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Sample records for barrier coating deposited

  1. Combustion chemical vapor deposited coatings for thermal barrier coating systems

    SciTech Connect

    Hampikian, J.M.; Carter, W.B.

    1995-12-31

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.

  2. Thermal Barrier Coatings Resistant to Glassy Deposits

    NASA Astrophysics Data System (ADS)

    Drexler, Julie Marie

    Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

  3. Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings

    SciTech Connect

    Hollis, Kendall J; Pena, Maria I

    2010-01-01

    Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

  4. Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Haven, Victor E.

    1999-01-01

    Ceramic thermal barrier coatings extend the operating temperature range of actively cooled gas turbine components, therefore increasing thermal efficiency. Performance and lifetime of existing ceram ic coatings are limited by spallation during heating and cooling cycles. Spallation of the ceramic is a function of its microstructure, which is determined by the deposition method. This research is investigating metalorganic chemical vapor deposition (MOCVD) of yttria stabilized zirconia to improve performance and reduce costs relative to electron beam physical vapor deposition. Coatings are deposited in an induction-heated, low-pressure reactor at 10 microns per hour. The coating's composition, structure, and response to the turbine environment will be characterized.

  5. In-situ formation of multiphase deposited thermal barrier coatings

    DOEpatents

    Subramanian, Ramesh

    2004-01-13

    A multiphase ceramic thermal barrier coating is provided. The coating is adapted for use in high temperature applications in excess of about 1200.degree. C., for coating superalloy components of a combustion turbine engine. The coating comprises a ceramic single or two oxide base layer disposed on the substrate surface; and a ceramic oxide reaction product material disposed on the base layer, the reaction product comprising the reaction product of the base layer with a ceramic single or two oxide overlay layer.

  6. CMAS Interactions with Advanced Environmental Barrier Coatings Deposited via Plasma Spray- Physical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Harder, B. J.; Wiesner, V. L.; Zhu, D.; Johnson, N. S.

    2017-01-01

    Materials for advanced turbine engines are expected to have temperature capabilities in the range of 1370-1500C. At these temperatures the ingestion of sand and dust particulate can result in the formation of corrosive glass deposits referred to as CMAS. The presence of this glass can both thermomechanically and thermochemically significantly degrade protective coatings on metallic and ceramic components. Plasma Spray- Physical Vapor Deposition (PS-PVD) was used to deposit advanced environmental barrier coating (EBC) systems for investigation on their interaction with CMAS compositions. Coatings were exposed to CMAS and furnace tested in air from 1 to 50 hours at temperatures ranging from 1200-1500C. Coating composition and crystal structure were tracked with X-ray diffraction and microstructure with electron microscopy.

  7. Degradation of Thermal Barrier Coatings from Deposits and Its Mitigation

    SciTech Connect

    Nitin Padture

    2011-12-31

    Ceramic thermal barrier coatings (TBCs) used in gas-turbine engines afford higher operating temperatures, resulting in enhanced efficiencies and performance. However, in the case of syngas-fired engines, fly ash particulate impurities that may be present in syngas can melt on the hotter TBC surfaces and form glassy deposits. These deposits can penetrate the TBCs leading to their failure. In experiments using lignite fly ash to simulate these conditions we show that conventional TBCs of composition 93wt% ZrO{sub 2} + 7wt% Y{sub 2}O{sub 3} (7YSZ) fabricated using the air plasma spray (APS) process are completely destroyed by the molten fly ash. The molten fly ash is found to penetrate the full thickness of the TBC. The mechanisms by which this occurs appear to be similar to those observed in degradation of 7YSZ TBCs by molten calcium-magnesium-aluminosilicate (CMAS) sand and by molten volcanic ash in aircraft engines. In contrast, APS TBCs of Gd{sub 2Zr{sub 2}O{sub 7} composition are highly resistant to attack by molten lignite fly ash under identical conditions, where the molten ash penetrates ~25% of TBC thickness. This damage mitigation appears to be due to the formation of an impervious, stable crystalline layer at the fly ash/Gd{sub 2}Zr{sub 2}O{sub 7} TBC interface arresting the penetrating moltenfly- ash front. Additionally, these TBCs were tested using a rig with thermal gradient and simultaneous accumulation of ash. Modeling using an established mechanics model has been performed to illustrate the modes of delamination, as well as further opportunities to optimize coating microstructure. Transfer of the technology was developed in this program to all interested parties.

  8. Deposition stress effects on thermal barrier coating burner rig life

    NASA Technical Reports Server (NTRS)

    Watson, J. W.; Levine, S. R.

    1984-01-01

    A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

  9. High Temperature Multilayer Environmental Barrier Coatings Deposited Via Plasma Spray-Physical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Harder, Bryan James; Zhu, Dongming; Schmitt, Michael P.; Wolfe, Douglas E.

    2014-01-01

    Si-based ceramic matrix composites (CMCs) require environmental barrier coatings (EBCs) in combustion environments to avoid rapid material loss. Candidate EBC materials have use temperatures only marginally above current technology, but the addition of a columnar oxide topcoat can substantially increase the durability. Plasma Spray-Physical Vapor Deposition (PS-PVD) allows application of these multilayer EBCs in a single process. The PS-PVD technique is a unique method that combines conventional thermal spray and vapor phase methods, allowing for tailoring of thin, dense layers or columnar microstructures by varying deposition conditions. Multilayer coatings were deposited on CMC specimens and assessed for durability under high heat flux and load. Coated samples with surface temperatures ranging from 2400-2700F and 10 ksi loads using the high heat flux laser rigs at NASA Glenn. Coating morphology was characterized in the as-sprayed condition and after thermomechanical loading using electron microscopy and the phase structure was tracked using X-ray diffraction.

  10. Investigation of failure mechanism of thermal barrier coatings (TBCs) deposited by EB-PVD technique

    NASA Astrophysics Data System (ADS)

    Shahid, M. R.; Abbas, Musharaf

    2013-06-01

    Failure mechanism of thermal barrier coatings (TBCs) prepared by electron beam physical vapor deposition (EB-PVD) technique owing to formation of micro cracks was investigated. The TBCs were deposited on the Ni-based super alloy IN-100 and the micro cracks were observed within the top ceramic coat of thermally cycled TBCs at 1050°C. It was observed that these cracks propagate in the ceramic coat in the direction normal to interface while no cracks were observed in the bond coat. SEM/EDS studies revealed that some non-uniform oxides were formed on the interface between ceramic top and metallic bond coat just below the cracks. Study proposed that the cracks were initiated due to stress owing to big difference in Pilling-Bed worth ratio of non-uniform oxides as well as thermal stress, which caused the formation of cracks in top ceramic coat leading to failure of TBCs

  11. Development of Diffusion barrier coatings and Deposition Technologies for Mitigating Fuel Cladding Chemical Interactions (FCCI)

    SciTech Connect

    Sridharan, Kumar; Allen, Todd; Cole, James

    2013-02-27

    The goal of this project is to develop diffusion barrier coatings on the inner cladding surface to mitigate fuel-cladding chemical interaction (FCCI). FCCI occurs due to thermal and radiation enhanced inter-diffusion between the cladding and fuel materials, and can have the detrimental effects of reducing the effective cladding wall thickness and lowering the melting points of the fuel and cladding. The research is aimed at the Advanced Burner Reactor (ABR), a sodium-cooled fast reactor, in which higher burn-ups will exacerbate the FCCI problem. This project will study both diffusion barrier coating materials and deposition technologies. Researchers will investigate pure vanadium, zirconium, and titanium metals, along with their respective oxides, on substrates of HT-9, T91, and oxide dispersion-strengthened (ODS) steels; these materials are leading candidates for ABR fuel cladding. To test the efficacy of the coating materials, the research team will perform high-temperature diffusion couple studies using both a prototypic metallic uranium fuel and a surrogate the rare-earth element lanthanum. Ion irradiation experiments will test the stability of the coating and the coating-cladding interface. A critical technological challenge is the ability to deposit uniform coatings on the inner surface of cladding. The team will develop a promising non-line-of-sight approach that uses nanofluids . Recent research has shown the feasibility of this simple yet novel approach to deposit coatings on test flats and inside small sections of claddings. Two approaches will be investigated: 1) modified electrophoretic deposition (MEPD) and 2) boiling nanofluids. The coatings will be evaluated in the as-deposited condition and after sintering.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  13. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    NASA Astrophysics Data System (ADS)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  14. A thick multilayer thermal barrier coating: Design, deposition, and internal stresses

    NASA Astrophysics Data System (ADS)

    Samadi, Hamed

    Yttria Partially Stabilized Zirconia (Y-PSZ) plasma-sprayed coatings are widely used in turbine engines as thermal barrier coatings. However, in diesel engines Y-PSZ TBCs have not met with wide success. To reach the desirable temperature of 850-900°C in the combustion chamber from the current temperature of 400-600°C, a coating with a thickness of approximately 1mm is required. This introduces different considerations than in the case of turbine blade coatings, which are on the order of 100mum thick. Of the many factors affecting the durability and failure mechanism of TBCs, in service and residual stresses play an especially important role as the thickness of the coating increases. For decreasing the residual stress in the system, a multi-layer coating is helpful. The design of a multilayer coating employing relatively low cost materials with complementary thermal properties is described. Numerical models were used to describe the residual stress after deposition and under operating conditions for a multilayer coating that exhibited the desired temperature gradient. Results showed that the multilayer coating had a lower maximum stress under service conditions than a conventional Y-PSZ coating. Model validation with experiments showed a good match between the two.

  15. Mechanisms of degradation and failure in a plasma deposited thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Demasi-Marcin, Jeanine T.; Sheffler, Keith D.; Bose, Sudhangshu

    1989-01-01

    Failure of a two layer plasma deposited thermal barrier coating is caused by cyclic thermal exposure and occurs by spallation of the outer ceramic layer. Spallation life is quantitatively predictable, based on the severity of cyclic thermal exposure. This paper describes and attempts to explain unusual constitutive behavior observed in the insulative ceramic coating layer, and presents details of the ceramic cracking damage accumulation process which is responsible for spallation failure. Comments also are offered to rationalize the previously documented influence of interfacial oxidation on ceramic damage accumulation and spallation life.

  16. Mechanistic Study on the Degradation of Thermal Barrier Coatings Induced by Volcanic Ash Deposition

    NASA Astrophysics Data System (ADS)

    Arai, Masayuki

    2017-08-01

    Thermal stress generated on thermal barrier coatings (TBCs) by volcanic ash (VA) deposition was assessed measuring the tip deflection of a multilayered beam structure as a function of temperature. The TBC in this study was deposited onto the surface of a blade utilized in a land-based gas turbine which is composed of 8 wt.%Y2O3-ZrO2/CoNiCrAlY on a Ni-based superalloy. The VA-deposited TBC sample was heated at 1453 K, and the effect of VA deposition on TBC delamination was examined in comparison with a TBC sample without VA deposition as a reference. On the basis of the VA attack damage mechanism which was investigated via the tip deflection measurement and a comprehensive microstructure examination, a damage-coupled constitutive model was proposed. The proposed model was based on the infiltration of the molten VA inside pores and phase transformations of yttria -tabilized zirconia in the TBC system. The numerical analysis results, which were simulated utilizing the finite element code installing the developed constitutive model, showed us that VA attack on the TBC sample induced near-interfacial cracks because of a significant increasing in the coating stress.

  17. Mechanism of spallation in platinum aluminide/electron beam physical vapor-deposited thermal barrier coatings

    SciTech Connect

    Gell, M.; Vaidyanathan, K.; Barber, B.; Cheng, J.; Jordan, E.

    1999-02-01

    The spallation failure of a commercial thermal barrier coating (TBC), consisting of a single-crystal RENE N5 superalloy, a platinum aluminide (Pt-Al) bond coat, and an electron beam-deposited 7 wt pct yttria-stabilized zirconia ceramic layer (7YSZ), was studied following cyclic furnace testing. In the uncycled state and prior to deposition of the ceramic, the Pt-Al bond-coat surface contains a cellular network of ridges corresponding to the underlying bond-coat grain-boundary structure. With thermal cycling, the ridges and associated grain boundaries are the sites of preferential oxidation and cracking, which results in the formation of cavities that are partially filled with oxide. Using a fluorescent penetrant dye in conjunction with a direct-pull test, it is shown that, when specimens are cycled to about 80 pct of life, these grain-boundary regions show extensive debonding. The roles of oxidation and cyclic stress in localized grain boundary region spallation are discussed. The additional factors leading to large-scale TBC spallation are described.

  18. Failure mechanisms of platinum aluminide bond coat/electron beam-physical vapor deposited thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Vaidyanathan, Krishnakumar

    Thermal barrier coatings (TBCs) allow operation of structural components, such as turbine blades and vanes in industrial and aircraft gas engines, at temperatures close to the substrate melting temperatures. They consist of four different layers; a high strength creep-resistant nickel-based superalloy substrate, an oxidation resistant bond coat (BC), a low thermal conductivity ceramic topcoat and a thermally grown oxide (TGO), that is predominantly alpha-Al 2O3, that forms between the BC and the TBC. Compressive stresses (3--5 GPa) that are generated in the thin TGO (0.25--8 mum) due to the mismatch in thermal coefficient of expansion between the TGO and BC play a critical role in the failure of these coatings. In this study, the failure mechanisms of a commercial yttria-stabilized zirconia (7YSZ) electron beam-physical vapor deposited (EB-PVD) coating on platinum aluminide (beta-(Ni,Pt)Al) bond coat have been identified. Two distinct mechanisms have been found responsible for the observed damage initiation and progression at the TGO/bond coat interface. The first mechanism leads to localized debonding at TGO/bond coat interface due to increased out-of-plane tensile stress, along bond coat features that manifest themselves as ridges. The second mechanism causes cavity formation at the TGO/bond coat interface, driven by cyclic plasticity of the bond coat. It has been found that the debonding at the TGO/bond coat interface due to the first mechanism is solely life determining. The final failure occurs by crack extension along either the TGO/bond coat interface or the TGO/YSZ interface or a combination of both, leading to large scale buckling. Based on these mechanisms, it is demonstrated that the bond coat grain size and the aspect ratio of the ridges have a profound influence on spallation lives of the coating. The removal of these ridges by fine polishing prior to TBC deposition led to a four-fold improvement in life. The failure mechanism identified for the

  19. Novel Prospects for Plasma Spray-Physical Vapor Deposition of Columnar Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Anwaar, Aleem; Wei, Lianglinag; Guo, Qian; Zhang, Baopeng; Guo, Hongbo

    2017-09-01

    Plasma spray-physical vapor deposition (PS-PVD) is an emerging coating technique that can produce columnar thermal barrier coatings from vapor phase. Feedstock treatment at the start of its trajectory in the plasma torch nozzle is important for such vapor-phase deposition. This study describes the effects of the plasma composition (Ar/He) on the plasma characteristics, plasma-particle interaction, and particle dynamics at different points spatially distributed inside the plasma torch nozzle. The results of calculations show that increasing the fraction of argon in the plasma gas mixture enhances the momentum and heat flow between the plasma and injected feedstock. For the plasma gas combination of 45Ar/45He, the total enthalpy transferred to a representative powder particle inside the plasma torch nozzle is highest ( 9828 kJ/kg). Moreover, due to the properties of the plasma, the contribution of the cylindrical throat, i.e., from the feed injection point (FIP) to the start of divergence (SOD), to the total transferred energy is 69%. The carrier gas flow for different plasma gas mixtures was also investigated by optical emission spectroscopy (OES) measurements of zirconium emissions. Yttria-stabilized zirconia (YSZ) coating microstructures were produced when using selected plasma gas compositions and corresponding carrier gas flows; structural morphologies were found to be in good agreement with OES and theoretical predictions. Quasicolumnar microstructure was obtained with porosity of 15% when applying the plasma composition of 45Ar/45He.

  20. Effects of surface deposition, hole blockage, and thermal barrier coating spallation on vane endwall film cooling

    SciTech Connect

    Sundaram, N.; Thole, K.A.

    2007-07-15

    With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

  1. Combustion chemical vapor desposited coatings for thermal barrier coating systems

    SciTech Connect

    Hampikian, J.M.; Carter, W.B.

    1995-10-01

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings.

  2. CHEMICALLY VAPOR DEPOSITED YTTRIA-STABILIZED ZIRCONIA (YSZ) FOR THERMAL AND ENVIRONMENTAL BARRIER COATING

    SciTech Connect

    Varanasi, V.G.; Besmann, T.M.; Lothian, J.L.; Xu, W.; Starr, T.L.

    2003-04-22

    Yttria-stabilized zirconia (YSZ) is used as a thermal barrier coating (TBC) to protect super-alloy blades such as Mar-M247 or Rene-N5 during engine operation. The current method for YSZ fabrication for TBC applications is by air-plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) (Haynes 1997). APS gives reasonable deposition rates, but has a limited life and aging effects due to its porous and lamellar structure. The EB-PVD coatings are more stable and can accommodate thermomechanical stresses due to their characteristic strain-tolerant, columnar microstructure. EB-PVD, however, is primarily line-of-sight, which often leaves ''hidden areas'' uncoated, has low throughput, and has high capital cost. The process of metal-organic chemical vapor deposition (MOCVD) is investigated here as an economical alternative to EB-PVD and APS, with the potential for better overall coverage as well as the ability to produce thick (100-250 {micro}m), strain-tolerant, columnar coatings. MOCVD of YSZ involves the use of zirconium and yttrium organometallic precursors reacting with an oxygen source. Previous researchers have used diketonate or chloride precursors and oxygen (Wahl et al. 2001a, Wahl et al. 2001b, Yamane and Harai 1989). These precursors have low transport rates due to their low carrier solvent solubility (Varanasi et al. 2003). Solvated zirconium and yttrium butoxide precursors were investigated here due to their higher vapor pressures and high solvent solubility. This work uses predictive equilibrium modeling and experiments involving butoxide precursors for tetragonal YSZ fabrication.

  3. Thermal Barrier Coating Workshop, 1997

    NASA Technical Reports Server (NTRS)

    Brindley, William J. (Compiler)

    1998-01-01

    This document contains papers from the 1997 Thermal Barrier Coatings Workshop, sponsored by the TBC Interagency Coordination Committee. The Workshop was held in Fort Mitchell, Kentucky, May 19-21, 1997. The papers cover the topics of heat transfer and conductivity of thermal barrier coatings, failure mechanisms and characterization of the coatings as well as characterization of coating deposition methods. Speakers included research, development and user groups in academia, industry and government.

  4. In-situ formation of multiphase electron beam physical vapor deposited barrier coatings for turbine components

    DOEpatents

    Subramanian, Ramesh

    2001-01-01

    A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base columnar thermal barrier coating (20) on the alloy surface, where a heat resistant ceramic oxide sheath material (32' or 34') covers the columns (28), and the sheath material is the reaction product of a precursor ceramic oxide sheath material and the base thermal barrier coating material.

  5. Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study

    NASA Astrophysics Data System (ADS)

    Bakan, Emine; Marcano, Diana; Zhou, Dapeng; Sohn, Yoo Jung; Mauer, Georg; Vaßen, Robert

    2017-08-01

    Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber.

  6. Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study

    NASA Astrophysics Data System (ADS)

    Bakan, Emine; Marcano, Diana; Zhou, Dapeng; Sohn, Yoo Jung; Mauer, Georg; Vaßen, Robert

    2017-06-01

    Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber.

  7. Thin film deposition at atmospheric pressure using dielectric barrier discharges: Advances on three-dimensional porous substrates and functional coatings

    NASA Astrophysics Data System (ADS)

    Fanelli, Fiorenza; Bosso, Piera; Mastrangelo, Anna Maria; Fracassi, Francesco

    2016-07-01

    Surface processing of materials by atmospheric pressure dielectric barrier discharges (DBDs) has experienced significant growth in recent years. Considerable research efforts have been directed for instance to develop a large variety of processes which exploit different DBD electrode geometries for the direct and remote deposition of thin films from precursors in gas, vapor and aerosol form. This article briefly reviews our recent progress in thin film deposition by DBDs with particular focus on process optimization. The following examples are provided: (i) the plasma-enhanced chemical vapor deposition of thin films on an open-cell foam accomplished by igniting the DBD throughout the entire three-dimensional (3D) porous structure of the substrate, (ii) the preparation of hybrid organic/inorganic nanocomposite coatings using an aerosol-assisted process, (iii) the DBD jet deposition of coatings containing carboxylic acid groups and the improvement of their chemical and morphological stability upon immersion in water.

  8. Deposition stress effects on the life of thermal barrier coatings on burner rigs

    NASA Technical Reports Server (NTRS)

    Watson, J. W.; Levine, S. R.

    1984-01-01

    A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

  9. Properties of Plasma Enhanced Chemical Vapor Deposition Barrier Coatings and Encapsulated Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Qi, Lei; Zhang, Chunmei; Chen, Qiang

    2014-01-01

    In this paper, we report silicon oxide coatings deposited by plasma enhanced chemical vapor deposition technology (PECVD) on 125 μm polyethyleneterephthalate (PET) surfaces for the purpose of the shelf lifetime extension of sealed polymer solar cells. After optimization of the processing parameters, we achieved a water vapor transmission rate (WVTR) of ca. 10-3 g/m2/day with the oxygen transmission rate (OTR) less than 0.05 cc/m2/day, and succeeded in extending the shelf lifetime to about 400 h in encapsulated solar cells. And then the chemical structure of coatings related to the properties of encapsulated cell was investigated in detail.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  11. Porous α-Al2O3 thermal barrier coatings with dispersed Pt particles prepared by cathode plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Wang, Peng; He, Ye-dong; Deng, Shun-jie; Zhang, Jin

    2016-01-01

    Porous α-Al2O3 thermal barrier coatings (TBCs) containing dispersed Pt particles were prepared by cathode plasma electrolytic deposition (CPED). The influence of the Pt particles on the microstructure of the coatings and the CPED process were studied. The prepared coatings were mainly composed of α-Al2O3. The average thickness of the coatings was approximately 100 μm. Such single-layer TBCs exhibited not only excellent high-temperature cyclic oxidation and spallation resistance, but also good thermal insulation properties. Porous α-Al2O3 TBCs inhibit further oxidation of alloy substrates because of their extremely low oxygen diffusion rate, provide good thermal insulation because of their porous structure, and exhibit excellent mechanical properties because of the toughening effect of the Pt particles and because of stress relaxation induced by deformation of the porous structure.

  12. Biomimetic thermal barrier coating in jet engine to resist volcanic ash deposition

    NASA Astrophysics Data System (ADS)

    Song, Wenjia; Major, Zsuzsanna; Schulz, Uwe; Muth, Tobias; Lavallée, Yan; Hess, Kai-Uwe; Dingwell, Donald B.

    2017-04-01

    The threat of volcanic ash to aviation safety is attracting extensive attention when several commercial jet aircraft were damaged after flying through volcanic ash clouds from the May 1980 eruptions of Mount St. Helen in Washington, U.S. and especially after the air traffic disruption in 2010 Eyjafjallajökull eruption. A major hazard presented by volcanic ash to aircraft is linked to the wetting and spreading of molten ash droplets on engine component surfaces. Due to the fact ash has a lower melting point, around 1100 °C, than the gas temperature in the hot section (between 1400 to 2000 °C), this cause the ash to melt and potentially stick to the internal components (e.g., combustor and turbine blades), this cause the ash to melt and potentially stick to the internal components of the engine creating, substantial damage or even engine failure after ingestion. Here, inspiring form the natural surface of lotus leaf (exhibiting extreme water repellency, known as 'lotus effect'), we firstly create the multifunctional surface thermal barrier coatings (TBCs) by producing a hierarchical structure with femtosecond laser pulses. In detail, we investigate the effect of one of primary femtosecond laser irradiation process parameter (scanning speed) on the hydrophobicity of water droplets onto the two kinds of TBCs fabricated by electron-beam physical vapor deposition (EB-PVD) and air plasma spray (APS), respectively as well as their corresponding to morphology. It is found that, comparison with the original surface (without femtosecond laser ablation), all of the irradiated samples demonstrate more significant hydrophobic properties due to nanostructuring. On the basis of these preliminary room-temperature results, the wettability of volcanic ash droplets will be analysed at the high temperature to constrain the potential impact of volcanic ash on the jet engines.

  13. Oxygen diffusion barrier coating

    NASA Technical Reports Server (NTRS)

    Unnam, Jalaiah (Inventor); Clark, Ronald K. (Inventor)

    1987-01-01

    A method for coating a titanium panel or foil with aluminum and amorphous silicon to provide an oxygen barrier abrogating oxidation of the substrate metal is developed. The process is accomplished with known inexpensive procedures common in materials research laboratories, i.e., electron beam deposition and sputtering. The procedures are conductive to treating foil gage titanium and result in submicron layers which virtually add no weight to the titanium. There are no costly heating steps. The coatings blend with the substrate titanium until separate mechanical properties are subsumed by those of the substrate without cracking or spallation. This method appreciably increases the ability of titanium to mechanically perform in high thermal environments such as those witnessed on structures of space vehicles during re-entry

  14. Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    1993-01-01

    In order to reduce heat transfer between a hot gas heat source and a metallic engine component, a thermal insulating layer of material is placed between them. This thermal barrier coating is applied by plasma spray processing the thin films. The coating has been successfully employed in aerospace applications for many years. Lewis Research Center, a leader in the development engine components coating technology, has assisted Caterpillar, Inc. in applying ceramic thermal barrier coatings on engines. Because these large engines use heavy fuels containing vanadium, engine valve life is sharply decreased. The barrier coating controls temperatures, extends valve life and reduces operating cost. Additional applications are currently under development.

  15. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S. (Inventor)

    1984-01-01

    A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.

  16. Processing-structure-property relationships of thermal barrier coatings deposited using the solution precursor plasma spray process

    NASA Astrophysics Data System (ADS)

    Xie, Liangde

    This research is intended to develop a novel process, solution-precursor plasma-spray (SPPS), for the deposition of highly durable thermal barrier coatings (TBCs). In the SPPS process a solution precursor feedstock, that results in ZrO2-7 wt% Y2O3 ceramic, is injected into the plasma jet and the coating is deposited on a metal substrate. The formed coating has the following novel microstructural features: (i) ultra-fine splats, (ii) through-thickness cracks, (iii) micrometer and nanometer porosity, and (iv) interpass boundaries. The deposition mechanisms of the solution precursor droplets injected into the different regions of the plasma jet were found to be different due to large temperature variation across the plasma jet. The solution precursor droplets injected into the core of the plasma jet are deposited on the substrate as ultra-fine splats that account for around 65 volume% of the coating. The other 35 volume% of the coating includes porosity and deposits formed from the solution precursor droplets injected into other regions of the plasma jet. The optimum processing condition for highly durable TBCs was determined using Taguchi design of experiments. Meanwhile, the relationship of the microstructural features and processing parameters was revealed. During thermal cycling, the unmelted particles in the coating were observed to pyloyze and/or sinter, while no sign of sintering was observed for the ultra-fine splats. The spacing of through-thickness cracks remains in the range of 160 to 190 mum throughout the thermal cycling test. Three stages of oxidation of the bond coat were observed. Failure of the SPPS TBC starts with the crack nucleation along the unmelted particles in the top coat and the Ni, Cr, Co-rich oxides of large thickness. These cracks propagate and coalesce with thermal cycling. The extensive cracking of the rapidly formed Ni, Cr, Co-rich oxides resulting from the depletion of aluminum in the bond coat leads to the development of large

  17. Catalytic thermal barrier coatings

    DOEpatents

    Kulkarni, Anand A.; Campbell, Christian X.; Subramanian, Ramesh

    2009-06-02

    A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

  18. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S.; Leibert, C. H. (Inventor)

    1977-01-01

    A coating system which contains a bond coating and a thermal barrier coating is applied to metal surfaces such as turbine blades and provides both low thermal conductivity and improved adherence when exposed to high temperature gases or liquids. The bond coating contains NiCrAlY and the thermal barrier coating contains a reflective oxide. The reflective oxides ZrO2-Y2O3 and ZrO2-MgO have demonstrated significant utility in high temperature turbine applications.

