliminated the amorphous phase and produced coatings with

Kang N. Lee; Robert A. Miller; Nathan S. Jacobson

1995-01-01

208

An integrated study of thermal spray process–structure–property correlations: A case study for plasma sprayed molybdenum coatings  

Microsoft Academic Search

Thermal spray coatings exhibit a wide variety of hierarchial and multiscale microstructural characteristics that lead to variation in their functional properties and performance. The array of defect structures, orthotropic behaviour and process-induced attributes (e.g. quenching stresses) all add to complexity in understanding and predicting their performance. A complete understanding of the plasma spray process includes examination of the particle–jet interaction,

A. Vaidya; T. Streibl; L. Li; S. Sampath; O. Kovarik; R. Greenlaw

2005-01-01

209

Angular distribution of plasma in the vacuum arc ion source.  

PubMed

This paper presents measurements of the angular distribution of the plasma components and different charge states of metal ions generated by a MEVVA-type ion source and measured by a time-of-flight mass-spectrometer. The experiments were performed for different cathode materials (Al, Cu, and Ti) and for different parameters of the vacuum arc discharge. The results are compared with prior results reported by other authors. The influence of different discharge parameters on the angular distribution in a vacuum arc source is discussed. PMID:22380199

Nikolaev, A G; Yushkov, G Yu; Savkin, K P; Oks, E M

2012-02-01

210

Heat transfer analysis of the plasma-spray deposition process  

NASA Astrophysics Data System (ADS)

A novel approach has been used to analyse the flow of heat during the plasma spray coating process. The approach couples heat transfer processes occurring at the micro scale, within the coating, and at the macro scale, in the substrate, using a combination of finite-element and finite-difference based models. One of the key boundary conditions employed in the model has been determined from an inverse heat conduction analysis of data recorded from an array of thermocouples embedded into a copper disk while being sprayed with a stationary gun in the absence of powder deposition. The models have been used to determine the evolution of temperature in 8 wt% yttria partially stabilized zirconia coatings deposited onto AISI-1008 steel for the deposition times of 1, 2 and 3 seconds. The results indicate that the cooling rate of the material deposited initially is of the order of 10sp7sp°C/s and that the first splat cools from its melting temperature to room temperature in approximately 10sp3 s. The predictions from the model have been compared qualitatively with the distribution and the shape of pores found in the coating after subsequent metallographic examination. Different size and distribution of pores found at different locations of the zirconia based coating appear consistent with a qualitative understanding of the evolution of temperature in the coatings examined. Pores located at the coating/substrate interface appeared larger and were inter-connected. At the centre near the free surface of the coating, however, pores were closed and isolated. In addition, the same models have been applied for the plasma spray deposition of 17% Co-WC and CP titanium on AISI-1008 steel. The particle temperatures predicted using the model were compared with the temperatures measured in an independent study using a pyrometer-based measurements on the same plasma spray system. The results of the heat flow-based analysis were found to agree with the pyrometer-based measurements to within 10% for the case of 17% Co-WC and to within 16% for CP titanium.

Wong, Henry Wing-Wo

211

Experiments and simulation of rapid solidification of air plasma sprayed alloy 625 on stainless steel  

Microsoft Academic Search

There is growing interest in the use of superalloy coatings to improve the high temperature properties of base materials. Thermal spraying methods such as air plasma spraying (APS) are convenient techniques to deposit such coatings. This work examines the rapid solidification of APS deposited alloy 625. While conventionally processed materials solidify near the equilibrium temperature, in the case of plasma

H. Liu; F. Azarmi; M. Bussmann; J. Mostaghimi; T. W. Coyle

2010-01-01

212

Characterization of suspension plasma-sprayed solid oxide fuel cell electrodes  

Microsoft Academic Search

Suspension plasma spray is a promising technique that uses fine particles dispersed in a liquid as feedstock material instead of dry powder as in conventional plasma spraying and has been implemented here to produce layers with appropriate morphologies and microstructures for SOFC applications.This study uses a pressurized gas delivery system to feed the slurry through a homemade two-fluid atomizing nozzle

O. Marchand; P. Bertrand; J. Mougin; C. Comminges; M.-P. Planche; G. Bertrand

2010-01-01

213

Using response surface methodology for optimizing deposited partially stabilized zirconia in plasma spraying  

Microsoft Academic Search

This paper presents the application of the surface response methodology and fractional factorial experiment in developing a robust partially stabilized zirconia (PSZ) coating in plasma spraying processes. In this study, a two-step experimental design with a nonlinear regression model is proposed. After conducting a series of initial experiments in a controlled environment, significant factors for plasma spraying processes are selected

Bor-Tsuen Lin; Ming-Der Jean; Jyh-Horng Chou

2007-01-01

214

Understanding crack formation in plasma sprayed thermal barrier coatings and their effects on coating properties  

Microsoft Academic Search

As a key microstructural feature of plasma sprayed thermal barrier coatings (TBCs), microcracks determine the performance and service lifetimes of the coatings by influencing their thermal conductivity and compliance. The goal of this research is to obtain a fundamental understanding of crack formation in plasma sprayed microstructures, and their effect on mechanical and thermal properties through a synergistic combination of

Guosheng Ye

2004-01-01

215

Characterization and comparison between ball milled and plasma processed iron-aluminium thermal spray coatings  

Microsoft Academic Search

Plasma spraying has wide ranging applications which include corrosion, thermal and abrasion resistance coatings. Plasma spray deposition is a process that combines particle melting, quenching and consolidation in a single operation. Ordered intermetallics based on aluminides of transition metals have been under investigation for their possible use as high temperature structural materials. Apart from their oxidation and carburization resistances, aluminides

S. Kumar; V. Selvarajan; P. V. A. Padmanabhan; K. P. Sreekumar

2006-01-01

216

Fully plasma-sprayed compliant backed ceramic turbine seal  

NASA Technical Reports Server (NTRS)

A seal with a high temperature abradable lining material which encircles the tips of turbine blades in turbomachinery was designed. The seal is directed to maintaining the minimum operating clearances between the blade tips and the lining of a high pressure turbine. A low temperature easily decomposable material in powder form is blended with a high temperature oxidation resistant metal powder. The two materials are simultaneously deposited on a substrate formed by the turbine casing. Alternately, the polymer powder may be added to the metal powder during plasma spraying. A ceramic layer is then deposited directly onto the metal-polymer composite. The polymer additive mixed with the metal is then completely volatilized to provide a porous layer between the ceramic layer and the substrate. Thermal stresses are reduced by the porous structure which gives a cushion effect. No brazing is required by using only plasma spraying for depositing both the powders of the metal and polymer material as well as the ceramic powder.

Bill, R. C.; Wisander, D. W. (inventors)

1981-01-01

217

Clogging and Lump Formation During Atmospheric Plasma Spraying with Powder Injection Downstream the Plasma Gun  

Microsoft Academic Search

This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder\\u000a injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the\\u000a powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder\\u000a injector. A new geometry

Isabelle Choquet; Stefan Björklund; Jimmy Johansson; Jan Wigren

2007-01-01

218

Phase transformation and wear studies of plasma sprayed yttria stabilized zirconia coatings containing various mol% of yttria  

SciTech Connect

Plasma sprayable grade zirconia powders doped with various mol% of yttria (0, 2, 3, 4, 6, 8 and 12 mol%) were synthesized by a chemical co-precipitation route. The coprecipitation conditions were adjusted such that the powders possessed good flowability in the as calcined condition and thus avoiding the agglomeration step like spray drying. Identical plasma spray parameters were used for plasma spraying all the powders on stainless steel plates. The powders and plasma sprayed coatings were characterized by X-ray diffractometry, Scanning Electron Microscopy and Raman spectroscopy. Zirconia powders are susceptible to phase transformations when subjected to very high temperatures during plasma spraying and XRD is insensitive to the presence of some non crystalline phases and hence Raman spectroscopy was used as an important tool. The microstructure of the plasma sprayed coatings showed a bimodal distribution containing fully melted and unmelted zones. The microhardness and wear resistance of the plasma sprayed coatings were determined. Among the plasma sprayed coatings, 3 mol% yttria stabilized zirconia coating containing pure tetragonal zirconia showed the highest wear resistance. - Research Highlights: {yields} Preparation plasma sprayable YSZ powders without any agglomeration process and plasma spraying {yields} Phase transformation studies of plasma sprayed YSZ coatings by XRD and Raman spectroscopy {yields} Microstructure of the plasma sprayed coatings exhibited bimodal distribution {yields} Plasma sprayed 3 mol% YSZ coating exhibited the highest wear resistance {yields} Higher wear resistance is due to the higher fracture toughness of tetragonal 3 mol% YSZ phase.

Aruna, S.T., E-mail: aruna_reddy@nal.res.in; Balaji, N.; Rajam, K.S.

2011-07-15

219

Strength degradation of SiC fiber during manufacture of titanium matrix composites by plasma spraying and hot pressing  

NASA Astrophysics Data System (ADS)

Titanium matrix composites (TMCs) reinforced with Sigma 1140+ SiC fiber have been manufactured by a combination of low pressure plasma spraying (LPPS spray/wind) and simultaneous fiber winding, followed by vacuum hot pressing (VHP). Fiber damage during TMC manufacture has been evaluated by measuring fiber tensile strength after fiber extraction from the TMCs at various processing stages, followed by fitting of these data to a Weibull distribution function. The LPPS spray/wind processing caused a decrease in mean fiber strength and Weibull modulus in comparison with as-received fibers. A number of fiber surface flaws, primarily in the outer C layer of the fiber, formed as a result of mechanical impact of poorly melted particles from the plasma spray. Coarse feedstock powders promoted an increase in the population of fiber surface flaws, leading to significant reduction in fiber strength. The VHP consolidation promoted further development of fiber surface flaws by fiber bending and stress localization because of nonuniform matrix shrinkage, resulting in further degradation in fiber strength. In the extreme case of fibers touching, the stress concentration on the fibers was sufficient to cause fiber cracking. Fractographic studies revealed that low strength fibers failed by surface flaw induced failure and contained a large fracture mirror zone. Compared with the more widely investigated foil-fiber-foil route to manufacture TMCs, LPPS/VHP resulted in less degradation in fiber strength for Sigma 1140+ fiber. Preliminary results for Textron SCS-6 fiber indicated a much greater tolerance to LPPS/VHP damage.

Baik, K. H.; Grant, P. S.

2001-12-01

220

Experimental study of particle deposition characteristics of alumina using plasma spraying  

NASA Astrophysics Data System (ADS)

Plasma spraying is one of the most versatile techniques used to form coatings for protection against oxidation, corrosion, and wear. The plasma spraying is ideally suited for refractory materials, but there are a number of variables that need to be controlled to obtain dense coatings. In spite of considerable progress made in the theoretical understanding of this complex process, there is a need for a simple method to evaluate the interaction between the plasma flame and powder particles that form the coatings. As reported in the literature, this involves metallographic observation of the powders collected from the plasma. In the present study, the structure and morphology of plasma-sprayed splats are experimentally investigated using different power levels and spray distances for alumina powder. The results show that the splashing occurs during splatting of a completely molten droplet. It is found that at higher power levels and shorter spray distances, spreading of molten droplets improves considerably.

Selvarajan, V.; Saravanan, P.; Srivastava, M. P.

2001-03-01

221

Numerical simulation of alumina spraying in argon-helium plasma jet  

SciTech Connect

A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

Chang, C.H.

1992-08-01

222

Numerical simulation of alumina spraying in argon-helium plasma jet  

SciTech Connect

A new numerical model is described for simulating thermal plasmas containing entrained particles, with emphasis on plasma spraying applications. The plasma is represented as a continuum multicomponent chemically reacting ideal gas, while the particles are tracked as discrete Lagrangian entities coupled to the plasma. Computational results are presented from a transient simulation of alumina spraying in a turbulent argon-helium plasma jet in air environment, including torch geometry, substrate, and multiple species with chemical reactions. Particle-plasma interactions including turbulent dispersion have been modeled in a fully self-consistent manner. Interactions between the plasma and the torch and substrate walls are modeled using wall functions. (15 refs.)

Chang, C.H.

1992-01-01

223

A study on phase stability observed in as sprayed Alumina13 wt.% Titania coatings grown by detonation gun and plasma spraying on low alloy steel substrates  

Microsoft Academic Search

AT-13 wt.% type powders, depending on the process used for spraying has shown variable type of resultant phases in the as sprayed conditions. In a detonation gun process it appears that freezing of the molten plume with the same composition as the liquid was possible, in contrast to this in a typical plasma spraying process preferential evaporation and phase separation of

R. Venkataraman; B. Ravikumar; R. Krishnamurthy; D. K. Das

2006-01-01

224

PLASMA WINDOW FOR VACUUM - ATMOSPHERE INTERFACE AND FOCUSING LENS OF SOURCES FOR NON-VACUUM MATERIAL MODIFICATION.  

SciTech Connect

Material modifications by ion implantation, dry etching, and micro-fabrication are widely used technologies, all of which are performed in vacuum, since ion beams at energies used in these applications are completely attenuated by foils or by long differentially pumped sections, which ate currently used to interface between vacuum and atmosphere. A novel plasma window, which utilizes a short arc for vacuum-atmosphere interface has been developed. This window provides for sufficient vacuum atmosphere separation, as well as for ion beam propagation through it, thus facilitating non-vacuum ion material modification.

HERSHCOVITCH,A.

1997-09-07

225

Thin films by metal-organic precursor plasma spray  

SciTech Connect

While most plasma spray routes to coatings utilize solids as the precursor feedstock, metal-organic precursor plasma spray (MOPPS) is an area that the authors have investigated recently as a novel route to thin film materials. Very thin films are possible via MOPPS and the technology offers the possibility of forming graded structures by metering the liquid feed. The current work employs metal-organic compounds that are liquids at standard temperature-pressure conditions. In addition, these complexes contain chemical functionality that allows straightforward thermolytic transformation to targeted phases of interest. Toward that end, aluminum 3,5-heptanedionate (Al(hd){sub 3}), triethylsilane (HSi(C{sub 2}H{sub 5}){sub 3} or HSiEt{sub 3}), and titanium tetrakisdiethylamide (Ti(N(C{sub 2}H{sub 5}){sub 2}){sub 4} or Ti(NEt{sub 2}){sub 4}) were employed as precursors to aluminum oxide, silicon carbide, and titanium nitride, respectively. In all instances, the liquids contain metal-heteroatom bonds envisioned to provide atomic concentrations of the appropriate reagents at the film growth surface, thus promoting phase formation (e.g., Si-C bond in triethylsilane, Ti-N bond in titanium amide, etc.). Films were deposited using a Sulzer Metco TriplexPro-200 plasma spray system under various experimental conditions using design of experiment principles. Film compositions were analyzed by glazing incidence x-ray diffraction and elemental determination by x-ray spectroscopy. MOPPS films from HSiEt{sub 3} showed the formation of SiC phase but Al(hd){sub 3}-derived films were amorphous. The Ti(NEt{sub 2}){sub 4} precursor gave MOPPS films that appear to consist of nanosized splats of TiOCN with spheres of TiO{sub 2} anatase. While all films in this study suffered from poor adhesion, it is anticipated that the use of heated substrates will aid in the formation of dense, adherent films.

Schulz, Douglas L.; Sailer, Robert A.; Payne, Scott; Leach, James; Molz, Ronald J. [North Dakota State University, Fargo, North Dakota 58108-6050 (United States); Sulzer Metco (United States) Inc., Westbury, New York 11590-2724 (United States)

2009-07-15

226

Laser-induced plasma generation and evolution in a transient spray.  

PubMed

The behaviors of laser-induced plasma and fuel spray were investigated by visualizing images with an ultra-high-speed camera. Time-series images of laser-induced plasma in a transient spray were visualized using a high-speed color camera. The effects of a shockwave generated from the laser-induced plasma on the evaporated spray behavior were investigated. The interaction between a single droplet and the laser-induced plasma was investigated using a single droplet levitated by an ultrasonic levitator. Two main conclusions were drawn from these experiments: (1) the fuel droplets in the spray were dispersed by the shockwave generated from the laser-induced plasma; and (2) the plasma position may have shifted due to breakdown of the droplet surface and the lens effect of droplets. PMID:24921999

Kawahara, Nobuyuki; Tsuboi, Kazuya; Tomita, Eiji

2014-01-13

227

Thermal shock characteristics of plasma sprayed mullite coatings  

NASA Astrophysics Data System (ADS)

Commercially available mullite (3Al2O3·2SiO2) powders containing oxides of calcium and iron as impurities, have been made suitable for plasma spraying by using an organic binder. Stainless steel substrates covered with Ni-22Cr-10Al-1.0Y bond coat were spray coated with mullite. The 425 µm thick coatings were subjected to thermal shock cycling under burner rig conditions between 1000 and 1200 °C and less than 200 °C with holding times of 1, 5, and 30 min. While the coatings withstood as high as 1000 shock cycles without failure between 1000 and 200 °C, spallation occurred early at 120 cycles when shocked from 1200 °C. The coatings appeared to go through a process of self erosion at high temperatures resulting in loss of material. Also observed were changes attributable to melting of the silicate grains, which smooth down the surface. Oxidation of the bond coat did not appear to influence the failure. These observations were supported by detailed scanning electron microscopy and quantitative chemical composition analysis, differential thermal analysis, and surface roughness measurements.

Ramaswamy, P.; Seetharamu, S.; Rao, K. J.; Varma, K. B. R.

1998-12-01

228

Effect of Powder Injection Location on Ceramic Coatings Properties When Using Plasma Spray  

Microsoft Academic Search

The effect of powder injecting location of the plasma spraying on spraying properties was studied. Three different powder-injecting\\u000a methods were applied in the experiment. In the first method, the particles were axially injected into the plasma flow from\\u000a the cathode tip. In the second method, the particles were radially injected into the plasma flow just downstream of the anode\\u000a arc

Liantong An; Yang Gao; Tao Zhang

2007-01-01

229

Thermal Barrier Coatings Made by the Solution Precursor Plasma Spray Process  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process is a relatively new and flexible thermal spray process that can produce\\u000a a wide variety of novel materials, including some with superior properties. The SPPS process involves injecting atomized droplets\\u000a of a precursor solution into the plasma. The properties of resultant deposits depend on the time-temperature history of the\\u000a droplets in the plasma,

Maurice Gell; Eric H. Jordan; Matthew Teicholz; Baki M. Cetegen; Nitin P. Padture; Liangde Xie; Dianying Chen; Xinqing Ma; Jeffrey Roth

2008-01-01

230

Contact damage in plasma-sprayed alumina-based coatings  

SciTech Connect

A study of Hertzian contact damage in plasma-sprayed alumina-based ceramic coatings on steel substrates has been made. Presectioned specimens are used to identify subsurface micromechanical damage processes within the coating and substrate layers as a function of increasing contact load, from both postcontact and in situ observations. Damage occurs principally by cracking in the ceramic coating and plastic deformation in the metal substrate, along with delamination at the coating/substrate interface. Coating thickness, cycling loading (fatigue), and processing history (coating microstructure) are shown to be important factors in the damage patterns and ensuing modes of failure. Indentation stress-strain curves are used to measure macroscopic mechanical responses, to quantify the maximum sustainable contact stresses and to determine the relative roles of coating and substrate in the net deformation.

Pajares, A.; Wei, L; Lawn, B.R. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Materials Science and Engineering Lab.; Berndt, C.C. [State Univ. of New York at Stony Brook, NY (United States). Dept. of Materials Science and Engineering

1996-07-01

231

Fully plasma-sprayed compliant backed ceramic turbine seal  

NASA Technical Reports Server (NTRS)

A seal having a high temperature abradable lining material encircling the tips of turbine blades in turbomachinery is discussed. The minimum operating clearances between the blade tips and the lining of a high pressure turbine are maintained. A low temperature easily decomposable material, such as a polymer, in powder form is blended with a high temperature oxidation resistant metal powder. The two materials are simultaneously deposited on a substrate formed by the turbine casing. Alternately, the polymer powder may be added to the metal powder during plasma spraying. A ceramic layer is then deposited directly onto the metal polymer composite. The polymer additive mixed with the metal is then completely volatilized to provide a porous layer between the ceramic layer and the substrate.

Bill, R. C.; Wisander, D. W. (inventors)

1982-01-01

232

Effect of rolling on the thermo-physical properties of SiCp\\/Al composites fabricated by plasma spraying  

Microsoft Academic Search

Aluminum (Al) matrix composites reinforced by SiC particulates (SiCp\\/Al) were fabricated by the atmospheric plasma spraying. The composite powder, as a feedstock for plasma spraying, was prepared by ball milling of pure Al powders with 55 vol.% SiC particles. The feedstock was deposited into a freestanding bulk composite sheet on a graphite substrate by atmospheric plasma spraying. As-sprayed composites had

Kwangjun Euh; Suk Bong Kang

2005-01-01

233

Plasma diagnostic by emission spectroscopy during vacuum arc remelting  

NASA Astrophysics Data System (ADS)

The plasma produced during vacuum arc remelting of a Zircaloy4 electrode has been investigated by optical emission spectroscopy. Spatial variations of plasma emission along the arc axis has been measured with a specific apparatus consisting of nine aligned optic fibres. The plasma consists of zirconium atoms, of singly and doubly charged zirconium ions and of chromium atoms. The non-observation of emissions of tin and iron particles, which are, with chromium, the three main alloy components of Zircaloy4, suggests that the concentrations of these two species in the plasma are negligibly small. Distribution temperatures of atomic and ionic species of the order of 1 eV and high ionization degree of the plasma (greater than 70%) have been determined. The similar decay of the line intensities of the various species with increasing axial distance from the cathode surface indicates that the plasma composition remains approximately unchanged within the interelectrode region. Synthesis of the spectroscopic results has shown that the emission of vapour into the plasma cannot be accounted for by a mechanism of metal volatilization from the cathodic and anodic liquid surfaces only. It also involves emission mechanisms occurring in the cathode spot region, like the expulsion of metal droplets which volatilize or the ejection of particles.

Chapelle, P.; Czerwiec, T.; Bellot, J. P.; Jardy, A.; Lasalmonie, D.; Senevat, J.; Ablitzer, D.

2002-08-01

234

Thermal contact resistance between plasma-sprayed particles and flat surfaces  

Microsoft Academic Search

Plasma-sprayed molybdenum and yttria-stabilized zirconia particles (38–63?m diameters) were sprayed onto glass and Inconel 625 held at either room temperature or 400°C. Samples of Inconel 625 were also preheated for 3h, and then air-cooled to room temperature before spraying. Photographs of the splats were captured by using a fast charge-coupled device (CCD) camera. A rapid two-color pyrometer was used to

André McDonald; Christian Moreau; Sanjeev Chandra

2007-01-01

235

BONDING OF CERAMICS TO METALS WITH ACTIVATED COATING LAYERS MADE BY PLASMA SPRAYING  

Microsoft Academic Search

Bonding of ceramics to metals was carried out by using thermal sprayed coatings as interlayer materials. This bonding method is referred as the thermal spray bonding. In the present study, Si3N4 and Al2O3 ceramics were bonded to SS41 mild steel using activated Ti-Cu multilayer coatings plasma-sprayed on the steel in a low pressure atmosphere. The bondability was estimated by SEM\\/EDX

A. Ohmori; Z. Zhou; A. Suzumura; Y. Arata

1993-01-01

236

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

Microsoft Academic Search

ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with\\u000a a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS)\\u000a and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were\\u000a tested by furnace isothermal

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

2000-01-01

237

Preparation of perovskite powders and coatings by radio frequency suspension plasma spraying  

NASA Astrophysics Data System (ADS)

Perovskite-type LaMnO3 powders and coatings have been prepared by a novel technique: reactive suspension plasma spraying (SPS) using an inductively coupled plasma of approximately 40 kW plate power and an oxygen plasma sheath gas. Suitable precursor mixtures were found on the basis of solid state reactions, solubility, and the phases obtained during the spray process. Best results were achieved by spraying a suspension of fine MnO2 powder in a saturated ethanol solution of LaCl3 with a 1 to 1 molar ratio of lanthanum and manganese. A low reactor pressure was helpful in diminishing the amount of corrosive chlorine compounds in the reactor. As-sprayed coatings and collected powders showed perovskite contents of 70 to 90%. After a posttreatment with an 80% oxygen plasma, an almost pure LaMnO3 deposit was achieved in the center of the incident plasma jet.