  19. Highly Segmented Thermal Barrier Coatings Deposited by Suspension Plasma Spray: Effects of Spray Process on Microstructure

    NASA Astrophysics Data System (ADS)

    Chen, Xiaolong; Honda, Hiroshi; Kuroda, Seiji; Araki, Hiroshi; Murakami, Hideyuki; Watanabe, Makoto; Sakka, Yoshio

    2016-12-01

    Effects of the ceramic powder size used for suspension as well as several processing parameters in suspension plasma spraying of YSZ were investigated experimentally, aiming to fabricate highly segmented microstructures for thermal barrier coating (TBC) applications. Particle image velocimetry (PIV) was used to observe the atomization process and the velocity distribution of atomized droplets and ceramic particles travelling toward the substrates. The tested parameters included the secondary plasma gas (He versus H2), suspension injection flow rate, and substrate surface roughness. Results indicated that a plasma jet with a relatively higher content of He or H2 as the secondary plasma gas was critical to produce highly segmented YSZ TBCs with a crack density up to 12 cracks/mm. The optimized suspension flow rate played an important role to realize coatings with a reduced porosity level and improved adhesion. An increased powder size and higher operation power level were beneficial for the formation of highly segmented coatings onto substrates with a wider range of surface roughness.

  20. Thermal barrier coating

    DOEpatents

    Bowker, Jeffrey Charles; Sabol, Stephen M.; Goedjen, John G.

    2001-01-01

    A thermal barrier coating for hot gas path components of a combustion turbine based on a zirconia-scandia system. A layer of zirconium scandate having the hexagonal Zr.sub.3 Sc.sub.4 O.sub.12 structure is formed directly on a superalloy substrate or on a bond coat formed on the substrate.

  1. Thermal barrier coating system

    NASA Technical Reports Server (NTRS)

    Stecura, S. (Inventor)

    1985-01-01

    An oxide thermal barrier coating comprises ZrO3-Yb2O3 that is plasma sprayed onto a previously applied bond coating. The zirconia is partially stabilized with about 124 w/o ytterbia to insure cubic, monoclinic, and terragonal phases.

  2. Westinghouse thermal barrier coatings development

    SciTech Connect

    Goedjen, J.G.; Wagner, G.

    1995-10-01

    Westinghouse, in conjunction with the Department of Energy and Oak Ridge National Laboratory, has embarked upon a program for the development of advanced thermal barrier coatings for industrial gas turbines. Development of thermal barrier coatings (TBC`s) for industrial gas turbines has relied heavily on the transfer of technology from the aerospace industry. Significant differences in the time/temperature/stress duty cycles exist between these two coating applications. Coating systems which perform well in aerospace applications may not been optimized to meet power generation performance requirements. This program will focus on development of TBC`s to meet the specific needs of power generation applications. The program is directed at developing a state-of-the-art coating system with a minimum coating life of 25,000 hours at service temperatures required to meet increasing operating efficiency goals. Westinghouse has assembled a team of university and industry leaders to accomplish this goal. Westinghouse will coordinate the efforts of all program participants. Chromalloy Turbine Technologies, Inc. and Sermatech International, Inc. will be responsible for bond coat and TBC deposition technology. Praxair Specialty Powders, Inc. will be responsible for the fabrication of all bond coat and ceramic powders for the program. Southwest Research Institute will head the life prediction modelling effort; they will also be involved in coordinating nondestructive evaluation (NDE) efforts. Process modelling will be provided by the University of Arizona.

  3. Multilayer thermal barrier coating systems

    DOEpatents

    Vance, Steven J.; Goedjen, John G.; Sabol, Stephen M.; Sloan, Kelly M.

    2000-01-01

    The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

  4. Thermal Barrier Coating Workshop

    NASA Technical Reports Server (NTRS)

    Brindley, W. J. (Compiler); Lee, W. Y. (Compiler); Goedjen, J. G. (Compiler); Dapkunas, S. J. (Compiler)

    1995-01-01

    This document contains the agenda and presentation abstracts for the Thermal Barrier Coating Workshop, sponsored by NASA, DOE, and NIST. The workshop covered thermal barrier coating (TBC) issues related to applications, processing, properties, and modeling. The intent of the workshop was to highlight the state of knowledge on TBC's and to identify critical gaps in knowledge that may hinder TBC use in advanced applications. The workshop goals were achieved through presentations by 22 speakers representing industry, academia, and government as well as through extensive discussion periods.

  5. Isothermal Oxidation Behavior of VC and Columnar Structured Thermal Barrier Coatings Deposited by Suspension Plasma Spray Technology

    NASA Astrophysics Data System (ADS)

    Li, Xiaolong; Yang, Qi; Huang, Xiao; Tang, Zhaolin

    2015-08-01

    The effects of different thermal barrier coating (TBC) top coat structures and substrate alloys on the isothermal oxidation behaviors of TBC systems were investigated at 1080 °C in lab air. The tested TBC systems consisted of two nickel-based superalloy substrates (CMSX-4 and IN738LC), a platinum aluminide bond coat and two 8YSZ top coats (vertical cracked and columnar structured). Samples with IN738LC substrate demonstrated longer isothermal oxidation lives than the counterparts with CMSX-4 substrate. Outward refractory elemental diffusion in coating systems with CMSX-4 substrate and void formation at the interface between thermally grown oxide and bond coat was found to be responsible for the early failure of TBCs. Columnar structured YSZ top coat seemed to provide better protection of the bond coating and substrate, marginally delaying the failure of the both coating systems with IN738LC and CMSX-4.

  6. Thermal barrier coatings

    DOEpatents

    Alvin, Mary Anne [Pittsburg, PA

    2010-06-22

    This disclosure addresses the issue of providing a metallic-ceramic overlay coating that potentially serves as an interface or bond coat layer to provide enhanced oxidation resistance to the underlying superalloy substrate via the formation of a diffusion barrier regime within the supporting base material. Furthermore, the metallic-ceramic coating is expected to limit the growth of a continuous thermally grown oxide (TGO) layer that has been primarily considered to be the principal cause for failure of existing TBC systems. Compositional compatibility of the metallic-ceramic with traditional yttria-stabilized zirconia (YSZ) top coats is provided to further limit debond or spallation of the coating during operational use. A metallic-ceramic architecture is disclosed wherein enhanced oxidation resistance is imparted to the surface of nickel-based superalloy or single crystal metal substrate, with simultaneous integration of the yttria stabilized zirconia (YSZ) within the metallic-ceramic overlayer.

  7. Microstructural evolution of the nickel platinum-aluminide bond coat on electron-beam physical-vapor deposition thermal-barrier coatings during high-temperature service

    NASA Astrophysics Data System (ADS)

    Zhang, L. C.; Heuer, A. H.

    2005-01-01

    The microstructural evolution of a (Ni,Pt)-aluminide bond coat underneath the ZrO2-based thermal-barrier coating (TBC) topcoat system on a René N5 Ni-based superalloy turbine blade during prolonged high-temperature service has been characterized using transmission electron microscopy (TEM). The as-deposited bond coat has a spatially varying microstructure, which consists of an outer layer of single-phase β-(Ni,Pt)Al, a middle layer of a β-(Ni,Pt)Al matrix containing a high number density of μ-phase precipitates, and an inner layer containing a γ/γ' matrix and numerous μ- and σ-phase precipitates. During service, microstructural changes in the hotter sections of the blade are more extensive than those in the cooler parts, as expected. As a result of interdiffusion, the inner layer grows into the γ/γ' substrate, with the formation of some M23C6 precipitates, and the β matrix in the middle layer is transformed into a two-phase mixture of β and γ'. Corresponding changes occur in the morphologies and volume fractions of the various precipitate phases present in the bond coat. The single-phase β material in the outer layer retains its basic structure, except that the compositional changes due to diffusion between the bond coat and turbine blade cause a martensitic transformation to occur in the hottest sections during the final cooling of the blade. The distribution of various elements in the different layers has also been analyzed, as has growth of the thermally grown oxide (TGO) at the bond coat/TBC interface.

  8. Electrospark deposition coatings

    NASA Astrophysics Data System (ADS)

    Sheely, W. F.

    1986-11-01

    Hard surfacing for wear resistant and low-friction coatings has been improved by means of advances in the computer controls in electronic circuitry of the electrospark deposition (ESD) process. coatings of nearly any electrically conductive metal alloy or cermet can be deposited on conductive materials. Thickness is usually two mils or less, but can be as high as 10 mils. ESD coatings can quadrupole cutting tool life.

  9. Electrospark deposition coatings

    SciTech Connect

    Sheely, W.F.

    1986-11-19

    Hard surfacing for wear resistant and low-friction coatings has been improved by means of advances in the computer controls in electronic circuitry of the electrospark deposition (ESD) process. coatings of nearly any electrically conductive metal alloy or cermet can be deposited on conductive materials. Thickness is usually two mils or less, but can be as high as 10 mils. ESD coatings can quadrupole cutting tool life. (DLC)

  10. Hydrogen Permeation Barrier Coatings

    SciTech Connect

    Henager, Charles H.

    2008-01-01

    Gaseous hydrogen, H2, has many physical properties that allow it to move rapidly into and through materials, which causes problems in keeping hydrogen from materials that are sensitive to hydrogen-induced degradation. Hydrogen molecules are the smallest diatomic molecules, with a molecular radius of about 37 x 10-12 m and the hydrogen atom is smaller still. Since it is small and light it is easily transported within materials by diffusion processes. The process of hydrogen entering and transporting through a materials is generally known as permeation and this section reviews the development of hydrogen permeation barriers and barrier coatings for the upcoming hydrogen economy.

  11. Advanced thermal barrier coating system development. Technical progress report, June 1, 1996--July 31, 1996

    SciTech Connect

    1996-08-07

    An improved thermal barrier coating system with good reliability and thermal performance is described. The report discusses the coating process, manufacturing, repair, deposition, and microstructure of the coatings.

  12. Thermal Conductivity and Temperature Limits of Electron-Beam Physical-Vapor-Deposited ZrO2-7wt%Y2O3 Thermal Barrier Coating

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1990-01-01

    The electron-beam physical-vapor-deposited (EB-PVD) ZrO2-7wt%Y2O3 thermal barrier coating has been widely used to protect engine hot section components in modem aircraft engines. Thermal conductivity and the conductivity increases due to sintering and phase changes are important coating design parameters. There is a need to characterize the coating thermal conductivity behavior and temperature limits, in order to potentially take full advantage of the coating capability. In addition, since the ZrO2-7wt%Y2O3 coating is often used as a baseline coating for the development of advanced lower thermal conductivity and higher temperature capability coatings, a thorough evaluation of the coating conductivity behavior at future higher engine operating temperatures will be useful for more accurately assessing the benefit gained from the new coating systems. In this study, thermal conductivity behavior of EB-PVD ZrO2-7wt%Y2O3 coating has been systematically investigated as a function of temperature (up to 2600 F) and time under steady-state and cyclic test conditions using a laser heat-flux technique. Thermal conductivity change kinetics were determined under realistic engine high temperature thermal gradient conditions, and correlated to the coating microstructural and phase changes. The thermal conductivity prediction models have been established in terms of heat flux, time, and testing temperatures.

  13. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Demasi, J. T.; Sheffler, K. D.

    1986-01-01

    The objective of this program is to establish a methodology to predict Thermal Barrier Coating (TBC) life on gas turbine engine components. The approach involves experimental life measurement coupled with analytical modeling of relevant degradation modes. The coating being studied is a flight qualified two layer system, designated PWA 264, consisting of a nominal ten mil layer of seven percent yttria partially stabilized zirconia plasma deposited over a nominal five mil layer of low pressure plasma deposited NiCoCrAlY. Thermal barrier coating degradation modes being investigated include: thermomechanical fatigue, oxidation, erosion, hot corrosion, and foreign object damage.

  14. Degradation of thermal barrier coatings on an Integrated Gasification Combined Cycle (IGCC) simulated film-cooled turbine vane pressure surface due to particulate fly ash deposition

    NASA Astrophysics Data System (ADS)

    Luo, Kevin

    Coal synthesis gas (syngas) can introduce contaminants into the flow of an Integrated Gasification Combined Cycle (IGCC) industrial gas turbine which can form molten deposits onto components of the first stage of a turbine. Research is being conducted at West Virginia University (WVU) to study the effects of particulate deposition on thermal barrier coatings (TBC) employed on the airfoils of an IGCC turbine hot section. WVU had been working with U.S. Department of Energy, National Energy Technology Laboratory (NETL) to simulate deposition on the pressure side of an IGCC turbine first stage vane to study the effects on film cooling. To simulate the particulate deposition, TBC coated, angled film-cooled test articles were subjected to accelerated deposition injected into the flow of a combustor facility with a pressure of approximately 4 atm and a gas temperature of 1560 K. The particle characteristics between engine conditions and laboratory are matched using the Stokes number and particulate loading. To investigate the degradation on the TBC from the particulate deposition, non-destructive evaluations were performed using a load-based multiple-partial unloading micro-indentation technique and were followed by scanning electron microscopy (SEM) evaluation and energy dispersive X-ray spectroscopy (EDS) examinations. The micro-indentation technique used in the study was developed by Kang et al. and can quantitatively evaluate the mechanical properties of materials. The indentation results found that the Young's Modulus of the ceramic top coat is higher in areas with deposition formation due to the penetration of the fly ash. The increase in the modulus of elasticity has been shown to result in a reduction of strain tolerance of the 7% yttria-stabilized zirconia (7YSZ) TBC coatings. The increase in the Young's modulus of the ceramic top coat is due to the stiffening of the YSZ columnar microstructure from the cooled particulate fly ash. SEM evaluation was used to

  15. Improvement of adhesion and barrier properties of biomedical stainless steel by deposition of YSZ coatings using RF magnetron sputtering

    SciTech Connect

    Sánchez-Hernández, Z.E.; Domínguez-Crespo, M.A.; Torres-Huerta, A.M.; Onofre-Bustamante, E.; Andraca Adame, J.; Dorantes-Rosales, H.

    2014-05-01

    The AISI 316L stainless steel (SS) has been widely used in both artificial knee and hip joints in biomedical applications. In the present study, yttria stabilized zirconia (YSZ, ZrO{sub 2} + 8% Y{sub 2}O{sub 3}) films were deposited on AISI 316L SS by radio-frequency magnetron sputtering using different power densities (50–250 W) and deposition times (30–120 min) from a YSZ target. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the surface modification on the corrosion performance of AISI 316L SS were evaluated in phosphate buffered saline (PBS) solution using an electrochemical test on both the virgin and coated samples. The YSZ coatings have a (111) preferred orientation during crystal growth along the c-axis for short deposition times (30–60 min), whereas a polycrystalline structure forms during deposition times from 90 to 120 min. The corrosion protective character of the YSZ coatings depends on the crystal size and film thickness. A significant increase in adhesion and corrosion resistance by at least a factor of 46 and a higher breakdown potential were obtained for the deposited coatings at 200 W (120 min). - Highlights: • Well-formed and protective YSZ coatings were achieved on AISI 316L SS substrates. • Films grown at high power and long deposition time have polycrystalline structures. • The crystal size varies from ∼ 5 to 30 nm as both power and deposition time increased. • The differences of corrosion resistance are attributed to internal film structure.

  16. A CFD-Based Study of the Feasibility of Adapting an Erosion Burner Rig for Examining the Effect of CMAS Deposition Corrosion on Environmental Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Kuczmarski, Maria A.

    2015-01-01

    Thermodynamic and computational fluid dynamics modeling has been conducted to examine the feasibility of adapting the NASA-Glenn erosion burner rigs for use in studies of corrosion of environmental barrier coatings by the deposition of molten CMAS. The effect of burner temperature, Mach number, particle preheat, duct heating, particle size, and particle phase (crystalline vs. glass) were analyzed. Detailed strategies for achieving complete melting of CMAS particles were developed, thereby greatly improving the probability of future successful experimental outcomes.

  17. Improving thermal barrier coatings by laser remelting.

    PubMed

    Múnez, C J; Gómez-García, J; Sevillano, F; Poza, P; Utrilla, M V

    2011-10-01

    Thermal barrier coatings are extensively used to protect metallic components in applications where the operating conditions include aggressive environment at high temperatures. These coatings are usually processed by thermal spraying techniques and the resulting microstructure includes thin and large splats, associated with the deposition of individual droplets, with porosity between splats. This porosity reduces the oxidation and corrosion resistance favouring the entrance of aggressive species during service. To overcome this limitation, the top coat could be modified by laser glazing reducing surface roughness and sealing open porosity. ZrO2(Y2O3) top coat and NiCrAlY bond coating were air plasma sprayed onto an Inconel 600 Ni base alloy. The top coat was laser remelted and a densified ceramic layer was induced in the top surface of the ceramic coating. This layer inhibited the ingress of aggressive species and delayed bond coat oxidation.

  18. Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming

    2005-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and requirements will be discussed. An experimental approach is established to monitor in real time the thermal conductivity of the coating systems subjected to high-heat-flux, steady-state and cyclic temperature gradients. Advanced low conductivity thermal barrier coatings have also been developed using a multi-component defect clustering approach, and shown to have improved thermal stability. The durability and erosion resistance of low conductivity thermal barrier coatings have been improved utilizing advanced coating architecture design, composition optimization, in conjunction with more sophisticated modeling and design tools.

  19. Pratt & Whitney thermal barrier coatings

    SciTech Connect

    Bornstein, N.; Marcin, J.

    1995-10-01

    The objective of the Advanced Turbine Systems (ATS) Program is to develop ultra-high efficient, environmentally superior, and cost competitive gas turbine systems. The operating profiles of these industrial gas turbines are long, less cyclic with fewer transients-compared with those for aircraft gas turbine engines. Therefore, creep rather than thermal fatigue, becomes primary life-limiting for hot section components. Thermal barrier coatings (TBCs) will be used to achieve the objectives of the program. TBCs allow surface temperatures to increase without compromising the structural properties of the alloy. TBCs typically consist of a ceramic insulating layer, deposited onto the substrate with an intervening metallic layer, which imparts oxidation protection to the substrate and provides a surface to which the ceramic layer can adhere.

  20. Chemical vapor deposition of yttria-stabilized zirconia as a thermal barrier coating for gas turbine engines

    NASA Astrophysics Data System (ADS)

    Varanasi, Venu Gopal

    The gas turbine engine uses an yttria-stabilized zirconia (YSZ) coating to provide thermal insulation for its turbine blades. This YSZ coating must be tetragonal in crystal structure, columnar in microstructure, and be 100--250 mum thick to provide for adequate protection for the turbine blades in the severe engine environment. Currently, YSZ coatings are fabricated by electron-beam physical vapor deposition (EB-PVD), but this fabrication method is cost intensive. Chemical vapor deposition (CVD) is a more commercially viable processing method and a possible alternative to EB-PVD. The deposition of tetragonal YSZ from gaseous metal and oxidation sources were studied. A chemical equilibrium analysis modeled the feasibility of depositing tetragonal YSZ for both chloride CVD (Zr-Y-C-O-Cl-H-Inert system) and metal-organic CVD (MOCVD) (Zr-Y-C-O-H system). Pure thermochemical properties and the assessed YSZ phase diagram were used in this analysis. Using the molar input of metals ((nY + nZr) and ( nY/(nY + nZr ) = 0.08)) as bases, equilibrium calculations showed that tetragonal YSZ formation was feasible. Tetragonal YSZ formation was feasible with high oxygen content (nO/(nY + nZr) > 8) and high temperature (T > 100°C) in the case of chloride CVD (Zr-Y-C-O-Cl-H-Inert). Tetragonal YSZ formation was feasible with high oxygen content (nO/( nY + nZr) > 5) and high temperature (T > 950°C) in the case of MOCVD (Zr-Y-C-O-H). Although solid carbon formation did not appear in chloride CVD, additional oxygen (nO/( nY + nZr) > 32) and low hydrogen content relative to carbon (nH/nC < 2) were required to avoid solid carbon formation in MOCVD. Coatings were deposited using a set of base conditions derived from the chemical equilibrium analysis. In chloride CVD, YCl3 was not included because of its low vapor pressure, thus, ZrCl4 was oxidized with the H2-CO2 gas mixture. Monoclinic ZrO2 coatings were deposited at the thermochemically optimized conditions (n O/(nY + nZr) > 8, T > 1004

  1. Advanced thermal barrier coating systems

    NASA Technical Reports Server (NTRS)

    Dorfman, M. R.; Reardon, J. D.

    1985-01-01

    Current state-of-the-art thermal barrier coating (TBC) systems consist of partially stabilized zirconia coatings plasma sprayed over a MCrAlY bond coat. Although these systems have excellent thermal shock properties, they have shown themselves to be deficient for a number of diesel and aircraft applications. Two ternary ceramic plasma coatings are discussed with respect to their possible use in TBC systems. Zirconia-ceria-yttria (ZCY) coatings were developed with low thermal conductivities, good thermal shock resistance and improved resistance to vanadium containing environments, when compared to the baseline yttria stabilized zirconia (YSZ) coatings. In addition, dense zirconia-titania-yttria (ZTY) coatings were developed with particle erosion resistance exceeding conventional stabilized zirconia coatings. Both coatings were evaluated in conjunction with a NiCr-Al-Co-Y2O3 bond coat. Also, multilayer or hybrid coatings consisting of the bond coat with subsequent coatings of zirconia-ceria-yttria and zirconia-titania-yttria were evaluated. These coatings combine the enhanced performance characteristics of ZCY with the improved erosion resistance of ZTY coatings. Improvement in the erosion resistance of the TBC system should result in a more consistent delta T gradient during service. Economically, this may also translate into increased component life simply because the coating lasts longer.

  2. Oxygen-Barrier Coating for Titanium

    NASA Technical Reports Server (NTRS)

    Clark, Ronald K.; Unnam, Jalaiah

    1987-01-01

    Oxygen-barrier coating for titanium developed to provide effective and low-cost means for protecting titanium alloys from oxygen in environment when alloys used in high-temperature mechanical or structural applications. Provides protective surface layer, which reduces extent of surface oxidation of alloy and forms barrier to diffusion of oxygen, limiting contamination of substrate alloy by oxygen. Consists of submicron layer of aluminum deposited on surface of titanium by electron-beam evaporation, with submicron layer of dioxide sputtered onto aluminum to form coat.

  3. Phosphor-Doped Thermal Barrier Coatings Deposited by Air Plasma Spray for In-Depth Temperature Sensing.

    PubMed

    Peng, Di; Yang, Lixia; Cai, Tao; Liu, Yingzheng; Zhao, Xiaofeng; Yao, Zhiqi

    2016-09-28

    Yttria-stabilized zirconia (YSZ)-based thermal barrier coating (TBC) has been integrated with thermographic phosphors through air plasma spray (APS) for in-depth; non-contact temperature sensing. This coating consisted of a thin layer of Dy-doped YSZ (about 40 µm) on the bottom and a regular YSZ layer with a thickness up to 300 µm on top. A measurement system has been established; which included a portable; low-cost diode laser (405 nm); a photo-multiplier tube (PMT) and the related optics. Coating samples with different topcoat thickness were calibrated in a high-temperature furnace from room temperature to around 900 °C. The results convincingly showed that the current sensor and the measurement system was capable of in-depth temperature sensing over 800 °C with a YSZ top layer up to 300 µm. The topcoat thickness was found to have a strong effect on the luminescent signal level. Therefore; the measurement accuracy at high temperatures was reduced for samples with thick topcoats due to strong light attenuation. However; it seemed that the light transmissivity of YSZ topcoat increased with temperature; which would improve the sensor's performance at high temperatures. The current sensor and the measurement technology have shown great potential in on-line monitoring of TBC interface temperature.

  4. Phosphor-Doped Thermal Barrier Coatings Deposited by Air Plasma Spray for In-Depth Temperature Sensing

    PubMed Central

    Peng, Di; Yang, Lixia; Cai, Tao; Liu, Yingzheng; Zhao, Xiaofeng; Yao, Zhiqi

    2016-01-01

    Yttria-stabilized zirconia (YSZ)-based thermal barrier coating (TBC) has been integrated with thermographic phosphors through air plasma spray (APS) for in-depth; non-contact temperature sensing. This coating consisted of a thin layer of Dy-doped YSZ (about 40 µm) on the bottom and a regular YSZ layer with a thickness up to 300 µm on top. A measurement system has been established; which included a portable; low-cost diode laser (405 nm); a photo-multiplier tube (PMT) and the related optics. Coating samples with different topcoat thickness were calibrated in a high-temperature furnace from room temperature to around 900 °C. The results convincingly showed that the current sensor and the measurement system was capable of in-depth temperature sensing over 800 °C with a YSZ top layer up to 300 µm. The topcoat thickness was found to have a strong effect on the luminescent signal level. Therefore; the measurement accuracy at high temperatures was reduced for samples with thick topcoats due to strong light attenuation. However; it seemed that the light transmissivity of YSZ topcoat increased with temperature; which would improve the sensor’s performance at high temperatures. The current sensor and the measurement technology have shown great potential in on-line monitoring of TBC interface temperature. PMID:27690037

  5. Thermal barrier coatings for heat engine components

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Miller, R. A.; Hodge, P. E.

    1980-01-01

    A comprehensive NASA-Lewis program of coating development for aircraft gas turbine blades and vanes is presented. Improved ceramic layer compositions are investigated, along the MCrAlY bond films and the methods of uniform deposition of the coatings; the thermomechanical and fuel impurity tolerance limits of the coatings are being studied. Materials include the ZrO2-Y2O3/NiCrAlY system; the effects of the bond coat and zirconia composition on coating life and Mach 1 burner rig test results are discussed. It is concluded that Diesel engines can also utilize thermal barrier coatings; they have been used successfully on piston crowns and exhaust valves of shipboard engines to combat lower grade fuel combustion corrosion.

  6. Article Including Environmental Barrier Coating System

    NASA Technical Reports Server (NTRS)

    Lee, Kang N. (Inventor)

    2015-01-01

    An enhanced environmental barrier coating for a silicon containing substrate. The enhanced barrier coating may include a bond coat doped with at least one of an alkali metal oxide and an alkali earth metal oxide. The enhanced barrier coating may include a composite mullite bond coat including BSAS and another distinct second phase oxide applied over said surface.

  7. Improved bond coatings for use with thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.

    1980-01-01

    The potential for improving the durability of thermal barrier coatings (TBC's) being developed for coal derived fuel fired gas turbines was studied. Furnace oxidation behavior of plasma deposited bond coatings was improved by increasing the thickness from 0.010 cm to 0.015 cm and by depositing the coatings at 20 kW with argon 3.5 vol % hydrogen arc gas rather than at 11 kW with argon. The most oxidation resistant plasma deposited bond coatings were Ni-14, 1Cr-13.4Al-0.10Zr, Ni-14.3Cr-14.4Al.0.16Y, and Ni-15.8Cr-12.8Al-0.36Y on B-1900 + Hf and Ni-30.9Cr-11.1Al-0.48Y on MAR-M-509. The oxidation resistant bond coatings improved TBC life when the coatings were deposited on the specimens supported on a nail bed fixture during coating.

  8. High temperature barrier coatings for refractory metals

    SciTech Connect

    Malone, G.A.; Walech, T.

    1995-06-01

    Improvements in high temperature oxidation resistant metal coating technology will allow NASA and commercial entities to develop competitive civil space transport and communication systems. The success of investigations completed in this program will have a positive impact on broadening the technology base for high temperature materials. The work reported herein describes processes and procedures for successfully depositing coherent oxidation barrier coatings on refractory metals to prevent degradation under very severe operating environments. Application of the new technology developed is now being utilized in numerous Phase 3 applications through several prominent aerospace firms. Major achievements have included: (1) development of means to deposit thick platinum and rhodium coatings with lower stress and fewer microcracks than could be previously achieved; (2) development of processes to deposit thick adherent coatings of platinum group metals on refractory substrates that remain bonded through high temperature excursions and without need for intermediate coatings (bonding processes unique to specific refractory metals and alloys have been defined); (3) demonstration that useful alloys of refractory and platinum coatings can be made through thermal diffusion means; (4) demonstration that selected barrier coatings on refractory substrates can withstand severe oxidizing environments in the range of 1260 deg and 1760 deg C for long time periods essential to the life requirements of the hardware; and (5) successful application of the processes and procedures to prototype hardware. The results of these studies have been instrumental in improved thermal oxidation barrier coatings for the NASP propulsion system. Other Phase 3 applications currently being exploited include small uncooled thrusters for spacecraft and microsatellite maneuvering systems.

  9. High temperature barrier coatings for refractory metals

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Walech, T.

    1995-01-01

    Improvements in high temperature oxidation resistant metal coating technology will allow NASA and commercial entities to develop competitive civil space transport and communication systems. The success of investigations completed in this program will have a positive impact on broadening the technology base for high temperature materials. The work reported herein describes processes and procedures for successfully depositing coherent oxidation barrier coatings on refractory metals to prevent degradation under very severe operating environments. Application of the new technology developed is now being utilized in numerous Phase 3 applications through several prominent aerospace firms. Major achievements have included: (1) development of means to deposit thick platinum and rhodium coatings with lower stress and fewer microcracks than could be previously achieved; (2) development of processes to deposit thick adherent coatings of platinum group metals on refractory substrates that remain bonded through high temperature excursions and without need for intermediate coatings (bonding processes unique to specific refractory metals and alloys have been defined; (3) demonstration that useful alloys of refractory and platinum coatings can be made through thermal diffusion means; (4) demonstration that selected barrier coatings on refractory substrates can withstand severe oxidizing environments in the range of 1260 deg and 1760 deg C for long time periods essential to the life requirements of the hardware; and (5) successful application of the processes and procedures to prototype hardware. The results of these studies have been instrumental in improved thermal oxidation barrier coatings for the NASP propulsion system. Other Phase 3 applications currently being exploited include small uncooled thrusters for spacecraft and microsatellite maneuvering systems.

  10. Study of barrier properties and chemical resistance of recycled PET coated with amorphous carbon through a plasma enhanced chemical vapour deposition (PECVD) process.

    PubMed

    Cruz, S A; Zanin, M; Nerin, C; De Moraes, M A B

    2006-01-01

    Many studies have been carried out in order to make bottle-to-bottle recycling feasible. The problem is that residual contaminants in recycled plastic intended for food packaging could be a risk to public health. One option is to use a layer of virgin material, named functional barrier, which prevents the contaminants migration process. This paper shows the feasibility of using polyethylene terephthalate (PET) recycled for food packaging employing a functional barrier made from hydrogen amorphous carbon film deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. PET samples were deliberately contaminated with a series of surrogates using a FDA protocol. After that, PET samples were coated with approximately 600 and 1200 Angstrons thickness of amorphous carbon film. Then, the migration tests using as food simulants: water, 10% ethanol, 3% acetic acid, and isooctane were applied to the sample in order to check the chemical resistance of the new coated material. After the tests, the liquid extracts were analysed using a solid-phase microextraction device (SPME) coupled to GC-MS.

  11. Thermal barrier coating for alloy systems

    DOEpatents

    Seals, Roland D.; White, Rickey L.; Dinwiddie, Ralph B.

    2000-01-01

    An alloy substrate is protected by a thermal barrier coating formed from a layer of metallic bond coat and a top coat formed from generally hollow ceramic particles dispersed in a matrix bonded to the bond coat.

  12. Thermal conductivity of zirconia thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

    1995-01-01

    Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor deposition (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard powder or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increases upon exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as-fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicate that if these coatings reach a temperature above 1100 C

  13. Modeling of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ferguson, B. L.; Petrus, G. J.; Krauss, T. M.

    1992-01-01

    The project examined the effectiveness of studying the creep behavior of thermal barrier coating system through the use of a general purpose, large strain finite element program, NIKE2D. Constitutive models implemented in this code were applied to simulate thermal-elastic and creep behavior. Four separate ceramic-bond coat interface geometries were examined in combination with a variety of constitutive models and material properties. The reason for focusing attention on the ceramic-bond coat interface is that prior studies have shown that cracking occurs in the ceramic near interface features which act as stress concentration points. The model conditions examined include: (1) two bond coat coefficient of thermal expansion curves; (2) the creep coefficient and creep exponent of the bond coat for steady state creep; (3) the interface geometry; and (4) the material model employed to represent the bond coat, ceramic, and superalloy base.

  14. Thermal barrier coating resistant to sintering

    DOEpatents

    Subramanian, Ramesh; Seth, Brij B.

    2004-06-29

    A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process.

  15. Low-Cost Protective Layer Coatings on Thermal Barrier Coatings via CCVD. Final Report

    SciTech Connect

    Hendrick, Michelle

    2003-09-18

    MicroCoating Technologies, Inc., investigated the use of the Combustion Chemical Vapor Deposition (CCVD) process to deposit oxygen or sintering barrier coatings for thermal barrier coating (TBC) applications. In addition, it looked at the use of its nanopowders by the NanoSpray process for developing smoothing layers on TBCs. Testing and analysis of coated substrates included heat treatments, scanning electron microscopy, x-ray diffraction and profilometry. Coatings on TBC-coated superalloy coupons were tested by an outside collaborator. Results from the investigations indicated that the thin film coatings were not well-suited as barrier layers on the rough bond coat or TBC. Subsequent investigations considered smoothing layers on the TBC, as suggested by the collaborator, using nanopowder-based coatings. Smoothing of substrate surfaces by 50% was observed by profilometry.

  16. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Meier, Susan M.; Nissley, David M.; Sheffler, Keith D.; Cruse, Thomas A.

    1991-01-01

    A thermal barrier coated (TBC) turbine component design system, including an accurate TBC life prediction model, is needed to realize the full potential of available TBC engine performance and/or durability benefits. The objective of this work, which was sponsored in part by NASA, was to generate a life prediction model for electron beam - physical vapor deposited (EB-PVD) zirconia TBC. Specific results include EB-PVD zirconia mechanical and physical properties, coating adherence strength measurements, interfacial oxide growth characteristics, quantitative cyclic thermal spallation life data, and a spallation life model.

  17. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Demasi, J. T.; Manning, S. L.; Ortiz, M.; Sheffler, K. D.

    1987-01-01

    The objectives of this program are to increase understanding of thermal barrier coating (TBC) degradation and failure modes, to generate quantitative ceramic failure life data under cyclic thermal conditions which simulate those encountered in gas turbine engine service, and to develop an analytical methodology for prediction of coating life in the engine. Observations of degradation and failure modes in plasma deposited ceramic indicate that spallation failure results from progressive cracking of the ceramic parallel to and adjacent to, but not coincident with the metal-ceramic interface.

  18. Low conductivity thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Zhao, Hengbei

    The dissertation begins by exploring the growth of 7YSZ coatings at different rotation rates. The experiments show that as the rotation rate was increased, the texture changes from <111> to <100> and the total pore fraction slowly decreased. The intercolumnar pores perpendicular to the coating surface are very effective at strain accommodation during thermal cycling. The intra-columnar pores appear the most effective for the reduction of thermal conductivity of the coatings. The minimum thermal conductivity occurs at a low rotation rate and is 0.8 W/mK. The failure modes and mechanisms of 7YSZ coatings during thermal cycling have been investigated. The primary mode of failure on rough bond coat surfaces involves delamination within the ceramic coating, just above the thermally-grown oxide (TGO). It was initiated by a bond coat rumpling mechanism. The delaminations were initiated preferentially at "corn kernel" growth defects in the coating. Ceramic coatings applied to polished bond coat surfaces had much longer spallation lifetimes and the delamination fracture shifted to the interface of TGO/bond coat. These delaminations were extended by a mechanism involving the formation and coalescence of interfacial voids. The enhanced coating life is shown to be a consequence of their lower density and hence, lower elastic modulus. Rare earth zirconates appear to be a promising candidate due to their reported low intrinsic thermal conductivity, good phase stability and greater resistance to sintering and CMAS attack compared to 7YSZ. The SZO coatings had as-deposited conductivities of 0.5+/-0.1 W/mK. When these SZO coatings were subjected to thermal cycling, it was found to have a much shorter lifetime (on both rough and smooth bond coats) than similarly deposited 7YSZ material. It was also found that samaria tended to react with alumina to form a SmAlO 3 interphase of the TBC/TGO interface which appears to significantly lower the interface toughness. To improve the

  19. Inspecting thermal barrier coatings by IR thermography

    NASA Astrophysics Data System (ADS)

    Bison, Paolo G.; Marinetti, Sergio; Grinzato, Ermanno G.; Vavilov, Vladimir P.; Cernuschi, Federico; Robba, Daniele

    2003-04-01

    As far as power generation is concerned, coating technologies find the main and more advanced applications. Nowadays, superalloys available for manufacturing hot path components in gas turbine like combustion liners, blades and vanes can not sustain temperatures up to 1100°C. In order to guarantee a significative temperature drop ceramic thermal barrier coatings are deposited onto the metallic core. The thickness of thermal barrier coatings (TBC) ranges from a few hundreds microns up to 1 millimetre or more, depending on component and deposition technique (mainly Air Plasma Spray or Electron Beam Physical Vapour Deposition). The structural integrity of both the substrate and the coating and their mutual adhesion is a key point because any loss of the protective layer exposes the bulk material to an extremely aggressive environment in terms of oxidation and temperature. Therefore, TBC must be tested for detecting of defects during both quality control and periodic in-service inspections. Because of the key role played by thickness and low thermal diffusivity of TBC in the decreasing of the substrate material temperature, both delaminations and thickness variation must be detected and classified. Pulsed Thermography has been successfully applied to this application field. Nevertheless, the procedure gives ambiguous results when thickness or thermal properties change in a continuous way within the thermal barrier. In this paper, a specific study on the detection performances of NDE techniques is presented, even when a non-uniform TBC thickness is superimposed to the disbonding defect. Tests performed at workshop on real and specifically manufactured components are reported. Dedicated processing algorithms improving the test reliability and effectiveness are presented as well. Tests on real components on the field are also reported.

  20. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Neumann, J. F.; Liu, A.

    1986-01-01

    Thermal barrier coatings (TBCs) for turbine airfoils in high-performance engines represent an advanced materials technology with both performance and durability benefits. The foremost TBC benefit is the reduction of heat transferred into air-cooled components, which yields performance and durability benefits. This program focuses on predicting the lives of two types of strain-tolerant and oxidation-resistant TBC systems that are produced by commercial coating suppliers to the gas turbine industry. The plasma-sprayed TBC system, composed of a low-pressure plasma-spray (LPPS) or an argon shrouded plasma-spray (ASPS) applied oxidation resistant NiCrAlY (or CoNiCrAlY) bond coating and an air-plasma-sprayed yttria (8 percent) partially stabilized zirconia insulative layer, is applied by Chromalloy, Klock, and Union Carbide. The second type of TBC is applied by the electron beam-physical vapor deposition (EB-PVD) process by Temescal.

  1. To Develop Nanostructured Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Zhao, Weixun; Wang, Ping; Wei, Zheng

    Advanced turbine engines require the application of thermal barrier coatings (TBCs) to provide still higher reliability, thermal insulation effect and longer lifetime under harsh operating conditions. TBCs with nanostructure proved to be promising to deliver the desired property and performance. To exploit full potentials of the current widely used yttria-partially-stabilized zirconia (YSZ), nano-sized YSZ powders were developed and used as the ceramic source material. By controlling the deposition processes, novel TBCs with outstanding nanostructure such as nano-sized grains and pores were produced by atmospheric plasma spray (APS) and electron beam physical vapor deposition (EB-PVD), respectively. The incorporated nanostructure in TBCs resulted in substantial increase in thermal barrier effect and their lifetime. The long-term microstructure stability of the nanocoating was also investigated.

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

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2002-01-01

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

  3. Ceramic thermal barrier coatings for commercial gas turbine engines

    NASA Technical Reports Server (NTRS)

    Meier, Susan Manning; Gupta, Dinesh K.; Sheffler, Keith D.

    1991-01-01

    The paper provides an overview of the short history, current status, and future prospects of ceramic thermal barrier coatings for gas turbine engines. Particular attention is given to plasma-sprayed and electron beam-physical vapor deposited yttria-stabilized (7 wt pct Y2O3) zirconia systems. Recent advances include improvements in the spallation life of thermal barrier coatings, improved bond coat composition and spraying techniques, and improved component design. The discussion also covers field experience, life prediction modeling, and future directions in ceramic coatings in relation to gas turbine engine design.

  4. Thermal barrier coating resistant to sintering

    DOEpatents

    Subramanian, Ramesh; Sabol, Stephen M.

    2001-01-01

    A device (10) having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10) and is not soluble with the underlying ceramic layer (16). For a YSZ ceramic layer (16) the sintering resistant layer (22) may preferably be aluminum oxide or yttrium aluminum oxide, deposited as a continuous layer or as nodules.

  5. Thermal barrier coating having high phase stability

    DOEpatents

    Subramanian, Ramesh

    2002-01-01

    A device (10) comprising a substrate (22) having a deposited ceramic thermal barrier coating characterized by a microstructure having gaps (28) where the thermal barrier coating comprises a first thermal barrier layer (40), and a second thermal barrier layer (30) with a pyrochlore crystal structure having a chemical formula of A.sup.n+.sub.2-x B.sup.m+.sub.2+x O.sub.7-y, where A is selected from the group of elements consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and mixtures thereof, where B is selected from the group of elements consisting of Zr, Hf, Ti and mixtures thereof, where n and m are the valence of A and B respectively, and for -0.5.ltoreq.x.ltoreq.0.5, ##EQU1## and excluding the following combinations for x=0, y=0: A=La and B=Zr; A=La and B=Hf; A=Gd and B=Hf; and A=Yb and B=Ti.

  6. Thermal barrier coating system with intermetallic overlay bond coat

    SciTech Connect

    Duderstadt, E.C.; Nagaraj, B A.

    1993-08-24

    A superalloy article is described having a thermal barrier coating system thereon, comprising: a substrate made of a material selected from the group consisting of a nickel-based superalloy and a cobalt-based superalloy; and a thermal barrier coating system on the substrate, the thermal barrier coating system including an intermetallic bond coat overlying the substrate, the bond coat being selected from the group consisting of a nickel aluminide and a platinum aluminide intermetallic compound, a thermally grown aluminum oxide layer overlying the intermetallic bond coat, and a ceramic topcoat overlying the aluminum oxide layer.

  7. Radiative Transport Modelling of Thermal Barrier Coatings

    DTIC Science & Technology

    2017-03-24

    AFRL-AFOSR-UK-TR-2017-0028 Radiative transport modeling of thermal barrier coatings Bauke Heeg Lumium Final Report 03/24/2017 DISTRIBUTION A... Thermal Barrier Coatings 5a. CONTRACT NUMBER FA9550-16-C-0006 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Heeg, Bauke, Dr. 5d...project is to develop an accurate analytical model of radiative transfer through porous ceramic thermal barrier coatings (TBCs). In particular, the

  8. Thermal barrier coating system having improved adhesion

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Sovey, J. S. (Inventor)

    1982-01-01

    The adherence between a ceramic thermal barrier coating and a metal bond coating is improved by ion sputtering a ceramic film on the bond cost. A ceramic thermal barrier coating is then plasma-sprayed onto this primer film. This improves the integrity and strength of the interface between the plasma-sprayed ceramic layer and metallic bond coat which insures stronger adherence between the metal and the ceramic.

  9. Thermal barrier coating evaluation needs

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Miller, Robert A.

    1990-01-01

    A 0.025 cm (0.010 in) thick thermal barrier coating (TBC) applied to turbine airfoils in a research gas turbine engine provided component temperature reductions of up to 190 C. These impressive temperature reductions can allow increased engine operating temperatures and reduced component cooling to achieve greater engine performance without sacrificing component durability. The significant benefits of TBCs are well established in aircraft gas turbine engine applications and their use is increasing. TBCs are also under intense development for use in the Low Heat Rejection (LHR) diesel engine currently being developed and are under consideration for use in utility and marine gas turbines. However, to fully utilize the benefits of TBCs it is necessary to accurately characterize coating attributes that affect the insulation and coating durability. The purpose there is to discuss areas in which nondestructive evaluation can make significant contributions to the further development and full utilization of TBCs for aircraft gas turbine engines and low heat rejection diesel engines.

  10. Advanced thermal barrier coating system development. Technical progress report, January 1, 1996--March 31, 1996

    SciTech Connect

    1996-04-08

    Objectives of this program are to provide a thermal barrier coating system with increased temperature capability and improved reliability relative to current state of the art systems. This report describes the bond coat deposition process, manufacturing, and repair.

  11. Low Thermal Conductivity Thermal Barrier Coatings Developed

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2003-01-01

    Thermal barrier coatings (TBCs) are used extensively in modern gas turbine engines to thermally insulate air-cooled metallic components from the hot gases in the engine. These coatings typically consist of a zirconia-yttria ceramic that has been applied by either plasma spraying or physical vapor deposition. Future engines will rely even more heavily on TBCs and will require materials that have even higher temperature capability with improved insulation (i.e., lower thermal conductivity even after many hours at high temperature). This report discusses new TBCs that have been developed with these future requirements in mind. The Ultra-Efficient Engine Technology Program at the NASA Glenn Research Center is funding this effort, which has been conducted primarily at Glenn with contractor support (GE and Howmet) for physical vapor deposition. As stated, the new TBC not only had to be more insulating but the insulation had to persist even after many hours of exposure-that is, the new TBC had to have both lower conductivity and improved sintering resistance. A new type of test rig was developed for this task. This new test approach used a laser to deliver a known high heat flux in an essentially uniform pattern to the surface of the coating, thereby establishing a realistic thermal gradient across its thickness. This gradient was determined from surface and backside pyrometry; and since the heat flux and coating thickness are known, this permitted continuous monitoring of thermal conductivity. Thus, this laser rig allowed very efficient screening of candidate low-conductivity, sinter-resistant TBCs. The coating-design approach selected for these new low-conductivity TBCs was to identify oxide dopants that had the potential to promote the formation of relatively large and stable groupings of defects known as defect clusters. This approach was used because it was felt that such clusters would reduce conductivity while enhancing stability. The approach proved to be

  12. Bond strength and stress measurements in thermal barrier coatings

    SciTech Connect

    Gell, M.; Jordan, E.

    1995-10-01

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. To meet the aggressive Advanced Turbine Systems goals for efficiency, durability and the environment, it will be necessary to employ thermal barrier coatings on turbine airfoils and other hot section components. For The successful application of TBCs to ATS engines with 2600{degrees}F turbine inlet temperatures and required component lives 10 times greater than those for aircraft gas turbine engines, it is necessary to develop quantitative assessment techniques for TBC coating integrity with time and cycles in ATS engines. Thermal barrier coatings in production today consist of a metallic bond coat, such as an MCrAlY overlay coating or a platinum aluminide (Pt-Al) diffusion coating. During heat treatment, both these coatings form a thin, tightly adherent alumina (Al{sub 2}O{sub 3}) film. Failure of TBC coatings in engine service occurs by spallation of the ceramic coating at or near the bond coat to alumina or the alumina to zirconia bonds. Thus, it is the initial strength of these bonds and the stresses at the bond plane, and their changes with engine exposure, that determines coating durability. The purpose of this program is to provide, for the first time, a quantitative assessment of TBC bond strength and bond plane stresses as a function of engine time and cycles.

  13. Fracture mechanism of a thermal barrier coating

    NASA Astrophysics Data System (ADS)

    Samoilenko, V. M.; Ravilov, R. G.; Drevnyak, V. V.; Petrova, M. A.

    2016-06-01

    The fracture mechanism of the thermal barrier coating of gas turbine blades is studied. The causes of the fracture of the ceramic layer are discussed and the possible ways to increase the fatigue life of the thermal barrier coating are considered.

  14. Metallic seal for thermal barrier coating systems

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor)

    1990-01-01

    The invention is particularly concerned with sealing thermal barrier coating systems of the type in use and being contemplated for use in diesel and other internal combustion engines. The invention also would find application in moderately high temperature regions of gas turbine engines and any other application employing a thermal barrier coating at moderate temperatures. Ni-35Cr-6Al-1Y, Ni-35Cr-6Al-1Yb, or other metallic alloy denoted as MCrAlx is applied over a zirconia-based thermal barrier overlayer. The close-out layer is glass-bead preened to densify its surface. This seals and protects the thermal barrier coating system.

  15. Porosity determination of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Van Roode, Mark; Beardsley, Brad

    1988-01-01

    Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBCs). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.

  16. Porosity determination of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Van Roode, Mark; Beardsley, Brad

    1988-01-01

    Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBCs). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.

  17. Thermal barrier coating having high phase stability

    DOEpatents

    Subramanian, Ramesh

    2001-01-01

    A device (10) comprising a substrate (22) having a deposited ceramic thermal barrier coating layer (20) characterized by a microstructure having gaps (28) where the thermal barrier coating (20) consists essentially of a pyrochlore crystal structure having a chemical formula consisting essentially of A.sup.n+.sub.2-x B.sup.m+.sub.2+x O.sub.7-y, where A is selected from the group of elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and mixtures thereof; where B is selected from the group of elements selected from Zr, Hf, Ti and mixtures thereof; n and m are the valence of A and B respectively, and for -0.5.ltoreq.x.ltoreq.0.5, ##EQU1## and excluding the following combinations for x=0, y=0: A=La and B=Zr; A=La and B=Hf; A=Gd and B=Hf; and A=Yb and B=Ti.

  18. Bond strength and stress measurements in thermal barrier coatings

    SciTech Connect

    Gell, M.; Jordan, E.

    1995-12-31

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. This program evaluates the bond strength of yttria stabilized zirconia coatings with MCrAlY and Pt-Al bond coats utilizing diffraction and fluorescence methods.

  19. DEGRADATION OF SM2ZR2O7 THERMAL BARRIER COATING CAUSED BY CALCIUM-MAGNESIUM-ALUMINUM-SILICON OXIDE (CMAS) DEPOSITION

    SciTech Connect

    Wang, Honglong; Sheng, Zhizhi; Tarwater, Emily; Zhang, Xingxing; Dasgupta, Sudip; Fergus, Jeffrey

    2015-03-16

    Rare earth zirconates are promising materials for use as thermal barrier coatings in gas turbine engines. Among the lanthanide zirconate materials, Sm2Zr2O7 with the pyrochlore structure has lower thermal conductivity and better corrosion resistance against calcium-magnesium-aluminum-silicon oxide (CMAS). In this work, after reaction with CMAS, the pyrochlore structure transforms to the cubic fluorite structure and Ca2Sm8(SiO4)6O2 forms in elongated grain.

  20. Thermal barrier coating resistant to sintering

    DOEpatents

    Subramanian, Ramesh; Seth, Brig B.

    2005-08-23

    A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process. The sintering inhibiting material (22) has a morphology adapted to improve the functionality of the sintering inhibiting material (22), characterized as continuous, nodule, rivulet, grain, crack, flake and combinations thereof and being disposed within at least some of the vertical and horizontal gaps.

  1. Lower-Conductivity Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2003-01-01

    Thermal-barrier coatings (TBCs) that have both initial and post-exposure thermal conductivities lower than those of yttria-stabilized zirconia TBCs have been developed. TBCs are thin ceramic layers, generally applied by plasma spraying or physical vapor deposition, that are used to insulate air-cooled metallic components from hot gases in gas turbine and other heat engines. Heretofore, yttria-stabilized zirconia (nominally comprising 95.4 atomic percent ZrO2 + 4.6 atomic percent Y2O3) has been the TBC material of choice. The lower-thermal-conductivity TBCs are modified versions of yttria-stabilized zirconia, the modifications consisting primarily in the addition of other oxides that impart microstructural and defect properties that favor lower thermal conductivity.

  2. Mechanical properties testing and results for thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Johnsen, B. P.; Nagy, Andrew

    1995-01-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  3. Mechanical properties testing and results for thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Johnsen, B. P.; Nagy, Andrew

    1995-01-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  4. Controlled Thermal Expansion Coat for Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Brindley, William J. (Inventor); Miller, Robert A. (Inventor); Aikin, Beverly J. M. (Inventor)

    1999-01-01

    A improved thermal barrier coating and method for producing and applying such is disclosed herein. The thermal barrier coating includes a high temperature substrate, a first bond coat layer applied to the substrate of MCrAlX, and a second bond coat layer of MCrAlX with particles of a particulate dispersed throughout the MCrAlX and the preferred particulate is Al2O3. The particles of the particulate dispersed throughout the second bond coat layer preferably have a diameter of less then the height of the peaks of the second bond coat layer, or a diameter of less than 5 microns. The method of producing the second bond coat layer may either include the steps of mechanical alloying of particles throughout the second bond coat layer, attrition milling the particles of the particulate throughout the second bond coat layer, or using electrophoresis to disperse the particles throughout the second bond coat layer. In the preferred embodiment of the invention, the first bond coat layer is applied to the substrate, and then the second bond coat layer is thermally sprayed onto the first bond coat layer. Further, in a preferred embodiment of die invention, a ceramic insulating layer covers the second bond coat layer.

  5. Indentation of zirconia thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Kernan, Brian Daniel

    Zirconia Thermal Barrier Coatings (TBCs) are widely used in gas turbine engines to protect metal parts from both heat and oxidation. However, TBCs fail after some time due to build up of stresses caused by microstructural changes, or by damage due to particle ingestion and impact commonly referred to as Foreign Object Damage (FOD). TBC mechanical properties are needed to be able to model stress development and the predication of cracking, particularly at high temperature. A TBC made by Electron Beam Physical Vapor Deposition (EBPVD) was found to be very strain rate sensitive in its hardness response in both the as-deposited and aged conditions from room temperature to 1200°C. The through-thickness hardness of the as-deposited TBC was measured from room temperature to 500°C. A high temperature vacuum displacement sensitive indenter was developed to measure both elastic modulus and hardness, as well as provide simulation of FOD under fast loading conditions. Some solutions to current performance problems of the machine are given.