Schiller, G.; Müller, M.; Gitzhofer, F.

1999-09-01

238

Plasma Spray-CVD: A New Thermal Spray Process to Produce Thin Films from Liquid or Gaseous Precursors  

NASA Astrophysics Data System (ADS)

New dedicated coating processes which are based on the well-known LPPS™ technology but operating at lower work pressure (100 Pa) are being actively developed. These hybrid technologies contribute to improve the efficiencies in the turbine industry such as aero-engines and land-based gas turbines. They also have a great potential in the domain of new energy concepts in applications like Solid Oxide Fuel Cells, membranes, and photovoltaic with the adoption of new ways of producing coatings by thermal spray. Such processes include Plasma Spray-Thin Film (PS-TF) which gives the possibility to coat thin and dense layers from splats through a classical thermal spray approach but at high velocities (400-800 m/s) and enthalpy (8000-15000 kJ/kg). Plasma Spray-PVD (PS-PVD) which allows producing thick columnar-structured Thermal Barrier Coatings (100-300 ?m) from the vapor phase with the employment of the high enthalpy gun and specific powder feedstock material. On the other hand, the Plasma Spray-CVD (PS-CVD) process uses modified conventional thermal spray components operated below 100 Pa which allows producing CVD-like coatings (<1-10 ?m) at higher deposition rates using liquid or gaseous precursors as feedstock material. The advantages of such thermal spray-enhanced CVD processes are the high ionization degree and high throughput for the deposition of thin layers. In this article, we present an overview of the possibilities and limitations encountered while producing thin film coatings using liquid and gaseous precursors with this new type of low pressure plasma spray equipment and point out the challenges faced to obtain efficient injection and mixing of the precursors in the plasma jet. In particular, SiO x thin films from Hexamethyldisiloxane (HMDSO or C6H18OSi2) can be deposited on wafers at deposition rates of up to 35 nm/s at an efficiency of about 50%. The process was also used for producing metal oxide coatings (Al2O3, ZnO, and SnO2) by evaporating different metals in combination with an oxygen gas flow. The effect of process parameters on the deposition rate, coating build up, uniformity, and quality of the coatings are discussed. An overview of different potential applications of this new technology will be also presented.

Gindrat, M.; Höhle, H.-M.; von Niessen, K.; Guittienne, Ph.; Grange, D.; Hollenstein, Ch.

2011-06-01

239

Densification of plasma sprayed YSZ electrolytes by spark plasma sintering (SPS)  

Microsoft Academic Search

Solid oxide fuel cells (SOFC) are promising candidates for alternative power generation systems due to their high-energy conversion efficiencies, and low emissions of environmentally hazardous by-products. Plasma spray (PS) is an effective, and relatively inexpensive process for fabricating high performance yttria stabilized zirconia (YSZ) electrolyte for SOFC. Yet, because of the numerous inter-granular defects introduced to the electrolyte by the

K. A Khor; L.-G Yu; S. H Chan; X. J Chen

2003-01-01

240

Preparation of artificial canine femoral stem with HA-Ti ladder-type coating on plasma-sprayed pure Ti substrate and its performance evaluation  

NASA Astrophysics Data System (ADS)

An ideal, biological-type, artificial femoral stem prosthesis has good stability and improved bone-prosthesis bonding capacity. In the current study, pure hydroxyapatite (HA)-coated, cementless, artificial femoral stems were prepared by adopting different plasma spray powers and distances and were tested in terms of shear strength. The pure titanium (Ti) substrates, HA coatings, and composite Ti-HA ladder-type coatings prepared under vacuum and atmospheric conditions were examined to compare the shear strengths, microscopic constitutions, and structures of the coatings. The coating was fabricated and the bond strength was improved by adopting 35 kW of spray power and an 80 mm spray distance. The comparisons show that the shear strength of the Ti coating prepared under vacuum conditions was higher than that of the coating prepared under atmospheric conditions (P < 0.05). Moreover, the pressure-shear strength of the Ti + HAG + Ti + V group coating was statistically significantly different from those of the HA + Ti + V and HA + Ti + A groups (P < 0.05). The coatings were compared using scanning electron microscopy, X-ray diffraction, and infrared spectrum analysis. The composite HA-Ti ladder-type coating group, where pure Ti substrate was sprayed onto the Ti alloy under vacuum conditions, had a successive laminate structure. In addition, the intergranular bond in the HA surface layer on the gradient coating was compact and highly crystallized. Under vacuum conditions, the plasma-sprayed layer was characterized by higher tightness, moderate porosity, higher bonding strength to HA, and higher HA crystallinity. The proposed coating can be used in new, cementless, artificial femoral stems with improved bone-prosthesis bonding capacity and stability.

Zeng, Xianlin; Li, Jingfeng; Yang, Shuhua; Zheng, Qixin; Zou, Zhenwei

2012-03-01

241

Plasma spraying of stainless-steel particles coated with an alumina shell  

Microsoft Academic Search

The effect of an alumina coating, obtained by mechanofusion, on stainless-steel particles used in plasma spraying has been studied by examining sprayed particles in mid-flight and their resulting splats and coatings. The mean size of the injected powders is about 65 ?m and the thickness of the alumina shell 4 ?m. The results show that without preheating the substrate the

Hélène Ageorges; Pierre Fauchais

2000-01-01

242

Process for producing plasma sprayed carbide-based coatings with minimal decarburization and near theoretical density  

SciTech Connect

Plasma spray deposition of carbide/metal hardcoatings is difficult because complex chemical transformations can occur while spraying, especially in the presence of oxygen. A commercial plasma spray torch has been modified to simultaneously inject carbide powder and a metal alloy powder at two different locations in the plasma stream. Composite hardcoatings of tungsten carbide/cobalt with a nickel-base alloy matrix have been produce with this dual-injection spray process and compared to coatings sprayed with a conventional plasma spray process. X-ray diffraction revealed very little change in the carbide phase composition of dual-injection coatings as compared to the original composition of the carbide spray powder. Conversely, the conventionally sprayed coatings showed significant transformation of the WC phase to the less desirable W{sub 2}C phase, and secondary oxy- carbide phases were also clearly evident. Porosity in the dual- injection coatings was consistently less than 2%, as measured by image analysis of polished metallographic samples. Microhardness results for the dual injection coatings also compared very favorably with values for the conventional coatings. Preliminary results from an ongoing abrasive wear study indicate that the dual-injection coatings are more wear resistant than the conventional coatings, but further research is needed. 6 refs., 3 figs., 3 tabs.

Lenling, W.J. (Fisher-Barton, Inc., Watertown, WI (USA)); Smith, M.F.; Henfling, J.A. (Sandia National Labs., Albuquerque, NM (USA))

1990-01-01

243

Plasma resistant aluminum oxide coatings for semiconductor processing apparatus by atmospheric aerosol spray method  

Microsoft Academic Search

To decrease the amount of contaminant particles generated during semiconductor manufacturing processes, coatings that can prevent erosion on the inner surfaces and parts of the chamber are required. In this study, plasma resistant dense Al2O3 film was formed on a silicon substrate through the atmospheric aerosol spray method (AAS). AAS is a novel powder spray method, which can form a

Hoomi Choi; Kwangsu Kim; Heesung Choi; Sangwoo Kang; Juyoung Yun; Yonghyeon Shin; Taesung Kim

2010-01-01

244

Optical emission spectra of a copper plasma produced by a metal vapour vacuum arc plasma source  

NASA Astrophysics Data System (ADS)

Optical emission spectroscopy in the range 200-800 nm was applied for investigation of the copper plasma produced by a metal vapour vacuum arc plasma source. The experiments were conducted for the cases when the plasma was guided by straight and ?-shaped curved solenoids as well as without solenoids, and also for different vacuum conditions. It was found that, besides singly- and doubly-charged ions, a relatively high concentration of excited neutral copper atoms was present in the plasma. The relative fraction of excited atoms was much higher in the region close to the cathode surface than in the plasma column inside the solenoid. The concentration of excited neutral, singly- and doubly-ionized atoms increased proportionally when the arc current was increased to 400 A. Some weak lines were attributed to more highly ionized copper species and impurities in the cathode material.

Yotsombat, B.; Davydov, S.; Poolcharuansin, P.; Vilaithong, T.; Brown, I. G.

2001-06-01

245

Sheared flow amplification by vacuum magnetic islands in stellarator plasmas  

SciTech Connect

There is some experimental evidence that the E x B flows have radial structure that may be linked to rational surfaces. This flow structure may result from a self-organization process involving nonlinear flow amplification through Reynolds stress and fluctuation reduction by sheared flows. In stellarators, a large contribution to the Reynolds stress comes from the coupling of the magnetic field component of a vacuum field island with a plasma instability. In this process, the self-organization principle seems to be marginal stability for the fluctuations driving the flow.

Garcia, L.; Carreras, B. A.; Lynch, V. E.; Pedrosa, M. A.; Hidalgo, C.

2001-09-01

246

Dynamic Model of the Wire Dispersion Process in Plasma-Arc Spraying  

NASA Astrophysics Data System (ADS)

The dynamic mathematical model is suggested, describing the jet flow of a molten wire material and formation of droplets, i.e. spraying particles, under conditions of plasma-arc wire spraying. Numerical analysis of the processes of formation and detachment of droplets was carried out, and the effect of spraying parameters on the above processes was investigated. It was shown that the size and interval of detachment of the droplets strongly depend on the diameter and feed speed of the anode wire being sprayed, as well as on the plasmatron operation mode.

Kharlamov, M. Yu.; Krivtsun, I. V.; Korzhyk, V. N.

2014-02-01

247

Nano Crystalline Ceramic and Ceramic Coatings Made by Conventional and Solution Plasma Spray.  

National Technical Information Service (NTIS)

Nanostructured ceramic coatings produced by plasma spray processes are being developed for a wide variety of applications that require resistance to wear, erosion, cracking and spallation. In addition the process is being developed to make near net shaped...

E. H. Jordan M. Gell

2006-01-01

248

The development of beryllium plasma spray technology for the International Thermonuclear Experimental Reactor (ITER)  

SciTech Connect

Over the past five years, four international parties, which include the European Communities, Japan, the Russian Federation and the United States, have been collaborating on the design and development of the International Thermonuclear Experimental Reactor (ITER), the next generation magnetic fusion energy device. During the ITER Engineering Design Activity (EDA), beryllium plasma spray technology was investigated by Los Alamos National Laboratory as a method for fabricating and repairing and the beryllium first wall surface of the ITER tokamak. Significant progress has been made in developing beryllium plasma spraying technology for this application. Information will be presented on the research performed to improve the thermal properties of plasma sprayed beryllium coatings and a method that was developed for cleaning and preparing the surface of beryllium prior to depositing plasma sprayed beryllium coatings. Results of high heat flux testing of the beryllium coatings using electron beam simulated ITER conditions will also be presented.

Castro, R.G.; Elliott, K.E.; Hollis, K.J. [Los Alamos National Lab., NM (United States). Material Science and Technology Div.; Bartlett, A.H. [Norsam Technologies Inc., Los Alamos, NM (United States); Watson, R.D. [Sandia National Lab., Albuquerque, NM (United States). Fusion Technology Dept.

1999-02-01

249

Ceramic plasma-sprayed coating of melting crucibles for casting metal fuel slugs  

NASA Astrophysics Data System (ADS)

Thermal cycling and melt reaction studies of ceramic coatings plasma-sprayed on Nb substrates were carried out to evaluate the performance of barrier coatings for metallic fuel casting applications. Thermal cycling tests of the ceramic plasma-sprayed coatings to 1450 °C showed that HfN, TiC, ZrC, and Y2O3 coating had good cycling characteristics with few interconnected cracks even after 20 cycles. Interaction studies by 1550 °C melt dipping tests of the plasma-sprayed coatings also indicated that HfN and Y2O3 do not form significant reaction layer between U-20 wt.% Zr melt and the coating layer. Plasma-sprayed Y2O3 coating exhibited the most promising characteristics among HfN, TiC, ZrC, and Y2O3 coating.

Kim, Ki Hwan; Lee, Chong Tak; Lee, Chan Bock; Fielding, R. S.; Kennedy, J. R.

2013-10-01

250

Plasma-Sprayed Poly (Metal Phosphinate) Coatings for High Temperature Applications.  

National Technical Information Service (NTIS)

Pigmented and unpigmented diphenylphosphinates of chromium, zirconium, and zinc have been investigated as material for plasma-sprayed coatings. The aluminum-pigmented zirconyl diphenylphosphinate hydroxide system provided coatings having good adhesion, ha...

J. P. King H. D. Gillman

1977-01-01

251

Study of Plasma- and Detonation Gun-Sprayed Alumina Coatings Using Taguchi Experimental Design  

NASA Astrophysics Data System (ADS)

Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al2O3) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al2O3 coatings deposited using the above techniques by using Taguchi experimental design. Alumina coating experiments were conducted using a Taguchi fractional-factorial (L8) design parametric study to optimize the spray process parameters for both APS and D-gun. The Taguchi design evaluated the effect of four APS and D-gun spray variables on the measured coating attributes. The coating qualities evaluated were surface roughness, porosity, microhardness, abrasion, and sliding wear. The results show that the coating quality is directly related to the corresponding coating microstructure, which is significantly influenced by the spray parameters employed. Though it is evident that the D-gun-sprayed coatings consistently exhibit dense and uniform microstructure, higher hardness, and superior tribological performance, the attainment of suitable plasma-sprayed coatings can be improved by employing the Taguchi analysis.

Saravanan, P.; Selvarajan, V.; Srivastava, M. P.; Rao, D. S.; Joshi, S. V.; Sundararajan, G.

2000-12-01

252

The effect of processing parameters on plasma sprayed beryllium for fusion applications  

Microsoft Academic Search

Plasma spraying is being investigated as a potential coating technique for applying thin (0.1--5mm) layers of beryllium on plasma facing surfaces of blanket modules in ITER and also as an in-situ repair technique for repairing eroded beryllium surfaces in high heat flux divertor regions. High density spray deposits (>98% of theoretical density) of beryllium will be required in order to

R. G. Castro; P. W. Stanek; L. A. Jacobson; D. F. Cowgill; L. L. Snead

1993-01-01

253

Laser and plasma hybrid spray coatings on carbon fiber reinforced composite materials  

Microsoft Academic Search

A hybrid laser\\/plasma spraying system has been developed to apply coatings to C\\/C composites that will exhibit superior oxidation resistance in high temperature oxidizing conditions via multilayer coatings. The hybrid system couples a high power CO2 laser with a low pressure plasma-spraying apparatus, and has been used to produce thick, multilayer WC\\/MoSi2\\/ZrO2 coatings on monolithic carbon components; the coatings have

H. Shimura; S. Sasaki; K. Hasegawa; K. Hirano

1991-01-01

254

Electrocatalytically Active Nickel-Based Electrode Coatings Formed by Atmospheric and Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Ni-based electrode coatings with enhanced surface areas, for hydrogen production, were developed using atmospheric plasma spray (APS) and suspension plasma spray (SPS) processes. The results revealed a larger electrochemical active surface area for the coatings produced by SPS compared to those produced by APS process. SEM micrographs showed that the surface microstructure of the sample with the largest surface area was composed of a large number of small cauliflower-like aggregates with an average diameter of 10 ?m.

Aghasibeig, M.; Mousavi, M.; Ben Ettouill, F.; Moreau, C.; Wuthrich, R.; Dolatabadi, A.

2014-01-01

255

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

256

Feasibility of Plasma Spraying in Developing MMC Coatings: Modeling the Heating of Coated Powder Particles  

Microsoft Academic Search

Coated powder particles composed of a ceramic core and a metallic coating are being considered for plasma spray applications. The goal of using these powders is to produce particulate-reinforced metal-matrix composite coatings. In this work, the feasibility of plasma spray processing in producing these composite coatings is evaluated. A numerical model is presented to analyze the in-flight thermal behavior and

Marios D. Demetriou; Adrienne S. Lavine; Nasr M. Ghoniem

2002-01-01

257

Evaluation of plasma-sprayed CoSâ cathodes for thermal batteries  

Microsoft Academic Search

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 CoSâ cathode films onto a stainless steel substrate was examined as an alternative to pressed-powder cathodes. The plasma-sprayed electrodes were

Guidotti

1999-01-01

258

Electrochemical Evaluation of Thin-Film Li-Si Anodes Prepared by Plasma Spraying  

Microsoft Academic Search

Thin-film electrodes of a plasma-sprayed Li-Si alloy were evaluated for use as anodes in high-temperature thermally activated (thermal) batteries. These anodes were prepared using 44% Li\\/56% Si (w\\/w) material as feed material in a special plasma-spray apparatus under helium or hydrogen, to protect this air- and moisture-sensitive material during deposition. Anodes were tested in single cells using conventional pressed-powder separators

RONALD A. GUIDOTTI; FREDERICK W. REINHARDT; GREGORY L. SCHARRER

1999-01-01

259

Wear resistance of laser cladding and plasma spray welding layer on stainless steel surface  

Microsoft Academic Search

The effect of coatings, which are formed with laser cladding and plasma spray welding on 1Cr18Ni9Ti base metal, on wear resistance is studied, A 5-kW transverse flowing CO2 laser is used for cladding Co base alloy powder pre-placed on the substrate. Comparing with the plasma spray coatings, the spoiled rate of products with laser clad layers was lower and the

Xinlin Wang; Shihong Shi; Qiguang Zheng

2004-01-01

260

Suspension and solution plasma spraying of finely structured layers: potential application to SOFCs  

NASA Astrophysics Data System (ADS)

Suspension direct current plasma spraying allows achieving finely structured coatings whose thickness is between few tens and few hundreds of micrometres. Drops (200-300 µm in diameter) or liquid jets are mechanically injected in the plasma jet. With radial injection they are rapidly (a few µs) fragmented into droplets (a few µm in diameter). The latter are vaporized (in a few µs) and the solid particles contained in suspension droplets are accelerated and melted by the plasma jet. As in conventional plasma spraying (CPS), much smaller splats (with diameters between 0.2 and 3 µm and thicknesses between 30 and 200 nm) are arranged in layers up to form the coating. The low inertia of particles requires spray distances between 40 and 60 mm which induces plasma heat fluxes up to 22 MW m-2 participating in coating densification. Even more than in CPS, the plasma jet fluctuations, particularly for plasmas containing di-atomic gases, perturb drops penetration and fragmentation. It has been chosen to illustrate difficulties and possibilities of this new method, through the spraying of the three layers of an element of solid oxide fuel cells. Indeed, it requires a dense stabilized zirconia electrolyte, if possible thin (15-20 µm) with two porous electrodes: cathode made of perovskite prone to decomposing upon spraying and anode made of two materials (nickel and zirconia) with very different melting points. These components were obtained by spraying ethanol suspensions, with, first, LaMnO3 perovskite particles doped with 10 mol% of MnO2 and 3 µm in mean diameter sprayed with pure argon to limit their decomposition and achieve porous coatings, second, Yttria (13 wt%) stabilized zirconia (YSZ) with two different particle size distributions and morphologies for which plasma compositions were adapted, producing in both cases 15 µm thick and fully dense coatings, third, porous Raneigh nickel by co-spraying the YSZ suspension and solution of nickel nitrate.

Fauchais, P.; Etchart-Salas, R.; Delbos, C.; Tognonvi, M.; Rat, V.; Coudert, J. F.; Chartier, T.

2007-04-01

261

Synthesis and characterization of aluminum oxide–boron carbide coatings by air plasma spraying  

Microsoft Academic Search

Aluminum oxide (Al2O3)–boron carbide (B4C) composites have been proposed for use as cutting tools as well as in high temperature applications due to their high hardness and fracture toughness. The air plasma spraying method was used to fabricate the composite coatings of Al2O3 and B4C. Three different Al2O3:B4C composition ratios of 90:10, 80:20, and 70:30 by weight were plasma sprayed

Amit Datye; Srinivasarao Koneti; George Gomes; Kuang-Hsi Wu; Hua-Tay Lin

2010-01-01

262

Isothermal oxidation of air plasma spray NiCrAlY bond coatings  

Microsoft Academic Search

The isothermal oxidation behaviors of plasma-sprayed NiCrAlY bond coatings (Ni22Cr10Al1Y and Ni31Cr11Al 0.6Y) have been evaluated. Two unique microstructures, oxide stringers and improperly flattened zones, can be observed in the air plasma spray (APS) bond coatings. The structures and chemical compositions of the oxide stringers were examined by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Improperly flattened zones

Hanshin Choi; Byounghyun Yoon; Hyungjun Kim; Changhee Lee

2002-01-01

263

Laser-induced surface acoustic waves for evaluation of elastic stiffness of plasma sprayed materials  

Microsoft Academic Search

The elastic properties of plasma sprayed deposits have been evaluated using a laser-excited surface acoustic wave (SAW) technique and an inversion processing analysis. The SAWs including Lamb and Rayleigh waves were generated in plasma sprayed NiCoCrAlY and ZrO2, respectively, and their group velocity dispersions were used to determine the elastic properties (i.e.Young's modulus, Poison's ratio and density) of the deposits.

X. Q. Ma; Y. Mizutani; M. Takemoto

2001-01-01

264

Origin of darkening in 8 wt% yttria-zirconia plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

This paper reports on the origins of darkening of 8 wt% YâOâ-ZrOâ air plasma-sprayed (APS) and low-pressure plasma-sprayed (LPPS) thermal barrier coatings (TBC) studied using x-ray photoelectron spectroscopy. The change of valence states of zirconium, due to the reduction of ZrOâ to ZrâOâ, was responsible for darkening of TBC. Quantification of Zr{sup 3+} oxide was related both to the black

Gabriel Maria Ingo

1991-01-01

265

Towards durable thermal barrier coatings with novel microstructures deposited by solution-precursor plasma spray  

Microsoft Academic Search

The feasibility of a new processing method—solution precursor plasma spray (SPPS)—for the deposition of ZrO2-based thermal barrier coatings (TBCs) with novel structures has been demonstrated. These desirable structures in the new TBCs appear to be responsible for their improved thermal cycling life relative to conventional plasma-sprayed TBCs. Preliminary results from experiments aimed at understanding the SPPS deposition mechanisms suggest that

N. P. Padture; K. W. Schlichting; T. Bhatia; A. Ozturk; B. Cetegen; E. H. Jordan; M. Gell; S. Jiang; T. D. Xiao; P. R. Strutt; E Garc??a; P Miranzo; M. I Osendi

2001-01-01

266

Influence of heat treatment on nanocrystalline zirconia powder and plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Nanostructured zirconia top coat was deposited by air plasma spray and NiCoCrAlTaY bond coat was deposited on Ni substrate by low pressure plasma spray. Nanostructured and conventional thermal barrier coatings were heat-treated at temperature varying from 1050 to 1 250 °C for 2-20 h. The results show that obvious grain growth was found in both nanostructured and conventional thermal barrier

Xian-liang JIANG; Chun-bo LIU; Min LIU; Hui-zhao ZHU

2010-01-01

267

Structure–property differences between supersonic and conventional atmospheric plasma sprayed zirconia thermal barrier coatings  

Microsoft Academic Search

Yttria-stabilized zirconia (YSZ) based thermal barrier coatings (TBCs) were deposited by high efficiency supersonic atmospheric plasma spraying (SAPS) system. The microstructure and thermal shock resistance of the SAPS-TBCs were investigated. As compared to conventional atmospheric plasma sprayed TBCs (APS-TBCs) with the same composition, the microstructure of SAPS-TBCs was much finer. It was found that the thickness of lamellar structure consisted

Y. Bai; Z. H. Han; H. Q. Li; C. Xu; Y. L. Xu; C. H. Ding; J. F. Yang

2011-01-01

268

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

Microsoft Academic Search

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,

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

1984-01-01

269

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

270

Measurement of total ion current from vacuum arc plasma sources  

SciTech Connect

The total ion current generated by a vacuum arc plasma source was measured. The discharge system investigated allowed ion collection from the arc plasma streaming through a hemispherical mesh anode with geometric transparency of 72%. A range of different cathode materials was investigated, and the arc current was varied over the range of 50-500 A. We find that the normalized ion current (I{sub ion}/I{sub arc}) depends on the cathode material, with values in the range from 5% to 19% and generally greater for elements of low cohesive energy. The application of a strong axial magnetic field in the cathode and arc region leads to increased normalized ion current, but only by virtue of enhanced ion charge states formed in a strong magnetic field.

Oks, E.M.; Savkin, K.P.; Yushkov, G.Yu.; Nikolaev, A.G.; Anders, A.; Brown, I.G. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2006-03-15

271

Plasma plume characterization of a vacuum arc thruster  

NASA Astrophysics Data System (ADS)

A Vacuum Arc Thruster (VAT) is a thruster that uses the plasma created in a vacuum arc, an electrical discharge in a vacuum that creates high velocity and highly ionized plasmas, as the propellant without additional acceleration. A VAT would be a small and inexpensive low thrust ion thruster, ideal for small satellites and formation flying spacecraft. The purpose of this thesis was to quantitatively and qualitatively examine the VAT plasma plume to determine operating characteristics and limitations. A VAT with a titanium cathode was operated in two regimes: (A) single ˜100mus pulse, discharge current JD=510A, and (B) multiple ˜1500mus pulses at f=40.8Hz, JD=14A. The cathode was 3.18mm diameter Ti rod, surrounded by a 0.80mm thick alumina insulator, set in a molybdenum anode. Three Configurations were tested: Cfg1 (Regime A, cathode recessed 3.00mm from anode), Cfg2 (Regime A, cathode and anode flush), Cfg3 (Regime B, cathode recessed 3.00mm). A semi-empirical model was derived for VAT performance based on the MHD equation of motion using data for ion velocity, ion charge state distribution, ion current fraction (F), and ion current density distribution (ICDD). Additional performance parameters were a2, the peak ion current density angular offset from the cathode normal, and a3, the width of the ion current distribution. Measurements were taken at 162 points on a plane in the plasma plume using a custom faraday probe, and the ICDD empirical form was determined to be a Gaussian. The discharge voltage (VD) and F were Cfg1: VD=25.5V, F=0.025-0.035; Cfg2: VD=40.7V, F=0.08-0.10; Cfg3: VD=14.9V, F=0.006-0.021. For Cfg1, a2 started 15° off-axis while a2˜0 for Cfg2 and 3. In Cfg1, a 3=0.7-0.6, and in Cfg2 a3=1.0-1.1, so the recessed cathode focused the plasma more. However, F is more important for VAT performance because upper and lower bounds for thrust, specific impulse, thrust-to-power, and efficiency were calculated and Cfg2 had the highest performance. High-speed videos captured cathode spot motion showing that the cathode spot had preferred attachment points at the cathode edge. Photographs show uneven cathode erosion at the edge, a deposited layer of cathode material on the anode and insulator, and large macroparticles.

Sekerak, Michael James

272

Evaluation of elastic properties of plasma-sprayed materials by laser-SAW technique  

NASA Astrophysics Data System (ADS)

The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiCrAlY and atmospheric plasma-sprayed ZrO2-8%Y2O3 materials at ambient and elevated temperatures up to 900 °C by using a laser surface acoustic wave (SAW) technique. Lamb (Rayleigh) waves were excited in free-standing films (sprayed coatings) by a pulsed-YAG-laser irradiation. The dispersive group velocities of A0-mode Lamb waves were utilized in evaluating the elastic properties of the films. The results indicated that the Young's moduli (E) and densities (?) of the sprayed materials, especially sprayed ZrO2, were lower than those of dense materials and decreased with increasing temperature. Deviation in the Rayleigh wave dispersion curves suggests a means of determining the integrity of interfaces.

Ma, X. Q.; Mizutani, Y.; Takemoto, M.; Ono, K.

1999-12-01

273

Thin and Dense Ceramic Coatings by Plasma Spraying at Very Low Pressure  

NASA Astrophysics Data System (ADS)

The very low pressure plasma spray (VLPPS) process operates at a pressure range of approximately 100 Pa. At this pressure, the plasma jet interaction with the surrounding atmosphere is very weak. Thus, the plasma velocity is almost constant over a large distance from the nozzle exit. Furthermore, at these low pressures the collision frequency is distinctly reduced and the mean free path is strongly increased. As a consequence, at low pressure the specific enthalpy of the plasma is substantially higher, but at lower density. These particular plasma characteristics offer enhanced possibilities to spray thin and dense ceramics compared to conventional processes which operate in the pressure range between 5 and 20 kPa. This paper presents some examples of gas-tight and electrically insulating coatings with low thicknesses <50 ?m for solid oxide fuel cell applications. Furthermore, plasma spraying of oxygen conducting membrane materials such as perovskites is discussed.

Mauer, Georg; Vaßen, Robert; Stöver, Detlev

2010-01-01

274

Investigations of some aspects of the spray process in a single wire arc plasma spray system using high speed camera  

NASA Astrophysics Data System (ADS)

A high speed camera has been used to record and analyze the evolution as well as particle behavior in a single wire arc plasma spray torch. Commercially available systems (spray watch, DPV 2000, etc.) focus onto a small area in the spray jet. They are not designed for tracking a single particle from the torch to the substrate. Using high speed camera, individual particles were tracked and their velocities were measured at various distances from the spray torch. Particle velocity information at different distances from the nozzle of the torch is very important to decide correct substrate position for the good quality of coating. The analysis of the images has revealed the details of the process of arc attachment to wire, melting of the wire, and detachment of the molten mass from the tip. Images of the wire and the arc have been recorded for different wire feed rates, gas flow rates, and torch powers, to determine compatible wire feed rates. High speed imaging of particle trajectories has been used for particle velocity determination using time of flight method. It was observed that the ripple in the power supply of the torch leads to large variation of instantaneous power fed to the torch. This affects the velocity of the spray particles generated at different times within one cycle of the ripple. It is shown that the velocity of a spray particle depends on the instantaneous torch power at the time of its generation. This correlation was established by experimental evidence in this paper. Once the particles leave the plasma jet, their forward speeds were found to be more or less invariant beyond 40 mm up to 500 mm from the nozzle exit.

Tiwari, N.; Sahasrabudhe, S. N.; Tak, A. K.; Barve, D. N.; Das, A. K.

2012-02-01

275

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

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

2011-03-01

276

Fabrication of copper-based anodes via atmosphoric plasma spraying techniques  

DOEpatents

A fuel electrode anode (18) for a solid oxide fuel cell is made by presenting a solid oxide fuel cell having an electrolyte surface (15), mixing copper powder with solid oxide electrolyte in a mixing step (24, 44) to provide a spray feedstock (30,50) which is fed into a plasma jet (32, 52) of a plasma torch to melt the spray feed stock and propel it onto an electrolyte surface (34, 54) where the spray feed stock flattens into lamellae layer upon solidification, where the layer (38, 59) is an anode coating with greater than 35 vol. % based on solids volume.

Lu, Chun (Monroeville, PA)

2012-04-24

277

Evaluation of elastic properties of plasma-sprayed materials by laser-SAW technique  

Microsoft Academic Search

The present work has evaluated the elastic properties of low-pressure plasma-sprayed NiCrAlY and atmospheric plasma-sprayed ZrO2-8%Y2O3 materials at ambient and elevated temperatures up to 900 °C by using a laser surface acoustic wave (SAW) technique. Lamb (Rayleigh) waves were excited in free-standing films (sprayed coatings) by a pulsed-YAG-laser irradiation. The dispersive group velocities of A0-mode Lamb waves were utilized in

X. Q. Ma; Y. Mizutani; M. Takemoto; K. Ono

1999-01-01

278

Formation of high heat resistant coatings by using gas tunnel type plasma spraying.  

PubMed

Zirconia sprayed coatings are widely used as thermal barrier coatings (TBC) for high temperature protection of metallic structures. However, their use in diesel engine combustion chamber components has the long run durability problems, such as the spallation at the interface between the coating and substrate due to the interface oxidation. Although zirconia coatings have been used in many applications, the interface spallation problem is still waiting to be solved under the critical conditions such as high temperature and high corrosion environment. The gas tunnel type plasma spraying developed by the author can make high quality ceramic coatings such as Al2O3 and ZrO2 coating compared to other plasma spraying method. A high hardness ceramic coating such as Al2O3 coating by the gas tunnel type plasma spraying, were investigated in the previous study. The Vickers hardness of the zirconia (ZrO2) coating increased with decreasing spraying distance, and a higher Vickers hardness of about Hv = 1200 could be obtained at a shorter spraying distance of L = 30 mm. ZrO2 coating formed has a high hardness layer at the surface side, which shows the graded functionality of hardness. In this study, ZrO2 composite coatings (TBCs) with Al2O3 were deposited on SS304 substrates by gas tunnel type plasma spraying. The performance such as the mechanical properties, thermal behavior and high temperature oxidation resistance of the functionally graded TBCs was investigated and discussed. The resultant coating samples with different spraying powders and thickness are compared in their corrosion resistance with coating thickness as variables. Corrosion potential was measured and analyzed corresponding to the microstructure of the coatings. Keywords: High Heat Resistant Coatings, Gas Tunnel Type Plasma Spraying, Hardness, PMID:22905586

Kobayashi, A; Ando, Y; Kurokawa, K

2012-06-01

279

Effect of Microstructure on the Electrical Properties of Nano-Structured TiN Coatings Deposited by Vacuum Cold Spray  

Microsoft Academic Search

TiN coatings on Al2O3 substrates were fabricated by vacuum cold spray (VCS) process using ultrafine starting ceramic powders of 20 nm in size at\\u000a room temperature (RT). Microstructure analysis of the samples was carried out by scanning electron microscopy, transmission\\u000a electron microscopy, and x-ray diffraction. Sheet resistance of the VCS TiN coatings was measured with a four-point probe.\\u000a The effects of

Y.-Y. Wang; Y. Liu; G.-J. Yang; J.-J. Feng; K. Kusumoto

2010-01-01

280

Plasma sprayed alumina coatings for radiation detector development  

NASA Astrophysics Data System (ADS)

Conventional design of radiation detectors uses sintered ceramic insulating modules. The major drawback of these ceramic components is their inherent brittleness. Ion chambers, in which these ceramic spacers are replaced by metallic components with plasma spray coated alumina, have been developed in our Research Centre. These components act as thin spacers that have good mechanical strength as well as high electrical insulation and replace alumina insulators with the same dimensions. As a result, the design of the beam loss monitor ion chamber for CAT could be simplified by coating the outer surface of the HT electrode with alumina. One of the chambers developed for isotope calibrator for brachytherapy gamma sources has its outer aluminium electrode (60 mm dia x 220 mm long) coated with 250 m thick alumina (97%) +titania (3%). In view of potential applications in neutron-sensitive ion chambers used in reactor control instrumentation, studies were carried out on alumina 100m to 500m thick coatings on copper, aluminium and SS components. The electrical insulation varied from 1012 ohms to 108 ohms for coating thicknesses above 200m. The porosity in the coating resulted in some fall in electrical insulation due to moisture absorption. An improvement could be achieved by providing the ceramic surface with moisture-repellent silicone oil coating. Irradiation at Apsara reactor core location showed that the coating on aluminium was found to be unaffected after exposure to 1017 nvt fluence.

Alex, Mary; Balagi, V.; Prasad, K. R.; Sreekumar, K. P.; Ananthapadmanabhan, P. V.

2000-11-01

281

Evaluation of the mechanical properties of plasma sprayed hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

The mechanical behaviour of plasma sprayed hydroxyapatite coatings was evaluated using Vickers hardness measurements on the cross-section as well as on the top surface of coatings. The effects of applied load, measurement direction and indent location on the microhardness were investigated. Indentation was performed on dense and porous areas of the coatings. After Vickers indentation on the polished cross-section, the surface roughness on the indenter horizontal impression was measured to establish any influence on local surface tropology. The data was statistically analysed using the Weibull distribution to examine their variability and distribution within the coatings. It was found that the effect of lower applied loads (50 and 100 gf) and higher applied loads (300 and 500 gf) showed two distinct trends concerning the microhardness, indent roughness, and Weibull modulus of microhardness throughout the coating thicknesses in the dense area. Top surface microhardness was higher compared to the cross-section microhardness for 100, 300 and 500 gf whereas equal for 50 gf. The statistical analyses showed that the Weibull modulus of microhardness was related to the applied load and indent position. The Weibull moduli of microhardness were high on the dense areas of the coatings.

Hasan, Md Fahad; Wang, James; Berndt, Christopher

2014-06-01

282

In vivo evaluation of plasma-sprayed wollastonite coating.  

PubMed

Wollastonite coatings were prepared by plasma spraying. The bioactivity of wollastonite coatings was investigated in vivo by implanting in dog's muscle, cortical bone and marrow, respectively. The behaviour of bone tissue around wollastonite coatings were examined by histological and SEM observation. After 1 month in the muscle, a bone-like apatite layer was found to form on the surface of the wollastonite coating. When implanted in cortical bone, histological observation demonstrated that bone tissue could extend and grow along the surface of the wollastonite coating. The coating bonded directly to the bone without any fibrous tissue, indicating good biocompatibility and bone conductivity. SEM and EDS analysis revealed that bone did not bond to wollastonite coating directly, but through a Ca/P layer. This suggested that the formation of bone-like apatite layer was very important for bonding to the bone tissue. The amount of bone-implant contact was also measured. Wollastonite coating was shown to stimulate more bone formation on its surface than titanium coating after implantation for 1 month, enhancing the short-term osseointegration properties of implant. The test in marrow indicated that wollastonite coatings could induce new bone formation on their surface showing good bone inductivity property. PMID:15621234

Xue, Weichang; Liu, Xuanyong; Zheng, Xuebin; Ding, Chuanxian

2005-06-01

283

LTE and non-LTE gas temperatures in loaded and unloaded plasmas during spraying of NiAl powders.  

National Technical Information Service (NTIS)

The purpose of this research is to contribute to the science of the complex particle plasma interaction in the plasma spray process. The relationship between the chaotic torch, the nonequilibrium plasma, the accelerating vaporizing particle, and the parti...

T. L. Eddy B. A. Detering G. C. Wilson

1990-01-01

284

Design of a new nozzle for direct current plasma guns with improved spraying parameters  

NASA Astrophysics Data System (ADS)

A new design is proposed for direct current plasma spray gas-shroud attachments. It has curvilinearly shaped internal walls aimed toward elimination of the cold air entrainment, recorded for commercially available conical designs of the shrouded nozzle. The curvilinear nozzle design was tested; it proved to be capable of withstanding high plasma temperatures and enabled satisfactory particle injection. Parallel measurements with an enthalpy probe were performed on the jet emerging from two different nozzles. Also, corresponding calculations were made to predict the plasma flow parameters and the particle parameters. Adequate spray tests were performed by spraying iron-aluminum and MCrAlY coatings onto stainless steel substrates. Coating analyses were performed, and coating qualities, such as microstructure, open porosity, and adhesion strength, were determined. The results indicate that the coatings sprayed with a curvilinear nozzle exhibited lower porosity, higher adhesion strength, and an enhanced microstructure.

Jankovic, M.; Mostaghimi, J.; Pershin, V.

2000-03-01

285

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

286

Reactive Plasma Nitriding of AL2O3 Powder in Thermal Spray  

NASA Astrophysics Data System (ADS)

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, ?-Al2O3, Al5O6N and ?-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.

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

287

Post-spray hot isostatic pressing of plasma sprayed Ti?6Al?4V\\/hydroxyapatite composite coatings  

Microsoft Academic Search

A series of Ti?6Al?4V\\/hydroxyapatite (HA) composite coating was produced by plasma spraying. Several compositions (20, 33 and 80 wt.% HA) were prepared. Subsequent examination of the coatings showed them to have a high level of porosity. However, some amount of porosity, within a specified size range, may be desirable in biomedical applications to enhance bony tissue ingrowth, although inter-lamella pores

K. A. Khor; C. S. Yip; P. Cheang

1997-01-01

288

Effect of powder loading on the excitation temperature of a plasma jet in DC thermal plasma spray torch  

Microsoft Academic Search

A DC non-transferred mode plasma spray torch was fabricated for plasma spheroidization. The effect of powder-carrier gas and powder loading on the temperature of the plasma jet generated by the torch has been studied. The experiment was done at different input power levels; the temperature of the jet was within 5000–7000K argon was used as plasma gas and powder-carrier gas.

G. Shanmugavelayutham; V. Selvarajan; P. V. A. Padmanabhan; K. P. Sreekumar; N. K. Joshi

2007-01-01

289

An evaluation of the electric arc spray and (HPPS) processes for the manufacturing of high power plasma spraying MCrAIY coatings  

Microsoft Academic Search

The high power plasma torch (PlazJet) can be used to spray refractory ceramics with high spray rates and deposition efficiency.\\u000a It can provide dense and hard coating with high bond strengths. When manufacturing thermal barrier coatings, the PlazJet gun\\u000a is well adapted to spraying the ceramic top coat but not the MCrAIY materials that are used as bond coat. Arc

D. Sacriste; N. Goubot; J. Dhers; M. Ducos; A. Vardelle

2001-01-01

290

Induction Plasma Synthesis of Nano-Structured SOFCs Electrolyte Using Solution and Suspension Plasma Spraying: A Comparative Study  

NASA Astrophysics Data System (ADS)

In this paper, two plasma spraying technologies: solution plasma spraying (SolPS) and suspension plasma spraying (SPS) were used to produce nano-structured solid oxide fuel cells (SOFCs) electrolytes. Both plasma spraying processes were optimized in order to achieve the thin gas-tight electrolytes. The comparison of the two plasma spraying processes is based on electrolyte phase, microstructure, morphology, as well as on plasma deposition rate. The results show that nano-structured thin electrolytes (~5 ?m thick) have been successfully SPS deposited on porous anodes with a high deposition rate. Compared to the electrolytes produced by SolPS, the SPS-deposited electrolyte layer is much denser. During the SPS process, fine droplets of 0.5-1 ?m in diameter impact on the surface of the coating and penetrate into the pores of the anode. As the stresses are reduced on the resulting 0.5-2 ?m splats, there is no apparent microcracks network on the splats, this resulting in highly gas-tight coatings. It is demonstrated that the SPS process is beneficial for the improvement of the performance of the films to be used as SOFC electrolytes.

Jia, Lu; Gitzhofer, François

2010-03-01

291

Experiments of new plasma concepts for enhanced microwave vacuum electronics  

SciTech Connect

Recently new schemes have been proposed for plasma based microwave sources that could lead to output power increases by orders of magnitude, as well as offer new possibilities such as broad band tuning and frequency chirping, ultra-short pulse generation, pulse design, etc. In the first scheme, the static field of an alternatively biased capacitor is directly converted into short pulses of turnable electromagnetic (em) radiation upon transmission through a relativistic; under dense ionization front. The structure presently under investigation consists of pin pairs (capacitors) inserted into an X-band waveguide through its narrow sidewall and separated by 1.134 cm. The generated frequency is in the X-band frequency range (8.4--12.4 GHz) when operated with plasma densities between 10{sup 11} and 10{sup 12} cm{sup {minus}3}. The output power is in the 100 W range with an applied voltage of 6 kV and is limited by high voltage (HV) breakdown inside the structure. Much higher output power levels are expected with the new, shorter pulse, HV pulser, since the output power is proportional to the square of the applied voltage. At larger plasma densities, generation of a higher order mode traveling in the backward direction is also observed. In the second scheme, a fraction of the large amplitude electrostatic (es) wave generated in a plasma beat wave acceleration (PBWA) experiment (up to 3 GeV/m) is converted into em radiation by applying a static magnetic field perpendicularly to the driving laser beam. The two-frequency CO{sub 2} laser beam resonantly drives the es wave, and couples to the L branch of the XO mode of the magnetized plasma through Cherenkov radiation. The radiation is emitted predominantly in the forward direction (direction of the laser beam), and is at the plasma frequency (n{sub c} {approximately}10{sup 16} cm{sup {minus}3}, f{approximately}1 THz). With an applied magnetic field of 6 kG the output power is calculated to be in the megawatt range (for a sharp plasma/vacuum boundary). The parameters of the emitted radiation will also be used as a diagnostic for the plasma wave of a PBWA experiment, measuring its amplitude, phase, lifetime, etc. Design and experimental results are presented.

Muggli, P.; Hoffman, J.R.; Yampolsky, J.; Cordell, J.F.; Gundersen, M.A.; Joshi, C.; Katsouleas, T.

1999-07-01

292

T55-L-712 turbine engine compressor housing refurbishment-plasma spray project  

NASA Technical Reports Server (NTRS)

A study was conducted to assess the feasibility of reclaiming T55-L-712 turbine engine compressor housings with an 88 wt percent aluminum to 12 wt percent silicon alloy applied by a plasma spray process. Tensile strength testing was conducted on as-sprayed and thermally cycled test specimens which were plasma sprayed with 0.020 to 0.100 in. coating thicknesses. Satisfactory tensile strength values were observed in the as-sprayed tensile specimens. There was essentially no decrease in tensile strength after thermally cycling the tensile specimens. Furthermore, compressor housings were plasma sprayed and thermally cycled in a 150-hr engine test and a 200-hr actual flight test during which the turbine engine was operated at a variety of loads, speeds and torques. The plasma sprayed coating system showed no evidence of degradation or delamination from the compressor housings. As a result of these tests, a procedure was designed and developed for the application of an aluminum-silicon alloy in order to reclaim T55-L-712 turbine engine compressor housings.

Leissler, George W.; Yuhas, John S.

1988-01-01

293

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal low power plasma (1.3-8 kW) and vortex which produces the main plasma with high power level (10-40 kW). Controlling the spraying parameters is the key role for spraying high crystalline HA coatings on the metallic implants. In this study, the arc gun current was changed while the vortex arc current was kept constant at 450 A during the spraying process of HA coatings. The objective of this study is to investigate the influence of gun current on the microstructure, phase crystallinity and hardness properties of HA coatings. The surface morphology and microstructure of as-sprayed coatings were examined by scanning electron microscope. The phase structure of HA coatings was investigated by X-ray diffraction analysis. HA coatings sprayed at high gun current (100 A) are dense, and have high hardness. The crystallinity of HA coatings was decreased with the increasing in the gun current. On the other hand, the hardness was slightly decreased and the coatings suffer from some porosity at gun currents 0, 30 and 50 A.

Morks, M. F.; Kobayashi, A.

2007-06-01

294

Parametric study of Al and Al 2O 3 ceramic coatings deposited by air plasma spray onto polymer substrate  

Microsoft Academic Search

Aluminum and ceramic (Al2O3) coatings were deposited onto the polymer substrate by air plasma spray (APS) to improve the mechanical properties of the polymer surface. The effect of spray parameters (current and spray distance in this paper) on the phase composition, microstructure and mechanical properties was investigated. Shear adhesion strength between the coatings and the substrates was also examined. The

Sun Guanhong; He Xiaodong; Jiang Jiuxing; Sun Yue

2011-01-01

295

Quenching, thermal and residual stress in plasma sprayed deposits: NiCrAlY and YSZ coatings  

Microsoft Academic Search

Residual stress is an important factor in thermally sprayed deposits which affects both processing and performance. High stress magnitudes and\\/or concentrations can undermine the structural integrity of sprayed parts and impair their functionality. Therefore, it is important to know the stress state, understand its generation and be able to control it. Results of experimental stress determination in plasma sprayed deposits

J. Matejicek; S. Sampath; P. C. Brand; H. J. Prask

1999-01-01

296

On the plasma rotation in a straight magnetized filter of a pulsed vacuum arc  

Microsoft Academic Search

In vacuum arcs of interest for ion deposition, in which a magnetic filter is used, significant plasma rotation about the filter axis can develop. In the present work we present experimental evidence and simplified models to interpret relatively fast rotation of plasma generated in a pulsed vacuum arc with a straight magnetic filter and with a magnetic field strength in

L. Giuliani; D. Grondona; H. Kelly; F. O. Minotti

2007-01-01

297

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings  

Microsoft Academic Search

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal

M. F. Morks; A. Kobayashi

2007-01-01

298

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

NASA Astrophysics Data System (ADS)

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 micron thick deposited by Low Pressure Plasma Spraying (LPPS) and a 300 micron thick ZrO2-7 wt pct Y2O3 top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying using internal air cooling through the cooling holes of the turbine blades. Coated blades were submitted to thermal cycling tests in a burner rig with hot gas temperature of 1485 C. In the case of ATCS coated blades the number of cycles until the first spallation at the leading edge of the blade was between 350 and 2400. The number of cycles of the thermal barrier coatings sprayed with internal cooling was between 1200 and 1800.