  6. Ruthenium-containing bond coats for thermal barrier coating systems

    NASA Astrophysics Data System (ADS)

    Tryon, B.; Cao, F.; Murphy, K. S.; Levi, C. G.; Pollock, T. M.

    2006-01-01

    Bond coats for zirconia-based thermal barrier coating systems applied to nickel-based superalloys are typically composed of the B2 NiAl phase. Since RuAl has the same B2 crystal structure but a melting point 400°C higher than NiAl, ruthenium-modified aluminide bond coats could provide improved system temperature capability. Creep experiments on ternary Al-Ni-Ru alloys demonstrate greatly improved creep properties with increasing ruthenium content. Processing paths for ruthenium-modified NiAl-based bond coatings have been established within the bounds of commercially available coating systems. The oxidation resistance of ruthenium-modified bond coats during thermal cycling has been examined, and potential thermal barrier coating system implications are discussed.

  7. Blanch Resistant and Thermal Barrier NiAl Coating Systems for Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

    A method of forming an environmental resistant thermal barrier coating on a copper alloy is disclosed. The steps include cleansing a surface of a copper alloy, depositing a bond coat on the cleansed surface of the copper alloy, depositing a NiAl top coat on the bond coat and consolidating the bond coat and the NiAl top coat to form the thermal barrier coating. The bond coat may be a nickel layer or a layer composed of at least one of copper and chromium-copper alloy and either the bond coat or the NiAl top coat or both may be deposited using a low pressure or vacuum plasma spray.

  8. Blanch Resistant and Thermal Barrier NiAl Coating Systems for Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

    A method of forming an environmental resistant thermal barrier coating on a copper alloy is disclosed. The steps include cleansing a surface of a copper alloy, depositing a bond coat on the cleansed surface of the copper alloy, depositing a NiAl top coat on the bond coat and consolidating the bond coat and the NiAl top coat to form the thermal barrier coating. The bond coat may be a nickel layer or a layer composed of at least one of copper and chromium-copper alloy and either the bond coat or the NiAl top coat or both may be deposited using a low pressure or vacuum plasma spray.

  9. Interaction of atomized colloid with an ac electric field in a dielectric barrier discharge reactor used for deposition of nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Profili, Jacopo; Dap, Simon; Levasseur, Olivier; Naude, Nicolas; Belinger, Antoine; Stafford, Luc; Gherardi, Nicolas

    2017-02-01

    Nanocomposite thin films can be obtained by polymerization of a colloidal solution in a dielectric barrier discharge (DBD) at atmospheric pressure. In such a process, the dispersion of nanoparticles into the matrix is driven by the charging, transport, and deposition dynamics of the atomized colloid. This work examines the interaction of atomized TiO2 nanoparticles with ac electric fields in a plane-to-plane dielectric barrier discharge reactor. Experiments are performed with the discharge off to examine transport and deposition phenomena over a wide range of experimental conditions with a fixed particle charge distribution. Scanning electron microscopy reveals that the size distribution of TiO2 nanoparticles collected at different locations along the substrate surface placed on the bottom electrode of the DBD reactor can judiciously be controlled by varying the amplitude and frequency of the ac electric field. These results are also compared to the predictions of a simple particle motion model accounting for the electrostatic force, the gravitational force, and the neutral drag force in the laminar flow. It is found that while the initial charge distribution of atomized particles strongly influences the total deposition yield, its maximal position on the substrate, and the width of the deposited area, the initial size distribution of the particles at the entrance of the reactor mostly changes the size distribution at each position along the substrate surface.

  10. Microstructure of vapor deposited coatings on curved substrates

    SciTech Connect

    Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G.

    2015-09-15

    Thermal barrier coating systems consisting of a metallic bond coat and ceramic over layer are widely used to extend the life of gas turbine engine components. They are applied using either high-vacuum physical vapor deposition techniques in which vapor atoms rarely experience scattering collisions during propagation to a substrate, or by gas jet assisted (low-vacuum) vapor deposition techniques that utilize scattering from streamlines to enable non-line-of-sight deposition. Both approaches require substrate motion to coat a substrate of complex shape. Here, direct simulation Monte Carlo and kinetic Monte Carlo simulation methods are combined to simulate the deposition of a nickel coating over the concave and convex surfaces of a model airfoil, and the simulation results are compared with those from experimental depositions. The simulation method successfully predicted variations in coating thickness, columnar growth angle, and porosity during both stationary and substrate rotated deposition. It was then used to investigate a wide range of vapor deposition conditions spanning high-vacuum physical vapor deposition to low-vacuum gas jet assisted vapor deposition. The average coating thickness was found to increase initially with gas pressure reaching a maximum at a chamber pressure of 8–10 Pa, but the best coating thickness uniformity was achieved under high vacuum deposition conditions. However, high vacuum conditions increased the variation in the coatings pore volume fraction over the surface of the airfoil. The simulation approach was combined with an optimization algorithm and used to investigate novel deposition concepts to tailor the local coating thickness.

  11. Chemical vapor deposition of mullite coatings

    DOEpatents

    Sarin, Vinod; Mulpuri, Rao

    1998-01-01

    This invention is directed to the creation of crystalline mullite coatings having uniform microstructure by chemical vapor deposition (CVD). The process comprises the steps of establishing a flow of reactants which will yield mullite in a CVD reactor, and depositing a crystalline coating from the reactant flow. The process will yield crystalline coatings which are dense and of uniform thickness.

  12. Thermal Barrier Coatings. Abstracts and figures

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The Thermal Barrier Coatings Workshop was held May 21 and 22, 1985, at the NASA Lewis Research Center in Cleveland, Ohio. Six sessions covered Failure Mechanisms and Life Modeling, Effects of Oxidation and Creep, Phase Stability and Microstructural Aspects, Nondestructive and Analytical Assessment, Coating Development, and Alternative Applications.

  13. Improved Metallography Of Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Leonhardt, Todd A.

    1991-01-01

    New technique for preparation of metallographic samples makes interpretation of images of pores and microcracks more reliable. Involves use of vacuum epoxy infiltration and interference-film coating to reduce uncertainty. Developed for inspection of plasma-sprayed ceramic thermal-barrier coatings on metals but applicable to other porous, translucent materials, including many important ceramics.

  14. Improved metallic and thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1981-01-01

    Low thermal conductivity two layer ceramic coatings are efficient thermal barriers between cooled matallic components and high temperature combustion gases. Potential components are combustors, blades, and vanes in aircraft engines of power-generating turbines. Presence of two layer coatings greatly reduces temperature and coolant requirements.

  15. Solid coatings deposited from liquid methyl methacrylate via Plasma Polymerization

    NASA Astrophysics Data System (ADS)

    Wurlitzer, Lisa; Maus-Friedrichs, Wolfgang; Dahle, Sebastian

    2016-09-01

    The polymerization of methyl methacrylate via plasma discharges is well known today. Usually, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit polymer coatings. Solid coatings are formed out of the liquid phase from methyl methacrylate via dielectric barrier discharge. The formation of the coating proceeds in the gas and the liquid phase. To learn more about the reactions in the two phases, the coatings from MMA monomer will be compared to those from MMA resin. Finally, attenuated total reflection infrared spectroscopy, confocal laser scanning microscopy and X-ray photoelectron spectroscopy are employed to characterize the solid coatings. In conclusion, the plasma enhanced chemical solution deposition is compared to the classical thermal polymerization of MMA.

  16. Thermal Residual Stress in Environmental Barrier Coated Silicon Nitride - Modeled

    NASA Technical Reports Server (NTRS)

    Ali, Abdul-Aziz; Bhatt, Ramakrishna T.

    2009-01-01

    When exposed to combustion environments containing moisture both un-reinforced and fiber reinforced silicon based ceramic materials tend to undergo surface recession. To avoid surface recession environmental barrier coating systems are required. However, due to differences in the elastic and thermal properties of the substrate and the environmental barrier coating, thermal residual stresses can be generated in the coated substrate. Depending on their magnitude and nature thermal residual stresses can have significant influence on the strength and fracture behavior of coated substrates. To determine the maximum residual stresses developed during deposition of the coatings, a finite element model (FEM) was developed. Using this model, the thermal residual stresses were predicted in silicon nitride substrates coated with three environmental coating systems namely barium strontium aluminum silicate (BSAS), rare earth mono silicate (REMS) and earth mono di-silicate (REDS). A parametric study was also conducted to determine the influence of coating layer thickness and material parameters on thermal residual stress. Results indicate that z-direction stresses in all three systems are small and negligible, but maximum in-plane stresses can be significant depending on the composition of the constituent layer and the distance from the substrate. The BSAS and REDS systems show much lower thermal residual stresses than REMS system. Parametric analysis indicates that in each system, the thermal residual stresses can be decreased with decreasing the modulus and thickness of the coating.

  17. Silicon oxide permeation barrier coating of PET bottles and foils

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Deilmann, Michael; Awakowicz, Peter

    2009-10-01

    Modern packaging materials such as polyethylene terephthalate (PET) have displaced established materials in many areas of food and beverage packaging. Plastic packing materials offer are various advantages concerning production and handling. PET bottles for instance are non-breakable and lightweight compared to glass and metal containers. However, PET offers poor barrier properties against gas permeation. Therefore, the shelf live of packaged food is reduced. Permeation of gases can be reduced by depositing transparent plasma polymerized silicon oxide (SiOx) barrier coatings. A microwave (2.45 GHz) driven low pressure plasma reactor is developed based on a modified Plasmaline antenna to treat PET foils or bottles. To increase the barrier properties of the coatings furthermore a RF substrate bias (13.56 MHz) is applied. The composition of the coatings is analyzed by means of Fourier transform infrared (FTIR) spectroscopy regarding carbon and hydrogen content. Influence of gas phase composition and substrate bias on chemical composition of the coatings is discussed. A strong relation between barrier properties and film composition is found: good oxygen barriers are observed as carbon content is reduced and films become quartz-like. Regarding oxygen permeation a barrier improvement factor (BIF) of 70 is achieved.

  18. Thermal barrier coating life prediction model

    NASA Technical Reports Server (NTRS)

    Hillery, R. V.; Pilsner, B. H.

    1985-01-01

    This is the first report of the first phase of a 3-year program. Its objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, then to develop and verify life prediction models accounting for these degradation modes. The first task (Task I) is to determine the major failure mechanisms. Presently, bond coat oxidation and bond coat creep are being evaluated as potential TBC failure mechanisms. The baseline TBC system consists of an air plasma sprayed ZrO2-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene'80 substrate. Pre-exposures in air and argon combined with thermal cycle tests in air and argon are being utilized to evaluate bond coat oxidation as a failure mechanism. Unexpectedly, the specimens pre-exposed in argon failed before the specimens pre-exposed in air in subsequent thermal cycles testing in air. Four bond coats with different creep strengths are being utilized to evaluate the effect of bond coat creep on TBC degradation. These bond coats received an aluminide overcoat prior to application of the top coat to reduce the differences in bond coat oxidation behavior. Thermal cycle testing has been initiated. Methods have been selected for measuring tensile strength, Poisson's ratio, dynamic modulus and coefficient of thermal expansion both of the bond coat and top coat layers.

  19. Thick thermal barrier coatings for diesel components

    NASA Technical Reports Server (NTRS)

    Yonushonis, T. M.

    1991-01-01

    An engineered thick thermal barrier coating consisting of multiple layers of zirconia and CoCrAlY with a zirconia top layer and having a system thermal conductance less than 410 w/m(exp 2)K exceeded the 100 hour engine durability goals set forth in this program. The thermal barrier coatings were intact at the test conclusion. Back to back single cylinder research engine tests were conducted with watercooled, metal hardware and oil-cooled, thermal barrier coating insulated hardware to determine apparent heat release and fuel economy. Apparent heat release data revealed that the insulated engine had a shorter ignition delay and a longer combustion duration than the metal engine. The insulated engine fuel economy was approximately two percent worse on average for this series of tests. There was no attempt to optimize engine efficiency of the insulated engine by modifying the engine timing, coating, or other techniques.

  20. Development of Advanced Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

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

  1. Study on Preparation Technologies of Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Ning; Li, Yang; Wang, Hao; Tang, Jie; Wang, Yunshan

    Thermal barrier coatings (TBCs) is one of the main key technology for the high-pressure turbine blades which are the main components of the high-performance aerospace engines. It offers protection for underline metallic components from corrosion, oxidation and localized melting by insulating the metal from hot gases in the engine core. The properties and lifetime of TBCs are greatly influenced by the preparation technology, which includes plasma spraying (PS), physical vapor deposition (PVD) and laser re-melting (LM). In this paper, three technologies used to prepare the TBCs are reviewed. Resulting features of coating fabricated by each technology are also discussed such as: the porosity, the thermally grown oxide (TGO), the erosion resistance, the thermal shock and so on. Especially, it is pointed out that the performances of gradient coating and nano-coating are better than the traditional coatings. In addition, it is widely accepted that laser can be applied to re-melt the PS coating and even directly clad the gradient coating. In the future, the traditional preparation technology should be improved continually in order to enhance the coating lifetime, enhance the properties of coating and lower the cost of process. Moreover, the researches on gradient-nano-structured coatings preparation are absent and should be done with emphasis since the nano-structure and gradient structure can both benefit the lifetime and properties of coatings.

  2. Ceramic thermal barrier coating for rapid thermal cycling applications

    DOEpatents

    Scharman, Alan J.; Yonushonis, Thomas M.

    1994-01-01

    A thermal barrier coating for metal articles subjected to rapid thermal cycling includes a metallic bond coat deposited on the metal article, at least one MCrAlY/ceramic layer deposited on the bond coat, and a ceramic top layer deposited on the MCrAlY/ceramic layer. The M in the MCrAlY material is Fe, Ni, Co, or a mixture of Ni and Co. The ceramic in the MCrAlY/ceramic layer is mullite or Al.sub.2 O.sub.3. The ceramic top layer includes a ceramic with a coefficient of thermal expansion less than about 5.4.times.10.sup.-6 .degree.C.sup.-1 and a thermal conductivity between about 1 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1 and about 1.7 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1.

  3. Thrust chamber thermal barrier coating techniques

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.

    1988-01-01

    Methods for applying thermal barrier coatings to the hot-gas side wall of rocket thrust chambers in order to significantly reduce the heat transfer in high heat flux regions was the focus of technology efforts for many years. This paper describes a successful technique developed by the Lewis Research Center that starts with the coating of a mandrel and then builds the thrust chamber around it by electroforming appropriate materials. This results in a smooth coating with exceptional adherence, demonstrated in hot fire rig tests. The low cycle fatigue life of chambers with coatings applied in this manner was increased dramatically compared to uncoated chambers.

  4. Thrust chamber thermal barrier coating techniques

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.

    1989-01-01

    Methods for applying thermal barrier coatings to the hot-gas side wall of rocket thrust chambers in order to significantly reduce the heat transfer in high heat flux regions has been the focus of technology efforts for many years. A successful technique developed by NASA-Lewis that starts with the coating on a mandrel and then builds the thrust chamber around it by electroforming appropriate materials is described. This results in a smooth coating with exceptional adherence, as was demonstrated in hot fire rig tests. The low cycle fatigue life of chambers with coatings applied in this manner was increased dramatically compared to uncoated chambers.

  5. Rocket thrust chamber thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Batakis, A. P.; Vogan, J. W.

    1985-01-01

    A research program was conducted to generate data and develop analytical techniques to predict the performance and reliability of ceramic thermal barrier coatings in high heat flux environments. A finite element model was used to analyze the thermomechanical behavior of coating systems in rocket thrust chambers. Candidate coating systems (using a copper substrate, NiCrAlY bond coat and ZrO2.8Y2O3 ceramic overcoat) were selected for detailed study based on photomicrographic evaluations of experimental test specimens. The effects of plasma spray application parameters on the material properties of these coatings were measured and the effects on coating performance evaluated using the finite element model. Coating design curves which define acceptable operating envelopes for seleted coating systems were constructed based on temperature and strain limitations. Spray gun power levels was found to have the most significant effect on coating structure. Three coating systems were selected for study using different power levels. Thermal conductivity, strain tolerance, density, and residual stress were measured for these coatings. Analyses indicated that extremely thin coatings ( 0.02 mm) are required to accommodate the high heat flux of a rocket thrust chamber and ensure structural integrity.

  6. Polyelectrolyte Coacervates Deposited as High Gas Barrier Thin Films.

    PubMed

    Haile, Merid; Sarwar, Owais; Henderson, Robert; Smith, Ryan; Grunlan, Jaime C

    2017-01-01

    Multilayer coatings consisting of oppositely charged polyelectrolytes have proven to be extraordinarily effective oxygen barriers but require many processing steps to fabricate. In an effort to prepare high oxygen barrier thin films more quickly, a polyelectrolyte complex coacervate composed of polyethylenimine and polyacrylic acid is prepared. The coacervate fluid is applied as a thin film using a rod coating process. With humidity and thermal post-treatment, a 2 µm thin film reduces the oxygen transmission rate of 0.127 mm poly(ethylene terephthalate) by two orders of magnitude, rivalling conventional oxygen barrier technologies. These films are fabricated in ambient conditions using low-cost, water-based solutions, providing a tremendous opportunity for single-step deposition of polymeric high barrier thin films. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Vacuum application of thermal barrier plasma coatings

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  8. Spray-Deposited Superconductor/Polymer Coatings

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Tran, Sang Q.; Hooker, Matthew W.

    1993-01-01

    Coatings that exhibit the Meissner effect formed at relatively low temperature. High-temperature-superconductor/polymer coatings that exhibit Meissner effect deposited onto components in variety of shapes and materials. Simple, readily available equipment needed in coating process, mean coatings produced economically. Coatings used to keep magnetic fields away from electronic circuits in such cryogenic applications as magnetic resonance imaging and detection of infrared, and in magnetic suspensions to provide levitation and/or damping of vibrations.

  9. Spray-Deposited Superconductor/Polymer Coatings

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Tran, Sang Q.; Hooker, Matthew W.

    1993-01-01

    Coatings that exhibit the Meissner effect formed at relatively low temperature. High-temperature-superconductor/polymer coatings that exhibit Meissner effect deposited onto components in variety of shapes and materials. Simple, readily available equipment needed in coating process, mean coatings produced economically. Coatings used to keep magnetic fields away from electronic circuits in such cryogenic applications as magnetic resonance imaging and detection of infrared, and in magnetic suspensions to provide levitation and/or damping of vibrations.

  10. Thermal barrier coatings application in diesel engines

    NASA Technical Reports Server (NTRS)

    Fairbanks, J. W.

    1995-01-01

    Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr,. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also to provide protection. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the thermal barrier coatings will be to reduce thermal fatigue as the engine peak cylinder pressure will nearly be doubled. As the coatings result in higher available energy in the exhaust gas, efficiency gains are achieved through use of this energy by turbochargers, turbocompounding or thermoelectric generators.

  11. Ceramic Top Coats of Plasma-Sprayed Thermal Barrier Coatings: Materials, Processes, and Properties

    NASA Astrophysics Data System (ADS)

    Bakan, Emine; Vaßen, Robert

    2017-08-01

    The ceramic top coat has a major influence on the performance of the thermal barrier coating systems (TBCs). Yttria-partially-stabilized zirconia (YSZ) is the top coat material frequently used, and the major deposition processes of the YSZ top coat are atmospheric plasma spraying and electron beam physical vapor deposition. Recently, also new thermal spray processes such as suspension plasma spraying or plasma spray-physical vapor deposition have been intensively investigated for TBC top coat deposition. These new processes and particularly the different coating microstructures that can be deposited with them will be reviewed in this article. Furthermore, the properties and the intrinsic-extrinsic degradation mechanisms of the YSZ will be discussed. Following the TBC deposition processes and standard YSZ material, alternative ceramic materials such as perovskites and hexaaluminates will be summarized, while properties of pyrochlores with regard to their crystal structure will be discussed more in detail. The merits of the pyrochlores such as good CMAS resistance as well as their weaknesses, e.g., low fracture toughness, processability issues, will be outlined.

  12. Comparison of Thermal Properties of Thermal Barrier Coating Deposited on IN738 Using Standard Air Plasma Spray with 100HE Plasma Spray System

    SciTech Connect

    Uppu, Nalini; Mensah, Patrick F.; Ofori, Daniel

    2006-07-31

    Thermal barrier coatings (TBCs) have low thermal conductivity values and have a primary benefit of providing an insulating layer that reduces the coated substrate temperature and mitigates the effects of hot streaking or uneven temperature distributions. Thermal conductivity, k, is a thermo-physical property that can be derived from the thermal diffusivity, α, of the specimen. It can be obtained from the formula k = α cp ρ, where cp is specific heat and ρ is the density of the material. Thermal conductivity, k, describes the quantity of heat that passes through a unit area of sample in unit time with a temperature gradient present. This thermal property of TBCs can be measured by flash method in which a nearly instantaneous pulse of energy (usually laser or other discharge source) is input to the frontal surface of a material sample and the temperature changes are measured on back side of sample with and INSb infrared detector as shown in Fig.1. A laser flash test has the advantage of being fast while providing values with excellent accuracy and reproducibility. In this study, an instantaneous triangular heat pulse from a laser heat flash system (FL5000) made by Anter corporation, Pittsburgh, PA was used. The technique satisfies the ASTM E 1461. The test method can measure thermal diffusivity values ranging from 10-7 to 10-3 m2/s from temperatures 75 to 2800 K.

  13. Thermal conductivity of zirconia thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

    1995-01-01

    Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor description (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard power or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increase upon being exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicates that if these coatings reach a temperature above

  14. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Demasi, J. T.

    1985-01-01

    A methodology was established to predict thermal barrier coating life in an environment simulative of that experienced by gas turbine airfoils. Specifically, work is being conducted to determine failure modes of thermal barrier coatings in the aircraft engine environment. Analytical studies coupled with appropriate physical and mechanical property determinations are being employed to derive coating life prediction model(s) on the important failure mode(s). An initial review of experimental and flight service components indicates that the predominant mode of TBC failure involves thermomechanical spallation of the ceramic coating layer. This ceramic spallation involves the formation of a dominant crack in the ceramic coating parallel to and closely adjacent to the metal-ceramic interface. Initial results from a laboratory test program designed to study the influence of various driving forces such as temperature, thermal cycle frequency, environment, and coating thickness, on ceramic coating spalling life suggest that bond coat oxidation damage at the metal-ceramic interface contributes significantly to thermomechanical cracking in the ceramic layer. Low cycle rate furnace testing in air and in argon clearly shows a dramatic increase of spalling life in the non-oxidizing environments.

  15. Thermal barrier coating life prediction model

    NASA Technical Reports Server (NTRS)

    Pilsner, B. H.; Hillery, R. V.; Mcknight, R. L.; Cook, T. S.; Kim, K. S.; Duderstadt, E. C.

    1986-01-01

    The objectives of this program are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. The program is divided into two phases, each consisting of several tasks. The work in Phase 1 is aimed at identifying the relative importance of the various failure modes, and developing and verifying life prediction model(s) for the predominant model for a thermal barrier coating system. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep. The work in Phase 2 will develop design-capable, causal, life prediction models for thermomechanical and thermochemical failure modes, and for the exceptional conditions of foreign object damage and erosion.

  16. Advanced thermal barrier coating system development. Technical progress report, April 1, 1996--May 31, 1996

    SciTech Connect

    1996-06-10

    Objectives of this program are to provide an improved thermal barrier system with increased temperature capability and reliability relative to current systems. This report describes the bond coat development and deposition, manufacturing, and repair.

  17. Environmental Barrier Coatings Having a YSZ Top Coat

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Gray, Hugh (Technical Monitor)

    2002-01-01

    Environmental barrier coatings (EBCs) with a Si bond coat, a yttria-stabilized zirconia (YSZ) top coat, and various intermediate coats were investigated. EBCs were processed by atmospheric pressure plasma spraying. The EBC durability was determined by thermal cycling tests in water vapor at 1300 C and 1400 C, and in air at 1400 C and 1500 C. EBCs with a mullite (3Al2O3 (dot) 2SiO2) + BSAS (1 - xBaO (dot) xSrO (dot) Al2O3 (dot) 2SiO2) intermediate coat were more durable than EBCs with a mullite intermediate coat, while EBCs with a mullite/BSAS duplex intermediate coat resulted in inferior durability. The improvement with a mullite + BSAS intermediate coat was attributed to enhanced compliance of the intermediate coat due to the addition of a low modulus BSAS second phase. Mullite + BSAS/YSZ and BSAS/YSZ interfaces produced a low melting (less than 1400 C) reaction product, which is expected to degrade the EBC performance by increasing the thermal conductivity. EBCs with a mullite + BSAS / graded mullite + YSZ intermediate coat showed the best durability among the EBCs investigated in this study. This improvement was attributed to diffused CTE (Coefficient of Thermal Expansion) mismatch stress and improved chemical stability due to the compositionally graded mullite+YSZ layer.

  18. Thick thermal barrier coatings for diesel engines

    NASA Technical Reports Server (NTRS)

    Beardsley, M. Brad

    1995-01-01

    Caterpillar's approach to applying thick thermal barrier coatings (TTBC's) to diesel engine combustion chambers has been to use advanced modeling techniques to predict engine conditions and combine this information with fundamental property evaluation of TTBC systems to predict engine performance and TTBC stress states. Engine testing has been used to verify the predicted performance of the TTBC systems and provide information on failure mechanisms. The objective Caterpillar's program to date has been to advance the fundamental understanding of thick thermal barrier coating systems. Previous reviews of thermal barrier coating technology concluded that the current level of understanding of coating system behavior is inadequate and the lack of fundamental understanding may impeded the application of TTBC's to diesel engines. Areas of TTBC technology being examined in this program include powder characteristics and chemistry; bond coat composition; coating design, microstructure, and thickness as they affect properties, durability, and reliability; and TTBC 'aging' effects (microstructural and property changes) under diesel engine operating conditions. Methods to evaluate the reliability and durability of TTBC's have been developed that attempt to understand the fundamental strength of TTBC's for particular stress states.

  19. Thick thermal barrier coatings for diesel engines

    NASA Technical Reports Server (NTRS)

    Beardsley, M. B.

    1995-01-01

    Caterpillar's approach to applying Thick Thermal Barrier Coatings (TTBC's) to diesel engine combustion chambers has been to use advanced modeling techniques to predict engine conditions and combine this information with fundamental property evaluation of TTBC systems to predict engine performance and TTBC stress states. Engine testing has been used to verify the predicted performance of the TTBC systems and provide information on failure mechanisms. The objective of Caterpillar's subcontract with ORNL is to advance the fundamental understanding of thick thermal barrier coating systems. Previous reviews of thermal barrier coating technology concluded that the current level of understanding of coating system behavior is inadequate and the lack of fundamental understanding may impede the application of TTBC's to diesel engines. Areas of TTBC technology being examined in this program include powder characteristics and chemistry; bond coat composition; coating design, microstructure, and thickness as they affect properties, durability, and reliability; and TTBC 'aging' effects (microstructural and property changes) under diesel engine operating conditions. Methods to evaluate the reliability and durability of TTBC's have been developed that attempt to understand the fundamental strength of TTBC's for particular stress states.

  20. Barrier Coatings for Refractory Metals and Superalloys

    SciTech Connect

    SM Sabol; BT Randall; JD Edington; CJ Larkin; BJ Close

    2006-02-23

    In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements. Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life.

  1. JT90 thermal barrier coated vanes

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Graziani, R. A.; Sinko, G. C.

    1982-01-01

    The technology of plasma sprayed thermal barrier coatings applied to turbine vane platforms in modern high temperature commercial engines was advanced to the point of demonstrated feasibility for application to commercial aircraft engines. The three thermal barrier coatings refined under this program are zirconia stabilized with twenty-one percent magnesia (21% MSZ), six percent yttria (6% YSZ), and twenty percent yttria (20% YSZ). Improvement in thermal cyclic endurance by a factor of 40 times was demonstrated in rig tests. A cooling system evolved during the program which featured air impingement cooling for the vane platforms rather than film cooling. The impingement cooling system, in combination with the thermal barrier coatings, reduced platform cooling air requirements by 44% relative to the current film cooling system. Improved durability and reduced cooling air requirements were demonstrated in rig and engine endurance tests. Two engine tests were conducted, one of 1000 cycles and the other of 1500 cycles. All three coatings applied to vanes fabricated with the final cooling system configuration completed the final 1500 cycle engine endurance test. Results of this test clearly demonstrated the durability of the 6% YSZ coating which was in very good condition after the test. The 21% MSZ and 20% YSZ coatings had numerous occurrences of significant spalling in the test.

  2. Degradation mechanisms in thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Shinde, S. L.; Olson, D. A.; Dejonghe, L. C.; Miller, R. A.

    1986-01-01

    The degradation mechanism in thermal barrier coating systems subjected to prolonged heating in air as well as to thermal cycling was studied. Bond coat oxidation was found to be the most important reason for degradation. The oxidation produced NiO as well as Al?O? in one set of samples, but the variation in initial coating structure made it difficult to resolve systematic differences between isothermally heated and thermally cycled samples. However, the contribution to degradation from changes in substrate composition seemed less in the cycled sample.

  3. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Hillery, R. V.; Pilsner, B. H.; Mcknight, R. L.; Cook, T. S.; Hartle, M. S.

    1988-01-01

    This report describes work performed to determine the predominat modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consisted of a low pressure plasma sprayed NiCrAlY bond coat, an air plasma sprayed ZrO2-Y2O3 top coat, and a Rene' 80 substrate. The work was divided into 3 technical tasks. The primary failure mode to be addressed was loss of the zirconia layer through spalling. Experiments showed that oxidation of the bond coat is a significant contributor to coating failure. It was evident from the test results that the species of oxide scale initially formed on the bond coat plays a role in coating degradation and failure. It was also shown that elevated temperature creep of the bond coat plays a role in coating failure. An empirical model was developed for predicting the test life of specimens with selected coating, specimen, and test condition variations. In the second task, a coating life prediction model was developed based on the data from Task 1 experiments, results from thermomechanical experiments performed as part of Task 2, and finite element analyses of the TBC system during thermal cycles. The third and final task attempted to verify the validity of the model developed in Task 2. This was done by using the model to predict the test lives of several coating variations and specimen geometries, then comparing these predicted lives to experimentally determined test lives. It was found that the model correctly predicts trends, but that additional refinement is needed to accurately predict coating life.

  4. Performance of Bond Coats Modified by Platinum Group Metals for Applications in Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Tawancy, H. M.; Alhems, Luai M.; Aboelfotoh, M. O.

    2017-07-01

    We have investigated the partial replacement of Pt with other less expensive Pt group metals on the properties of γ' + γ bond coats used in thermal barrier coatings (TBCs) deposited on a nickel-base superalloy. The microstructure, thermal stability, oxidation behavior and performance in TBC systems of bond coats synthesized with Pt + Ru, Pt + Ir and Pt + Rh are compared with those of a reference bond coat synthesized with Pt. Yttria-stabilized zirconia has been employed as top coat in all coating systems. It is shown that at high temperatures all bond coats are degraded by interdiffusion and oxidation, however, with different kinetics. The lifetime of each TBC system is found to be limited by the cohesion between the thermally grown oxide and underlying bond coat. Differences in the behavior of various bond coats are correlated with their properties. Among the three Pt group metals investigated, the properties of the Pt + Ru bond coat are shown to closely approach those of the Pt bond coat. It is concluded that Ru with much lower cost presents a potential candidate for reducing the consumption of Pt.

  5. Alternating-Composition Layered Ceramic Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2008-01-01

    Ceramic thermal and environmental barrier coatings (T/EBCs) that contain multiple layers of alternating chemical composition have been developed as improved means of protecting underlying components of gas-turbine and other heat engines against both corrosive combustion gases and high temperatures.

  6. Electro-spark deposited coatings for protection of materials

    SciTech Connect

    Johnson, R.N.

    1995-08-01

    Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The coating is fused (metallurgically bonded) to the substrate with such a low total heat input that the bulk substrate material remains at or near ambient temperature. Rapid solidification of the deposit typically results in an extremely fine-grained deposit that may be amorphous for some materials. Nearly any electrically conductive metal, alloy or cermet can be applied to metallic substrates. The ESD process allows multi-layer coatings to be built-up using different materials to create graded structures or surface compositions that would be difficult to achieve by other means. A series of iron-aluminide coatings based on Fe{sub 3}Al and FeAl in combination with refractory metal diffusion-barrier coatings and supplementary additions of other elements are in corrosion testing at ANL. The most recent FeAl coatings are showing a factor of three better corrosion performance than the best previous coatings. Technology transfer activities are a significant portion of the ESD program effort. Notable successes now include the start-up of a new business to commercialize the ESD technology, major new applications in gas turbine engines and steam turbine blade coatings, and in military, medical, metal-working, and recreational equipment applications.

  7. Delamination-Indicating Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.

    2007-01-01

    The risk of premature failure of thermal barrier coatings (TBCs), typically composed of yttria-stabilized zirconia (YSZ), compromises the reliability of TBCs used to provide thermal protection for turbine engine components. Unfortunately, TBC delamination proceeds well beneath the TBC surface and cannot be monitored by visible inspection. Nondestructive diagnostic tools that could reliably probe the subsurface damage state of TBCs would alleviate the risk of TBC premature failure by indicating when the TBC needs to be replaced before the level of TBC damage threatens engine performance or safety. To meet this need, a new coating design for thermal barrier coatings (TBCs) that are self-indicating for delamination has been successfully implemented by incorporating a europium-doped luminescent sublayer at the base of a TBC composed of YSZ. The luminescent sublayer has the same YSZ composition as the rest of the TBC except for the addition of low-level europium doping and therefore does not alter TBC performance.

  8. Thermal barrier coating life-prediction model development

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Neumann, J.; Liu, A.

    1986-01-01

    The program focuses on predicting the lives of two types of strain-tolerant and oxidation-resistant thermal barrier coating (TBC) systems that are produced by commercial coating suppliers to the gas turbine industry. The plasma-sprayed TBC system, composed of a low-pressure plasma-spray (LPPS) or an argon shrouded plasma-spray (ASPS) applied oxidation resistant NiCrAlY or (CoNiCrAlY) bond coating and an air-plasma-sprayed yttria partially stabilized zirconia insulative layer, is applied by both Chromalloy, Klock, and Union Carbide. The second type of TBS is applied by the electron beam-physical vapor deposition (EB-PVD) process by Temescal. The second year of the program was focused on specimen procurement, TMC system characterization, nondestructive evaluation methods, life prediction model development, and TFE731 engine testing of thermal barrier coated blades. Materials testing is approaching completion. Thermomechanical characterization of the TBC systems, with toughness, and spalling strain tests, was completed. Thermochemical testing is approximately two-thirds complete. Preliminary materials life models for the bond coating oxidation and zirconia sintering failure modes were developed. Integration of these life models with airfoil component analysis methods is in progress. Testing of high pressure turbine blades coated with the program TBS systems is in progress in a TFE731 turbofan engine. Eddy current technology feasibility was established with respect to nondestructively measuring zirconia layer thickness of a TBC system.

  9. Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dongming

    2006-01-01

    Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high-temperature thermal-barrier coatings (TBCs). In comparison with partially-yttria-stabilized zirconia (YSZ), which is the state-of-the-art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages: For a given difference in temperature between an outer coating surface and the coating/substrate interface, the coating could be thinner. Reductions in coating thicknesses could translate to reductions in weight of hot-section components of turbine engines (e.g., combustor liners, blades, and vanes) to which TBCs are typically applied. For a given coating thickness, the difference in temperature between the outer coating surface and the coating/substrate interface could be greater. For turbine engines, this could translate to higher operating temperatures, with consequent increases in efficiency and reductions in polluting emissions. TBCs are needed because the temperatures in some turbine-engine hot sections exceed the maximum temperatures that the substrate materials (superalloys, Si-based ceramics, and others) can withstand. YSZ TBCs are applied to engine components as thin layers by plasma spraying or electron-beam physical vapor deposition. During operation at higher temperatures, YSZ layers undergo sintering, which increases their thermal conductivities and thereby renders them less effective as TBCs. Moreover, the sintered YSZ TBCs are less tolerant of stress and strain and, hence, are less durable.

  10. Compilation of diamond-like carbon properties for barriers and hard coatings

    SciTech Connect

    Outka, D.A.; Hsu, Wen L.; Boehme, D.R.; Yang, N.Y.C.; Ottesen, D.K.; Johnsen, H.A.; Clift, W.M.; Headley, T.J.

    1994-02-01

    Diamond-like carbon (DLC) is an amorphous form of carbon which resembles diamond in its hardness, lubricity, and interest for hardness, lubricity, and resistance to chemical attack. Such properties make DLC of use in barrier and hard coating technology. This report examines a variety of properties of DLC coatings which are relevant to its use as a protective coating. This includes examining substrates on which DLC coatings can be deposited; the resistance of DLC coatings to various chemical agents; adhesion of DLC coatings; and characterization of DLC coatings by electron microscopy, FTIR, sputter depth profiling, stress measurements, and nanoindentation.

  11. Sand effects on thermal barrier coatings for gas turbine engines

    NASA Astrophysics Data System (ADS)

    Walock, Michael; Barnett, Blake; Ghoshal, Anindya; Murugan, Muthuvel; Swab, Jeffrey; Pepi, Marc; Hopkins, David; Gazonas, George; Kerner, Kevin

    Accumulation and infiltration of molten/ semi-molten sand and subsequent formation of calcia-magnesia-alumina-silicate (CMAS) deposits in gas turbine engines continues to be a significant problem for aviation assets. This complex problem is compounded by the large variations in the composition, size, and topology of natural sands, gas generator turbine temperatures, thermal barrier coating properties, and the incoming particulate's momentum. In order to simplify the materials testing process, significant time and resources have been spent in the development of synthetic sand mixtures. However, there is debate whether these mixtures accurately mimic the damage observed in field-returned engines. With this study, we provide a direct comparison of CMAS deposits from both natural and synthetic sands. Using spray deposition techniques, 7% yttria-stabilized zirconia coatings are deposited onto bond-coated, Ni-superalloy discs. Each sample is coated with a sand slurry, either natural or synthetic, and exposed to a high temperature flame for 1 hour. Test samples are characterized before and after flame exposure. In addition, the test samples will be compared to field-returned equipment. This research was sponsored by the US Army Research Laboratory, and was accomplished under Cooperative Agreement # W911NF-12-2-0019.

  12. Burner rig evaluation of thermal barrier coating

    SciTech Connect

    Gedwill, M.A.

    1981-02-01

    Eight plasma sprayed bond coatings were evaluated for their potential use with ZrO/sub 2/-Y/sub 2/O/sub 3/ thermal barrier coatings (TBCs) which are being developed for coal derived fuel fired gas turbines. Longer TBC lives in cyclic burner rig oxidation to 1050 C were achieved with the more oxidation resistant bond coatings. These were Ni-14.1Cr-13.4A1-0.10Ar, Ni-14.1C4-14.4Al-0.16Y, and Ni-15.8Cr-12.8Al-0.36Y on Rene 41. The TBC systems performed best when 0.015-cm thick bond coatings were employed that were sprayed at 20 kW using argon 3.5v/o hydrogen. Cycling had a more life limiting influence on the TBC than accumulated time at 1050 C.

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

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Miller, R. A.; Doychak, J.

    1992-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

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

  16. Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2005-01-01

    Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttria-partially stabilized zirconia. As used here, "thermal-barrier coatings" (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components. A TBC as deposited has some porosity, which is desirable in that it reduces the thermal conductivity below the intrinsic thermal conductivity of the fully dense form of the material. Undesirably, the thermal conductivity gradually increases because the porosity gradually decreases as a consequence of sintering during high-temperature service. Because of these and other considerations such as phase transformations, the maximum allowable service temperature for yttria-partially stabilized zirconia TBCs lies in the range of about 1,200 to 1,300 C. In contrast, the present multicomponent, rare-earth-doped, perovskite-type TBCs can withstand higher temperatures.

  17. Thermal barrier coatings: A near term, high payoff technology

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Clark, J. S.

    1977-01-01

    The present status of thermal barrier coatings is reviewed including both experimental results and forecasts of the benefits derived from use of these coatings in aircraft and utility gas turbines. The potential of thermal barrier coatings relative to structural ceramics is discussed along with a development plan for these coatings.

  18. Thermal barrier coating life prediction model

    NASA Technical Reports Server (NTRS)

    Hillery, R. V.; Pilsner, B. H.; Cook, T. S.; Kim, K. S.

    1986-01-01

    This is the second annual report of the first 3-year phase of a 2-phase, 5-year program. The objectives of the first phase are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consists of an air plasma sprayed ZrO-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene' 80 substrate. Task I was to evaluate TBC failure mechanisms. Both bond coat oxidation and bond coat creep have been identified as contributors to TBC failure. Key property determinations have also been made for the bond coat and the top coat, including tensile strength, Poisson's ratio, dynamic modulus, and coefficient of thermal expansion. Task II is to develop TBC life prediction models for the predominant failure modes. These models will be developed based on the results of thermmechanical experiments and finite element analysis. The thermomechanical experiments have been defined and testing initiated. Finite element models have also been developed to handle TBCs and are being utilized to evaluate different TBC failure regimes.

  19. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Demasi, J. T.

    1986-01-01

    A methodology is established to predict thermal barrier coating life in a environment similar to that experienced by gas turbine airfoils. Experiments were conducted to determine failure modes of the thermal barrier coating. Analytical studies were employed to derive a life prediction model. A review of experimental and flight service components as well as laboratory post evaluations indicates that the predominant mode of TBC failure involves thermomechanical spallation of the ceramic coating layer. This ceramic spallation involves the formation of a dominant crack in the ceramic coating parallel to and closely adjacent to the topologically complex metal ceramic interface. This mechanical failure mode clearly is influenced by thermal exposure effects as shown in experiments conducted to study thermal pre-exposure and thermal cycle-rate effects. The preliminary life prediction model developed focuses on the two major damage modes identified in the critical experiments tasks. The first of these involves a mechanical driving force, resulting from cyclic strains and stresses caused by thermally induced and externally imposed mechanical loads. The second is an environmental driving force based on experimental results, and is believed to be related to bond coat oxidation. It is also believed that the growth of this oxide scale influences the intensity of the mechanical driving force.

  20. Thermal barrier coatings application in diesel engines

    NASA Technical Reports Server (NTRS)

    Fairbanks, J. W.

    1995-01-01

    Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the

  1. Thermal barrier coatings application in diesel engines

    NASA Technical Reports Server (NTRS)

    Fairbanks, J. W.

    1995-01-01

    Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the

  2. Cold Sprayed Intermetallic Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Leshchinsky, Evgeny

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

  3. Dip Process Thermal Barrier Coating for Superalloys.

    DTIC Science & Technology

    1982-02-02

    the Project Supervisor is Dr. David J. Rowcliffe, Program Manager, Ceramics . Dr. Kai-Hung Lau, Materials Chemist performed the thermogravimetric...ever increasing demand for higher turbine inlet temperature in gas turbines has created an extensive interest in using ceramic materials to protect...airfoil surfaces. During the past decade, a concentrated effort was devoted to developing ceramic thermal barrier coatings to improve turbine

  4. The effect of environment on thermal barrier coating lifetime

    SciTech Connect

    Pint, Bruce A.; Unocic, Kinga A.; Haynes, James Allen

    2016-03-15

    While the water vapor content of the combustion gas in natural gas-fired land-based turbines is ~10%, it can be 20–85% with coal-derived (syngas or H2) fuels or innovative turbine concepts for more efficient carbon capture. Additional concepts envisage working fluids with high CO2 contents to facilitate carbon capture and sequestration. To investigate the effects of changes in the gas composition on thermal barrier coating (TBC) lifetime, furnace cycling tests (1-h and 100-h cycles) were performed in air with 10, 50, and 90 vol. % water vapor and CO2-10% H2O and compared to prior results in dry air or O2. Two types of TBCs were investigated: (1) diffusion bond coatings (Pt-diffusion or Pt-modified aluminide) with commercial electron-beam physical vapor-deposited yttria-stabilized zirconia (YSZ) top coatings on second-generation superalloy N5 and N515 substrates and (2) high-velocity oxygen fuel (HVOF) sprayed MCrAlYHfSi bond coatings with air plasma-sprayed YSZ top coatings on superalloys X4, 1483, or 247 substrates. For both types of coatings exposed in 1-h cycles, the addition of water vapor resulted in a decrease in coating lifetime, except for Pt-diffusion coatings which were unaffected by the environment. In 100-h cycles, environment was less critical, perhaps because coating failure was chemical (i.e., due to interdiffusion) rather than mechanical. As a result, in both 1-h and 100-h cycles, CO2 did not appear to have any negative effect on coating lifetime.

  5. The effect of environment on thermal barrier coating lifetime

    DOE PAGES

    Pint, Bruce A.; Unocic, Kinga A.; Haynes, James Allen

    2016-03-15

    While the water vapor content of the combustion gas in natural gas-fired land-based turbines is ~10%, it can be 20–85% with coal-derived (syngas or H2) fuels or innovative turbine concepts for more efficient carbon capture. Additional concepts envisage working fluids with high CO2 contents to facilitate carbon capture and sequestration. To investigate the effects of changes in the gas composition on thermal barrier coating (TBC) lifetime, furnace cycling tests (1-h and 100-h cycles) were performed in air with 10, 50, and 90 vol. % water vapor and CO2-10% H2O and compared to prior results in dry air or O2. Twomore » types of TBCs were investigated: (1) diffusion bond coatings (Pt-diffusion or Pt-modified aluminide) with commercial electron-beam physical vapor-deposited yttria-stabilized zirconia (YSZ) top coatings on second-generation superalloy N5 and N515 substrates and (2) high-velocity oxygen fuel (HVOF) sprayed MCrAlYHfSi bond coatings with air plasma-sprayed YSZ top coatings on superalloys X4, 1483, or 247 substrates. For both types of coatings exposed in 1-h cycles, the addition of water vapor resulted in a decrease in coating lifetime, except for Pt-diffusion coatings which were unaffected by the environment. In 100-h cycles, environment was less critical, perhaps because coating failure was chemical (i.e., due to interdiffusion) rather than mechanical. As a result, in both 1-h and 100-h cycles, CO2 did not appear to have any negative effect on coating lifetime.« less

  6. An analytical model of rumpling in thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Balint, D. S.; Hutchinson, J. W.

    2005-04-01

    Multilayer thermal barrier coatings (TBCs) deposited on superalloy turbine blades provide protection from combustion temperatures in excess of 1500 °C. One of the dominant failure modes comprises cracking from undulation growth, or rumpling, of the highly compressed oxide layer that grows between the ceramic top coat and the intermetallic bond coat. In this paper, a mechanistic model providing an analytical approximation of undulation growth is presented for realistic cyclic thermal histories. Thickening, lateral growth straining and high temperature yielding of the oxide layer are taken into account. Undulation growth in TBC systems is highly nonlinear and characterized by more than 20 material and geometric parameters, highlighting the importance of a robust yet computationally efficient model. At temperatures above 600 °C, the bond coat creeps. Thermal expansion mismatch occurs between the superalloy substrate and the oxide layer and, in some systems, the bond coat. In addition, some bond coats, such as PtNiAl, exhibit a martensitic phase transformation accompanied by nearly a 1% linear expansion, giving rise to a large effective mismatch. These two mismatches promote undulation growth. Nonlinear interaction between the stress in the bond coat induced by the constraining effect of the thick substrate and normal tractions applied at the surface of the bond coat by the compressed, undulating oxide layer produces an increment of undulation growth during each thermal cycle, before the stress decays by creep. A series of problems for systems without the ceramic top coat are used to elucidate the mechanics of undulation growth and to replicate trends observed in a series of experiments and in prior finite-element simulations. The model is employed to study for the first time the effect on undulation growth of a shift in the temperature range over which the transformation occurs, as well as the relative importance of the transformation compared to thermal expansion

  7. Compilation of diamond-like carbon properties for barriers and hard coatings

    SciTech Connect

    Outka, D.A.; Hsu, Wen L.; Phillips, K.; Boehme, D.R.; Yang, N.Y.C.; Ottesen, D.K.; Johnsen, H.A.; Clift, W.M.; Headley, T.J.

    1994-05-01

    Diamond-like carbon (DLC) is an amorphous form of carbon which resembles diamond in its hardness, lubricity, and resistance to chemical attack. Such properties make DLC of interest for use in barrier and hard coating technology. This report examines a variety of properties of DLC coatings. This includes examining substrates on which DLC coatings can be deposited; the resistance of DLC coatings to various chemical agents; adhension of DLC coatings; and characterization of DLC coatings by electron microscopy, FTIR, sputter depth profiling, stress measurements and nanoindentation.

  8. Multi-layered ruthenium-containing bond coats for thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Tryon, Brian S.

    Advances in thermal barrier coating (TBC) technology for Ni-base superalloys have shown that B2 Pt-modified NiAl-based bond coatings outperform conventional NiAl bond coat layers for high temperature TBC multilayer systems. This thesis addresses the potential improvement in the high temperature capability of a 132 Ru-modified aluminide bond coat layer due to improved high temperature properties of RuAl over NiAl. The objectives of this research have been to define a processing path for fabrication of a multi-layered Ru-modified aluminide bond coating and to investigate its performance within a TBC system. Microstructural development and the oxidation behavior of Ru-modified and Ru/Pt-modified bond coatings have been studied in detail. Two types of Ru-modified bond coatings have been fabricated: one by means of high temperature, low activity chemical vapor deposition (CVD) processing, and one via high temperature, high activity pack-aluminization. The location of the RuAl-rich layer has been shown to be process dependent with a low activity Ru-containing bond coating producing an exterior B2 NiAl layer with an interior B2 RuAl layer and a high activity Ru-containing bond coat producing the reverse arrangement of B2 layers. While all bond coating systems studied offer some oxidation protection by forming alpha-Al2O3, the low activity Ru/Pt-modified bond coatings exhibited a higher resistance to oxidation-induced failure compared to Ru-modified bond coatings. Through 1000 cyclic oxidation exposures, the Ru/Pt-modified coatings with an initial Ru deposition of 3mum are comparable to conventional Pt-modified aluminide coatings. The Ru-Al-Ni ternary system is the basis for Ru-modifed aluminide coating systems. An experimental assessment of the Ru-Al-Ni phase diagram at 1000°C and 1100°C has been produced via a series of diffusion couple experiments. A continuous solid-solution has been shown to exist between the RuAl and NiAl phases in the ternary system at the

  9. Ion beam assisted deposition of tribological coatings

    SciTech Connect

    Sartwell, B.D.

    1993-01-01

    TiN coatings 5 micrometers thick were deposited in UHV IBAD chamber onto M50 and Si substrates over a wide range of R (Ar-ion-to-Ti-atom ratio) values. Sputtering reduced the actual thickness at high R values, with two out of every three deposited Ti atoms being removed at R = 0.7. Because of charge exchange neutralization, it was possible to obtain coatings in the UHV IBAD system with properties equivalent to those deposited in the high vacuum IBAD system by using a higher apparent R value. Unless the extent of the charge exchange neutralization is known, it will not be possible to duplicate coating properties. Adhesion of the thick TiN coating deposited at R - 0.5 was equivalent to a magnetron sputtered TiN coating. Thick Cr[sub 2]O[sub 3] coatings were deposited onto M50 and Si substrates and wear testing was initiated. At high R values, sputtering prevented chemisorption of oxygen at surface. The wear process eliminated most of the surface topography.

  10. Evaluation of thermal barrier coating systems on novel substrates

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Wright, I. G.; Brindley, W. J.

    2000-06-01

    Testing was conducted on both plasma-sprayed (PS) and electron beam-physical vapor deposited (EB-PVD) Y2O3-stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) applied directly to oxidation-resistant substrates such as β-NiAl, oxide-dispersed FeCrAl, and NiCr. On an alloy that forms a very adherent alumina scale, β-NiAl+Zr, the coating lifetime of YSZ in furnace cyclic tests was 6 or more times longer than on state-of-the-art, YSZ coatings on single-crystal Ni-base superalloys with MCrAlY or Pt aluminide bond coats. Coatings on FeCrAl alloys appear to be a viable option for applications such as the external skin of the X-33, single stage to orbit, reusable launch vehicle. Model chromia-forming bond coat compositions also show promise for power generation applications at temperatures where hot corrosion may be a major problem. In general, while this work examined unique materials systems, many of the same fundamental failure mechanisms observed in conventional TBCs were observed.

  11. Failure analysis of plasma-sprayed thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Miller, R. A.

    1984-01-01

    Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.

  12. Bond Coating Performance of Thermal Barrier Coatings for Industrial Gas Turbines

    SciTech Connect

    Wright, Ian G; Pint, Bruce A

    2005-01-01

    Thermal barrier coatings are intended to work in conjunction with internal cooling schemes to reduce the metal temperature of critical hot gas path components in gas turbine engines. The thermal resistance is typically provided by a 100--250 {mu}m thick layer of ceramic (most usually zirconia stabilized with an addition of 7--8 wt% of yttria), and this is deposited on to an approximately 50 {mu} thick, metallic bond coating that is intended to anchor the ceramic to the metallic surface, to provide some degree of mechanical compliance, and to act as a reservoir of protective scale-forming elements (Al) to protect the underlying superalloy from high-temperature corrosion. A feature of importance to the durability of thermal barrier coatings is the early establishment of a continuous, protective oxide layer (preferably {alpha}-alumina) at the bond coating-ceramic interface. Because zirconia is permeable to oxygen, this oxide layer continues to grow during service. Some superalloys are inherently resistant to high-temperature oxidation, so a separate bond coating may not be needed in those cases. Thermal barrier coatings have been in service in aeroengines for a number of years, and the use of this technology for increasing the durability and/or efficiency of industrial gas turbines is currently of significant interest. The data presented were taken from an investigation of routes to optimize bond coating performance, and the focus of the paper is on the influences of reactive elements and Pt on the oxidation behaviour of NiAl-based alloys determined in studies using cast versions of bond coating compositions.

  13. Oxidation behavior of a thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.

    1984-01-01

    Thermal barrier coatings, consisting of a plasma sprayed calcium silicate ceramic layer and a CoCrAlY or NiCrAlY bond coat, were applied on B-1900 coupons and cycled hourly in air in a rapid-response furnace to maximum temperatures of 1030, 1100, or 1160 C. Eight specimens were tested for each of the six conditions of bond-coat composition and temperature. Specimens were removed from test at the onset of failure, which was taken to be the formation of a fine surface crack visible at 10X magnification. Specimens were weighed periodically, and plots of weight gain vs time indicate that weight is gained at a parabolic rate after an initial period where weight was gained at a much greater rate. The high initial oxidation rate is thought to arise from the initially high surface area in the porous bond coat. Specimen life (time to first crack) was found to be a strong function of temperature. However, while test lives varied greatly with time, the weight gain at the time of specimen failure was quite insensitive to temperature. This indicates that there is a critical weight gain at which the coating fails when subjected to this test.