Cosack, T.; Pawlowski, L.; Schneiderbanger, S.; Sturlese, S.

1992-06-01

299

Surface modification of air plasma spraying WC-12%Co cermet coating by laser melting technique  

NASA Astrophysics Data System (ADS)

Tungsten carbide cermet powder with 12%Co was deposited on stainless steel substrate by air plasma spraying method. Two types of coatings were produced i.e. thick (430 µm) and thin (260 µm) with varying porosity and splat morphology. The coated samples were treated with CO2 laser under the shroud of inert atmosphere. A series of experimentation was done in this regard, to optimize the laser parameters. The plasma sprayed coated surfaces were then laser treated on the same parameters. After laser melting the treated surfaces were characterized and compared with as-sprayed surfaces. It was observed that the thickness of the sprayed coatings affected the melt depth and the achieved microstructures. It was noted that phases like Co3W3C, Co3W9C4 and W were formed during the laser melting in both samples. The increase in hardness was attributed to the formation of these phases.

Afzal, M.; Ajmal, M.; Nusair Khan, A.; Hussain, A.; Akhter, R.

2014-03-01

300

Microstructures and Dielectric Properties of PZT Coatings Prepared by Supersonic Plasma Spraying  

NASA Astrophysics Data System (ADS)

This paper studied the microstructures and dielectric properties of PZT coatings prepared by supersonic plasma spraying. Samples of the PZT coatings were evaluated by various techniques. The phases and microstructures of the coatings were investigated by XRD, SEM, and TEM, respectively. The results showed that the coatings deposited on steel substrate had a dense microstructure, and there was no phase transformation during spraying. Additionally, the Curie temperature of the PZT coatings was about 370 °C by the investigation of dielectric constant.

Li, Guolu; Gu, Linsong; Wang, Haidou; Xing, Zhiguo; Zhu, Lina

2014-02-01

301

Plasma spray forming: An alternate route for manufacturing free-standing components  

Microsoft Academic Search

The present study uses plasma spray technology as a production process for the fabrication of free- stand-ing, near- net-\\u000a shaped NiAl components. Attention is especially focused on the in situ synthesis of NiAl. A new internal, dual powder injector\\u000a blade has been designed to improve the gun performance as well as the spray efficiency of the feedstock powder. The specific

A. Geibel; L. Froyen; L. Delaey; K. U. Leuven

1996-01-01

302

Characterization of microstructural defects in plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings with a NiCrAlY bond coating and a 1.5 mm thick zirconia top coating were air plasma sprayed onto\\u000a a nickel-base substrate. The top coatings were deposited with the same spraying parameters except for the amount of external\\u000a cooling, which varied from no cooling to the maximum available. This resulted in four sets of samples produced with different

P. Bengtsson; T. Johannesson

1995-01-01

303

Residual stresses in ceramic plasma-sprayed thermal barrier coatings: measurement and calculation  

Microsoft Academic Search

The present work concerns the residual stresses in plasma-sprayed ZrO2-7Y2O3 thermal barrier coatings deposited on Ni-base superalloy substrates which were kept at different temperatures. The stress measurements were carried out on as-sprayed specimens with X-ray diffraction equipment using the “sin2?” technique. It was found that the residual stresses in the ceramic layer changed from tensile to compressive with increasing substrate

M. Levit; I. Grimberg; B.-Z. Weiss

1996-01-01

304

Modelled and measured residual stresses in plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coatings consisting of a NiCrAlY bond coating and a 1.4 mm thick partially stabilised zirconia top coating were air plasma sprayed onto grit blasted nickel-base substrates. Two samples were produced using different amounts of external cooling during spraying of the top coatings. The residual stress profiles in the samples were measured after each manufacturing process step with a

Per Bengtsson; Christer Persson

1997-01-01

305

Effect of residual stresses on air plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Thermal barrier coating with a CoNiCrAlY bond coating and a 0.3 mm thick zirconia, (7% yttria stabilized) top coating were air plasma sprayed onto a Hastelloy-X nickel based super alloy substrate coupons. Substrate preparation is a key initial step in the production of quality thermal sprayed coatings. Grit blasting is usually used to roughen the substrate surface so that better

A. Nusair Khan; J. Lu; H. Liao

2003-01-01

306

Laser surface modification and characterization of air plasma sprayed alumina coatings  

Microsoft Academic Search

Surface modification and characterization of engineering components using high energy beams is an ever expanding and innovative area of research. Laser surface modification of plasma sprayed alumina coatings were carried out for transforming metastable ?-Al2O3 phase predominantly present in as-sprayed coating to a thermodynamically stable ?-Al2O3 phase. These laser treated coatings were characterized using laser based non-destructive techniques like laser

R. Krishnan; S. Dash; R. Kesavamoorthy; C. Babu Rao; A. K. Tyagi; Baldev Raj

2006-01-01

307

Electrochemical Evaluation of Thin-Film Li-Si Anodes Prepared by Plasma Spraying  

SciTech Connect

Thin-film electrodes of a plasma-sprayed Li-Si alloy were evaluated for use as anodes in high-temperature thermally activated (thermal) batteries. These anodes were prepared using 44% Li/56% Si (w/w) material as feed material in a special plasma-spray apparatus under helium or hydrogen, to protect this air- and moisture-sensitive material during deposition. Anodes were tested in single cells using conventional pressed-powder separators and lithiated pyrite cathodes at temperatures of 400 to 550 C at several different current densities. A limited number of 5-cell battery tests were also conducted. The data for the plasma-sprayed anodes was compared to that for conventional pressed-powder anodes. The performance of the plasma-sprayed anodes was inferior to that of conventional pressed-powder anodes, in that the cell emfs were lower (due to the lack of formation of the desired alloy phases) and the small porosity of these materials severely limited their rate capability. Consequently, plasma-sprayed Li-Si anodes would not be practical for use in thermal batteries.

GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; SCHARRER,GREGORY L.

1999-09-08

308

Wear behavior of gas tunnel type plasma sprayed Zr-based metallic glass composite coatings  

NASA Astrophysics Data System (ADS)

Gas tunnel type plasma spraying is a prospective method to produce metallic glass composite coatings with high quality due to its noteworthy feature of process controllability. In this study, Zr55Cu30Al10Ni5 metallic glass composite coatings were produced by gas tunnel type plasma spraying torch under optimum spraying conditions with selected plasma currents. The formation mechanism, sliding, and erosive wear behaviors of the coatings with respect to plasma current was examined. The phase and thermal analyses as well as microstructure of the plasma sprayed coatings produced at different plasma currents were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) techniques. The sliding and erosive wear behaviors of the coatings were studied using a pin-on-disc and a specially designed erosive wear tester, respectively. The results showed that an increase in plasma current increased the crystalline content in the metallic glass composite coatings, which enhanced the hardness and wear resistance of the coatings.

Yugeswaran, S.; Kobayashi, A.; Suresh, K.; Rao, K. P.; Subramanian, B.

2012-09-01

309

A fabrication process for vacuum-deposited strain gauges on thermally sprayed Al2O3  

NASA Astrophysics Data System (ADS)

Electrically insulating films of Al2O3 were deposited using thermal spray technology followed by the sputter deposition of a strain gauge pattern using shadow masking techniques. For the first time, a thin film strain gauge of chromium was successfully fabricated on thermally sprayed Al2O3 insulation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and profilometer characterization techniques were used to examine structure and surface morphologies of the Al2O3 coatings. A gauge factor of around 2 was found for chromium film as well as hysteresis and creep for loads exceeding 1700 micro strain. The results are discussed.

Djugum, R.; Jolic, K. I.

2006-02-01

310

Effects of Anode Arc Root Fluctuation on Coating Quality During Plasma Spraying  

NASA Astrophysics Data System (ADS)

To obtain a coating of high quality, a new type of plasma torch was designed and constructed to increase the stability of the plasma arc and reduce the air entrainment into the plasma jet. The torch, called bi-anode torch, generates an elongated arc with comparatively high arc voltage and low arc fluctuation. Spraying experiments were carried out to compare the quality of coatings deposited by a conventional torch and a bi-anode torch. Alumina coatings and tungsten carbide coatings were prepared to appraise the heating of the sprayed particles in the plasma jets and the entrainment of the surrounding air into the plasma jets, respectively. The results show that anode arc root fluctuation has only a small effect on the melting rate of alumina particles. On the other hand, reduced air entrainment into the plasma jet of the bi-anode torch will drastically reduce the decarbonization of tungsten carbide coatings.

An, Lian-Tong; Gao, Yang; Sun, Chengqi

2011-06-01

311

The evolution of ion charge states in cathodic vacuum arc plasmas: a review  

SciTech Connect

Cathodic vacuum arc plasmas are known to contain multiply charged ions. 20 years after “Pressure Ionization: its role in metal vapour vacuum arc plasmas and ion sources” appeared in vol. 1 of Plasma Sources Science and Technology, it is a great opportunity to re-visit the issue of pressure ionization, a non-ideal plasma effect, and put it in perspective to the many other factors that influence observable charge state distributions, such as the role of the cathode material, the path in the density-temperature phase diagram, the “noise” in vacuum arc plasma as described by a fractal model approach, the effects of external magnetic fields and charge exchange collisions with neutrals. A much more complex image of the vacuum arc plasma emerges putting decades of experimentation and modeling in perspective.

Anders, Andre

2011-12-18

312

Bond Characterization of Plasma Sprayed Zirconium on Uranium Alloy by Microcantilever Testing  

NASA Astrophysics Data System (ADS)

The future production of low enriched uranium nuclear fuel for test reactors requires a well-adhered diffusion barrier coating of zirconium (Zr) on the uranium/molybdenum (U-Mo) alloy fuel. In this study, the interfacial bond between plasma sprayed Zr coatings and U-Mo fuel was characterized by microcantilever beam testing. Test results revealed the effect of specific flaws such as cracks and pores on the bonding of interfaces with a sampling area of approximately 20 ?m2. TEM examination showed the Zr/U-Mo interface to contain rows of very fine grains (5-30 nm) with the Zr in contact with UO2. Bond characteristics of plasma sprayed samples were measured that are similar to those of roll bonded samples showing the potential for plasma sprayed Zr coatings to have high bond strength.

Hollis, K. J.; Mara, N. A.; Field, R. D.; Wynn, T. A.; Crapps, J. M.; Dickerson, P. O.

2013-03-01

313

Oxidation Control of Atmospheric Plasma Sprayed FeAl Intermetallic Coatings Using Dry-Ice Blasting  

NASA Astrophysics Data System (ADS)

The performance of atmospheric plasma sprayed FeAl coatings has been remarkably limited because of oxidation and phase transformation during the high-temperature process of preparation. In the present work, FeAl intermetallic coatings were prepared by atmospheric plasma spraying combined with dry-ice blasting. The microstructure, oxidation, porosity, and surface roughness of FeAl intermetallic coatings were investigated. The results show that a denser FeAl coating with a lower content of oxide and lower degree of phase transformation can be achieved because of the cryogenic, the cleaning, and the mechanical effects of dry-ice blasting. The surface roughness value decreased, and the adhesive strength of FeAl coating increased after the application of dry-ice blasting during the atmospheric plasma spraying process. Moreover, the microhardness of the FeAl coating increased by 72%, due to the lower porosity and higher dislocation density.

Song, Bo; Dong, Shujuan; Coddet, Pierre; Hansz, Bernard; Grosdidier, Thierry; Liao, Hanlin; Coddet, Christian

2013-03-01

314

Morphological Evaluation of Plasma Sprayed Ceramic Coatings using Cavitation Erosion Test  

NASA Astrophysics Data System (ADS)

The microstructure of plasma sprayed ceramic coatings is characterized by the existence of splats along with other morphological features such as interlamellar and globular pores, intrasplat microcracks and splat boundaries. These various process-dependant micro- defects extremely influence physical and mechanical properties such as thermal conductivity and elastic modulus and then influence coating behavior. In this approach, the process involved in the cavitation erosion of plasma sprayed ceramic coatings have been studied using the ultrasonic vibratory technique. The weight loss occurring during fifteen minute intervals of exposure to cavitational erosion was determined, the surface of specimens and the wear debris were examined by Scanning electron microscopy (SEM). The results suggest that the improvement in coating performance could be achieved by controlling the effective contact between lamellae of which the coating is made up using the plasma spray conditions, such as sufficient preheat, short standoff distance and slow gun traversing movement.

Uematsu, Susumu; Tani, Kazumi; Sugasawa, Shinobu; Kawanami, Yasutaka; Namba, Yoshio; Takabatake, Tsuyoshi; Yoshioka, Masaru; Ishihara, Yasuaki

315

Mechanical Properties and Microstructure of Plasma Sprayed Ni-Based Metallic Glass Coating  

NASA Astrophysics Data System (ADS)

Various developmental research works on the metallic glass have been conducted in order to broaden its application field. Thermal spraying method is one of the potential techniques to enhance the excellent properties such as high toughness and corrosion resistance of the metallic glass material. The gas tunnel type plasma spraying is useful to obtain high quality ceramic coatings such as Al2O3 and ZrO2 coatings. In this study, the Ni-based metallic glass coatings were produced by the gas tunnel type plasma spraying under various experimental conditions, and their microstructure and mechanical properties were investigated. At the plasma current of 200-300 A, the Ni-based metallic glass coatings of more than 200 ?m in thickness were formed densely with Vickers hardness of about Hv = 600.

Kobayashi, Akira; Kuroda, Toshio; Kimura, Hisamichi; Inoue, Akihisa

2010-10-01

316

Wear resistance of laser cladding and plasma spray welding layer on stainless steel surface  

NASA Astrophysics Data System (ADS)

The effect of coatings, which are formed with laser cladding and plasma spray welding on 1Cr18Ni9Ti base metal, on wear resistance is studied, A 5-kW transverse flowing CO2 laser is used for cladding Co base alloy powder pre-placed on the substrate. Comparing with the plasma spray coatings, the spoiled rate of products with laser clad layers was lower and the rate of finished products was higher. Their microstructure is extremely fine. They have close texture and small size grain. Their dilution resulting from the compositions of the base metal and thermal effect on base metal are less. The hardness, toughness, and strength of the laser cladding layers are higher. Wear tests show that the laser layers have higher properties of anti-friction, anti-scour and high-temperature sliding strike. The wear resistance of laser clad layers are about one time higher than that of plasma spray welding layer.

Wang, Xinlin; Shi, Shihong; Zheng, Qiguang

2004-03-01

317

Plasma-sprayed, self-lubricating coatings for use from cryogenic temperatures to 870 deg C (1600 deg F)  

NASA Technical Reports Server (NTRS)

A plasma-sprayed coating is described with good lubricating properties over a wide temperature range. The coating, designated NASA LUBE PS101, contains silver, nichrome, calcium fluoride, and an oxidation protective glass. Oscillating tests were conducted of self-aligning, plain cylindrical bearings, in which the bore was lined with 0.025 cm (0.010 in.) thick coatings of PS101; these were conducted at a radial load of 3.5 x 10 to the 7th power N/sq m (5000 psi) in nitrogen gas at -107 C (-160 F), in vacuum at room temperature, and in air from room temperature to 870 C (1600 F). Friction coefficients were less than 0.25 in all cases and wear rates were low. The coating is not brittle, and it has adequate oxidation resistance in air to at least 870 C.

Sliney, H. E.

1975-01-01

318

Plasma spraying of lanthanum chromite films for solid oxide fuel cell interconnection application  

SciTech Connect

This paper discusses a novel plasma-spraying process for depositing dense LaCrO{sub 3}-based interconnection for solid oxide fuel cells (SOFCs). Calcium aluminate was mixed with LaCrO{sub 3} in a slurry containing PVA binder and spray dried to form free-flowing agglomerates. These free-flowing agglomerates were plasma sprayed onto a porous substrate of doped LaMnO{sub 3} and then heat-treated to form a gas-tight and electrically conducting interconnection. Samples of the plasma-sprayed interconnection were characterized for morphology, phase constituents, and coefficient of thermal expansion, as well as electrical resistivity and oxygen nonstoichiometry at 1,000 C in the P{sub O{sub 2}} range from 1 to {approximately}1 {times} 10{sup {minus}16} atm. The calcium aluminate additive was found to facilitate densification of the interconnection, most likely through the formation of low-temperature melting phase(s) in the system Ca-Cr-Al-O. A SOFC with such a plasma-sprayed interconnection was fabricated and electrically tested. This cell exhibited good electrical performance, and the interconnection was stable under fuel cell operation conditions.

Kuo, L.J.H.; Vora, S.D.; Singhal, S.C. [Westinghouse Electric Corp., Pittsburgh, PA (United States). Science and Technology Center

1997-03-01

319

Laser and plasma hybrid spray coatings on carbon fiber reinforced composite materials  

NASA Astrophysics Data System (ADS)

A hybrid laser/plasma spraying system has been developed to apply coatings to C/C composites that will exhibit superior oxidation resistance in high temperature oxidizing conditions via multilayer coatings. The hybrid system couples a high power CO2 laser with a low pressure plasma-spraying apparatus, and has been used to produce thick, multilayer WC/MoSi2/ZrO2 coatings on monolithic carbon components; the coatings have been found to have high density and stability to 2000 C in an inert atmosphere.

Shimura, H.; Sasaki, S.; Hasegawa, K.; Hirano, K.

320

The Tribological Behavior of Plasma-Sprayed Al-Si Composite Coatings Reinforced with Nanodiamond  

NASA Astrophysics Data System (ADS)

Al-Si composite coatings reinforced with 0 vol.%, 0.5 vol.%, and 2 vol.% nanodiamond were synthesized by plasma spraying. The effect of the addition of nanodiamond on the microstructure, hardness, and tribological performance of the composite coatings is investigated. The addition of 2 vol.% nanodiamond results in 45% improvement in the wear resistance of Al-Si coating. Al-Si coating with 0.5 vol.% nanodiamond exhibited lower coefficient of friction (0.45) with a 12% improvement in the wear resistance. Plasma-sprayed AlSi coatings with nanodiamond have excellent potential as wear-resistant coatings in automotive applications.

Bao, Mingdong; Zhang, Cheng; Lahiri, Debrupa; Agarwal, Arvind

2012-06-01

321

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

NASA Technical Reports Server (NTRS)

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.

Miller, R. A.; Doychak, J.

1992-01-01

322

Deflection, spraying, and induced scattering of intense laser beams in plasmas  

SciTech Connect

Investigations into laser beam spraying, deflection, and induced scattering in plasmas are presented. Recent calculations and experiments on beam spraying due to filamentation are discussed. A simple model is presented for an enhanced beam deflection associated with nearly sonic plasma flow transverse to the beam. This model provides useful insights on the laser beam deflection, its scaling and the importance of self-consistent profile modifications. Finally, some discussion is given of recent experiments demonstrating the interplay between stimulated.Raman and Brillouin scattering.

Kruer, W.L.

1996-09-01

323

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

NASA Astrophysics Data System (ADS)

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.

Miller, R. A.; Doychak, J.

1992-09-01

324

The abrasive wear of plasma sprayed nanoscale tungsten carbide-cobalt (WC-Co)  

NASA Astrophysics Data System (ADS)

Thermal spray coatings composed of a variety of carbide sizes and cobalt contents were sprayed with a high energy plasma spray system. The size of the carbides used fell into three rough groupings, micrometer scale carbides (1--2 mum), submicrometer (700--300 nm), and nanoscale (?100 nm). The feedstock powder was evaluated in terms of their size distribution, external morphology, internal morphology, and initial carbide size. Two different fixtures were used in spraying to evaluate the effect of cooling rate on the wear resistance of the coatings. The microstructures of the sprayed coatings were examined using optical metallography, SEM, FESEM, TEM, XRD and chemical analysis. The coatings were evaluated in low stress abrasive wear by the ASTM G-65 Dry Sand Rubber Wheel test. Furthermore, the porosity and hardness of the coatings were evaluated. The cobalt content was found to be the predominant influence on the wear rate of the coatings. The decrease in the carbide size was not found to effect the wear rate of the coatings. Coatings sprayed on the 'hot' fixture were found to have slightly improved wear resistance as compared to coatings sprayed on the 'cold' fixture. The wear rates of the coatings were found to be a function of the WC/Co volume ratio.

Tewksbury, Graham Alfred

325

Effect of critical plasma spray parameter on complex permittivity and microstructure by plasma spraying Cr/Al2O3 coatings  

NASA Astrophysics Data System (ADS)

In this paper, Cr/Al2O3 coatings formed via a plasma spray approach with different critical plasma spray parameters using Al2O3 and Cr powder feeds were prepared. The effects of CPSP on the phase composition, microstructure, complex permittivity, porosity and adhesive strength of the coatings were investigated. The microstructure and phase composition of coatings were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD). XRD analysis reveal that Cr, ?-Al2O3 and ?-Al2O3 are found in all the coatings, and percentage of ?-Al2O3 is increased due to complete melting of the particles and their consequent rapid solidification. The experimental results have shown that the CPSP condition has significant influence on the microstructure and complex permittivity of the coatings. Both the real part (?') and imaginary part (??) of relative complex permittivity are increased with improving the CPSP condition.

Zhao, Dong; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

2013-01-01

326

Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow  

SciTech Connect

One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.

Khutsishvili, M.; Kikvadze, L. [Plasma Spray Laboratory, Georgian Technical University, M. Kostava street 77, Tbilisi 0175 (Georgia)

2008-03-19

327

Behavior of plasma-sprayed TiC coatings under electron beam thermal shocks  

SciTech Connect

Within the framework of a research program on materials for fusion machine, plasma-sprayed TiC coatings over Inconel 625 substrates were investigated. In order to evaluate the potential of these coatings in fusion environment, the existing thermal flux conditions on limiters of tokamaks are simulated with an electron beam thermal shock experiment. TiC coatings sprayed in air show severe damages when exposed to 2.5 kW cm/sup -2/, 1.0 s, heat pulses. Coatings sprayed in an inert gas enclosure withstood 3.0 kW cm/sup -2/, 1.0 s, heat pulses without melting. Surface melting and subsurface crystal growth are observed in the case of coatings sprayed in air.

Brunet, C.; Dallaire, S.; St-Jacques, R.G.

1985-11-01

328

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications  

NASA Technical Reports Server (NTRS)

Development of the plasma sprayed graded, layered ZrO2/CoCrAlY seal system for gas turbine engine blade tip seal application up to 1589 K (2400 F) surface temperature was continued. Methods of improvement of the cyclic thermal shock resistance of the sprayed zirconia seal system were investigated. The most promising method, reduction of the ceramic thickness and metallic substrate stiffness were selected based upon potential and feasibility. Specimens were fabricated and experimentally evaluated to: (1) substantiate the capacity of the geometry changes to reduce operating stresses in the sprayed structure; and (2) define the abradability, erosion, thermal shock and physical property characteristic for the sprayed ceramic seal system. Thermal stress analysis was performed and correlated with thermal shock test results.

Shiembob, L. T.; Hyland, J. F.

1979-01-01

329

Mechanical, in vitro antimicrobial, and biological properties of plasma-sprayed silver-doped hydroxyapatite coating.  