  14. Vacuum deposited optical coatings experiment

    NASA Technical Reports Server (NTRS)

    Charlier, Jean

    1992-01-01

    The 138-4 Frecopa experiment consisted of 20 sorts of optical components and coatings subjected to space exposure. They covered a large range of use from the UV to IR spectrum: filters, mirrors, dichroics, beam splitters, and antireflection coatings made of several different materials as layers and substrates. By comparing pre- and post-flight spectral performances, it was possible to put into evidence the alterations due to space exposure.

  15. Low VOC Barrier Coating for Industrial Maintenance

    DTIC Science & Technology

    2007-11-01

    paints and materials such as acrylic latex, calcium sulfonated alkyd, epoxy, conventional oil/alkyd, polyurethane, moisture-cured urethanes, waxes , and...surfaces, and remove marks prior to coating. Do not use any wax or grease based markers, or any other markers that leave a residue or stain. 3.9.1...Characterization of Atmospheric Test Sites G 140 Standard Method for Determining Atmospheric Chloride Deposition Rate by Wet Candle Method

  16. Thermal barrier coatings for gas turbine and diesel engines

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Brindley, William J.; Bailey, M. Murray

    1989-01-01

    The present state of development of thin thermal barrier coatings for aircraft gas turbine engines and thick thermal barrier coatings for truck diesel engines is assessed. Although current thermal barrier coatings are flying in certain gas turbine engines, additional advances will be needed for future engines. Thick thermal barrier coatings for truck diesel engines have advanced to the point where they are being seriously considered for the next generation of engine. Since coatings for truck engines is a young field of inquiry, continued research and development efforts will be required to help bring this technology to commercialization.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  18. Deposition of SiOx barrier films by O2/TMDSO RF-PECVD

    NASA Astrophysics Data System (ADS)

    Zhou, Mei-Li; Fu, Ya-Bo; Chen, Qiang; Ge, Yuan-Jing

    2007-04-01

    This paper reports that the SiOx barrier films are deposited on polyethylene terephthalate substrate by plasma-enhanced chemical vapour deposition (PECVD) for the application of transparent barrier packaging. The variations of O2/ Tetramethyldisiloxane (TMDSO) ratio and input power in radio frequency (RF) plasma are carried out to optimize barrier properties of the SiOx coated film. The properties of the coatings are characterized by Fourier transform infrared, water vapour transmission rate (WVTR), oxygen transmission rate (OTR), and atomic force microscopy analysers. It is found that the O2/TMDSO ratio exceeding 2:1 and the input power over 200 W yield SiOx films with low carbon contents which can be good to the barrier (WVTR and OTR) properties of the SiOx coatings. Also, the film properties not only depend on oxygen concentration of the inlet gas mixtures and input power, but also relate to the surface morphology of the coating.

  19. Composite layers for barrier coatings on polymers

    NASA Astrophysics Data System (ADS)

    Brochhagen, Markus; Vorkoetter, Christoph; Boeke, Marc; Benedikt, Jan

    2016-09-01

    Amorphous hydrogenated carbon (a-C:H), amorphous hydrogenated silicon (a-Si:H), and SiO2 thin films are of high interest because they can serve as a gas barrier on polymers. To understand how the coating changes the overall barrier properties of the thin film-polymer system, optical, mechanical, and barrier properties have to be studied. One of the important characteristic of such coatings is their compressive stress, which has beneficial as well as unwanted effects. The stress can cause deformation of the bulk material or de-lamination of the film. The mechanical stability can be improved and it is possible to reduce cracking due to elongation, as the compressive stress can compensate externally applied tensile strain. Stress and mechanical properties of composite layers can be manipulated directly by embedding nanoparticles in an amorphous matrix film. Therefore nanoparticles and amorphous layers are investigated before they can be assembled in a composite layer. Growth rates as well as optical and mechanical properties are explored in this work. An inductively coupled plasma source was used for all amorphous layers and the silicon nanoparticles with diameter around 5 nm were produced in a capacitively coupled plasma reactor. This work is supported by DFG within SFB-TR87.

  20. Chemical vapor deposition coating for micromachines

    SciTech Connect

    MANI,SEETHAMBAL S.; FLEMING,JAMES G.; SNIEGOWSKI,JEFFRY J.; DE BOER,MAARTEN P.; IRWIN,LAWRENCE W.; WALRAVEN,JEREMY A.; TANNER,DANELLE M.; DUGGER,MICHAEL T.

    2000-04-21

    Two major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, the authors will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF{sub 6}, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleanings prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.

  1. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Stewart, S. E.; Ortiz, M.

    1988-01-01

    A life prediction model for correlating the spallation life of ceramic thermal barrier coatings is developed which includes both cyclic and time-dependent damage. The cyclic damage is related to the calculated cyclic inelastic strain range, while the time-dependent damage is related to the oxidation kinetics at the bond-ceramic interface. The cyclic inelastic strain range is calculated using a modified form of the Walker viscoplastic material model; calculation of the oxidation kinetics is based on traditional oxidation algorithms using experimentally determined parameters. The correlation between the actual and predicted spallation lives is within a factor of 3.

  2. Amorphous alumina coatings: processing, structure and remarkable barrier properties.

    PubMed

    Samélor, Diane; Lazar, Ana-Maria; Aufray, Maëlenn; Tendero, Claire; Lacroix, Loïc; Béguin, Jean-Denis; Caussat, Brigitte; Vergnes, Hugues; Alexis, Joël; Poquillon, Dominique; Pébère, Nadine; Gleizes, Alain; Vahlas, Constantin

    2011-09-01

    Amorphous aluminium oxide coatings were processed by metalorganic chemical vapour deposition (MOCVD); their structural characteristics were determined as a function of the processing conditions, the process was modelled considering appropriate chemical kinetic schemes, and the properties of the obtained material were investigated and were correlated with the nanostructure of the coatings. With increasing processing temperature in the range 350 degrees C-700 degrees C, subatmospheric MOCVD of alumina from aluminium tri-isopropoxide (ATI) sequentially yields partially hydroxylated amorphous aluminium oxides, amorphous Al2O3 (415 degrees C-650 degrees C) and nanostructured gamma-Al2O3 films. A numerical model for the process allowed reproducing the non uniformity of deposition rate along the substrate zone due to the depletion of ATI. The hardness of the coatings prepared at 350 degrees C, 480 degrees C and 700 degrees C is 6 GPa, 11 GPa and 1 GPa, respectively. Scratch tests on films grown on TA6V titanium alloy reveal adhesive and cohesive failures for the amorphous and nanocrystalline ones, respectively. Alumina coating processed at 480 degrees C on TA6V yielded zero weight gain after oxidation at 600 degrees C in lab air. The surface of such low temperature processed amorphous films is hydrophobic (water contact angle 106 degrees), while the high temperature processed nanocrystalline films are hydrophilic (48 degrees at a deposition temperature of 700 degrees C). It is concluded that amorphous Al2O3 coatings can be used as oxidation and corrosion barriers at ambient or moderate temperature. Nanostructured with Pt or Ag nanoparticles, they can also provide anti-fouling or catalytic surfaces.

  3. Environmental Barrier Coatings for Ceramic Matrix Composites - An Overview

    NASA Technical Reports Server (NTRS)

    Lee, Kang; van Roode, Mark; Kashyap, Tania; Zhu, Dongming; Wiesner, Valerie

    2017-01-01

    SiC/SiC Ceramic Matrix Composites (CMCs) are increasingly being considered as structural materials for advanced power generation equipment because of their light weight, higher temperature capability, and oxidation resistance. Limitations of SiC/SiC CMCs include surface recession and component cracking and associated chemical changes in the CMC. The solutions pursued to improve the life of SiC/SiC CMCs include the incorporation of coating systems that provide surface protection, which has become known as an Environmental Barrier Coating (EBC). The development of EBCs for the protection of gas turbine hot section CMC components was a continuation of coating development work for corrosion protection of silicon-based monolithics. Work on EBC development for SiC/SiC CMCs has been ongoing at several national laboratories and the original gas turbine equipment manufacturers. The work includes extensive laboratory, rig and engine testing, including testing of EBC coated SiC/SiC CMCs in actual field applications. Another EBC degradation issue which is especially critical for CMC components used in aircraft engines is the degradation from glassy deposits of calcium-magnesium-aluminosilicate (CMAS) with other minor oxides. This paper addresses the need for and properties of external coatings on SiC/SiC CMCs to extend their useful life in service and the retention of their properties.

  4. Method of depositing a coating on Si-based ceramic composites

    NASA Technical Reports Server (NTRS)

    Wang, Hongyu (Inventor); Lau, Yuk-Chiu (Inventor); Spitsberg, Irene (Inventor); Henry, Arnold T. (Inventor)

    2004-01-01

    A process of depositing a coating system suitable for use as an environmental barrier coating on various substrate materials, particularly those containing silicon and intended for high temperature applications such as the hostile thermal environment of a gas turbine engine. The process comprises depositing a first coating layer containing mullite, and preferably a second coating layer of an alkaline earth aluminosilicate, such as barium-strontium-aluminosilicate (BSAS), by thermal spraying while maintaining the substrate at a temperature of 800.degree. C. or less, preferably 500.degree. C. or less, by which a substantially crack-free coating system is produced with desirable mechanical integrity.

  5. Argon trapping in the depositing metal coating

    NASA Astrophysics Data System (ADS)

    Begrambekov, L. B.; Grunin, A. V.; Sadovskiy, Ya A.; Puntakov, N. A.; Utkov, N. S.; Zaharov, A. M.

    2017-05-01

    The paper has investigated conditions and parameters of argon trapping in molybdenum, tantalum and tungsten layers during their deposition on tungsten substrate by the atoms sputtered from the respective targets in argon plasma. The substrate temperature during deposition was 1273 K. The rate of deposition was 1 μm/h. It was shown that electron irradiation of the deposited layer with the beam intensity of 4 mA/cm2 initiated argon trapping in tungsten and tantalum coating with approx. 2 x 1027 at/m3 and 8 x 1026 at/cm3, respectively, but did not stimulate argon trapping in the molybdenum layers. Features of argon trapping in the tungsten coating and its release are investigated in detail.

  6. Metallographic techniques for evaluation of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Leonhardt, Todd A.

    1990-01-01

    The performance of ceramic thermal barrier coatings is strongly dependent on the amount and shape of the porosity in the coating. Current metallographic techniques do not provide polished surfaces that are adequate for a repeatable interpretation of the coating structures. A technique recently developed at NASA-Lewis for preparation of thermal barrier coating sections combines epoxy impregnation, careful sectioning and polishing, and interference layering to provide previously unobtainable information on processing-induced porosity. In fact, increased contrast and less ambiguous structure developed by the method make automatic quantitative metallography a viable option for characterizing thermal barrier coating structures.

  7. Metallographic techniques for evaluation of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Brindley, William J.; Leonhardt, Todd A.

    1990-01-01

    The performance of ceramic thermal barrier coatings is strongly dependent on the amount and shape of the porosity in the coating. Current metallographic techniques do not provide polished surfaces that are adequate for a repeatable interpretation of the coating structures. A technique recently developed at NASA-Lewis for preparation of thermal barrier coating sections combines epoxy impregnation, careful sectioning and polishing, and interference layering to provide previously unobtainable information on processing-induced porosity. In fact, increased contrast and less ambiguous structure developed by the method make automatic quantitative metallography a viable option for characterizing thermal barrier coating structures.

  8. Mechanisms of oxygen permeation through plastic films and barrier coatings

    NASA Astrophysics Data System (ADS)

    Wilski, Stefan; Wipperfürth, Jens; Jaritz, Montgomery; Kirchheim, Dennis; Mitschker, Felix; Awakowicz, Peter; Dahlmann, Rainer; Hopmann, Christian

    2017-10-01

    Oxygen and water vapour permeation through plastic films in food packaging or other applications with high demands on permeation are prevented by inorganic barrier films. Most of the permeation occurs through small defects (<3 µm) in the barrier coating. The defects were visualized by etching with reactive oxygen in a capacitively coupled plasma and subsequent SEM imaging. In this work, defects in SiO x -coatings deposited by plasma-enhanced chemical vapour deposition on polyethylene terephthalate (PET) are investigated and the mass transport through the polymer is simulated in a 3D approach. Calculations of single defects showed that there is no linear correlation between the defect area and the resulting permeability. The influence of adjacent defects in different distances was observed and led to flow reduction functions depending on the defect spacing and defect area. A critical defect spacing where no interaction between defects occurs was found and compared to other findings. According to the superposition principle, the permeability of single defects was added up and compared to experimentally determined oxygen permeation. The results showed the same trend of decreasing permeability with decreasing defect densities.

  9. Adhesion Issues with Polymer/Oxide Barrier Coatings on Organic Displays

    SciTech Connect

    Matson, Dean W.; Martin, Peter M.; Graff, Gordon L.; Gross, Mark E.; Burrows, Paul E.; Bennett, Wendy D.; Hall, Michael G.; Mast, Eric S.; Bonham, Charles C.; Zumhoff, Mac R.; Rutherford, Nicole M.; Moro, Lorenza; Rosenblum, Martin; Praino, Robert F.; Visser, Robert J.

    2005-01-01

    Multilayer polymer/oxide coatings are being developed to protect sensitive organic display devices, such as OLEDs, from oxygen and water vapor permeation. The coatings have permeation levels ~ 10-6 g/m2/d for water vapor and ~10-6 cc/m2/d for oxygen, and are deposited by vacuum polymer technology. The coatings consist of either a base Al2O3 or acrylate polymer adhesion layer followed by alternating Al2O3/polymer layers. The polymer is used to decouple the 30 nm-thick Al2O3 barrier layers. Adhesion of the barrier coating to the substrate and display device is critical for the operating lifetime of the device. The substrate material could be any transparent flexible plastic. The coating technology can also be used to encapsulate organic-based electronic devices to protect them from atmospheric degradation. Plasma pretreatment is also needed for good adhesion to the substrate, but if it is too aggressive, it will damage the organic display device. We report on the effects of plasma treatment on the adhesion of barrier coatings to plastic substrates and the performance of OLED devices after plasma treatment and barrier coating deposition. We find that initial OLED performance is not significantly affected by the deposition process and plasma treatment, as demonstrated by luminosity and I-V curves.

  10. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Demasi, J.; Sheffler, K.

    1984-01-01

    The objective of this program is to develop an integrated life prediction model accounting for all potential life-limiting Thermal Barrier Coating (TBC) degradation and failure modes including spallation resulting from cyclic thermal stress, oxidative degradation, hot corrosion, erosion, and foreign object damage (FOD). The mechanisms and relative importance of the various degradation and failure modes will be determined, and the methodology to predict predominant mode failure life in turbine airfoil application will be developed and verified. An empirically based correlative model relating coating life to parametrically expressed driving forces such as temperature and stress will be employed. The two-layer TBC system being investigated, designated PWA264, currently is in commercial aircraft revenue service. It consists of an inner low pressure chamber plasma-sprayed NiCoCrAlY metallic bond coat underlayer (4 to 6 mils) and an outer air plasma-sprayed 7 w/o Y2O3-ZrO2 (8 to 12 mils) ceramic top layer.

  11. Optical Diagnostics for Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Spuckler, C. M.; Bencic, T. J.; Martin, R. E.

    2004-01-01

    The translucent nature of ceramic oxide thermal barrier coatings (TBCs) provides an opportunity to employ optical probes to monitor temperature gradients and buried damage propagation within the coating. An important advantage of noncontact optical diagnostics is that they are amendable to health monitoring of TBCs in service. In this paper, two optical diagnostic approaches, operating in different wavelength regimes, are discussed. The first approach is the use of mid-infrared reflectance (MIR) to monitor the progression of TBC delamination produced by thermal cycling. This approach takes advantage of the maximum transparency of the TBCs at mid-infrared wavelengths, in particular, between 3 and 5 microns. Recent progress in extending the MIR method to a more practical visual inspection tool will be presented. A second approach, using visible wavelengths, is the embedding of thermographic phosphors within the TBC to add sensing functions to the coating that can provide depth-selective information about temperature gradients and TBC integrity. Emphasis will be given to the use of fluorescence decay time measurements to provide temperature readings from a thermographic phosphor layer residing beneath the TBC.

  12. Evaluation of hot corrosion behavior of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Hodge, P. E.; Miller, R. A.; Gedwill, M. A.

    1980-01-01

    Calcium silicate and yttria stabilized zirconia/MCrAlY thermal barrier coating systems on air-cooled specimens were exposed to sodium plus vanadium doped Mach 0.3 combustion gases. Thermal barrier coating endurance was determined to be a strong inverse function of ceramic coating thickness. Coating system durability was increased through the use of higher Cr + Al NiCrAl and CoCrAlY bond coatings. Chemical and electron microprobe analyses supported the predictions of condensate compositions and the determination of their roles in causing spalling of the ceramic coatings.

  13. Ceramic thermal barrier coatings for electric utility gas turbine engines

    NASA Technical Reports Server (NTRS)

    Miller, R. A.

    1986-01-01

    Research and development into thermal barrier coatings for electric utility gas turbine engines is reviewed critically. The type of coating systems developed for aircraft applications are found to be preferred for clear fuel electric utility applications. These coating systems consists of a layer of plasma sprayed zirconia-yttria ceramic over a layer of MCrAly bond coat. They are not recommended for use when molten salts are presented. Efforts to understand coating degradation in dirty environments and to develop corrosion resistant thermal barrier coatings are discussed.

  14. Continuous Sputter Deposition Coating of Long Monofilaments

    DTIC Science & Technology

    2014-04-01

    terminal. A length of fishing line, microtubing, or polylactic acid (PLA) coated with copper could be left to cure within an epoxy, and upon removal...inductance, capacitance, resistance min minute MSD magnetron sputter deposition PLA polylactic acid RPM revolutions per minute R resistance (units

  15. Two-layer thermal barrier coating for high temperature components

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1977-01-01

    A simple two-layer plasma-sprayed thermal barrier coating system was developed which has the potential for protecting high temperature air-cooled gas turbine components. Of the initially examined coatings, the most promising system is an Ni-16Cr-6Al-0.6Y (in wt%) bond coating (about 0.005 to 0.010 cm thick) and a ZrO2-12Y2O3 (in wt%) thermal barrier coating (about 0.025 to 0.064 cm thick). This thermal barrier substantially lowered the metal temperature of the air-cooled airfoil. The coating withstood 3200 cycles (80 s at 1280 C surface temperature) and 275 cycles (1 hr at 1490 C surface temperature) without cracking or spalling. No separation of the thermal barrier from the bond coating or the bond coating from the substrate was observed.

  16. Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2008-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

  17. Thermal barrier coating life-prediction model development

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Neumann, J.

    1985-01-01

    Life predictions are made for two types of strain-tolerant and oxidation-resistant Thermal Barrier Coating (TBC) systems produced by commercial coating suppliers to the gas turbine industry. The plasma-sprayed TBC system, composed of a low-pressure plasma spray (LPPS) applied oxidation-resistant NiCrAlY bond coating and an air-plasma-sprayed yttria (8 percent) partially stabilized zirconia insulative layer, is applied by both Chromalloy and Klock. The second type of TBC is applied by the electron-beam/physical vapor deposition process by Temescal. Thermomechanical and thermochemical testing of the program TBCs is in progress. A number of the former tests has been completed. Fracture mechanics data for the Chromalloy plasma-sprayed TBC system indicate that the cohesive toughness of the zirconia layer is increased by thermal cycling and reduced by high temperature exposure at 1150 C. Eddy current technology feasibility has been established with respect to nondestructively measuring zirconia layer thickness of a TBC system. High pressure turbine blades have been coated with program TBC systems for a piggyback test in a TFE731-5 turbofan factory engine test. Data from this test will be used to validate the TBC life models.

  18. Thermal Barrier Coatings for Advanced Gas Turbine and Diesel Engines

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1999-01-01

    Ceramic thermal barrier coatings (TBCS) have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, durability issues of these thermal barrier coatings under high temperature cyclic conditions are still of major concern. The coating failure depends not only on the coating, but also on the ceramic sintering/creep and bond coat oxidation under the operating conditions. Novel test approaches have been established to obtain critical thermomechanical and thermophysical properties of the coating systems under near-realistic transient and steady state temperature and stress gradients encountered in advanced engine systems. This paper presents detailed experimental and modeling results describing processes occurring in the ZrO2-Y2O3 thermal barrier coating systems, thus providing a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.

  19. Novel hybrid polymeric materials for barrier coatings

    NASA Astrophysics Data System (ADS)

    Pavlacky, Erin Christine

    Polymer-clay nanocomposites, described as the inclusion of nanometer-sized layered silicates into polymeric materials, have been widely researched due to significant enhancements in material properties with the incorporation of small levels of filler (1--5 wt.%) compared to conventional micro- and macro-composites (20--30 wt.%). One of the most promising applications for polymer-clay nanocomposites is in the field of barrier coatings. The development of UV-curable polymer-clay nanocomposite barrier coatings was explored by employing a novel in situ preparation technique. Unsaturated polyesters were synthesized in the presence of organomodified clays by in situ intercalative polymerization to create highly dispersed clays in a precursor resin. The resulting clay-containing polyesters were crosslinked via UV-irradiation using donor-acceptor chemistry to create polymer-clay nanocomposites which exhibited significantly enhanced barrier properties compared to alternative clay dispersion techniques. The impact of the quaternary alkylammonium organic modifiers, used to increase compatibility between the inorganic clay and organic polymer, was studied to explore influence of the organic modifier structure on the nanocomposite material properties. By incorporating just the organic modifiers, no layered silicates, into the polyester resins, reductions in film mechanical and thermal properties were observed, a strong indicator of film plasticization. An alternative in situ preparation method was explored to further increase the dispersion of organomodified clay within the precursor polyester resins. In stark contrast to traditional in situ polymerization methods, a novel "reverse" in situ preparation method was developed, where unmodified montmorillonite clay was added during polyesterification to a reaction mixture containing the alkylammonium organic modifier. The resulting nanocomposite films exhibited reduced water vapor permeability and increased mechanical properties

  20. Thermal barrier coatings for turbine components

    DOEpatents

    Subramanian, Ramesh; Sabol, Stephen M.; Goedjen, John G.; Sloan, Kelly M.; Vance, Steven J.

    2002-01-01

    A turbine component, such as a turbine blade having a metal substrate (22) is coated with a metal MCrAlY alloy layer (24) and then a thermal barrier layer (20) selected from LaAlO.sub.3, NdAlO.sub.3, La.sub.2 Hf.sub.2 O.sub.7, Dy.sub.3 Al.sub.5 O.sub.12, HO.sub.3 Al.sub.3 O.sub.12, ErAlO.sub.3, GdAlO.sub.3, Yb.sub.2 Ti.sub.2 O.sub.7, LaYbO.sub.3, Gd.sub.2 Hf.sub.2 O.sub.7 or Y.sub.3 Al.sub.5 O.sub.12.

  1. Enhancing thermal barrier coatings performance through reinforcement of ceramic topcoat

    NASA Astrophysics Data System (ADS)

    Bogdanovich, V. I.; Giorbelidze, M. G.

    2016-11-01

    This paper studies structure of thermal barrier coatings applied to hot gas path components in gas turbine engines and produced in a number of ways, and its impact on performance. Methods of structural reinforcement for ceramic topcoat in thermal barrier coatings are considered.

  2. Advanced Thermal-Barrier Bond Coatings for Alloys

    NASA Technical Reports Server (NTRS)

    Secura, Stephen

    1987-01-01

    New and improved bond coatings developed for use in thermal-barrier systems on Ni, Co-, and Fe-base alloy substrates. Use of these new bond coatings, containing ytterbium instead of yttrium, significantly increased lives of resultant thermal-barrier systems. Uses include many load-bearing applications in high-temperature, hostile environments.

  3. Hemocompatible, pulsed laser deposited coatings on polymers.

    PubMed

    Lackner, Juergen M; Waldhauser, Wolfgang; Major, Roman; Major, Boguslaw; Bruckert, Franz

    2010-02-01

    State-of-the-art non-thrombogenic blood contacting surfaces are based on heparin and struggle with the problem of bleeding. However, appropriate blood flow characteristics are essential for clinical application. Thus, there is increasing demand to develop new coating materials for improved human body acceptance. Materials deposited by vacuum coating techniques would be an excellent alternative if the coating temperatures can be kept low because of the applied substrate materials of low temperature resistance (polymers). Most of the recently used plasma-based deposition techniques cannot fulfill this demand. However, adequate film structure and high adhesion can be reached by the pulsed laser deposition at room temperature, which was developed to an industrial-scaled process at Laser Center Leoben. Here, this process is described in detail and the resulting structural film properties are shown for titanium, titanium nitride, titanium carbonitride, and diamond-like carbon on polyurethane, titanium and silicon substrates. Additionally, we present the biological response of blood cells and the kinetic mechanism of eukaryote cell attachment. In conclusion, high biological acceptance and distinct differences for the critical delamination shear stress were found for the coatings, indicating higher adhesion at higher carbon contents.

  4. Experimental techniques for the characterization and development of thermal barrier coating bond coat alloys

    NASA Astrophysics Data System (ADS)

    Thompson, Robert J.

    Thermal barrier coatings, commonly used in modern gas turbines and jet engines, are dynamic, multilayered structures consisting of a superalloy substrate, an Al-rich bond coat, a thermally grown oxide, and a ceramic top coat. Knowledge of the disparate material properties for each of the constituents of a thermal barrier coating is crucial to both better understanding and improving the performance of the system. The efforts of this dissertation quantify fundamental aspects of two intrinsic strain mechanisms that arise during thermal cycling. This includes measurement of the thermal expansion behavior for bond coats and superalloys as well as establishing specific ternary compositions associated with a strain-inducing martensitic phase transformation, which is known to occur in Ni-rich bond coat alloys. In order to quantify the coefficient of thermal expansion for a number of actual alloys extracted from contemporary thermal barrier coating systems, this work employs a noncontact high temperature digital image correlation technique to nearly 1100°C. The examined materials include: two commercial superalloys, two as-deposited commercial bond coat alloys, and three experimental bond coat alloys. The as-deposited specimens were created using a diffusion aluminizing and a low pressure plasma spray procedure to thicknesses on the order of 50 and 100 mum, respectively. For the plasma sprayed bond coat, a comparison with a bulk counterpart of identical composition indicated that deposition procedures have little effect on thermal expansion. An analytical model of oxide rumpling is used to show that the importance of thermal expansion mismatch between a commercial bond coat and its superalloy substrate is relatively small. Considerably higher expansion values are noted for a Ni-rich bond coat alloy, however, and modeling which includes this layer suggests that it may have a substantial influence on rumpling. Combinatorial methods based on diffusion multiples are also

  5. Infrared laser deposition of Teflon coatings on microstructures

    NASA Astrophysics Data System (ADS)

    Papantonakis, M. R.; HaglundJr., R. F.

    2006-01-01

    Polytetrafluoroethylene (PTFE, trade name Teflon) has a wide range of unique and desirable physical, electrical and chemical properties. Its tribological properties are well-suited to anti-stiction applications, and its chemical inertness commends it as a barrier and passivation layer. However, conventional thin-film techniques are not suited for depositing Teflon films on microstructures. Spin coating is impossible because of the well-known insolubility of PTFE. Plasma polymerization of fluorocarbon monomers, ion beam and rf sputtering produce PTFE films that are deficient in fluorine. Pulsed laser deposition (PLD) using excimer and Ti:sapphire lasers is unsatisfactory because UV or near-IR laser ablation "unzips" the PTFE, and requires high-temperature annealing to re-polymerize the deposited monomeric film. We have demonstrated that a completely dry, vapor-phase coating technique - resonant infrared pulsed laser deposition (RIR-PLD) at a wavelength of 8.26 μm -produces crystalline, smooth Teflon films at low process temperatures. Indeed, the films as deposited by RIR-PLD exhibit a surprising degree of crystallinity even at room temperature. The stoichiometry and local electronic structure are preserved during the laser vaporization process, as demonstrated by IR absorption and X-ray photoelectron spectroscopy. Films deposited on microscale structures show good adhesion, excellent smoothness, and a high degree of conformability to the structures. We also discuss experiments planned for the near future to compare the tribological properties of the PTFE films deposited by RIR-PLD with those of other tribological coatings. We will also discuss the implementation of RIR-PLD in practical processing schemes for MEMS applications, including the challenge in adapting existing solid-state mid-IR laser technology for this purpose.

  6. Overview of thermal barrier coatings in diesel engines

    NASA Technical Reports Server (NTRS)

    Yonushonis, T. M.

    1995-01-01

    An understanding of delamination mechanisms in thermal barrier coatings has been developed for diesel applications through nondestructive evaluation, structural analysis modeling and engine evaluation of various thermal barrier coatings. This knowledge has resulted in improved thermal barrier coatings which survive abusive cyclic fatigue tests in high output diesel engines. Significant efforts are still required to improve the plasma spray processing capability and the economics for complex geometry diesel engine components. Data obtained from advanced diesel engines on the effect of thermal barrier coatings on engine fuel economy and emission has not been encouraging. Although the underlying metal component temperatures have been reduced through the use of thermal barrier coating, engine efficiency and emission trends have not been promising.

  7. Combination Thermal Barrier And Wear Coatings For Engines

    NASA Technical Reports Server (NTRS)

    Weingart, Mike; Moller, Paul

    1995-01-01

    Thermal-barrier layers covered with self-lubricating surface layers. Zirconia thermal-barrier coat applied to surface of combustion chamber in engine by plasma-arc spraying. Then PS-200 plasma-arc sprayed onto zirconia. Self-lubricating coat prevents sliding contact between thermal barrier and piston ring, effectively preventing both wear and production of additional heat via friction. Other combinations of thermal-barrier and self-lubricating, wear-resistant coating materials used as long as two materials adhere to each other, applied by use of similar or compatible processes, have similar coefficients of thermal expansion, sufficiently strong at high temperatures, and affordable.

  8. Advances in the electrospark deposition coating process

    SciTech Connect

    Johnson, R.N.; Sheldon, G.L.

    1986-11-01

    Electrospark deposition (ESD) is a pulsed-arc microwelding process using short-duration, high-current electrical pulses to deposit an electrode material on a metallic substrate. It is one of the few methods available by which a fused, metallurgically bonded coating can be applied with such a low total heat input that the bulk substrate material remains at or near ambient temperatures. The short duration of the electrical pulse allows an extremely rapid solidification of the deposited material and results in an exceptionally fine-grained, homogeneous coating that approaches (and with some materials, actually is) an amorphous structure. This structure is believed to contribute to the good tribological and corrosion performance observed for hardsurfacing materials used in the demanding environments of high temperatures, liquid metals, and neutron irradiation. A brief historical review of the process is provided, followed by descriptions of the present state of the art and of the performance and applications of electrospark deposition coating in liquid--metal-cooled nuclear reactors.

  9. Permeation Barrier Coatings for the Helical Heat Exchanger

    SciTech Connect

    Korinko, P.S.

    1999-05-26

    A permeation barrier coating was specified for the Helical Heat Exchanger (HHE) to minimize contamination through emissions and/or permeation into the nitrogen system for ALARA reasons. Due to the geometry of the HHE, a special coating practice was needed since the conventional method of high temperature pack aluminization was intractable. A survey of many coating companies was undertaken; their coating capabilities and technologies were assessed and compared to WSRC needs. The processes and limitations to coating the HHE are described. Slurry coating appears to be the most technically sound approach for coating the HHE.

  10. Gas permeation barriers deposited by atmospheric pressure plasma enhanced atomic layer deposition

    SciTech Connect

    Hoffmann, Lukas Theirich, Detlef; Hasselmann, Tim; Räupke, André; Schlamm, Daniel; Riedl, Thomas

    2016-01-15

    This paper reports on aluminum oxide (Al{sub 2}O{sub 3}) thin film gas permeation barriers fabricated by atmospheric pressure atomic layer deposition (APPALD) using trimethylaluminum and an Ar/O{sub 2} plasma at moderate temperatures of 80 °C in a flow reactor. The authors demonstrate the ALD growth characteristics of Al{sub 2}O{sub 3} films on silicon and indium tin oxide coated polyethylene terephthalate. The properties of the APPALD-grown layers (refractive index, density, etc.) are compared to that deposited by conventional thermal ALD at low pressures. The films films deposited at atmospheric pressure show water vapor transmission rates as low as 5 × 10{sup −5} gm{sup −2}d{sup −1}.

  11. Dip Process Thermal-Barrier Coatings for Superalloys.

    DTIC Science & Technology

    1983-03-01

    thermal barrier coatings are needed in aircraft gas turbine engines to increase the thermal efficiency and extend the life of the coated components. In... gas turbine alloys was investigated. This process involves hot dipping alloy substrates in low-melting cerium-nickel or zirconium-nickel eutectics...important conclusion from the work so far is that dense adherent ZrO 2 thermal barrier coatings can be successfully applied on gas turbine alloys by the hot

  12. Indentation methods for adhesion measurement in thermal barrier coating systems

    NASA Astrophysics Data System (ADS)

    Ma, Qin

    This thesis investigates the fundamentals of indentation-induced delamination of electron beam physical vapor deposition thermal barrier coatings (EB-PVD TBCs). Thermal barrier coatings are thin ceramic coatings used to insulate gas turbine components. In the as-processed state, TBCs are well-bonded to the metallic substrate they are deposited upon. However, as these coatings are exposed to high temperatures during turbine operation, they lose their adhesion. The goal of this thesis is to determine how to use indentation testing techniques, coupled with fracture mechanics principles, to track this loss of adhesion and to identify mechanisms causing it. This thesis addresses four primary topics. First, a detailed fracture mechanics analysis of indentation-induced delamination is made, including the quantification of energy release rates, interfacial toughnesses and mode mix. The second topic addressed is application of the indentation test to track toughness losses in TBC systems subjected to a variety of thermal exposures. Three subtopics are included: (1) mechanism-based tests for the isothermal dry air exposures; (2) mechanism-based tests for exposures with water vapor and (3) mechanism-based tests for cyclic thermal exposures. In the first subtopic, TGO thickening and TBC sintering are modeled. Various mechanisms that lead to toughness degradation are discussed and analyzed quantitatively. An Arrhenius analysis has been performed to understand accelerated testing methods. The second subtopic presents the results of toughness degradation and the evolution of microstructures due to isothermal exposure with water vapor. The third subtopic investigates the toughness degradation for cyclic thermal exposures in dry air. Piezospectroscopy method has been applied to track the evolution of residual stresses in the TGO layer with thermal cycles. Quantitative analysis has been provided to give insights into the effects of oxide damage during thermal cycling. The final two

  13. Plasma deposition of antimicrobial coating on organic polymer

    NASA Astrophysics Data System (ADS)

    Rżanek-Boroch, Zenobia; Dziadczyk, Paulina; Czajkowska, Danuta; Krawczyk, Krzysztof; Fabianowski, Wojciech

    2013-02-01

    Organic materials used for packing food products prevent the access of microorganisms or gases, like oxygen or water vapor. To prolong the stability of products, preservatives such as sulfur dioxide, sulfites, benzoates, nitrites and many other chemical compounds are used. To eliminate or limit the amount of preservatives added to food, so-called active packaging is sought for, which would limit the development of microorganisms. Such packaging can be achieved, among others, by plasma modification of a material to deposit on its surface substances inhibiting the growth of bacteria. In this work plasma modification was carried out in barrier discharge under atmospheric pressure. Sulfur dioxide or/and sodium oxide were used as the coating precursors. As a result of bacteriological studies it was found that sulfur containing coatings show a 16% inhibition of Salmonella bacteria growth and 8% inhibition of Staphylococcus aureus bacteria growth. Sodium containing coatings show worse (by 10%) inhibiting properties. Moreover, films with plasma deposited coatings show good sealing properties against water vapor. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  14. Oleophobic optical coating deposited by magnetron PVD

    NASA Astrophysics Data System (ADS)

    Bernt, D.; Ponomarenko, V.; Pisarev, A.

    2016-09-01

    Thin oxinitride films of Zn-Sn-O-N and Si-Al-O-N were deposited on glass by reactive magnetron sputtering at various nitrogen-to-oxygen ratios. Nitrogen added to oxygen led to decrease of the surface roughness and increase of oleophobic properties studied by the oil-drop test. The best oleophobity was obtained for Zn-Sn-O-N oxinitride at Zn:Sn=1:1 and N:O=1:2. Improved oleophobic properties were also demonstrated if the oxinitride film was deposited on top of the multilayer coating as the final step in the industrial cycle of production of energy efficient glass.

  15. Diffusion Barriers to Increase the Oxidative Life of Overlay Coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Lei, Jih-Fen

    1999-01-01

    Currently, most blades and vanes in the hottest section of aero gas turbine engines require some type of coating for oxidation protection. Newly developed single crystal superalloys have the mechanical potential to operate at increasingly higher component temperatures. However, at these elevated temperatures, coating/substrate interdiffusion can shorten the protective life of the coating. Diffusion barriers between overlay coatings and substrates are being examined to extend the protective life of the coating. A previously- developed finite-difference diffusion model has been modified to predict the oxidative life enhancement due to use of a diffusion barrier. The original diffusion model, designated COSIM, simulates Al diffusion in the coating to the growing oxide scale as well as Al diffusion into the substrate. The COSIM model incorporates an oxide growth and spalling model to provide the rate of Al consumption during cyclic oxidation. Coating failure is predicted when the Al concentration at the coating surface drops to a defined critical level. The modified COSIM model predicts the oxidative life of an overlay coating when a diffusion barrier is present eliminating diffusion of Al from the coating into the substrate. Both the original and the modified diffusion models have been used to predict the effectiveness of a diffusion barrier in extending the protective life of a NiCrAl overlay coating undergoing cyclic oxidation at 1100 C.

  16. Development of sputtering process to deposit stoichiometric zirconia coatings for the inside wall of regeneratively cooled rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Busch, R.

    1978-01-01

    Thermal barrier coatings of yttria stabilized zirconia and zirconia-ceria mixtures were deposited by RF reactive sputtering. Coatings were 1-2 mils thick, and were deposited on copper cylinders intended to simulate the inner wall of a regeneratively cooled thrust chamber. Coating stoichiometry and adherence were investigated as functions of deposition parameters. Modest deposition rates (approximately 0.15 mil/hr) and subambient sustrate temperatures (-80 C) resulted in nearly stoichiometric coatings which remained adherent through thermal cycles between -196 and 400 C. Coatings deposited at higher rates or substrates temperatures exhibited greater oxygen deficiences, while coatings deposited at lower temperatures were not adherent. Substrate bias resulted in structural changes in the coating and high krypton contents; no clear effect on stoichiometry was observed.

  17. Controlled drug release through a plasma polymerized tetramethylcyclo-tetrasiloxane coating barrier.

    PubMed

    Osaki, Shigemasa; Chen, Meng; Zamora, Paul O

    2012-01-01

    A plasma polymerized tetramethylcyclo-tetrasiloxane (TMCTS) coating was deposited onto a metallic biomaterial, 316 stainless steel, to control the release rate of drugs, including daunomycin, rapamycin and NPC-15199 (N-(9-fluorenylmethoxy-carbonyl)-leucine), from the substrate surface. The plasma-state polymerized TMCTS thin film was deposited in a vacuum plasma reactor operated at a radio-frequency of 13.56 MHz, and was highly adhesive to the stainless steel, providing a smooth and hard coating layer for drugs coated on the substrate. To investigate the influence of plasma coating thickness on the drug diffusion profile, coatings were deposited at various time lengths from 20 s to 6 min, depending on the type of drug. Atomic force spectroscopy (AFM) was utilized to characterize coating thickness. Drug elution was measured using a spectrophotometer or high-performance liquid chromatography (HPLC) system. The experimental results indicate that plasma polymerized TMCTS can be used as an over-coating to control drug elution at the desired release rate. The drug-release rate was also found to be dependent on the molecular weight of the drug with plasma coating barrier on top of it. The in vitro cytotoxicity test result suggested that the TMCTS plasma coatings did not produce a cytotoxic response to mammalian cells. The non-cytotoxicity of TMCTS coating plus its high thrombo-resistance and biocompatibility are very beneficial to drug-eluting devices that contact blood.

  18. NASA thermal barrier coatings: Summary and update

    NASA Technical Reports Server (NTRS)

    Stepka, F. S.

    1978-01-01

    A durable, two-layer, plasma-sprayed coating consisting of a ceramic layer over a metallic layer was developed that has the potential of insulating hot engine parts and thereby reducing metal temperatures and coolant flow requirements and/or permitting use of less costly and complex cooling configurations and materials. The results are summarized of analytical and experimental investigations of the coatings on flat metal specimens, turbine vanes and blades, and combustor liners. Discussed are results of investigations to determine coating adherence and durability, coating thermal, strength and fatigue properties, and chemical reactions of the coating with oxides and sulfates. Also presented are the effect of the coating on aerodynamic performance of a turbine vane, measured vane and combustor liner temperatures with and without the coating, and predicted turbine metal temperatures and coolant flow reductions potentially possible with the coating. Included also are summaries of some current research related to the coating and potential applications for the coating.

  19. Microlaminate composites: An alternate approach to thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Bunshah, R. F.; Deshpandey, C. V.; Obrien, B. P.

    1985-01-01

    Ceramic thermal barrier coatings suffer from a major drawback, i.e., brittle behavior. An alternate approach is microlaminate composite coatings consisting of alternate layers of metal and oxide. As the thickness of the individual laminae decrease while keeping the total thickness of the coating constant, the thermal conductivity drops markedly. Data on the Fe-Cu system will be presented. A model is proposed for an MCrAlY-Al2O3 microlaminate coating for thermal barriers. The methods of fabrication will also be discussed.

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

    SciTech Connect

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

    2012-10-01

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

  1. Thermal and Environmental Barrier Coatings for Advanced Propulsion Engine Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. For future high performance engines, the development of advanced ceramic barrier coating systems will allow these coatings to be used to simultaneously increase engine operating temperature and reduce cooling requirements, thereby leading to significant improvements in engine power density and efficiency. In order to meet future engine performance and reliability requirements, the coating systems must be designed with increased high temperature stability, lower thermal conductivity, and improved thermal stress and erosion resistance. In this paper, ceramic coating design and testing considerations will be described for high temperature and high-heat-flux engine applications in hot corrosion and oxidation, erosion, and combustion water vapor environments. Further coating performance and life improvements will be expected by utilizing advanced coating architecture design, composition optimization, and improved processing techniques, in conjunction with modeling and design tools.

  2. Overview of thermal barrier coatings in diesel engines

    NASA Technical Reports Server (NTRS)

    Yonushonis, Thomas M.

    1995-01-01

    An understanding of delamination mechanisms in thermal barrier coatings has been developed for diesel engine applications through rig tests, structural analysis modeling, nondestructive evaluation, and engine evaluation of various thermal barrier coatings. This knowledge has resulted in improved thermal barrier coatings which survive abusive cyclic fatigue tests in high output diesel engines. Although much conflicting literature now exists regarding the impact of thermal barrier coatings on engine performance and fuel consumption, the changes in fuel consumption appear to be less than a few percent and can be negative for state-of-the-art diesel engines. The ability of the thermal barrier coating to improve fuel economy tends to be dependent on a number of factors including the fuel injection system, combustion chamber design, and the initial engine fuel economy. Limited investigations on state-of-the-art diesel engines have indicated that the surface connected porosity and coating surface roughness may influence engine fuel economy. Current research efforts on thermal barrier coatings are primarily directed at reducing in-cylinder heat rejection, thermal fatigue protection of underlying metal surfaces and a possible reduction in diesel engine emissions. Significant efforts are still required to improve the plasma spray processing capability and the economics for complex geometry diesel engine components.

  3. Overview of thermal barrier coatings in diesel engines

    NASA Technical Reports Server (NTRS)

    Yonushonis, Thomas M.

    1995-01-01

    An understanding of delamination mechanisms in thermal barrier coatings has been developed for diesel engine applications through rig tests, structural analysis modeling, nondestructive evaluation, and engine evaluation of various thermal barrier coatings. This knowledge has resulted in improved thermal barrier coatings which survive abusive cyclic fatigue tests in high output diesel engines. Although much conflicting literature now exists regarding the impact of thermal barrier coatings on engine performance and fuel consumption, the changes in fuel consumption appear to be less than a few percent and can be negative for state-of-the-art diesel engines. The ability of the thermal barrier coating to improve fuel economy tends to be dependent on a number of factors including the fuel injection system, combustion chamber design, and the initial engine fuel economy. Limited investigations on state-of-the-art diesel engines have indicated that the surface connected porosity and coating surface roughness may influence engine fuel economy. Current research efforts on thermal barrier coatings are primarily directed at reducing in-cylinder heat rejection, thermal fatigue protection of underlying metal surfaces and a possible reduction in diesel engine emissions. Significant efforts are still required to improve the plasma spray processing capability and the economics for complex geometry diesel engine components.

  4. Vacuum arc deposited DLC based coatings

    SciTech Connect

    Monteiro, Othon R.; Delplancke-Ogletree, Marie-Paule

    2002-05-01

    The great interest in the use of diamond-like carbon (DLC) films as a coating material is justified by the superior wear resistance and hardness, chemical inertness, and very low friction coefficients of these coatings. Vacuum arc deposition is well suited to prepare superhard films with high sp{sup 3}/sp{sup 2} ratios. However, the high level of internal stresses originating during growth prevents the deposition of thick films, and their hardness makes it difficult for DLC layers to comply with substrate deformations. In order to overcome these limitations, different approaches are possible. Multilayer structures are one means to maintain the surface mechanical properties of the DLC while relieving the internal stresses. Another possibility is to dope the DLC films in order to reduce the internal stress and to stabilize the desirable sp{sup 3} bonds to higher temperatures. At higher doses of dopants, the formation of nanocrystals is possible and the properties of the coatings change drastically. All these approaches were investigated on films prepared by cathodic arc and a synthesis of the results is presented here.

  5. Measurement methods and standards for processing and application of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Dapkunas, S. J.

    1995-01-01

    Application of thermal barrier coatings deposited by thermal spray, physical vapor and possibly other methods is expected to be extended from aircraft gas turbines to industrial and utility gas turbines as well as diesel engines. This increased usage implies the participation of greater numbers of processors and users, making the availability of standards for process control and property measurement more important. Available standards for processing and evaluation of thermal barrier coatings are identified as well as those needed in the future but currently unavailable.

  6. Measurement methods and standards for processing and application of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Dapkunas, Stanley J.

    1995-01-01

    Application of thermal barrier coatings deposited by thermal spray, physical vapor and possibly other methods is expected to be extended from aircraft gas turbines to industrial and utility gas turbines as well as diesel engines. This increased usage implies the participation of greater numbers of processors and users, making the availability of standards for process control and property measurement more important. Available standards for processing and evaluation of thermal barrier coatings are identified as well as those needed in the future but currently unavailable.

  7. Thermal barrier coating on high temperature industrial gas turbine engines

    NASA Technical Reports Server (NTRS)

    Carlson, N.; Stoner, B. L.

    1977-01-01

    The thermal barrier coating used was a yttria stabilized zirconia material with a NiCrAlY undercoat, and the base engine used to establish improvements was the P&WA FT50A-4 industrial gas turbine engine. The design benefits of thermal barrier coatings include simplified cooling schemes and the use of conventional alloys in the engine hot section. Cooling flow reductions and improved heating rates achieved with thermal barrier coating result in improved performance. Economic benefits include reduced power production costs and reduced fuel consumption. Over the 30,000 hour life of the thermal barrier coated parts, fuel savings equivalent to $5 million are projected and specific power (megawatts/mass of engine airflow) improvements on the order of 13% are estimated.

  8. Thermal-barrier coatings for utility gas turbines

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Miller, R. A.

    1982-01-01

    The potential of thermal barrier coatings for use in utility gas turbines was assessed. Pressurized passage and ambient pressure doped fuel burner rig tests revealed that thermal barrier coatings are not resistant to dirty combustion environments. However, present thermal barrier coatings, such as duplex partially stabilized zirconia and duplex Ca2SiO4 have ample resistance to the thermo-mechanical stress and temperature levels anticipated for heavy duty gas turbines firing clean fuel as revealed by clean fuel pressurized passage and ambient pressure burner rig tests. Thus, it is appropriate to evaluate such coatings on blades, vanes and combustors in the field. However, such field tests should be backed up with adequate effort in the areas of coating application technology and design analysis so that the field tests yield unequivocal results.

  9. Effect of Suspension Plasma-Sprayed YSZ Columnar Microstructure and Bond Coat Surface Preparation on Thermal Barrier Coating Properties

    NASA Astrophysics Data System (ADS)

    Bernard, Benjamin; Quet, Aurélie; Bianchi, Luc; Schick, Vincent; Joulia, Aurélien; Malié, André; Rémy, Benjamin

    2017-08-01

    Suspension plasma spraying (SPS) is identified as promising for the enhancement of thermal barrier coating (TBC) systems used in gas turbines. Particularly, the emerging columnar microstructure enabled by the SPS process is likely to bring about an interesting TBC lifetime. At the same time, the SPS process opens the way to a decrease in thermal conductivity, one of the main issues for the next generation of gas turbines, compared to the state-of-the-art deposition technique, so-called electron beam physical vapor deposition (EB-PVD). In this paper, yttria-stabilized zirconia (YSZ) coatings presenting columnar structures, performed using both SPS and EB-PVD processes, were studied. Depending on the columnar microstructure readily adaptable in the SPS process, low thermal conductivities can be obtained. At 1100 °C, a decrease from 1.3 W m-1 K-1 for EB-PVD YSZ coatings to about 0.7 W m-1 K-1 for SPS coatings was shown. The higher content of porosity in the case of SPS coatings increases the thermal resistance through the thickness and decreases thermal conductivity. The lifetime of SPS YSZ coatings was studied by isothermal cyclic tests, showing equivalent or even higher performances compared to EB-PVD ones. Tests were performed using classical bond coats used for EB-PVD TBC coatings. Thermal cyclic fatigue performance of the best SPS coating reached 1000 cycles to failure on AM1 substrates with a β-(Ni,Pt)Al bond coat. Tests were also performed on AM1 substrates with a Pt-diffused γ-Ni/γ'-Ni3Al bond coat for which more than 2000 cycles to failure were observed for columnar SPS YSZ coatings. The high thermal compliance offered by both the columnar structure and the porosity allowed the reaching of a high lifetime, promising for a TBC application.

  10. Effect of Suspension Plasma-Sprayed YSZ Columnar Microstructure and Bond Coat Surface Preparation on Thermal Barrier Coating Properties

    NASA Astrophysics Data System (ADS)

    Bernard, Benjamin; Quet, Aurélie; Bianchi, Luc; Schick, Vincent; Joulia, Aurélien; Malié, André; Rémy, Benjamin

    2017-06-01

    Suspension plasma spraying (SPS) is identified as promising for the enhancement of thermal barrier coating (TBC) systems used in gas turbines. Particularly, the emerging columnar microstructure enabled by the SPS process is likely to bring about an interesting TBC lifetime. At the same time, the SPS process opens the way to a decrease in thermal conductivity, one of the main issues for the next generation of gas turbines, compared to the state-of-the-art deposition technique, so-called electron beam physical vapor deposition (EB-PVD). In this paper, yttria-stabilized zirconia (YSZ) coatings presenting columnar structures, performed using both SPS and EB-PVD processes, were studied. Depending on the columnar microstructure readily adaptable in the SPS process, low thermal conductivities can be obtained. At 1100 °C, a decrease from 1.3 W m-1 K-1 for EB-PVD YSZ coatings to about 0.7 W m-1 K-1 for SPS coatings was shown. The higher content of porosity in the case of SPS coatings increases the thermal resistance through the thickness and decreases thermal conductivity. The lifetime of SPS YSZ coatings was studied by isothermal cyclic tests, showing equivalent or even higher performances compared to EB-PVD ones. Tests were performed using classical bond coats used for EB-PVD TBC coatings. Thermal cyclic fatigue performance of the best SPS coating reached 1000 cycles to failure on AM1 substrates with a β-(Ni,Pt)Al bond coat. Tests were also performed on AM1 substrates with a Pt-diffused γ-Ni/γ'-Ni3Al bond coat for which more than 2000 cycles to failure were observed for columnar SPS YSZ coatings. The high thermal compliance offered by both the columnar structure and the porosity allowed the reaching of a high lifetime, promising for a TBC application.

  11. Ultrasonic Detection of Delamination and Material Characterization of Thermal Barrier Coatings

    SciTech Connect

    Chen, Hung-Liang Roger; Zhang, Binwei; Alvin, Mary Anne; Lin, Yun

    2012-12-01

    This article describes ultrasonic nondestructive evaluation (NDE) to detect the changes of material properties and provide early warning of delamination in thermal barrier coating (TBC) systems. NDE tests were performed on single-crystal René N5 superalloy coupons that were coated with a commercially available MCrAlY bond coat and an air plasma sprayed 7% yttria-stabilized zirconia (YSZ) top coat deposited by Air Plasma Spray method, as well as Haynes 230 superalloy coupons coated with MCrA1Y bond coat, and an electron beam physical vapor deposit of 7% YSZ top coat. The TBC coupons were subjected to either cyclic or isothermal exposure for various lengths of time at temperatures ranging from 900 to 1100 °C. The ultrasonic measurements performed on the coupons had provided an early warning of delamination along the top coat/TGO interface before exposure time, when delamination occurred. The material's property (Young’s modulus) of the top coat was estimated using the measured wave speeds. Finite element analysis (FEA) of the ultrasonic wave propagation was conducted on a simplified TBC system to verify experimental observations. The technique developed was also demonstrated on an as-manufactured turbine blade to estimate normalized top coat thickness measurements.