PubMed

Implant-related infection is one of the key concerns in total joint hip arthroplasties. To reduce bacterial adhesion, we used silver (Ag)/silver oxide (Ag(2)O) doping in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0, and 6.0 wt % Ag, heat-treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas aeruginosa (PAO1). Live/dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Our results suggest that the plasma-sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag-doped HA coatings. PMID:22313742

Roy, Mangal; Fielding, Gary A; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

2012-03-01

330

Adhesive and cohesive properties by indentation method of plasma-sprayed hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

Adhesive and cohesive properties of the plasma-sprayed hydroxyapatite (HA) coatings, deposited on Ti-6Al-4V substrates by varying the plasma power level and spray distance (SD), were evaluated by an indentation method. The crystallinity and the porosity decreased with increasing both of these two parameters. The microhardness value, Young's modulus ( E) and coating fracture toughness ( KC) were found to increase with a combinational increase in spray power and SD. The Knoop and Vickers indentation methods were used to estimate E and KC, respectively. The critical point at which no crack appears at the interface was determined by the interface indentation test. This was used to define the apparent interfacial toughness ( KCa) which is representative of the crack initiation resistance of the interface. It was found that KCa reaches to a maximum at a medium increase in both spray power and SD, while other mechanical properties of the coatings reaches to the highest value with further increase in these two plasma parameters. The tensile adhesion strength of the coatings, measure by the standard adhesion test, ISO 13779-4, was shown to alter in the same manner with KCa results. It was deduced that a combinational increase in spray power and SD which leads to a higher mechanical properties in the coatings, does not necessarily tends to a better mechanical properties at the interface.

Mohammadi, Z.; Ziaei-Moayyed, A. A.; Mesgar, A. Sheikh-Mehdi

2007-03-01

331

An evaluation of nickel-aluminum coatings fabricated with the plasma-spray process  

SciTech Connect

As part of an investigation of the dynamics that occur in the plasma-spray process, an experimental study of the plasma spraying of nickel-aluminum powder was conducted. The coating experiments used typical process parameters that were varied in a Taguchi fractional factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments to display the range of plasma-processing conditions and their effect on the resultant coating. Parameters varied include the working gas mixture, power, powder injection location, spray distance, traverse rate, and powder feed rate. Typical operating conditions for the torch of this study were 35 V, 800 A, 100 standard ft{sup 3}/h (scfh) argon primary gas flow, 47 scfh helium secondary gas flow, and 7 lb/h powder feedrate. These parameter settings were used with a 3-in. spray distance and a gun traverse rate of 20 in./sec. The statistical scheme varied around these nominal parameter settings. The coatings were fabricated with ten passes, which yielded relatively even coatings that ranged in thickness from 187 to 603 microns. The coatings were characterized by hardness tests, optical metallography, and x-ray diffraction. Coating qualities are discussed with respect to thickness, hardness, porosity, and phase content.

Varacalle, D.J. Jr.; Knibloe, J.R.; Smith-Wackerle, V.L. (EG and G Idaho, Inc., Idaho Falls, ID (USA)); Walter, J.A. (Miller Thermal, Inc., Appleton, WI (USA)); Irons, G. (TAFA, Inc., Concord, NH (USA))

1990-01-01

332

Hypersonic plasma particle deposition—A hybrid between plasma spraying and vapor deposition  

NASA Astrophysics Data System (ADS)

In the hypersonic plasma particle deposition process, vapor phase reactants are injected into a plasma and rapidly quenched in a supersonic nozzle, leading to nucleation of nanosize particles. These particles impact a substrate at high velocity, forming a coating with grain sizes of 10 to 40 nm. As previously reported, coatings of a variety of materials have been obtained, including silicon, silicon carbide, titanium carbide and nitride, and composites of these, all deposited at very high rates. Recent studies have shown that slight modifications of the process can result in nanosize structures consisting of single crystal silicon nanowires covered with nanoparticles. These nanowires are believed to grow in a vapor deposition process, catalyzed by the presence of titanium in the underlying nanoparticle film. However, simultaneously nanoparticles are nucleated in the nozzle and deposited on the nanowires, leading to structures that are the result of a plasma chemical vapor deposition (CVD) process combined with a nanoparticle spray process. The combination of these two process paths opens new dimensions in the nanophase materials processing area.

Hafiz, J.; Mukherjee, R.; Wang, X.; McMurry, P. H.; Heberlein, J. V. R.; Girshick, S. L.

2006-12-01

333

On the Self-Affine Fractal Geometry of Plasma-Sprayed Surfaces  

NASA Astrophysics Data System (ADS)

Surface roughness strongly controls essential properties of thermally sprayed wear- and corrosion-resistant coatings including their mechanical adhesion to the substrate, tribological performance, efficient retention of lubricating materials, and also the presence of sufficient carrying surface able to support the wear couple along the line of contact expressed by the Abbott-Firestone curve. The determination of the surface fractal geometry may yield useful information on the topography of plasma-sprayed coatings beyond that provided by a single roughness parameter such as R a or R z. The fractal geometry of atmospheric plasma-sprayed chromium oxide coatings, deposited according to two different statistical experimental design protocols, was assessed through determination of the Hurst exponent H of fractal Brownian motion (fBM), as well as the area-scaled fractal complexity (ASFC) obtained by triangular tessellation ("patchwork" method). Attempts were made to correlate fractality with coating adhesion strength.

Heimann, Robert B.

2011-06-01

334

Effect of Gun Current on Electrical Properties of Atmospheric Plasma-Sprayed Lanthanum Silicate Coatings  

NASA Astrophysics Data System (ADS)

Apatite-type lanthanum silicate (ATLS) electrolyte coatings for use in intermediate-temperature solid oxide fuel cells were deposited by atmospheric plasma spraying (APS). Plasma-sprayed coatings with typical composition La10(SiO4)6O3 exhibiting good densification and high oxide ionic conductivity were obtained by properly adjusting the spraying parameters, particularly the gun current. The highest obtained ionic conductivity value of 3.3 mS/cm at 1,173 K in air is comparable to other ATLS conductors. This work demonstrated empirically that utilization of the APS technique is feasible to synthesize dense La10(SiO4)6O3 electrolyte coatings using gun currents within an unusually broad range.

Gao, Wei; Liao, Han-Lin; Coddet, Christian

2013-10-01

335

Improvement in mechanical properties of plasma sprayed hydroxyapatite coatings by Al2O3 reinforcement.  

PubMed

Thermal sprayed hydroxyapatite coatings suffer from poor mechanical properties like tensile strength, wear resistance, hardness, toughness and fatigue. The mechanical properties of hydroxyapatite coatings can be enhanced via incorporation of secondary bioinert reinforcement material. In this study an attempt has been made to improve the mechanical properties of plasma sprayed hydroxyapatite by reinforcing it with 10, 20 and 30% Al2O3. The plasma sprayed coatings have been characterized using FE-SEM/EDAX, XRD, AFM and FTIR spectroscopy. Corrosion studies have been done in simulated body fluid and abrasive wear studies have been performed on flat specimens on a disk wear tester. Microhardness, tensile strength and wear resistance are found to be increased with increasing Al2O3 content. All types of coatings show superior resistance against corrosion in simulated body fluid. PMID:23623104

Mittal, Manoj; Nath, S K; Prakash, Satya

2013-07-01

336

Application of Suspension Plasma Spraying (SPS) for Manufacture of Ceramic Coatings  

NASA Astrophysics Data System (ADS)

Conventional thermal spray processes as atmospheric plasma spraying (APS) have to use easily flowable powders with a size up to 100 ?m. This leads to certain limitations in the achievable microstructural features. Suspension plasma spraying (SPS) is a new promising processing method which employs suspensions of sub-micrometer particles as feedstock. Therefore much finer grain and pore sizes as well as dense and also thin ceramic coatings can be achieved. Highly porous coatings with fine pore sizes are needed as electrodes in solid-oxide fuel cells. Cathodes made of LaSrMn perovskites have been produced by the SPS process. Their microstructural and electrochemical properties will be presented. Another interesting application is thermal barrier coating (TBC). SPS allows the manufacture of high-segmented TBCs with still relatively high porosity levels. In addition to these specific applications also the manufactures of new microstructures like nano-multilayers and columnar structures are presented.

Kassner, Holger; Siegert, Roberto; Hathiramani, Dag; Vassen, Robert; Stoever, Detlev

2008-03-01

337

Al2O3-ZrO2 Finely Structured Multilayer Architectures from Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Suspension plasma spraying (SPS) is an alternative to conventional atmospheric plasma spraying (APS) aiming at manufacturing thinner layers (i.e., 10-100 ?m) due to the specific size of the feedstock particles, from a few tens of nanometers to a few micrometers. The staking of lamellae and particles, which present a diameter ranging from 0.1 to 2.0 ?m and an average thickness from 20 to 300 nm, permits to manufacture finely structured layers. Moreover, it appears as a versatile process able to manufacture different coating architectures according to the operating parameters (suspension properties, injection configuration, plasma properties, spray distance, torch scan velocity, scanning step, etc.). However, the different parameters controlling the properties of the coating, and their interdependences, are not yet fully identified. Thus, the aim of this paper is, on the one hand, to better understand the influence of operating parameters on the coating manufacturing mechanisms (in particular, the plasma gas mixture effect) and, on the other hand, to produce Al2O3-ZrO2 finely structured layers with large varieties of architectures. For this purpose, a simple theoretical model was used to describe the plasma torch operating conditions at the nozzle exit, based on experimental data (mass enthalpy, arc current intensity, thermophysical properties of plasma forming gases, etc.) and the influences of the spray parameters were determined by mean of the study of sizes and shapes of spray beads. The results enabled then to reach a better understanding of involved phenomena and their interactions on the final coating architectures permitting to manufacture several types of microstructures.

Tingaud, Olivier; Montavon, Ghislain; Denoirjean, Alain; Coudert, Jean-François; Rat, Vincent; Fauchais, Pierre

2010-01-01

338

Process Conditions and Microstructures of Ceramic Coatings by Gas Phase Deposition Based on Plasma Spraying  

NASA Astrophysics Data System (ADS)

Plasma spraying at very low pressure (50-200 Pa) is significantly different from atmospheric plasma conditions (APS). By applying powder feedstock, it is possible to fragment the particles into very small clusters or even to evaporate the material. As a consequence, the deposition mechanisms and the resulting coating microstructures could be quite different compared to conventional APS liquid splat deposition. Thin and dense ceramic coatings as well as columnar-structured strain-tolerant coatings with low thermal conductivity can be achieved offering new possibilities for application in energy systems. To exploit the potential of such a gas phase deposition from plasma spray-based processes, the deposition mechanisms and their dependency on process conditions must be better understood. Thus, plasma conditions were investigated by optical emission spectroscopy. Coating experiments were performed, partially at extreme conditions. Based on the observed microstructures, a phenomenological model is developed to identify basic growth mechanisms.

Mauer, G.; Hospach, A.; Zotov, N.; Vaßen, R.

2013-03-01

339

The deformation and cooling of ceramic particles sprayed with a thermal radio-frequency plasma under atmospheric conditions  

NASA Astrophysics Data System (ADS)

Common thermal-spray techniques use the strong acceleration of powder particles to produce dense ceramic coatings with high bond strength. The residence time of the powder particles within the plasma jet is correspondingly low, and only relatively small particles can be molten. In this work, on the contrary, an inductively coupled radio-frequency (RF) inductively coupled plasma (ICP) torch was used to spray large oxide-ceramic powder particles under atmospheric conditions. The slow plasma flow of a RF plasma leads to large residence times of the powder particles, so that the powder size of the feedstock can be 100 µm and more. It was observed that these particles will not be strongly accelerated in the plasma and that their velocity at the moment of impact is in the range of 10 to 20 m/s. Ceramic coatings were ICP sprayed with a low porosity and a high bond strength, similar to direct current (DC) or high-velocity-oxygen-fuel (HVOF) sprayed coatings. The morphology of ICP-sprayed particles on smooth steel surfaces, as a function of the surface temperature, is described and compared with DC plasma-sprayed splats. Furthermore, the degree of deformation was measured and determined by different models, and the pronounced contact zones formed between the pancake and the substrate were investigated. The ICP-sprayed ceramic coatings show some special properties, such as the absence of metastable crystalline phases, which are common in other spray technologies.

Dzur, B.; Wilhelmi, H.; Nutsch, G.

2001-12-01

340

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

341

Thermal plasma-sprayed nickel catalysts in the clean-up of biomass gasification gas  

Microsoft Academic Search

Plasma spraying is a potential catalyst preparation method for hot gas clean-up which requires very durable catalytic coatings. In this work, the multi-layer composite coating powders consisted of a gibbsite or boehmite core together with a hydrotalcite coating. We used the coating powders in the preparation of the powder form Ni catalysts, which were characterized by XRD, BET, XPS, and

Hanne Rönkkönen; Kristina Klemkait?; Alexander Khinsky; Ar?nas Baltušnikas; Pekka Simell; Matti Reinikainen; Outi Krause; Marita Niemelä

2011-01-01

342

Small intestinal morphology in weaned piglets fed a diet containing spray-dried porcine plasma  

Microsoft Academic Search

The hypothesis tested in this study was that the reported beneficial effects of spray-dried porcine plasma (SDPP) on piglet post-weaning performance and health are associated with a trophic effect on small intestinal mucosa. At 24 days of age, the piglets of seven sows were assigned to one of three treatment groups. One group continued to be suckled. The other two

A. J Van Dijk; T. A. Niewold; R. J. C. F. Margry; S. G. C Van Den Hoven; M. J. A. Nabuurs; N Stockhofe-Zurwieden; A. C. Beynen

2001-01-01

343

Growth performance of weanling pigs fed spray-dried animal plasma: a review  

Microsoft Academic Search

Spray-dried animal plasma (SDAP), mostly of porcine origin, is frequently used as an ingredient of weanling piglets diets in order to improve feed intake and to reduce post-weaning diarrhoea. On the basis of 15 published studies it is concluded that dietary SDAP levels up to 6% increase both average daily gain (ADG) and feed intake (ADFI) in the first 2

A. J. van Dijk; H. Everts; M. J. A. Nabuurs; R. J. C. F. Margry; A. C. Beynen

2001-01-01

344

Functional properties of spray-dried animal plasma in canned petfood  

Microsoft Academic Search

Over the last 15 years, spray-dried animal plasma (SDAP) has become a commonly used gelling ingredient in canned petfood diets. However, little is known about the functional properties of this product in this application.SDAP is a concentrate of proteins with the property of producing a very stable and compact gel when submitted to high temperatures. High gel strength capacities are

Javier Polo; Carmen Rodríguez; Neus Saborido; Jesús Ródenas

2005-01-01

345

Apatite formed on the surface of plasma-sprayed wollastonite coating immersed in simulated body fluid  

Microsoft Academic Search

Wollastonite coatings on titanium alloys substrates were prepared by plasma spraying and incubated in simulated body fluids for different periods to investigate the nucleation and growth of apatite on their surface. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of wollastonite coatings

Xuanyong Liu; Chuanxian Ding; Zhenyao Wang

2001-01-01

346

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

National Technical Information Service (NTIS)

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 stre...

S. R. Choi D. M. Zhu R. A. Miller

2004-01-01

347

A sintering model for plasma-sprayed zirconia TBCs. Part I: Free-standing coatings  

Microsoft Academic Search

A sintering model is presented for prediction of changes in the microstructure and dimensions of free-standing, plasma-sprayed (PS) thermal barrier coatings (TBCs). It is based on the variational principle. It incorporates the main microstructural features of PS TBCs and simulates the effects of surface diffusion, grain boundary diffusion and grain growth. The model is validated by comparison with experimental data

A. Cipitria; I. O. Golosnoy; T. W. Clyne

2009-01-01

348

Evaluation of thickness, porosity and pore shape of plasma sprayed TBC by electrochemical impedance spectroscopy  

Microsoft Academic Search

An equivalent circuit of electrochemical impedance spectroscopy (EIS) was suggested to model the morphological structure of nonexposure thermal barrier coating (TBC). The morphological properties of as-coated air plasma sprayed (APS) TBC were correlated with the EIS parameters. A linear relationship between TBC topcoat thickness, Dc, and ceramic resistance, Rc, has been found particularly when the TBC have the same porosity.

J. Zhang; V. Desai

2005-01-01

349

Influence of powder-characteristics on the microstructure of ceramic plasma spray coatings  

Microsoft Academic Search

The relationship between the properties of plasma spray powders and the resultant coating has been investigated. ZrO2 powders, differing in grain size, state of agglomeration and morphology, have been used and coating properties such as microstructure, porosity, roughness, hardness, and wear resistance are described. Agglomerated powders cause high porosity, while sphericalized particles yield very dense layers. The homogeneity of an

W. Kollenberg; J. Decker

1993-01-01

350

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

351

Effect of Plasma Nitriding and Nitrocarburizing on HVOF-Sprayed Stainless Steel Coatings  

NASA Astrophysics Data System (ADS)

In this work, the effects of plasma nitriding (PN) and nitrocarburizing on HVOF-sprayed stainless steel nitride layers were investigated. 316 (austenitic), 17-4PH (precipitation hardening), and 410 (martensitic) stainless steels were plasma-nitrided and nitrocarburized using a N2 + H2 gas mixture and the gas mixture containing C2H2, respectively, at 550 °C. The results showed that the PN and nitrocarburizing produced a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer depending on the crystal structures of the HVOF-sprayed stainless steel coatings. Also, the diffusion depth of nitrogen increased when a small amount of C2H2 (plasma nitrocarburizing process) was added. The PN and nitrocarburizing resulted in not only an increase of the surface hardness, but also improvement of the load bearing capacity of the HVOF-sprayed stainless steel coatings because of the formation of CrN, Fe3N, and Fe4N phases. Also, the plasma-nitrocarburized HVOF-sprayed 410 stainless steel had a superior surface microhardness and load bearing capacity due to the formation of Cr23C6 on the surface.

Park, Gayoung; Bae, Gyuyeol; Moon, Kyungil; Lee, Changhee

2013-12-01

352

Structure and mechanical properties of boron carbide coatings formed by electromagnetically accelerated plasma spraying  

Microsoft Academic Search

Structural and mechanical properties are investigated on thick boron carbide (B4C) coatings, which are formed onto stainless steel substrates by using an electromagnetically accelerated plasma spraying. Hardness, porosity and surface roughness of the coatings show dependences on both the size of raw powder and the substrates distance. Within the coating conditions using two different sized raw powders; 30±10 ?m and

J. Kitamura; S. Usuba; Y. Kakudate; H. Yokoi; K. Yamamoto; A. Tanaka; S. Fujiwara

2003-01-01

353

Laser drilling of cooling holes through plasma sprayed thermal barrier coatings  

Microsoft Academic Search

Laser drilling is a non-contact process that can be used to form small holes in a wide variety of materials with a high degree of precision and reproducibility. The advantages of being able to drill difficult materials, specifically superalloys and ceramics, are exploited in the laser drilling of cooling holes in thermal barrier coated superalloys. Plasma sprayed thermal barrier coatings

K. T. Voisey; T. W. Clyne

2004-01-01

354

Synthesis and characterization of plasma spray formed carbon nanotube reinforced aluminum composite  

Microsoft Academic Search

A trend has been perceived in the field of composite materials to employ carbon nanotubes as reinforcement in synthesizing composites of unique properties. In this endeavor, free standing structures of Al-based nanostructured composite with carbon nanotubes as second phase particles has been synthesized by plasma spray forming technique. Optical microscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy has been

T. Laha; A. Agarwal; Tim McKechnieb; S. Seal

2004-01-01

355

Tensile properties of carbon nanotube reinforced aluminum nanocomposite fabricated by plasma spray forming  

Microsoft Academic Search

Uniaxial tensile tests were performed on plasma spray formed (PSF) Al–Si alloy reinforced with multiwalled carbon nanotubes (MWCNTs). The addition of CNTs leads to 78% increase in the elastic modulus of the composite. There was a marginal increase in the tensile strength of CNT reinforced composite with degradation in strain to failure by 46%. The computed critical pullout length of

T. Laha; Y. Chen; D. Lahiri; A. Agarwal

2009-01-01

356

Supersaturated Ni10 wt% Ti Alloys Fabricated by Mechanical Alloying and Plasma Spraying  

Microsoft Academic Search

A supersaturated Ni-10Ti alloy powder was produced from Ni and Ti elemental powders by solid state synthesis utilizing high energy mechanical alloying with times up to 5 h. Then, the milled powders were deposited on AISI 304 stainless steel substrate using air plasma spraying (APS) process. The microstructure and phase composition of the products were evaluated by scanning electron microscopy (SEM)

M. M. Verdian

2011-01-01

357

Atmospheric plasma sprayed thick thermal barrier coatings with high segmentation crack density  

Microsoft Academic Search

Atmospheric plasma sprayed thick thermal barrier coatings (TBCs), comprising of 1.5 mm thickness yttria stabilized zirconia (YSZ) coating, have been developed for increasing thermal protection of combustor applications. Different segmentation crack densities of the YSZ coating were created by controlling the deposition conditions. It was found that the substrate temperature played a dominant role in determining the segmentation crack density.

H. B. Guo; R. Vaßen; D. Stöver

2004-01-01

358

Current-voltage characteristics of a non-transferred plasma spray torch  

NASA Astrophysics Data System (ADS)

I- V characteristics of a non-transferred DC plasma spray torch operating on argon and argon + nitrogen mixtures are reported. Arc voltage is decreased with increase in arc current and increased with increase in electrode gap. Arc power is higher at higher percentage of nitrogen in argon. Nottingham co-efficients were calculated using numerical method.

Ramasamy, R.; Selvarajan, V.

2000-01-01

359

Stress and cracking behavior of plasma sprayed thermal barrier coatings using an advanced constitutive model  

Microsoft Academic Search

A finite element simulation of a plasma sprayed thermal barrier coating (TBC) system represented as a three-layer structure with an interface asperity is presented. Loading due to thermal expansion mismatch and geometry changes from oxide growth are included. A realistic viscoplastic model is used to represent the behavior of the ceramic layer, which includes both time dependent behavior and strong

Wangang Xie; Eric Jordan; Maurice Gell

2006-01-01

360

Titanium carbide–iron composite coatings by reactive plasma spraying of ilmenite  

Microsoft Academic Search

Titanium carbide–iron composite coatings have been developed by reactive plasma spray synthesis using ilmenite ore concentrate as the feedstock powder and methane as the reactive gas. The coatings have been characterized by X-ray diffraction and SEM. The microstructure of the coatings indicate good interparticle cohesion with very little porosity.

P. V Ananthapadmanabhan; Patrick R Taylor

1999-01-01

361

Efficacy of spray-drying to reduce infectivity of pseudorabies and porcine reproductive and respiratory syndrome (PRRS) viruses and seroconversion in pigs fed diets containing spray-dried animal plasma1  

Microsoft Academic Search

Three experiments were conducted to evaluate viral inactivation by the spray-drying process used in the production of spray-dried animal plasma (SDAP). In Exp. 1, bovine plasma was inoculated with pseudorabies virus (PRV) grown in PK 15 cells. Three 4-L batches were spray-dried in the same manner and conditions of industrial SDAP production but with labo- ratory spray-drying equipment. Presence of

J. Polo; J. D. Quigley; L. E. Russell; J. M. Campbell; J. Pujols; P. D. Lukert

362

Numerical Modeling in Radio Frequency Suspension Plasma Spray of Zirconia Powders  

Microsoft Academic Search

A comprehensive model was developed to investigate the suspension spraying for a radio frequency (RF) inductively coupled\\u000a plasma torch. Firstly, the electromagnetic field is solved with the Maxwell equations and validated by the analytical solutions.\\u000a Secondly, the plasma field with different power inputs is simulated by solving the governing equations of the fluid flow coupled\\u000a with the RF heating. Then,

Lijuan Qian; Jianzhong Lin; Hongbin Xiong

2010-01-01

363

Design of a new nozzle for direct current plasma guns with improved spraying parameters  

Microsoft Academic Search

A new design is proposed for direct current plasma spray gas-shroud attachments. It has curvilinearly shaped internal walls\\u000a aimed toward elimination of the cold air entrainment, recorded for commercially available conical designs of the shrouded\\u000a nozzle. The curvilinear nozzle design was tested; it proved to be capable of withstanding high plasma temperatures and enabled\\u000a satisfactory particle injection. Parallel measurements with

M. Jankovic; J. Mostaghimi; V. Pershin

2000-01-01

364

Experimental design of plasma spraying and laser treatment of hydroxyapatite coatings  

Microsoft Academic Search

Plasma spray process of hydroxyapatite (Ca10(PO4)6(OH)2, HA) followed by laser treatment of obtained coatings were optimized by an advanced statistical planning of experiments. The full factorial design of 24 experiments was used to find effects of four principal parameters, i.e. electric power, plasma forming gas composition, carrier gas flow rate and laser power density onto microstructure of hydroxyapatite (HA) coatings

S. Dyshlovenko; C. Pierlot; L. Pawlowski; R. Tomaszek; P. Chagnon

2006-01-01

365

Plasma spray joining of Al-matrix particulate reinforced composites  

SciTech Connect

Aluminum matrix composite joints have been produced on both aluminum alloy and metal matrix composite (MMC) substrates using powders containing SiC and Al{sub 2}O{sub 3} particulates. Most of the composite powders were produced by ball milling, but the most effective joints were produced using Osprey composite powders. The results of preliminary joining experiments indicate that the substrate should be preheated to 200 C and a very wide bevel angle should be provided in order to obtain the highest strength joints. Silicon alloy additions to the matrix significantly improved strength but titanium additions had no effect. Heat treatment after spraying significantly improved the bond strength and restored precipitation hardening in the matrix. Significant amounts of Mg were lost from the deposit during spraying while some free silicon was produced by pyrolysis of the SiC powder; hence, further efforts must develop powder compositions that produce the optimum matrix composition in the sprayed deposit. Hot isostatic pressing of the samples to eliminate porosity had only a small effect on the final strength of the joints. No significant amount of Al{sub 4}C{sub 3} was detected in deposits which contained SiC.

Itsukaichi, T.; Eagar, T.W.; Unemoto, M.; Okane, I.

1996-09-01

366

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications  

NASA Technical Reports Server (NTRS)

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the graded layered system were evaluated by rig tests. Satisfactory abradability and erosion resistance was demonstrated. Encouraging thermal fatigue tolerance was shown. Initial properties for the plasma sprayed materials in the graded, layered seal system was obtained, and thermal stress analyses were performed. Sprayed residual stresses were determined. Thermal stability of the sprayed layer materials was evaluated at estimated maximum operating temperatures in each layer. Anisotropic behavior in the layer thickness direction was demonstrated by all layers. Residual stresses and thermal stability effects were not included in the analyses. Analytical results correlated reasonably well with results of the thermal fatigue tests. Analytical application of the seal system to a typical gas turbine engine application predicted performance similar to rig specimen thermal fatigue performance. A model for predicting crack propagation in the sprayed ZrO2/CoCrAlY seal system was proposed, and recommendations for improving thermal fatigue resistance were made. Seal system layer thicknesses were analytically optimized to minimize thermal stresses in the abradability specimen during thermal fatigue testing. Rig tests on the optimized seal configuration demonstrated some improvement in thermal fatigue characteristics.

Shiembob, L. T.

1977-01-01

367

Improving the thermal shock resistance of plasma sprayed CYSZ thermal barrier coatings by laser surface modification  

NASA Astrophysics Data System (ADS)

In this study, substrates of Inconel 738 LC superalloy coupons were first sprayed with a NiCoCrAlY bondcoat and then with a ceria and yttria stabilized zirconia (CYSZ) topcoat by air plasma spraying (APS). After that, the plasma sprayed CYSZ thermal barrier coatings (TBCs) were treated using a pulsed Nd:YAG laser. The effects of laser glazing on the microstructure and thermal shock resistance of the coatings were evaluated. Thermal shock test was administered by holding specimens at 950 °C for 5 min and then water quenching. More than 20% of the spalled region of the surface of the topcoat was adopted as the criterion for the failure of samples. The microstructures of both the as processed and the tested TBCs were investigated using scanning electron microscope (SEM). The phases of the coatings were analyzed with X-ray diffractometry (XRD). XRD analysis revealed that both as sprayed and laser glazed topcoats consisted of nonequilibrium tetragonal (T') phase. The results showed that the life times of the as sprayed TBCs were enhanced around fourfold by the formation of a continuous network of segmented cracks perpendicular to the surface and the increase in strain accommodation.

Ahmadi-Pidani, Raheleh; Shoja-Razavi, Reza; Mozafarinia, Reza; Jamali, Hossein

2012-05-01

368

Effect of spraying power on microstructure and bonding strength of MoSi 2-based coatings prepared by supersonic plasma spraying  

Microsoft Academic Search

MoSi2-based oxidation protective coatings for SiC-coated carbon\\/carbon composites were prepared using a supersonic plasma spraying at the power of 40kW, 45kW, 50kW and 55kW, respectively. Effect of spraying power on the microstructure and bonding strength of MoSi2-based coatings was studied. The results show that coatings become more and more compact and the bonding strength increases when the spraying power increases

Heng Wu; He-jun Li; Qing Lei; Qian-gang Fu; Chao Ma; Dong-jia Yao; Yong-jie Wang; Can Sun; Jian-feng Wei; Zhi-hai Han

2011-01-01

369

Optimization of Atmospheric Plasma Spray Process Parameters using a Design of Experiment for Alloy 625 coatings  

NASA Astrophysics Data System (ADS)

Alloy 625 is a Ni-based superalloy which is often a good solution to surface engineering problems involving high temperature corrosion, wear, and thermal degradation. Coatings of alloy 625 can be efficiently deposited by thermal spray methods such as Air Plasma Spraying. As in all thermal spray processes, the final properties of the coatings are determined by the spraying parameters. In the present study, a D-optimal experimental design was used to characterize the effects of the APS process parameters on in-flight particle temperature and velocity, and on the oxide content and porosity in the coatings. These results were used to create an empirical model to predict the optimum deposition conditions. A second set of coatings was then deposited to test the model predictions. The optimum spraying conditions produced a coating with less than 4% oxide and less than 2.5% porosity. The process parameters which exhibited the most important effects directly on the oxide content in the coating were particle size, spray distance, and Ar flow rate. The parameters with the largest effects directly on porosity were spray distance, particle size, and current. The particle size, current, and Ar flow rate have an influence on particle velocity and temperature but spray distance did not have a significant effect on either of those characteristics. Thus, knowledge of the in-flight particle characteristics alone was not sufficient to control the final microstructure. The oxidation index and the melting index incorporate all the parameters that were found to be significant in the statistical analyses and correlate well with the measured oxide content and porosity in the coatings.

Azarmi, F.; Coyle, T. W.; Mostaghimi, J.

2008-03-01

370

Vacuum arc plasma thrusters with inductive energy storage driver  

NASA Technical Reports Server (NTRS)

A plasma thruster with a cylindrical inner and cylindrical outer electrode generates plasma particles from the application of energy stored in an inductor to a surface suitable for the formation of a plasma and expansion of plasma particles. The plasma production results in the generation of charged particles suitable for generating a reaction force, and the charged particles are guided by a magnetic field produced by the same inductor used to store the energy used to form the plasma.

Krishnan, Mahadevan (Inventor)

2009-01-01

371

Abrasive wear behavior of cast iron coatings plasma-sprayed at different mild steel substrate temperatures  

NASA Astrophysics Data System (ADS)

Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240°C, respectively. Abrasive wear tests were conducted on the coatings under a dry friction condition. It is found that the abrasive wear resistance is enhanced with the substrate temperature increasing. SEM observations show that the wear losses of the coatings during the wear tests mainly result from the spalling of the splats. Furthermore, the improved wear resistance of the coatings mainly owes to the formation of oxides and the enhancement in the mechanical properties with the substrate temperature increasing.

Xing, Ya-zhe; Wei, Qiu-lan; Jiang, Chao-ping; Hao, Jian-min

2012-08-01

372

Process, properties, and environmental response of plasma sprayed thermal barrier coatings  

NASA Technical Reports Server (NTRS)

Experimental results are shown which demonstrate that the properties of plasma sprayed fully stabilized zirconia are strongly influenced by the process parameters. Properties of the coatings in the as-sprayed condition are shown to be additionally influenced by environmental exposure. This behavior is dependent on raw material considerations and processing conditions as well as exposure time and temperature. Process control methodology is described which can take into consideration these complex interactions and help to produce thermal barrier coatings in a cost effective way while meeting coating technical requirements.

Novak, Richard C.

1995-01-01

373

Phase transformation and bond coat oxidation behavior of plasma-sprayed zirconia thermal barrier coating  

Microsoft Academic Search

ZrO2–CeO2–Y2O3 and ZrO2–Y2O3 thermal barrier coatings were prepared using the air plasma spray process. Phase transformation in the ceramic top coating, bond coat oxidation and thermal barrier properties were investigated to compare ZrO2–CeO2–Y2O3 with ZrO2–Y2O3 at 1300°C under high temperature thermal cycles. In the as-sprayed condition, both coatings showed a 7?11% porosity fraction and typical lamellar structures formed by continuous

C. H. Lee; H. K. Kim; H. S. Choi; H. S. Ahn

2000-01-01

374

An electron microscopy study of the effect of Ce on plasma sprayed bronze coatings  

NASA Astrophysics Data System (ADS)

The Cu-Al eutectoid alloy is an excellent material for mould due to its superior low friction. The conventional sand casting technique, however, is not feasible to fabricate high Al bronze because of high hardness and brittleness. Plasma arc spray has been used to produce high Al/Fe bronze coatings for mould. The inherent impurities such as H, O, N, S during the spray, however, may affect the coating's mechanical strength. One approach is to utilise the active rare earth Ce to clean up these impurities. The study is to investigate the effect of Ce on the microstructure, which has few reported in the literature.

Wensheng, Li; Wang, S. C.; Ma, Chao; Zhiping, Wang

2012-07-01

375

Modelling of plasma generation and expansion in a vacuum arc: application to the vacuum arc remelting process  

NASA Astrophysics Data System (ADS)

As part of a complete theoretical description of the behaviour of the electric arc in the vacuum arc remelting process, a model has been developed for the column of plasma generated by a single cluster of cathode spots. The model combines a kinetic approach, taking into account the formation of the plasma in the cathodic region, and a hydrodynamic approach, describing the expansion of the plasma in the vacuum between the electrodes. The kinetic model is based on a system of Boltzmann-Vlasov-Poisson equations and uses a particle-type simulation procedure, combining the PIC (particle in cell) and FPM (finite point set method) methods. In the two-dimensional hydrodynamic model, the plasma is assimilated to a mixture of two continuous fluids (the electrons and the ions), each described by a system of coupled transport equations. Finally, a simplified method has been defined for calculating the electric current density and the energy flux density transmitted by the plasma to the anode. The results of the numerical simulation presented are consistent with a certain number of experimental data available in the literature. In particular, the model predicts a percentage of the electric power of the cluster transmitted to the anode (25%) in good agreement with the value indicated in the literature.

Chapelle, P.; Bellot, J. P.; Duval, H.; Jardy, A.; Ablitzer, D.

2002-01-01

376

Plasma modeling of MFTF-B and the sensitivity to vacuum conditions  

SciTech Connect

The Mirror Fusion Test Facility (MFTF-B) is a large tandem mirror device currently under construction at Lawrence Livermore National Laboratory. The completed facility will consist of a large variety of components. Specifically, the vacuum vessel that houses the magnetic coils is basically a cylindrical vessel 60 m long and 11 m in diameter. The magnetics system consists of some 28 superconducting coils, each of which is located within the main vacuum vessel. Twenty of these coils are relatively simple solenoidal coils, but the remaining eight are of a more complicated design to provide an octupole component to certain regions of the magnetic field. The vacuum system is composed of a rough vacuum chain, used to evacuate the vessel from atmospheric pressure, and a high vacuum system, used to maintain good vacuum conditions during a plasma shot. High vacuum pumping is accomplished primarily by cryogenic panels cooled to 4.5/sup 0/K. The MFTF-B coil set is shown together with typical axial profiles of magnetic field (a), electrostatic potential (b), and plasma density (c). The plasma is divided into nine regions axially, as labelled on the coil set in Figure 1. The central cell, which is completely azimuthally symmetric, contains a large volume plasma that is confined by a combination of the magnetic fields and the electrostatic potentials in the yin-yang cell.

Porter, G.D.; Rensink, M.

1984-09-12

377

Atmospheric Plasma Spraying of High Melting Temperature Complex Perovskites for TBC Application  

NASA Astrophysics Data System (ADS)

High melting materials have always been very attractive candidates for materials development in thermal barrier coating (TBC) applications. Among these materials, complex perovskites with Ba(Mg1/3Ta2/3)O3 and La(Al1/4Mg1/2T1/4)O3 compositions have been developed and deposited in TBC systems by atmospheric plasma spraying. Spray parameters were optimized and in-flight particle temperatures were recorded using Accuraspray-g3 and DPV 2000. Plasma sprayed coatings were found to undergo non-stoichiometric decomposition of components which could have contributed to early failure of the coatings. Particle temperature diagnostics suggest that gun power of ~15 kW or lower where majority of the particles have already solidified upon impact to the substrate could probably prevent the decomposition of phases. Additionally, it has been found that the morphology of the powder feedstock plays a critical role during atmospheric plasma spraying of complex perovskites.

Jarligo, M. O.; Mack, D. E.; Mauer, G.; Vaßen, R.; Stöver, D.

2010-01-01

378

Surface characterization of plasma sprayed oxide materials: estimation of surface acidity using mass titration.  

PubMed

The aim of this study was to characterize the influence of plasma spraying on the point of zero charge (PZC) of Al2O3-, Cr2O3- and TiO2-based materials. PZC is one of the most important parameter, which describes the acidity of oxide material in aqueous environments. PZC values of several plasma sprayed oxides were determined using mass titration method. Studies were performed for initial spray powders and plasma sprayed coating materials. In addition, mass titration experiments were performed for water-washed and nonwashed samples. It was found that mass titration is a suitable method to estimate the surface acidity of relatively coarse sample powders. It was found for most of the studied materials that the limiting pH values (assumed to be close PZC) were close to those reported in literature for the PZC values of traditionally manufactured oxide materials. On the other hand, mass titration curves of some oxide samples showed unexpected deviation in curve shapes and limiting pH. These deviations were probably due to selective dissolution of sample contaminations or sample material. PMID:15271562

Harju, Mika; Levänen, Erkki; Mäntylä, Tapio

2004-08-15

379

Evaluation of methods to reduce bacteria concentrations in spray-dried animal plasma and its effects on nursery pig performance.  

PubMed

Four experiments with 1,040 weanling pigs (17 +/- 2 d of age at weaning) were conducted to evaluate the effects of spray-dried animal plasma source, drying technique, and methods of bacterial reduction on nursery pig performance. In Exp. 1, 180 barrows and gilts (initial BW 5.9 +/- 1.8 kg) were used to compare effects of animal plasma, animal plasma source, drying technique (spray-dried or freeze-dried), and plasma irradiation in nursery pig diets. From d 0 to 10, pigs fed diets containing irradiated spray-dried animal plasma had increased ADG and ADFI (P < 0.05) compared with pigs fed diets containing nonirradiated spray-dried animal plasma. Pigs fed irradiated animal plasma Sources 1 and 2 were similar in ADG and ADFI, but pigs fed animal plasma Source 1 had greater ADG (P < 0.05) than pigs fed animal plasma Source 2 and pigs not fed plasma. Pigs fed freeze-dried animal plasma had growth performance similar (P > 0.36) to pigs fed spray-dried animal plasma. Overall (d 0 to 24), pigs fed irradiated spray-dried animal plasma were heavier (P < 0.05) than pigs fed no animal plasma, whereas pigs fed nonirradiated spray-dried plasma were intermediate. In Exp. 2, 325 barrows and gilts (initial BW 5.8 +/- 1.7 kg) were used to compare the effects of irradiation or formaldehyde treatment of animal plasma and formaldehyde treatment of the whole diet. Pigs fed diets containing irradiated animal plasma had greater ADG (P < 0.05) than pigs fed nonirradiated plasma. Pigs fed formaldehyde-treated plasma had greater ADG and ADFI (P < 0.05) than pigs fed diets with either nonirradiated plasma or whole diet treated with formaldehyde. In Exp. 3 (360 barrows and gilts; initial BW 6.3 +/- 2.7 kg) and Exp. 4 (175 barrows and gilts; initial BW 6.1 +/- 1.7 kg), the irradiation of feed (high bacteria) and food-grade (low bacteria) animal plasma in nursery pig diets was examined. Pigs fed irradiated feed-grade plasma Product 2 had increased ADG (P < 0.05) compared with pigs fed nonirradiated plasma Product 2 and pigs fed the control diet without plasma. In Exp. 3 and 4, pigs fed irradiated food-grade plasma had growth performance similar to pigs fed nonirradiated food-grade plasma (P > 0.12). These studies indicate that bacterial reduction of feed-grade, but not food-grade animal plasma, improves nursery pig performance. PMID:14753369

DeRouchey, J M; Tokach, M D; Nelssen, J L; Goodband, R D; Dritz, S S; Woodworth, J C; James, B W; Webster, M J; Hastad, C W

2004-01-01

380

Nano-composite Si particle formation by plasma spraying for negative electrode of Li ion batteries  

NASA Astrophysics Data System (ADS)

Nano-composite silicon powders have been produced at a maximum process throughput of 6 g/min by plasma spraying with metallurgical grade silicon powder as raw material. The obtained powders are found to be fundamentally composed of crystalline silicon particles of 20-40 nm in diameter, and are coated with an ˜5-nm-thick amorphous carbonous layer when methane gas is additionally introduced during plasma spraying. The performance of half-cell batteries containing the powders as negative electrodes has shown that the capacity decay observed for the raw Si coarse particles is significantly improved by plasma treatment. The carbonous coating potentially contributes to an improvement in capacity retention, although coexisting SiC particles that inevitably form during high-temperature processing reduce the overall capacity.

Kambara, M.; Kitayama, A.; Homma, K.; Hideshima, T.; Kaga, M.; Sheem, K.-Y.; Ishida, S.; Yoshida, T.

2014-04-01

381

Plasma processing and synthesis of materials  

SciTech Connect

These proceedings compile papers about plasma. Topics include: Plasma arc spraying, vacuum melting, plasma melters for nuclear waste vitrification, thermal degradation of metal oxides in plasma, electrohydrodynamics, laser-induced fluorescence, measurements of temperature in plasma, and modeling and diagnostics in plasma processing.

Apelian, D.; Szekely, J.

1987-01-01

382

Robust Low Cost Aerospike/RLV Combustion Chamber by Advanced Vacuum Plasma Process  

NASA Technical Reports Server (NTRS)

Next-generation, regeneratively cooled rocket engines will require materials that can withstand high temperatures while retaining high thermal conductivity. At the same time, fabrication techniques must be cost efficient so that engine components can be manufactured within the constraints of a shrinking NASA budget. In recent years, combustion chambers of equivalent size to the Aerospike chamber have been fabricated at NASA-Marshall Space Flight Center (MSFC) using innovative, relatively low-cost, vacuum-plasma-spray (VPS) techniques. Typically, such combustion chambers are made of the copper alloy NARloy-Z. However, current research and development conducted by NASA-Lewis Research Center (LeRC) has identified a Cu-8Cr-4Nb alloy which possesses excellent high-temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability. In fact, researchers at NASA-LeRC have demonstrated that powder metallurgy (P/M) Cu-8Cr-4Nb exhibits better mechanical properties at 1,200 F than NARloy-Z does at 1,000 F. The objective of this program was to develop and demonstrate the technology to fabricate high-performance, robust, inexpensive combustion chambers for advanced propulsion systems (such as Lockheed-Martin's VentureStar and NASA's Reusable Launch Vehicle, RLV) using the low-cost, VPS process to deposit Cu-8Cr-4Nb with mechanical properties that match or exceed those of P/M Cu-8Cr-4Nb. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the hot wall of the liner during the VPS process. Tensile properties of Cu-8Cr-4Nb material produced by VPS are reviewed and compared to material produced previously by extrusion. VPS formed combustion chamber liners have also been prepared and will be reported on following scheduled hot firing tests at NASA-Lewis.

Holmes, Richard; Ellis, David; McKechnie

1999-01-01

383

Robust Low Cost Liquid Rocket Combustion Chamber by Advanced Vacuum Plasma Process  

NASA Technical Reports Server (NTRS)

Next-generation, regeneratively cooled rocket engines will require materials that can withstand high temperatures while retaining high thermal conductivity. Fabrication techniques must be cost efficient so that engine components can be manufactured within the constraints of shrinking budgets. Three technologies have been combined to produce an advanced liquid rocket engine combustion chamber at NASA-Marshall Space Flight Center (MSFC) using relatively low-cost, vacuum-plasma-spray (VPS) techniques. Copper alloy NARloy-Z was replaced with a new high performance Cu-8Cr-4Nb alloy developed by NASA-Glenn Research Center (GRC), which possesses excellent high-temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability. Functional gradient technology, developed building composite cartridges for space furnaces was incorporated to add oxidation resistant and thermal barrier coatings as an integral part of the hot wall of the liner during the VPS process. NiCrAlY, utilized to produce durable protective coating for the space shuttle high pressure fuel turbopump (BPFTP) turbine blades, was used as the functional gradient material coating (FGM). The FGM not only serves as a protection from oxidation or blanching, the main cause of engine failure, but also serves as a thermal barrier because of its lower thermal conductivity, reducing the temperature of the combustion liner 200 F, from 1000 F to 800 F producing longer life. The objective of this program was to develop and demonstrate the technology to fabricate high-performance, robust, inexpensive combustion chambers for advanced propulsion systems (such as Lockheed-Martin's VentureStar and NASA's Reusable Launch Vehicle, RLV) using the low-cost VPS process. VPS formed combustion chamber test articles have been formed with the FGM hot wall built in and hot fire tested, demonstrating for the first time a coating that will remain intact through the hot firing test, and with no apparent wear. Material physical properties and the hot firing tests are reviewed.

Holmes, Richard; Elam, Sandra; Ellis, David L.; McKechnie, Timothy; Hickman, Robert; Rose, M. Franklin (Technical Monitor)

2001-01-01

384

Robust Low Cost Liquid Rocket Combustion Chamber by Advanced Vacuum Plasma Process  

NASA Technical Reports Server (NTRS)

Next-generation, regeneratively cooled rocket engines require materials that can meet high temperatures while resisting the corrosive oxidation-reduction reaction of combustion known as blanching, the main cause of engine failure. A project was initiated at NASA-Marshal Space Flight Center (MSFC) to combine three existing technologies to build and demonstrate an advanced liquid rocket engine combustion chamber that would provide a 100 mission life. Technology developed in microgravity research to build cartridges for space furnaces was utilized to vacuum plasma spray (VPS) a functional gradient coating on the hot wall of the combustion liner as one continuous operation, eliminating any bondline between the coating and the liner. The coating was NiCrAlY, developed previously as durable protective coatings on space shuttle high pressure fuel turbopump (HPFTP) turbine blades. A thermal model showed that 0.03 in. NiCrAlY applied to the hot wall of the combustion liner would reduce the hot wall temperature 200 F, a 20% reduction, for longer life. Cu-8Cr-4Nb alloy, which was developed by NASA-Glenn Research Center (GRC), and which possesses excellent high temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability, was utilized as the liner material in place of NARloy-Z. The Cu-8Cr-4Nb material exhibits better mechanical properties at 650 C (1200 F) than NARloy-Z does at 538 C (1000 F). VPS formed Cu-8Cr-4Nb combustion chamber liners with a protective NiCrAlY functional gradient coating have been hot fire tested, successfully demonstrating a durable coating for the first time. Hot fire tests along with tensile and low cycle fatigue properties of the VPS formed combustion chamber liners and witness panel specimens are discussed.

Holmes, Richard; Elam, Sandra; McKechnie, Timothy; Hickman, Robert; Stinson, Thomas N. (Technical Monitor)

2002-01-01

385

Effect of Deposition Rate on the Stress Evolution of Plasma-Sprayed Yttria-Stabilized Zirconia  

NASA Astrophysics Data System (ADS)

The deposition rate plays an important role in determining the thickness, stress state, and physical properties of plasma-sprayed coatings. In this article, the effect of the deposition rate on the stress evolution during the deposition (named evolving stress) of yttria-stabilized zirconia coatings was systematically studied by varying the powder feed rate and the robot-scanning speed. The evolving stress during the deposition tends to increase with the increased deposition rate, and this tendency was less significant at a longer spray distance. In some cases, the powder feed rate had more significant influence on the evolving stress than the robot speed. This tendency can be associated with a deviation of a local deposition temperature at a place where sprayed particles are deposited from an average substrate temperature. At a further higher deposition rate, the evolving stress was relieved by introduction of macroscopic vertical cracks as well as horizontal branching cracks.

Shinoda, Kentaro; Colmenares-Angulo, Jose; Valarezo, Alfredo; Sampath, Sanjay

2012-12-01

386

Deposition of titanium nitride and hydroxyapatite-based biocompatible composite by reactive plasma spraying  

NASA Astrophysics Data System (ADS)

Titanium nitride is a bioceramic material successfully used for covering medical implants due to the high hardness meaning good wear resistance. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters. The paper presents the experimental results in obtaining composite layers of titanium nitride and hydroxyapatite by reactive plasma spraying in ambient atmosphere. X-ray diffraction analysis shows that in both cases of powders mixtures used (10% HA + 90% Ti; 25% HA + 75% Ti), hydroxyapatite decomposition occurred; in variant 1 the decomposition is higher compared with the second variant. Microstructure of the deposited layers was investigated using scanning electron microscope, the surfaces presenting a lamellar morphology without defects such as cracks or microcracks. Surface roughness values obtained vary as function of the spraying distance, presenting higher values at lower thermal spraying distances.

Ro?u, Radu Alexandru; ?erban, Viorel-Aurel; Bucur, Alexandra Ioana; Drago?, U?u

2012-02-01

387

The Effect of Spray-Dried Porcine Plasma on Growth Performance in the Early-Weaned Pig'f2  

Microsoft Academic Search

~ ~ ~ ~ ~ ~ ~~ ~ ABSTRACT: A total of 904 weanling pigs were used to investigate the effects of 1) spray-dried porcine plasma (SDPP), 2) blends of SDPP and spray-dried blood meal (SDBM), and 3) added dietary methionine in a SDPP-based diet on starter pig performance. In Exp. 1, 534 weanling pigs (initially 6.4 kg and 21

L. J. Kats; J. L. Nelssen; M. D. Tokach; R. D. Goodband; J. A. Hansen; J. L. Laurin

2009-01-01

388

Characterization of alumina scales formed during isothermal and cyclic oxidation of plasma-sprayed TBC systems at 1150 C  

SciTech Connect

The isothermal- and cyclic-oxidation behavior of thermal barrier coating (TBC) systems consisting of vacuum plasma-sprayed (VPS) Ni-22Cr-10Al/Y (wt%) bond coatings and air plasma-sprayed (APS) Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} (YSZ) top coatings (on single-crystal superalloys) was investigated. The microstructures, flaw contents, and fracture behavior of the Al{sub 2}O{sub 3} scales formed during oxidation testing at 1150 C were characterized (by analysis of coating and scale fracture surfaces and metallographic cross sections). Significant localized fracture and buckling of the Al{sub 2}O{sub 3} scales that formed along the bond-coat--top-coat interfaces were observed after cyclic oxidation of TBCs. However, substantial amounts of localized scale damage did not induce rapid TBC failure. Decohesion of the columnar alumina scales on the rough bond-coat surfaces occurred by both internal Al{sub 2}O{sub 3} fracture (parallel to the metal surface) and oxide-metal delamination. There were microstructural indications of Al{sub 2}O{sub 3} scale crack healing by sintering into planar arrays of voids. Alumina scales that formed on convex NiCrAlY surfaces (with radii of 50 {micro}m or less) after cyclic oxidation, whereas scales formed by isothermal oxidation contained few visible voids. Accelerated void growth in Al{sub 2}O{sub 3} scales on the irregular NiCrAlY surfaces appeared to be creep-related and was attributed to the synergistic effects of geometric and thermal stresses.

Haynes, J.A.; Ferber, M.K.; Porter, W.D. [Oak Ridge National Lab., TN (United States). High Temperature Materials Lab.] [Oak Ridge National Lab., TN (United States). High Temperature Materials Lab.; Rigney, E.D. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering] [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering

1999-08-01

389

Thermophysical processes in vacuum plasma electric furnaces for heating powdered materials  

Microsoft Academic Search

Vacuum hollow-cathode plasmatrons permit heating, melting, and refining of fine powders in plasma during the flight of particles from the introduction zone to a receiver. A powder in plasma is heated through its interaction with electrons and ions. Such a plasmatron exhibits the following performance characteristics: the total heat flow per particle is 10 6 ?10 7 W\\/m 2 ,

V. S. Cherednichenko; B. I. Yudin

2008-01-01

390

Characteristics of Ceramic Coatings Made by Thin Film Low Pressure Plasma Spraying (LPPS-TF)  

NASA Astrophysics Data System (ADS)

The thin film low pressure plasma spray process (LPPS-TF) has been developed with the aim of efficient depositing uniform and thin coatings with large area coverage by plasma spraying. At high power input (~150 kW) and very low pressure (~100 Pa) the plasma jet properties change considerably and it is even possible to evaporate the powder feedstock material providing advanced microstructures of the deposits. This relatively new technique bridges the gap between conventional plasma spraying and physical vapor deposition. In addition, the resulting microstructures are unique and can hardly be obtained by other processes. In this paper, microstructures made by LPPS-TF are shown and the columnar layer growth by vapor deposition is demonstrated. In addition to the ceramic materials TiO2, Al2O3 or MgAl2O4, the focus of the research was placed on partially yttria-stabilized zirconia. Variations of the microstructures are shown and discussed concerning potential coating applications.

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

2012-06-01

391

Plasma Spray Synthesis Of Nanostructured V2O5 Films For Electrical Energy Storage  

SciTech Connect

We demonstrate for the first time, the synthesis of nanostructured vanadium pentoxide (V2O5) films and coatings using plasma spray technique. V2O5 has been used in several applications such as catalysts, super-capacitors and also as an electrode material in lithium ion batteries. In the present studies, V2O5 films were synthesized using liquid precursors (vanadium oxychloride and ammonium metavanadate) and powder suspension. In our approach, the precursors were atomized and injected radially into the plasma gun for deposition on the substrates. During the flight towards the substrate, the high temperature of the plasma plume pyrolyzes the precursor particles resulting into the desired film coatings. These coatings were then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Differential Scanning Calorimetry (DSC). Among the precursors, vanadium oxychloride gave the best results in terms of nanocrystalline and monophasic films. Spraying of commercial powder suspension yielded multi-phasic mixture in the films. Our approach enables deposition of large area coatings of high quality nanocrystalline films of V2O5 with controllable particle morphology. This has been optimized by means of control over precursor composition and plasma spray conditions. Initial electrochemical studies of V2O5 film electrodes show potential for energy storage studies.

Nanda, Jagjit [ORNL

2011-01-01

392

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

393

Thermal barrier coatings on turbine blades by plasma spraying with improved cooling  

SciTech Connect

Turbine blades were coated with a thermal barrier coating system consisting of an MCrAlY bond coat about 100 [mu]m thick deposited by Low-Pressure Plasma Spraying (LPPS) and a 300 [mu]m thick ZrO[sub 2]-7 wt.% Y[sub 2]O[sub 3] top coat. The latter was manufactured by both Atmosphere and Temperature Controlled Spraying (ATCS) and Air Plasma Spraying (APS) using internal air cooling through the cooling holes of the turbine blades. Coated blades were submitted to thermal cycling tests in a burner rig with hot gas temperature of 1,485 C. In the case of ATCS coated blades the number of cycles until the first spallation at the leading edge of the blade was between 350 and 2,400. The number of cycles of the thermal barrier coatings sprayed with internal cooling was between 1,200 and 1,800. Furnace cycling tests were also carried out with ATCS coated blades at temperatures of 1,100 and 1,200 C. The results of thermal cycle tests and the investigations of the microstructure are discussed.

Cosack, T.; Schneiderbanger, S. (MTU Motoren- und Turbinen-Union, Munchen (Germany)); Pawlowski, L.; Sturlese, S. (CSM Centro Sviluppo Materiali, Pergine di Valsugana (Italy))

1994-01-01

394

MCrAlY Bondcoats by High-Velocity Atmospheric Plasma Spraying  

NASA Astrophysics Data System (ADS)

MCrAlY bondcoats (M = Co, Ni) are used to protect metallic substrates from oxidation and to improve adhesion of ceramic thermal barrier coatings for high temperature applications, such as in land-based and aviation turbines. Since MCrAlYs are prone to take up oxygen during thermal spraying, bondcoats often are manufactured under inert gas conditions at low pressure. Plasma spraying at atmospheric conditions is a cost-effective alternative if it would be possible to limit the oxygen uptake as well as to obtain sufficiently dense microstructures. In the present work, high-velocity spray parameters were developed for the TriplexPro 210 three-cathode plasma torch using MCrAlY powders of different particle size fractions to achieve these objectives. The aims are conflictive since the former requires cold conditions, whereas the latter is obtained by more elevated particle temperatures. High particle velocities can solve this divergence as they imply shorter time for oxidation during flight and contribute to coating densification by kinetic rather than thermal energy. Further aims of the experimental work were high deposition efficiencies as well as sufficient surface roughness. The oxidation behavior of the sprayed coatings was characterized by thermal gravimetric analyses and isothermal heat treatments.

Mauer, G.; Sebold, D.; Vaßen, R.

2014-01-01

395

Mechanical Properties of Yttria- and Ceria-Stabilized Zirconia Coatings Obtained by Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Plasma generated by the SG-100 torch was applied to spray suspension formulated with the use of ZrO2 + 8 wt.% Y2O3 (8YSZ) and ZrO2 + 24 wt.% CeO2 + 2.5 wt.% Y2O3 (24CeYSZ) as solid phases. The suspensions were formulated with the use of 20 wt.% solid phase, 40 wt.% water, and 40 wt.% ethanol. The plasma spray parameters were optimized by keeping constant: (a) the electric power of 40 kW and (b) the working gas compositions of 45 slpm for Ar and 5 slpm for H2. On the other hand, the spray distance was varied from 40 to 60 mm and the torch linear speed was varied from 300 to 500 mm/s. The coatings were sprayed onto stainless steel substrates, and their thicknesses were in the range from 70 to 110 ?m. The coating microstructures were analyzed with a scanning electron microscope. Mechanical properties were tested with the different methods including the indentation and scratch tests. The indentation test, carried out with various loads ranging from 100 to 10,000 mN, enabled to determine elastic modulus and Martens microhardness. Young's modulus of the coatings was in the range of 71-107 GPa for 8YSZ and 68-130 GPa for 24CeYSZ coatings. The scratch test enabled the authors to find the scratch macrohardness.

?atka, Leszek; Cattini, Andrea; Chicot, Didier; Paw?owski, Lech; Kozerski, Stefan; Petit, Fabrice; Denoirjean, Alain

2013-03-01

396

High Charge State Ions Extracted from Metal Plasmas in the Transition Regime from Vacuum Spark to High Current Vacuum Arc  

SciTech Connect

Metal ions were extracted from pulsed discharge plasmas operating in the transition region between vacuum spark (transient high voltage of kV) and vacuum arc (arc voltage ~;; 20 V). At a peak current of about 4 kA, and with a pulse duration of 8 ?s, we observed mean ion charges states of about 6 for several cathode materials. In the case of platinum, the highest average charge state was 6.74 with ions of charge states as high as 10 present. For gold we found traces of charge state 11, with the highest average charge state of 7.25. At currents higher than 5 kA, non-metallic contaminations started to dominate the ion beam, preventing further enhancement of the metal charge states.

Yushkov, Georgy Yu.; Anders, A.

2008-06-19

397

Effects of spray-dried animal plasma and immunoglobulins on performance of early weaned pigs1,2  

Microsoft Academic Search

Five experiments were conducted to evaluate the effects of dietary spray-dried porcine plasma (SDPP) and spray-dried bovine plasma (SDBP) and their various molecular weight fractions on perfor- mance of pigs weaned at approximately 14 or 21 d of age. In addition, the efficacy of various levels of the immunoglobulin G (IgG)-rich fraction of SDPP and SDBP were evaluated. Experiment 1

J. L. Pierce; G. L. Cromwell; M. D. Lindemann; L. E. Russell; E. M. Weaver

398

Effects of Spray-Dried Animal Plasma in Calf Milk Replacer on Health and Growth of Dairy Calves1  

Microsoft Academic Search

Male Holstein calves (n = 120) purchased from local dairy farms were fed one of three calf milk replacers for 42 d. Experimental milk replacers were formulated to contain whey protein concentrate (WPC) as the pri- maryproteinsourceorWPCplus5%spray-driedbovine plasma (SDBP) or spray-dried porcine plasma (SDPP). The SDPP was heated to remove heat-insoluble materi- als and provide products with similar IgG content.

J. D. Quigley III; T. M. Wolfe

2003-01-01

399

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

400

A study of wear resistance of plasma-sprayed and laser-remelted coatings on aluminium alloy  

Microsoft Academic Search

Two kinds of alloys Ni–Cr–B–Si and Ni–Cr–B–Si+WC were plasma sprayed onto aluminium alloy. The coatings were remelted successively with a CO2 laser. A comparison of the wear resistance properties of both laser-treated and plasma-sprayed samples with those of aluminium alloy was conducted. A scanning electron microscope (SEM) was used to analyse wear phenomena of samples. Experimental results showed that the

G. Y. Liang; T. T. Wong; J. M. K. MacAlpine; J. Y. Su

2000-01-01

401

An experimental and computational methodology for near net shape fabrication of thin walled ceramic structures by plasma spray forming  

Microsoft Academic Search

Near net shape (NNS) fabrication by plasma spray forming (PSF) is a rapid prototyping technique to fabricate engineering components having axi-symmetric geometry out of ceramics and refractory metals which are difficult to manufacture by conventional techniques. This study establishes an experimental and computational protocol to manufacture thin walled ceramic (Al2O3) structures on the graphite mandrel (substrate) via plasma spray forming.

Riken R. Patel; Anup Kumar Keshri; George S. Dulikravich; Arvind Agarwal

2010-01-01

402

Friction and wear characteristics of aluminum bronze coatings on steel substrates sprayed by a low pressure plasma technique  

Microsoft Academic Search

In the present research work, the tribological characteristics of low pressure plasma sprayed aluminum bronze coatings against steel ball (SUJ2), have been studied. The effects of different loads, as well as high speed and boundary lubrication conditions, have been examined using the sliding tester.The films were synthesized using a low-pressure plasma spraying technique under different operating conditions. The correlation between

S Alam; S Sasaki; H Shimura

2001-01-01

403

Stress distributions in plasma-sprayed thermal barrier coatings as a function of interface roughness and oxide scale thickness  

Microsoft Academic Search

During thermal cyclic loading, plasma-sprayed thermal barrier coatings (TBCs) often show failure within the top coat close to the interface. In all cases this results from crack propagation of pre-existing cracks near the bond coat (BC)–top coat interface. Stresses developing on a microscopic scale near the BC–TBC interface of plasma-sprayed thermal barrier coatings govern crack growth in an initial phase

M Ahrens; R Vaßen; D Stöver

2002-01-01

404

Wettability of Atmospheric Plasma Sprayed Fe, Ni, Cr and Their Mixture Coatings  

NASA Astrophysics Data System (ADS)

Wetting behaviors of plasma sprayed Fe, Ni, Cr and their mixture coatings were investigated. The contact angle of water droplets on the surfaces increases with time when the surfaces are exposed to air, with the highest value greater than 150°. To the best of our knowledge, this is the first report that superhydrophobicity can be achieved by one step plasma spraying. It is found that the feedstock particle size distribution has a significant influence on the coating morphology. For the mixture coating, a micro/submicro dual scale roughness is obtained. The carbon content in the surface is found increasing with time. Results of X-ray diffraction, X-ray photoelectron spectroscope analysis and heat treatment in CO2/Ar atmospheres suggest that the surface may contain some active ferrites which can decompose carbon dioxide into carbon. The origin of the superhydrophobicity is attributed to the accumulation of surface carbon materials and the dual scale roughness.

Li, Zhengfeng; Zheng, Yanjun; Zhao, Jing; Cui, Lishan

2012-03-01

405

Analysis of powder particles of high carbon cast iron after air plasma spraying  

NASA Astrophysics Data System (ADS)

Structure and phase analysis of high carbon cast iron prepared by plasma spraying was performed using X-ray diffraction and Mössbauer spectroscopy. The sprayed powder particles were trapped in liquid nitrogen to fix their composition during the flight from the plasma torch. The results show decarburization and oxidation of the powder. The carbon content decrease is more pronounced on surfaces of the particles. The fresh powder exhibits an anomalous magnetic transition from ferromagnetic to paramagnetic state during the sample cooling from room temperature down to 28 K. This effect was explained as result of high concentration of defects and strains. The long time ageing at room temperature caused transition to more stable phase composition and diminishing of the anomalous magnetic transition.

Schneeweiss, O.; Voleník, K.

2009-02-01

406

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

SciTech Connect

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.

Guidotti, R.A.

1999-12-22

407

The structure, properties and performance of plasma-sprayed beryllium for fusion applications  

SciTech Connect

Plasma-spray technology is under investigation as a method for producing high thermal conductivity beryllium coatings for use in magnetic fusion applications. Recent investigations have focused on optimizing the plasma-spray process for depositing beryllium coatings on damaged beryllium surfaces. Of particular interest has been optimizing the processing parameters to maximize the through-thickness thermal conductivity of the beryllium coatings. Experimental results will be reported on the use of secondary H{sub 2} gas additions to improve the melting of the beryllium powder and transferred-arc cleaning to improve the bonding between the beryllium coatings and the underlying surface. Information will also be presented on thermal fatigue tests which were done on beryllium coated ISX-B beryllium limiter tiles using 10 sec cycle times with 60 sec cooldowns and an International Thermonuclear Experimental Reactor (ITER) relevant divertor heat flux slightly in excess of 5 MW/m{sup 2}.

Castro, R.G.; Stanek, P.W.; Elliott, K.E. [and others

1995-09-01

408

Development of improved-durability plasma sprayed ceramic coatings for gas turbine engines  

NASA Technical Reports Server (NTRS)

As part of a NASA program to reduce fuel consumption of current commercial aircraft engines, methods were investigated for improving the durability of plasma sprayed ceramic coatings for use on vane platforms in the JT9D turbofan engine. Increased durability concepts under evaluation include use of improved strain tolerant microstructures and control of the substrate temperature during coating application. Initial burner rig tests conducted at temperatures of 1010 C (1850 F) indicate that improvements in cyclic life greater than 20:1 over previous ceramic coating systems were achieved. Three plasma sprayed coating systems applied to first stage vane platforms in the high pressure turbine were subjected to a 100-cycle JT9D engine endurance test with only minor damage occurring to the coatings.

Sumner, I. E.; Ruckle, D. L.

1980-01-01

409

Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low Young's modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400 °C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore coarsening and stiffening of the coating. In-situ measurements at 1400 °C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.

Guignard, Alexandre; Mauer, Georg; Vaßen, Robert; Stöver, Detlev

2012-06-01

410

Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation  

NASA Technical Reports Server (NTRS)

Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work.

Berndt, C. C.; Miller, R. A.

1984-01-01

411

A design of experiment study of plasma sprayed alumina-titania coatings  

SciTech Connect

An experimental study of the plasma spraying of alumina-titania powder is presented in this paper. This powder system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Coating experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and their effect on the resultant coating. The coatings were characterized by hardness and electrical tests, image analysis, and optical metallography. Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. The attributes of the coatings are correlated with the changes in operating parameters.

Steeper, T.J. (Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.); Varacalle, D.J. Jr.; Wilson, G.C. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Riggs, W.L. II (Tubal Cain Co., Loveland, OH (United States)); Rotolico, A.J.; Nerz, J.E. (Metco/Perkin-Elmer, Westbury, NY (United States))

1992-01-01

412

Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation  

SciTech Connect

Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work. 13 references.

Berndt, C.C.; Miller, R.A.

1984-07-01

413

Hybrid Plasma-Sprayed Thermal Barrier Coatings Using Powder and Solution Precursor Feedstock  

NASA Astrophysics Data System (ADS)

A novel approach of hybridizing the conventional atmospheric plasma spraying (APS) technique with the solution precursor plasma spray (SPPS) route to achieve thermal barrier coatings (TBCs) with tailored configurations is presented. Such a hybrid process can be conveniently adopted for forming composite, multi-layered and graded coatings employing simultaneous and/or sequential feeding of solution precursor as well as powder feedstock, yielding distinct TBC microstructures that bear promise to further extend coating durability. TBC specimens generated using conventional APS technique, the SPPS method and through APS-SPPS hybrid processing have been comprehensively characterized for microstructure, phase constitution, hardness and thermal cycling life, and the results were compared to demonstrate the advantages that can ensue from hybrid processing.

Joshi, S. V.; Sivakumar, G.; Raghuveer, T.; Dusane, R. O.

2014-04-01

414

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

SciTech Connect

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.

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

2012-10-01

415

A parallel implementation of a two-dimensional fluid laser plasma integrator for stratified plasma vacuum systems  

NASA Astrophysics Data System (ADS)

A two-dimensional fluid laser-plasma integrator for stratified plasma-vacuum systems is presented. Inside a plasma, a laser pulse can be longitudinally compressed from ten or more wave-lengths to one or two cycles. However, for physically realistic simulations, transversal effects have to be included, because transversal instabilities can destroy the pulse and transversal compression in the plasma as well as focusing in vacuum allows much higher intensities to be reached. In contrast to the one-dimensional case, where a two-step implementation of the Gautschi-type exponential integrator with constant step-size turned out to be sufficient, it is essential to enable changes of the time step-size for the two-dimensional case. The use of a one-step version of the Gautschi-type integrator, being accurate of second order independent of the highest frequencies arising in the system, is proposed. In vacuum this allows to take arbitrarily large time-steps. To optimize runtime and memory requirements within the plasma, a splitting of the Laplacian is suggested. This splitting allows to evaluate the matrix functions arising in the Gautschi-type method by one-dimensional Fourier transforms. It is also demonstrated how the different variants of the scheme can be parallelized. Numerical experiments illustrate the superior performance and accuracy of the integrator compared to the standard leap-frog method. Finally, we discuss the simulation of a layered plasma-vacuum structure using the new method.

Karle, Ch.; Schweitzer, J.; Hochbruck, M.; Spatschek, K. H.

2008-08-01

416

Plasma-sprayed coatings as surface treatments of aluminum and titanium adherends  

Microsoft Academic Search

Plasma-sprayed coatings have been evaluated as surface treatments for aluminum and titanium adherends. The best aluminum treatment is found to be a 50-?m thick blend of an aluminum-12% silicon alloy and polyester with 20-40% polyester. For FM-300M film adhesive, this coating gives a wedge test performance equivalent to phosphoric acid anodization (PAA). For FM-123 film adhesive, its performance is between

G. D. Davis; P. L. Whisnant; D. K. Shaffer; G. B. Groff; J. D. Venables

1995-01-01

417

Flexural properties of sandwich beams consisting of air plasma sprayed alloy 625 and nickel alloy foam  

Microsoft Academic Search

Sandwich structures are considered as viable engineering constructions due to their unique structural, physical, and mechanical\\u000a properties. An investigation of the mechanical characteristics of sandwich structures suitable for high temperature application\\u000a is presented. A process has developed to produce high temperature sandwich structures by depositing alloy 625 skins on Ni\\u000a alloy foam cores using air plasma spraying (APS). The experimental

F. Azarmi; T. W. Coyle; J. Mostaghimi

2009-01-01

418

Measurements of residual stress and bond strength of plasma sprayed laminated coatings  

Microsoft Academic Search

Laminated coatings of Al2O3-NiCrAl and Al2O3 + 13 wt% TiO2-NiCrAl were deposited on low carbon steel substrates by plasma spraying. The bond strengths of the coatings were measured by pull-off test, and the residual stresses in the outermost surface layers were measured by X-ray diffraction. The effect of additive SiO2 on bond strength and stress of the coatings in the

Yuanzheng Yang; Zhengyi Liu; Chengping Luo; Yuzhi Chuang

1997-01-01

419

Morphology and immersion behavior of plasma-sprayed hydroxyapatite/bioactive glass coatings.  

PubMed

A series of hydroxyapatite/bioactive glass (HA/BG) coatings have been plasma-sprayed on Ti6Al-4V substrate using HA/BG powders that were prepared by both sinter-granulation and direct mixing methods. The morphology and immersion behavior of these coatings in a simulated body fluid (SBF) were investigated. The results showed that in-house fabricated BG and sinter-granulated HA powders were irregularly shaped and dense. When 5 wt % or more BG was added in HA, the powder became rough and porous. X-ray diffraction (XRD) patterns showed that the presence of BG enhanced the decomposition of HA structure during fabrication of the powders. Reasonably high bond strengths were obtained from all coatings. The granulated type HA/BG coatings showed no significant differences in bond strength from the mixed type HA/BG coatings. The plasma spray process itself and the presence of BG enhanced the decomposition of apatite. Surface morphology of all sinter-granulated type coatings was similar to that of monolithic HA coating, that was comprised of patches of smooth and shiny glassy film and irregularly-shaped particles on its surface. The dissolution depth of plasma-sprayed coatings immersed in SBF was largely dependent on the type and composition of the coating. Granulated type HA/BG coatings were much less dissolvable than monolithic HA or mixed type HA/BG coatings. It seems that the presently used granulation method for the preparation of HA/BG powders plays a predominant role in determining the dissolution behavior of the plasma-sprayed coatings. PMID:15348047

Ding, S J; Ju, C P; Lin, J H

2000-03-01

420

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

NASA Technical Reports Server (NTRS)

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.

Eldridge, Jeffrey I.; Bencic, Timothy J.

2006-01-01

421

Biological effects of aluminium diffusion from plasma-sprayed alumina coatings  

Microsoft Academic Search

Plasma-sprayed alumina (Al2O3) coatings on metal stems of hip prostheses are used to favour bone apposition on the stem without fibrous interposition. We tested both in vitro and in vivo in rabbits, alumina coatings in order to evaluate the biological effect of this material on bone. Mice fibroblasts were grown on Al2O3-coated discs and time course of aluminium concentration was

P. Frayssinet; F. Tourenne; N. Rouquet; G. Bonel; P. Conte

1994-01-01

422

Efficacy of experimentally produced spray-dried plasma on infectivity of porcine circovirus type 2.  

PubMed

The value of incorporating spray-dried plasma (SDP) into the diet of weanling pigs to improve feed intake and growth performance has been well documented. However, limited work has been done to confirm that the spray-drying process eliminates all viral contaminates including porcine circovirus type 2 (PCV2). To determine the effect of spray-drying on PCV2 infectivity, colostrum-fed, crossbred, specific-pathogen-free (SPF) pigs were inoculated with PCV2-contaminated SDP intraperitoneally (SDP-IP) or by oral gavage (SDP-OG), inoculated intraperitoneally with PCV2-positive plasma (POS), or left uninoculated (NEG). The plasma used for the experimentally produced SDP was collected from a SPF pig experimentally infected with a PCV2b isolate. Pigs in the NEG group remained seronegative, and PCV2 viremia was not detected. All pigs in the POS group became PCV2 viremic by 14 d postinoculation (DPI) and seroconverted by 28 DPI. In the SDP-IP group, all pigs became viremic by 35 DPI and seroconverted by 49 DPI. In the SDP-OG group, all animals became viremic by 35 DPI and 2/3 pigs seroconverted by 35 DPI. There were no significant (P > 0.05) differences between anti-PCV2-IgG antibody sample-to-positive ratios among pigs in the POS, SDP-OG, or SDP-IP groups. This work provides direct evidence that the experimental spray-drying process used in this study was not effective in inactivating PCV2b in the plasma of a PCV2-infected pig based on a swine bioassay using PCV2-naïve pigs. This work suggests that SDP sourced from pigs could represent a biosecurity risk for the industry. PMID:20675601

Patterson, A R; Madson, D M; Opriessnig, T

2010-12-01

423

Spray-dried porcine plasma affects intestinal morphology and immune cell subsets of weaned pigs  

Microsoft Academic Search

The aim of this study was to evaluate the effects of dietary spray-dried porcine plasma (SDPP) on the productive performance, intestinal morphology and leukocyte cell subsets of piglets. Sixteen early-weaned piglets (20±2 d) were distributed into two dietary treatments: 1) free access to control diet or 2) 6% SDPP in the control diet instead of soy-protein concentrate. Intestinal morphometry of the

M. Nofrarías; E. G. Manzanilla; J. Pujols; X. Gibert; N. Majó; J. Segalés; J. Gasa

2007-01-01

424

Abrasive wear characteristics of plasma sprayed nanostructured alumina\\/titania coatings  

Microsoft Academic Search

In this paper, the plasma spray technique was used to deposit coatings with reconstituted nanostructured Al2O3\\/TiO2 powders. The abrasive wear resistance of the ceramic coatings was evaluated using diamond abrasives. The result showed that the abrasive wear resistance of the coatings produced using the nanostructured Al2O3\\/TiO2 powders is greatly improved compared with the coating produced using the conventional Al2O3\\/TiO2 powder

You Wang; Stephen Jiang; Meidong Wang; Shihe Wang; T. Danny Xiao; Peter R Strutt

2000-01-01

425

Tribological Behavior of Bronze Composite Coatings Obtained by Plasma Thermal Spraying  

Microsoft Academic Search

Bronze aluminum composite coatings containing different amounts of alumina were fabricated by plasma spray process and their\\u000a tribological properties were investigated using ball-on-disk (BOD) and rubber wheel (RW) tests at room temperature. Main wear\\u000a mechanisms in pure bronze coatings during the ball-on-disk friction test were abrasion and intersplat delamination. The addition\\u000a of alumina in bronze coatings clearly enhances their wear

J. M. Miguel; S. Vizcaino; C. Lorenzana; N. Cinca; J. M. Guilemany

2011-01-01

426

Microstructure and Wear Behavior of Conventional and Nanostructured Plasma-Sprayed WC-Co Coatings  

Microsoft Academic Search

WC-12%Co coatings were deposited by atmospheric plasma spraying using conventional and nanostructured powders and two secondary\\u000a plasmogenous gases (He and H2). Coating microstructure and phase composition were characterized using scanning electron microscopy (SEM), transmission\\u000a electron microscopy (TEM), and x-ray diffraction techniques (XRD) techniques. This study examined wear and friction properties\\u000a of the coatings under dry friction conditions. SEM was used

E. Sánchez; E. Bannier; M. D. Salvador; V. Bonache; J. C. García; J. Morgiel; J. Grzonka

2010-01-01

427

Preparation and antibacterial properties of plasma sprayed nano-titania\\/silver coatings  

Microsoft Academic Search

In this work, plasma sprayed nano-titania\\/silver coatings were deposited on titanium substrates to obtain an implant material having excellent antibacterial property. The surface characteristics of nano-titania\\/silver coatings were investigated by scanning electron microscopy, energy dispersive spectrometer, optical emission spectrometry and X-ray diffraction. The bioactivity of nano-titania\\/silver coatings was examined by simulated body fluid soaking test. The antibacterial activity against Escherichia

Baoe Li; Xuanyong Liu; Fanhao Meng; Jiang Chang; Chuanxian Ding

2009-01-01

428

Heat Transfer Applications of Meshless Local Petrov-Galerkin (MLPG) Method during Plasma Spray  

Microsoft Academic Search

In this work, a compact computational formulation is established based on the truly meshless method MLPG, and is firstly used\\u000a to solve steady and transient heat conductions of the plasma spray. The unknown function of temperature distribution is approximated\\u000a by moving least square approximation functions. These approximants are constructed by using a weight function, a polynomial\\u000a basis and a set

S. C. Wu; H. O. Zhang; G. L. Wang; W. S. Xia

429

Microstructural study of aluminum phosphate-sealed, plasma-sprayed chromium oxide coating  

Microsoft Academic Search

Microstructural characterization of aluminum phosphate-sealed, plasma-sprayed chromium oxide coating was carried out in order\\u000a to study the strengthening mechanisms of the aluminum phosphate sealant in the coating. Characterization was performed using\\u000a x-ray diffractometry, scanning electron microscopy, and analytical transmission electron microscopy. The structure of the\\u000a sealed coating was lamellar with columnar ?-Cr2O3 grains extending through the lamella thickness. Amorphous aluminum

Minnamari Vippola; Samppa Ahmaniemi; Petri Vuoristo; Toivo Lepistö; Tapio Mäntylä; Eva Olsson

2002-01-01

430

Wear behaviour of plasma-sprayed AlSi\\/B 4C composite coatings  

Microsoft Academic Search

This paper describes the wear behaviour of AlSi\\/B4C composite coatings with 0–25wt% B4C particles for diesel engine motors. These coatings were successfully fabricated on AlSi substrates using an atmospheric plasma spray technique. The produced samples were characterized by means of an optical microscope, scanning electron microscope and microhardness tester. The obtained results pointed out that an increase of B4C particles

Ozkan Sarikaya; Selahaddin Anik; Erdal Celik; S. Cem Okumus; Salim Aslanlar

2007-01-01

431

Residual stresses in plasma sprayed partially stabilised zirconia TBCs: influence of the deposition temperature  

Microsoft Academic Search

Yttria-partially stabilised zirconia (Y-PSZ) coatings were plasma sprayed in air on aluminium bars under controlled conditions of surface cooling. The effect of the deposition temperature (Tdep) on coating microstructure and residual stresses was studied. X-ray diffraction (XRD) line broadening analysis showed crystallites to be much smaller than the columnar grains visible on scanning electron microscopy micrographs. Moreover, the stabilising oxide

Paolo Scardi; Matteo Leoni; Luca Bertamini

1996-01-01

432

In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components  

SciTech Connect

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

Subramanian, Ramesh (Oviedo, FL)

2001-01-01

433

Fabrication of Aluminum Nitride Coating onto Carbon Steel Substrate by Reactive Plasma Spraying  

Microsoft Academic Search

Aluminum nitride (AlN) is one of the attractive ceramics in respect of its excellent properties. It was possible to fabricate Al\\/AlN composite coatings onto carbon steel substrate by reactive plasma spray process. However, most of the coatings, which include more nitride phase, peeled off due to the difference of thermal expansion coefficient between AlN and carbon steel. It might be

Hajime Nakamura; Motohiro Yamada; Masahiro Fukumoto; Toshiaki Yasui; Koyata Takahashi

2006-01-01

434

The Failure of Protective Oxides on Plasma-Sprayed NiCrAlY Overlay Coatings  

Microsoft Academic Search

The oxidation behavior in air of air-plasma sprayed (APS) overlay coatingsof Ni–25Cr–6Al–Y have been studied at 1100°C. Aprotective alumina scale developed after 5- to 10-hr exposure with, initially,parabolic growth kinetics. With protracted exposures (>100 hr),subparabolic behavior developed, associated with aluminum depletion withinthe coating caused, principally, by internal oxidation of the low-densityAPS structure. This depletion caused intrinsic chemical failure, manifestedby the

P. Niranatlumpong; C. B. Ponton; H. E. Evans

2000-01-01

435

Effect of the thickness of plasma-sprayed coating on bond strength and thermal fatigue characteristics  

Microsoft Academic Search

NiCrAlY bond coat and ZrO2–8 wt% Y2O3 top coat with various thicknesses were deposited on Hastelloy X by plasma spraying. Residual stress was calculated by the finite element method (FEM) to explain the variations in the bond strength and thermal fatigue characteristics with the thickness of the bond coat and top coat. The bond strength of thermal barrier coatings (TBCs)

H. M. Choi; B. S. Kang; W. K. Choi; D. G. Choi; S. K. Choi; J. C. Kim; Y. K. Park; G. M. Kim

1998-01-01

436

Studies on a combined reactive plasma sprayed\\/arc deposited duplex coating for titanium alloys  

Microsoft Academic Search

A new type of duplex layered coating especially developed for titanium alloys is described in this paper. This coating comprises a combination of a graded thick TixNy-based coating and a thin TiN top coat. The graded coating was obtained by reactive plasma spray (RPS) deposition of a Ti–4,5Al–3V–2Mo–2Fe powder onto a Ti6Al4V alloy substrate under an N2 atmosphere. Such a

F. Casadei; R. Pileggi; R. Valle; A. Matthews

2006-01-01

437

Highly durable thermal barrier coatings made by the solution precursor plasma spray process  

Microsoft Academic Search

The solution precursor plasma spray (SPPS) process offers the prospect of depositing highly durable thermal barrier coatings (TBCs) of low thermal conductivity. In this study, a Taguchi design of experiments was employed to optimize the SPPS process. The spallation life of SPPS TBCs on a MCrAlY bond coated Ni-base superalloy substrate deposited under the optimized processing conditions was demonstrated to

Maurice Gell; Liangde Xie; Xinqing Ma; Eric H. Jordan; Nitin P. Padture

2004-01-01

438

Microstructure of zirconia-yttria plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The objective of this paper is to report on the characterization of the highly complex microstructure of zirconia coatings,\\u000a which arise as a result of the plasma-spraying process. The fine structure has been observed to change through the thickness\\u000a of the coating, behaviour which has been related to the cooling rate and crystallization of the deposited material. Microstructural\\u000a features such

P. D. Harmsworth; R. Stevens

1992-01-01

439

Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 °C in flowing argon for 50 h was found to significantly increase the\\u000a thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy\\u000a (TEM) examination of the microstructures of

Rollie Dutton; Robert Wheeler; K. S. Ravichandran; K. An

2000-01-01

440

Thermal properties of plasma-sprayed functionally graded thermal barrier coatings  

Microsoft Academic Search

Plasma-sprayed thermal barrier coatings often have the problems of spallation and cracking in service owing to their poor bond strength and high residual stresses. Functionally graded thermal barrier coatings with a gradual compositional variation from heat resistant ceramics to fracture-resistant metals are proposed to mitigate these problems. In this paper, functionally graded yttria stabilized ZrO2\\/NiCoCrAlY coatings were prepared using pre-alloyed

K. A Khor; Y. W Gu

2000-01-01

441

Influence of isothermal and cyclic heat treatments on the adhesion of plasma sprayed thermal barrier coatings  

Microsoft Academic Search

The adhesion of thermal barrier coatings (TBC) has been studied using the standard method described in ASTM C633, which makes use of a tensile test machine to measure the adhesion. The studied specimens consist of air plasma sprayed (APS) TBC deposited on disc-shaped substrates of Ni-base alloy Hastelloy X. The bond coat (BC) is of a NiCoCrAlY type and the

Robert Eriksson; Håkan Brodin; Sten Johansson; Lars Östergren; Xin-Hai Li

2011-01-01

442

Plasma-sprayed graded ceramic coatings on refractory materials for improved chemical resistance  

Microsoft Academic Search

Plasma-sprayed ceramic coatings were manufactured on sintered alumina–mullite refractory bricks to improve their chemical resistance to molten glass. Mullite and alumina powders were employed. Graded layered coatings were designed and produced, to reduce the thermal expansion mismatch with the substrate: in all cases, the upper layer consisted in pure alumina (very resistant to chemical attack); alumina–mullite intermediate layers were added

G. Bolelli; V. Cannillo; C. Lugli; L. Lusvarghi; T. Manfredini

2006-01-01

443

Phase composition and its changes during annealing of plasma-sprayed YSZ  

Microsoft Academic Search

The phase composition of plasma-sprayed yttria stabilized zirconia (YSZ), ZrO2 with 8% by mass Y2O3, was studied using neutron and X-ray diffraction. Comparison shows that neutron diffraction is superior for analysis of the phase composition as well as for the analysis of the yttria content of the tetragonal phase. The presence of large amounts of the cubic phase is probably

Jan Ilavsky; Judith K. Stalick

2000-01-01

444

Some observations on the high temperature oxidation behaviour of plasma sprayed Ni 3Al coatings  

Microsoft Academic Search

High temperature oxidation resistance of the superalloys can be greatly enhanced by plasma sprayed coatings and this is a growing industry of considerable economic importance. The purpose of these coatings is to form long-lasting oxidation protective scales. In the current investigation, Ni3Al powder was prepared by mechanical mixing of pure nickel and aluminium powders in a ball mill. Subsequently Ni3Al

H. Singh; S. Prakash; D. Puri

2007-01-01

445

Miniature pulsed vacuum arc plasma gun and apparatus for thin-film fabrication  

DOEpatents

A miniature (dime-size in cross-section) vapor vacuum arc plasma gun is described for use in an apparatus to produce thin films. Any conductive material can be layered as a film on virtually any substrate. Because the entire apparatus can easily be contained in a small vacuum chamber, multiple dissimilar layers can be applied without risk of additional contamination. The invention has special applications in semiconductor manufacturing.

Brown, Ian G. (Berkeley, CA); MacGill, Robert A. (Richmond, CA); Galvin, James E. (Emmeryville, CA); Ogletree, David F. (El Cerrito, CA); Salmeron, Miquel (El Cerrito, CA)

1998-01-01

446

Miniature pulsed vacuum arc plasma gun and apparatus for thin-film fabrication  

DOEpatents

A miniature (dime-size in cross-section) vapor vacuum arc plasma gun is described for use in an apparatus to produce thin films. Any conductive material can be layered as a film on virtually any substrate. Because the entire apparatus can easily be contained in a small vacuum chamber, multiple dissimilar layers can be applied without risk of additional contamination. The invention has special applications in semiconductor manufacturing. 8 figs.

Brown, I.G.; MacGill, R.A.; Galvin, J.E.; Ogletree, D.F.; Salmeron, M.

1998-11-24

447

Tailored plasma sprayed MCrAlY coatings for aircraft gas turbine applications  

NASA Technical Reports Server (NTRS)

Eighteen plasma sprayed coating systems, nine based on the NiCoCrAly chemistry and nine based on the CoCrAly composition, were evaluated to identify coating systems which provide equivalent or superior life to that shown by the electron beam physical vapor deposited NiCoCrAly and CoCrAly coatings respectively. NiCoCrAly type coatings were examined on a single crystal alloy and the CoCrAly based coatings were optimized on the B1900+ Hf alloy. Cyclic burner rig oxidation and hot corrosion and tensile ductility tests used to evaluate the various coating candidates. For the single crystal alloy, a low pressure chamber plasma sprayed NiCoCrAly + Si coating exhibited a 2x oxidation life improvement at 1394 K (2050 F) over the vapor deposited NiCoCrAly material while showing equivalent tensile ductility. A silicon modified low pressure chamber plasma sprayed CoCrAly coating was found to be more durable than the baseline vapor deposited CoCrAly coating on the B1900+ Hf alloy.

Pennisi, F. J.; Gupta, D. K.

1981-01-01

448

Mechanical and Tribological Behavior of Ni(Al)-Reinforced Nanocomposite Plasma Spray Coatings  

NASA Astrophysics Data System (ADS)

The mechanical and tribological behavior and microstructural evolutions of the Ni(Al)-reinforced nanocomposite plasma spray coatings were studied. At first, the feedstock Ni(Al)-15 wt.% (Al2O3-13% TiO2) nanocomposite powders were prepared using low-energy mechanical milling of the pure Ni and Al powders as well as Al2O3-13% TiO2 nanoparticle mixtures. The characteristics of the powder particles and the prepared coatings depending on their microstructures were examined in detail. The results showed that the feedstock powders after milling contained only ?-Ni solid solution with no trace of the intermetallic phase. However, under the air plasma spraying conditions, the NiAl intermetallic phase in the ?-Ni solid solution matrix appeared. The lack of nickel aluminide formation during low-energy ball milling is beneficial hence, the exothermic reaction can occur between Ni and Al during plasma spraying, improving the adhesive strength of the nanocomposite coatings. The results also indicated that the microhardness of the ?-Ni phase was 3.91 ± 0.23 GPa and the NiAl intermetallic phase had a mean microhardness of 5.69 ± 0.12 GPa. The high microhardness of the nanocomposite coatings must be due to the presence of the reinforcing nanoparticles. Due to the improvement in mechanical properties, the Ni(Al) nanocomposite coatings showed significant modifications in wear resistance with low frictional coefficient.

Movahedi, B.

2014-02-01

449

Bulk electrical conductivity of plasma-sprayed insulators exposed to cesium vapor  

SciTech Connect

A thin layer of plasma-sprayed alumina is used in single cell thermionic fuel elements to provide electrical insulation of the outer surface of the collector from ground. Under normal operating conditions this material is not exposed to cesium vapor. However under abnormal conditions, such as the leaking of a TFE seal, the plasma-sprayed insulator surface may be expected to come into contact with cesium. The porous nature of these materials raises the concern that the metal vapor may penetrate beyond the surface and degrade the bulk electrical resistance properties. In this paper we describe experiments to determine the effect of cesium vapor on the bulk electrical conductivity of two different plasma-sprayed insulators: alumina and magnesium aluminate spinel. The results clearly demonstrate that cesium is easily able to penetrate beyond the surface and into the bulk of these materials and does indeed cause a dramatic increase in the bulk electrical conductivity. This effect may be a potential degradation mechanism for thermionic reactor systems operated over an extended period. {copyright} {ital 1996 American Institute of Physics.}

Agnew, P.; Ing, J.L. [AEA Technology, Topaz International Program, 901 University Blvd. SE, Albuquerque, New Mexico 87106-4439 (United States); Olson, D. [Team Specialty Services Corporation, 11030 Cochiti SE, Albuquerque, New Mexico 87123 (United States)

1996-03-01

450

Copper-titanium diboride coatings obtained by plasma spraying reactive micropellets  

NASA Astrophysics Data System (ADS)

Electrotribological applications require materials with both high electrical conductivity and wear resisance. For this purpose, a copper- base plasma sprayed coating containing titanium diboride particles was developed. The process for fabricating this CU- TiB2 coating consists of plasma spraying reactive powders that contain a Cu- Ti alloy and boron. The reaction between the copper alloy and boron proceeds in different steps going from solid- state diffusion of titanium and copper to the synthesis of TiB2 in a liquid below 1083 ‡C. Plasma sprayed copper coatings contain finer TiB2 crystals than Cu- TiB2 materials synthesized in a furnace at 1200 ‡C. Coatings with 25 vol% TiB2 have hardnesses that are comparable to Cu- Co- Be and Cu- Ni- Be alloys and to Cu- W and Cu- Mo alloys used in spot welding. Their low electrical resistivity of 52 ?? cm could be increased by lowering the oxygen content with coatings and controlling the formation of TiB2 clusters, the titanium content in solution in copper remaining low after the synthesis reaction.

Legoux, J. G.; Dallaire, S.

1993-09-01

451

Bond-coating in plasma-sprayed calcium-phosphate coatings.  

PubMed

The influence of bond-coating on the mechanical properties of plasma-spray coatings of hydroxyatite on Ti was investigated. Plasma-spray powder was produced from human teeth enamel and dentine. Before processing the main apatite coating, a very thin layer of Al2O3/TiO2 was applied on super clean and roughened, by Al2O3 blasting, Ti surface as bond-coating. The experimental results showed that bond-coating caused significant increase of the mechanical properties of the coating layer: In the case of the enamel powder from 6.66 MPa of the simple coating to 9.71 MPa for the bond-coating and in the case of the dentine powder from 6.27 MPa to 7.84 MPa, respectively. Both tooth derived powders feature high thermal stability likely due to their relatively high content of fluorine. Therefore, F-rich apatites, such those investigated in this study, emerge themselves as superior candidate materials for calcium phosphate coatings of producing medical devices. The methods of apatite powder production and shaping optimization of powder particles are both key factors of a successful coating. The methods used in this study can be adopted as handy, inexpensive and reliable ways to produce high quality of powders for plasma spray purposes. PMID:17122932

Oktar, F N; Yetmez, M; Agathopoulos, S; Lopez Goerne, T M; Goller, G; Peker, I; Ipeker, I; Ferreira, J M F

2006-11-01

452

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

PubMed

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