  12. Failure Morphologies of Cyclically Oxidized ZrO2-Based Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    Advanced and baseline thermal barrier coatings (TBCs) were thermal cycle tested in air at 1163 C until delamination or spallation of the ceramic top coat. The top coat of the advanced TBC s consisted of ZrO2 with various amounts of Y2O3, Yb2O3, Gd2O3, or Nd2O3 dopants. The composition of the top coat of the baseline TBC was ZrO2-8wt.%Y2O3. All top coats were deposited by air plasma spraying. A NiCrAlY or NiCoCrAlY bond coat was deposited by low pressure plasma spraying onto a single-crystal, Ni-base superalloy. The TBC lifetime for the baseline coatings was approximately 190 cycles (45 minutes at 1163 C per cycle) while the lifetime for the advanced coatings was as high as 425 cycles. The fracture surfaces and sample cross sections were examined after TBC failure by SEM and optical microscopy, and the top coats were further examined by X-ray diffraction. These post-test studies revealed that the fracture path largely followed splat boundaries with some trans-splat fracture. However, there were no obvious distinguishing features which explained the difference in TBC lifetimes between some of the advanced and baseline coatings.

  13. Characterisation of the TiO2 coatings deposited by plasma spraying

    NASA Astrophysics Data System (ADS)

    Benea, M. L.; Benea, L. P.

    2016-02-01

    Plasma spraying of materials such as ceramics and non-metals, which have high melting points, has become a well-established commercial process. Such coatings are increasingly used in aerospace, automobile, textile, medical, printing and electrical industries to impart proprieties such as corrosion resistance, thermal resistance, wear resistance, etc. One of the most important characteristics of thermal barrier coatings is the ability to undergo fast temperature changes without failing, the so called thermal shock resistance. The formation of residual stresses in plasma sprayed ceramic and metallic coatings is a very complex process. Several factors, such as substrate material, substrate thickness, physical properties of both the substrate and the coating material, deposition rate, relative velocity of the plasma torch, etc. determine the final residual stress state of the coating at room temperature. Our objective is to characterize the titanium oxide and aluminium oxide coatings deposited by plasma spraying in structural terms, the resistance to thermal shock and residual stresses.

  14. Optical Diagnostics of Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Majewski, Mark Steven

    The high temperature properties of ceramic materials make them suitable for the extreme environments of gas combustion powered turbines. They are instrumental in providing thermal insulation for the metallic turbine components from the combustion products. Also, the addition of specific rare earth elements to ceramics creates materials with temperature diagnostic applications. Laser based methods have been applied to these ceramic coatings to predict their remaining thermal insulation service life and to explore their high temperature diagnostic capabilities. A method for cleaning thermal barrier coatings (TBCs) contaminated during engine operation has been developed using laser ablation. Surface contamination on the turbine blades hinders nondestructive remaining life prediction using photo luminescence piezospectroscopy (PLPS). Real time monitoring of the removed material is employed to prevent damage to the underlying coating. This method relies on laser induced breakdown spectroscopy (LIBS) to compute the cross correlation coefficient between the spectral emissions of a sample TBC that is contaminated and a reference clean TBC. It is possible to remove targeted contaminants and cease ablation when the top surface of the TBC has been reached. In collaboration with this work, Kelley's thesis [1] presents microscopy images and PLPS measurements indicating the integrity of the TBC has been maintained during the removal of surface contaminants. Thermographic phosphors (TGP) have optical emission properties when excited by a laser that are temperature dependent. These spectral and temporal properties have been investigated and utilized for temperature measurement schemes by many previous researchers. The compounds presented in this dissertation consist of various rare earth (Lanthanide) elements doped into a host crystal lattice. As the temperature of the lattice changes, both the time scale for vibrational quenching and the distribution of energy among atomic energy

  15. Rocket thrust chamber thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Quentmeyer, R. J.

    1985-01-01

    Subscale rocket thrust chamber tests were conducted to evaluate the effectiveness and durability of thin yttria stabilized zirconium oxide coatings applied to the thrust chamber hot-gas side wall. The fabrication consisted of arc plasma spraying the ceramic coating and bond coat onto a mandrell and then electrodepositing the copper thrust chamber wall around the coating. Chambers were fabricated with coatings .008, and .005 and .003 inches thick. The chambers were thermally cycled at a chamber pressure of 600 psia using oxygen-hydrogen as propellants and liquid hydrogen as the coolant. The thicker coatings tended to delaminate, early in the cyclic testing, down to a uniform sublayer which remained well adhered during the remaining cycles. Two chambers with .003 inch coatings were subjected to 1500 thermal cycles with no coating loss in the throat region, which represents a tenfold increase in life over identical chambers having no coatings. An analysis is presented which shows that the heat lost to the coolant due to the coating, in a rocket thrust chamber design having a coating only in the throat region, can be recovered by adding only one inch to the combustion chamber length.

  16. Thermal barrier coating life prediction model development, phase 1

    NASA Technical Reports Server (NTRS)

    Demasi, Jeanine T.; Ortiz, Milton

    1989-01-01

    The objective of this program was to establish a methodology to predict thermal barrier coating (TBC) life on gas turbine engine components. The approach involved experimental life measurement coupled with analytical modeling of relevant degradation modes. Evaluation of experimental and flight service components indicate the predominant failure mode to be thermomechanical spallation of the ceramic coating layer resulting from propagation of a dominant near interface crack. Examination of fractionally exposed specimens indicated that dominant crack formation results from progressive structural damage in the form of subcritical microcrack link-up. Tests conducted to isolate important life drivers have shown MCrAlY oxidation to significantly affect the rate of damage accumulation. Mechanical property testing has shown the plasma deposited ceramic to exhibit a non-linear stress-strain response, creep and fatigue. The fatigue based life prediction model developed accounts for the unusual ceramic behavior and also incorporates an experimentally determined oxide rate model. The model predicts the growth of this oxide scale to influence the intensity of the mechanic driving force, resulting from cyclic strains and stresses caused by thermally induced and externally imposed mechanical loads.

  17. Advanced Thermal Barrier and Environmental Barrier Coating Development at NASA GRC

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Robinson, Craig

    2017-01-01

    This presentation summarizes NASA's advanced thermal barrier and environmental barrier coating systems, and the coating performance improvements that has recently been achieved and documented in laboratory simulated rig test conditions. One of the emphases has been placed on the toughness and impact resistance enhancements of the low conductivity, defect cluster thermal barrier coating systems. The advances in the next generation environmental barrier coatings for SiCSiC ceramic matrix composites have also been highlighted, particularly in the design of a new series of oxide-silicate composition systems to be integrated with next generation SiC-SiC turbine engine components for 2700F coating applications. Major technical barriers in developing the thermal and environmental barrier coating systems are also described. The performance and model validations in the rig simulated turbine combustion, heat flux, steam and calcium-magnesium-aluminosilicate (CMAS) environments have helped the current progress in improved temperature capability, environmental stability, and long-term fatigue-environment system durability of the advanced thermal and environmental barrier coating systems.

  18. Oxidation and degradation of thermal barrier coating systems

    NASA Astrophysics Data System (ADS)

    Haynes, James Allen

    Thermal barrier coatings (TBCs), which consist of an oxidation-resistant metallic bond coating overlaid with a thermally-insulating Ysb2Osb3-stabilized ZrOsb2 (YSZ) top coating, are used to protect superalloy hardware in gas turbine engines. Spallation of the YSZ is accelerated by growth of an interfacial Alsb2Osb3 scale at high temperatures. The mechanisms of oxidation-related degradation are not well understood for air plasma-sprayed (APS) TBCs, whereas Alsb2Osb3 thermomechanical failure is the dominant degradation mode in electron beam-physical vapor deposition (EB-PVD) TBCs. This work investigated the isothermal oxidation and thermocyclic degradation of various TBC systems; with particular emphasis on the growth kinetics, microstructures, flaw content, fracture behavior and micro-mechanical properties of the Alsb2Osb3 interfacial scales. The isothermal oxidation kinetics of plasma-sprayed NiCrAlY were not influenced by the presence of an APS YSZ top coating (at 1150sp°C). However, the isothermal oxidation rate constants of NiCoCrAlY bond coatings were accelerated by a factor of 2 (at 950, 1050 and 1150sp°C) when overlaid with a commercial EB-PVD TBC. Thermocyclic failure of APS TBCs occurred by progressive YSZ fracture and crack link-up. Severe fracture and buckling of the interfacial Alsb2Osb3 during thermal cycling did not induce rapid failure of APS TBCs. Evaluation of the interfacial Alsb2Osb3 scale microstructures (on APS TBCs) after thermal cycling revealed the following: thermocyclic damage occurred by both oxide-metal delamination and by internal fracture; Alsb2Osb3 scale crack healing by sintering occurred at 1150sp°C; surfaces with a sharp radius of curvature induced less Alsb2Osb3 damage than gradually convex surfaces; scale grain boundary void growth was accelerated by thermal cycling; and higher void contents were observed in scales which formed on convex surfaces. There were no significant changes in the hardness or Young's modulus of the Alsb2

  19. Thermal Fatigue and Fracture Behavior of Ceramic Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    Thermal fatigue and fracture behavior of plasma-sprayed ceramic thermal barrier coatings has been investigated under high heat flux and thermal cyclic conditions. The coating crack propagation is studied under laser heat flux cyclic thermal loading, and is correlated with dynamic fatigue and strength test results. The coating stress response and inelasticity, fatigue and creep interactions, and interface damage mechanisms during dynamic thermal fatigue processes are emphasized.

  20. Preparation of SrZrO3 Thermal Barrier Coating by Solution Precursor Plasma Spray

    NASA Astrophysics Data System (ADS)

    Li, Xinhui; Ma, Wen; Wen, Jing; Bai, Yu; Sun, Li; Chen, Baodong; Dong, Hongying; Shuang, Yingchai

    2017-02-01

    The solution precursor plasma spray (SPPS) process is capable of depositing highly durable thermal barrier coatings (TBCs). In this study, an aqueous chemical precursor feedstock was injected into the plasma jet to deposit SrZrO3 thermal barrier coating on metal substrate. Taguchi design of experiments was employed to optimize the SPPS process. The thermal characteristics and phase evolution of the SrZrO3 precursor, as well as the influence of various spray parameters on the coating deposition rate, microhardness, microstructure, and phase stability, were investigated. The experimental results showed that, at given spray distance, feedstock flow rate, and atomization pressure, the optimized spray parameters were arc current of 600 A, argon flow rate of 40 L/min, and hydrogen flow rate of 10 L/min. The SrZrO3 coating prepared using the optimized spray parameters had single-pass thickness of 6.0 μm, porosity of 18%, and microhardness of 6.8 ± 0.1 GPa. Phase stability studies indicated that the as-sprayed SrZrO3 coating had good phase stability in the temperature range from room temperature to 1400 °C, gradually exhibiting a phase transition from t'-ZrO2 to m-ZrO2 in the SrZrO3 coating at 1450 °C with increasing time, while the SrZrO3 phase did not change.

  1. Development and Testing of Ceramic Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating behavior and temperature limits, in order to potentially take full advantage of the current coating capability, and also accurately assess the benefit gained from advanced coating development. In this study, thermal conductivity behavior and cyclic durability of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under laser heat-flux simulated high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack propagation driving forces and resulting failure modes will be discussed in light of high temperature mechanical fatigue and fracture testing results.

  2. Thermophysical and Thermomechanical Properties of Thermal Barrier Coating Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2000-01-01

    Thermal barrier coatings have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, the issue of coating durability under high temperature cyclic conditions is still of major concern. The coating failure is closely related to thermal stresses and oxidation in the coating systems. Coating shrinkage cracking resulting from ceramic sintering and creep at high temperatures can further accelerate the coating failure process. The purpose of this paper is to address critical issues such as ceramic sintering and creep, thermal fatigue and their relevance to coating life prediction. Novel test approaches have been established to obtain critical thermophysical and thermomechanical properties of the coating systems under near-realistic temperature and stress gradients encountered in advanced engine systems. Emphasis is placed on the dynamic changes of the coating thermal conductivity and elastic modulus, fatigue and creep interactions, and resulting failure mechanisms during the simulated engine tests. Detailed experimental and modeling results describing processes occurring in the thermal barrier coating systems provide a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.

  3. Thermal Barrier Coatings on Copper Substrates for Rocket Applications

    NASA Astrophysics Data System (ADS)

    Schloesser, Jana; Fedorova, Tatiana; Bäker, Martin; Rösler, Joachim

    Currently a new generation of relaunchable space transportation system using liquid hydrogen/ liquid oxygen rocket engines is under development. The inner combustion chamber is exposed to extreme thermal loads and environmental attack during starts. To prevent failure of the cooling channels, a thermal barrier coating to provide thermal and oxidation protection could be applied. Thermal barrier coatings are state of the art for gas turbines and this concept should be transferred to copper substrates in rocket engine applications. The thermomechanical loading conditions are quite different from the gas turbine applications as heat fluxes and temperature gradients are much higher while overall service time is much shorter. As a start for optimization of a suitable coating, a material system known for gas turbines is employed. In this work a thermal barrier coating system is applied by atmospheric plasma spraying to the copper-based high strength alloy Cu-1%Cr-0.3%Zr. The bond coat consists of a NiCrAlY alloy, while partially stabilized zirconia is used as a top coat. Spraying parameter optimization for the new substrate is described. The reached coating system is tested in thermal cycling experiments, where no failure of the coating could be detected. In oxidation experiments good environmental protection of the coating is shown.

  4. Evaluation of Oxidation Damage in Thermal Barrier Coating Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1996-01-01

    A method based on the technique of dilatometry has been established to quantitatively evaluate the interfacial damage due to the oxidation in a thermal barrier coating system. Strain isolation and adhesion coefficients have been proposed to characterize the thermal barrier coating (TBC) performance based on its thermal expansion behavior. It has been found that, for a thermal barrier coating system consisting of ZrO2-8%Y2O3/FeCrAlY/4140 steel substrate, the oxidation of the bond coat and substrate significantly reduced the ceramic coating adherence, as inferred from the dilatometry measurements. The in-situ thermal expansion measurements under 30 deg C to 700 deg C thermal cycling in air showed that the adhesion coefficient, A(sub i) decreased by 25% during the first 35 oxidation cycles. Metallography showed that delamination occurred at both the ceramic/bond coat and bond coat/substrate interfaces. In addition, the strain isolation effect has been improved by increasing the FeCrAlY bond coat thickness. The strain isolation coefficient, Si, increased from about 0.04 to 0.25, as the bond coat thickness changed from 0.1 mm to 1.0 mm. It may be possible to design optimum values of strain isolation and interface adhesion coefficients to achieve the best TBC performance.

  5. Electrospark Deposited Coating Technology for Naval Applications (Briefing Charts)

    DTIC Science & Technology

    2002-09-01

    Electrospark Deposited Coating Technology for Naval Applications Denise A. Aylor Naval Surface Warfare Center Carderock Division Marine Corrosion...number. 1. REPORT DATE SEP 2002 2. REPORT TYPE 3. DATES COVERED 00-00-2002 to 00-00-2002 4. TITLE AND SUBTITLE Electrospark Deposited Coating...ANSI Std Z39-18 Objective • Produce good quality coatings using electrospark deposition (ESD) Approach • Identify Navy components for repair

  6. ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating

    DTIC Science & Technology

    2001-04-26

    roger.johnson@pnl.gov, 509-375-6906 ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating (SERDP Project 1147) Report Documentation...3. DATES COVERED 00-00-2001 to 00-00-2001 4. TITLE AND SUBTITLE ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating 5a...Northwest National Laboratory 2 Electrospark Deposition Technology Coatings: Electrically conductive metals, alloys, or cermets Micro-welding

  7. Accelerated electrospark deposition and the wear behavior of coatings

    NASA Astrophysics Data System (ADS)

    Wang, P.-Z.; Pan, G.-S.; Zhou, Y.; Qu, J.-X.; Shao, H.-S.

    1997-12-01

    Electrospark deposition (ESD) is a coating process that is featured by low heat input to the substrate. Low coating efficiency and other limitations influence its wider application. The present paper introduces newly designed ESD equipment, by which a higher coating rate can be reached. The relationship among coating thickness, surface roughness, and process parameters such as pulse energy, pulse frequency, and deposition time are presented. Electrospark deposition coating by the new equipment on AISI 1045 steel (with WC-8% Co as electrode) increases the wear resistance by 5 to 8 times. The micromechanism is investigated by scanning electron microscopy observation.

  8. Advanced Environmental Barrier Coatings Development for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Choi, R. Sung; Robinson, Raymond C.; Lee, Kang N.; Bhatt, Ramakrishna T.; Miller, Robert A.

    2005-01-01

    Advanced environmental barrier coating concepts based on multi-component HfO2 (ZrO2) and modified mullite systems are developed for monolithic Si3N4 and SiC/SiC ceramic matrix composite (CMC) applications. Comprehensive testing approaches were established using the water vapor cyclic furnace, high pressure burner rig and laser heat flux steam rig to evaluate the coating water vapor stability, cyclic durability, radiation and erosion resistance under simulated engine environments. Test results demonstrated the feasibility and durability of the environmental barrier coating systems for 2700 to 3000 F monolithic Si3N4 and SiC/SiC CMC component applications. The high-temperature-capable environmental barrier coating systems are being further developed and optimized in collaboration with engine companies for advanced turbine engine applications.

  9. Microstructural aspects of zirconia thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Mitchell, T. E.; Suhr, D. S.; Keller, R. J.; Lanteri, V.; Heuer, A. H.

    1985-01-01

    Various combination of plasma-sprayed bond coatings and zirconia ceramic coatings on a nickel-based superalloy substrate were tested by static thermal exposure at 1200 C and cyclic thermal exposure to 1000 C. The bond coats were based on Ni-Cr-Al alloys with additions of rare earth elements and Si. The ceramic coats were various ZrO2-Y2O3 compositions, of which the optimum was found to be ZrO2-8.9 wt percent Y2O3. Microstructural analysis showed that resistance to cracking during thermal exposure is strongly related to deleterious phase changes. Zones depleted of Al formed at the bond coat/ceramic coat interface due to oxidation and at the bond coat/substrate interface due to interdiffusion, leading eventually to breakdown of the bond coat. The 8.9 percent Y2O3 coating performed best because the as-sprayed metastable tetragonal phase converted slowly into the low-Y2O3 tetragonal plus high-Y2O3 cubic-phase mixture, so that the deleterious monoclinic phase was inhibited from forming. Failure appeared to start with the formation of circumferential cracks in the zirconia, probably due to compressive stresses during cooling, followed by the formation of radial cracks due to tensile stresses during heating. Cracks appeared to initiate at the Al2O3 scale/bond coat interface and propagate through the zirconia coating. Comparisons were made with the behavior of bulk ZrO2-Y2O3 and the relationship between the microstructure of the tetragonal phase and the phase diagram. A separate investigation was also made of the ZrO2-Al2O3 interface.

  10. Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

  11. Mechanical behavior of thermal barrier coatings for gas turbine blades

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Phucharoen, W.; Chang, G. C.

    1984-01-01

    Plasma-sprayed thermal barrier coatings (TBCs) will enable turbine components to operate at higher temperatures and lower cooling gas flow rates; thereby improving their efficiency. Future developments are limited by precise knowledge of the material properties and failure mechanisms of the coating system. Details of this nature are needed for realistic modeling of the coating system which will, in turn, promote advancements in coating technology. Complementary experiments and analytical modeling which were undertaken in order to define and measure the important failure processes for plasma-sprayed coatings are presented. The experimental portion includes two different tests which were developed to measure coating properties. These are termed tensile adhesion and acoustic emission tests. The analytical modeling section details a finite element method which was used to calculate the stress distribution in the coating system. Some preliminary results are presented.

  12. Ceramic thermal barrier coatings for gas turbine engines

    NASA Technical Reports Server (NTRS)

    Bratton, R. J.; Lau, S. K.; Andersson, C. A.; Lee, S. Y.

    1982-01-01

    The results of studies concerning the high temperature corrosion resistance of ZrO2-Y2O3, ZrO2-MgO, and Ca2SiO4 plasma-sprayed coatings, which may be used as gas turbine engine thermal barriers, are reported. The coatings were evaluated in atmospheric burner rig and pressurized passage tests, using GT No. 2 fuel in pure form and with sodium, sulfur and vanadium corrosive impurities doping. It is found that, while the coatings performed well in both pressurized passage and burner rig tests with pure fuel chemical reactions between the ceramic coatings and combustion gases/condensates resulted in coating degradation with impure fuels. Chemical reactions between the ceramic coatings and vanadium compounds played a critical role in coating degradation.

  13. Method of Producing Controlled Thermal Expansion Coat for Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Brindley, William J. (Inventor); Miller, Robert A. (Inventor); Aikin, Beverly J. M. (Inventor)

    2000-01-01

    An improved thermal barrier coating and method for producing and applying such is disclosed herein. The thermal barrier coatings includes a high temperature substrate, a first bond coat layer applied to the substrate of MCrAlX and a second bond coat layer of MCrAlX with particles of a particulate dispersed throughout the MCrAlX and the preferred particulate is Al2O3. The particles of the particulate dispersed throughout the second bond coat layer preferably have a diameter of less then the height of the peaks of the second bond coat layer or a diameter of less than 5 micron. The method of producing the second bond coat layer may either include the steps of mechanical alloying of particles throughout the second bond coat layer, attrition milling the particles of the particulate throughout the second bond coat layer, or using electrophoresis to disperse the particles throughout the second bond coat layer. In the preferred embodiment of the invention the first bond coat layer is applied to the substrate. and then the second bond coat layer is thermally sprayed onto the first bond coat layer. Further, in a preferred embodiment of the invention a ceramic insulating layer covers the second bond coat layer.

  14. Nano-structured yttria-stabilized zirconia coating by electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Maleki-Ghaleh, H.; Rekabeslami, M.; Shakeri, M. S.; Siadati, M. H.; Javidi, M.; Talebian, S. H.; Aghajani, H.

    2013-09-01

    The most important role of thermal barrier coatings is to reduce the temperature of the substrate in high temperature applications. Nano particle zirconia might be a suitable choice for improving the efficiency of thermal barrier coatings. Nanostructured coatings have lower thermal conduction, higher thermal expansion and lower dimensional variations at higher temperatures in comparison with the microstructured coatings. Electrophoretic deposition has been preferred for thermal barrier coatings due to its simplicity, controllability and low cost. In the present study, three different suspensions of ZrO2-8 wt%Y2O3 (40 nm) made with ethanol, acetone and acetyl acetone were used. Electrophoretic deposition was conducted at a fixed voltage of 60 V for 120 s on aluminized Inconel 738-LC, and then heat treated at 1100 ̊C for 4 h in air atmosphere. The coating morphology and elemental distribution were studied using scanning electron microscopy. It was observed that suspension media have an important effect on the quality of the final product. Acetyl acetone showed better dispersion of particles than the other two media. Consequently, deposition from acetyl acetone resulted in uniform and crack-free layers while those from ethanol and acetone were completely non-uniform due to agglomeration and low viscosity, respectively.

  15. A Study of Deposition Coatings Formed by Electroformed Metallic Materials

    PubMed Central

    Shimura, Kojiro; Tobayama, Go; Togashi, Toshio

    2016-01-01

    Major joining methods of dental casting metal include brazing and laser welding. However, brazing cannot be applied for electroformed metals since heat treatment could affect the fit, and, therefore, laser welding is used for such metals. New methods of joining metals that do not impair the characteristics of electroformed metals should be developed. When new coating is performed on the surface of the base metal, surface treatment is usually performed before re-coating. The effect of surface treatment is clinically evaluated by peeling and flex tests. However, these testing methods are not ideal for deposition coating strength measurement of electroformed metals. There have been no studies on the deposition coating strength and methods to test electroformed metals. We developed a new deposition coating strength test for electroformed metals. The influence of the negative electrolytic method, which is one of the electrochemical surface treatments, on the strength of the deposition coating of electroformed metals was investigated, and the following conclusions were drawn: 1. This process makes it possible to remove residual deposits on the electrodeposited metal surface layer. 2. Cathode electrolysis is a simple and safe method that is capable of improving the surface treatment by adjustments to the current supply method and current intensity. 3. Electrochemical treatment can improve the deposition coating strength compared to the physical or chemical treatment methods. 4. Electro-deposition coating is an innovative technique for the deposition coating of electroformed metal. PMID:27326757

  16. A Study of Deposition Coatings Formed by Electroformed Metallic Materials.

    PubMed

    Hayashi, Shoji; Sugiyama, Shuta; Shimura, Kojiro; Tobayama, Go; Togashi, Toshio

    2016-01-01

    Major joining methods of dental casting metal include brazing and laser welding. However, brazing cannot be applied for electroformed metals since heat treatment could affect the fit, and, therefore, laser welding is used for such metals. New methods of joining metals that do not impair the characteristics of electroformed metals should be developed. When new coating is performed on the surface of the base metal, surface treatment is usually performed before re-coating. The effect of surface treatment is clinically evaluated by peeling and flex tests. However, these testing methods are not ideal for deposition coating strength measurement of electroformed metals. There have been no studies on the deposition coating strength and methods to test electroformed metals. We developed a new deposition coating strength test for electroformed metals. The influence of the negative electrolytic method, which is one of the electrochemical surface treatments, on the strength of the deposition coating of electroformed metals was investigated, and the following conclusions were drawn: 1. This process makes it possible to remove residual deposits on the electrodeposited metal surface layer. 2. Cathode electrolysis is a simple and safe method that is capable of improving the surface treatment by adjustments to the current supply method and current intensity. 3. Electrochemical treatment can improve the deposition coating strength compared to the physical or chemical treatment methods. 4. Electro-deposition coating is an innovative technique for the deposition coating of electroformed metal.

  17. The Lattice and Thermal Radiation Conductivity of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Spuckler, Charles M.

    2008-01-01

    The lattice and radiation conductivity of thermal barrier coatings was evaluated using a laser heat flux approach. A diffusion model has been established to correlate the apparent thermal conductivity of the coating to the lattice and radiation conductivity. The radiation conductivity component can be expressed as a function of temperature and the scattering and absorption properties of the coating material. High temperature scattering and absorption of the coating systems can also be derived based on the testing results using the modeling approach. The model prediction is found to have good agreement with experimental observations.

  18. Large-scale, thick, self-assembled, nacre-mimetic brick-walls as fire barrier coatings on textiles

    NASA Astrophysics Data System (ADS)

    Das, Paramita; Thomas, Helga; Moeller, Martin; Walther, Andreas

    2017-01-01

    Highly loaded polymer/clay nanocomposites with layered structures are emerging as robust fire retardant surface coatings. However, time-intensive sequential deposition processes, e.g. layer-by-layer strategies, hinders obtaining large coating thicknesses and complicates an implementation into existing technologies. Here, we demonstrate a single-step, water-borne approach to prepare thick, self-assembling, hybrid fire barrier coatings of sodium carboxymethyl cellulose (CMC)/montmorillonite (MTM) with well-defined, bioinspired brick-wall nanostructure, and showcase their application on textile. The coating thickness on the textile is tailored using different concentrations of CMC/MTM (1–5 wt%) in the coating bath. While lower concentrations impart conformal coatings of fibers, thicker continuous coatings are obtained on the textile surface from highest concentration. Comprehensive fire barrier and fire retardancy tests elucidate the increasing fire barrier and retardancy properties with increasing coating thickness. The materials are free of halogen and heavy metal atoms, and are sourced from sustainable and partly even renewable building blocks. We further introduce an amphiphobic surface modification on the coating to impart oil and water repellency, as well as self-cleaning features. Hence, our study presents a generic, environmentally friendly, scalable, and one-pot coating approach that can be introduced into existing technologies to prepare bioinspired, thick, fire barrier nanocomposite coatings on diverse surfaces.

  19. Large-scale, thick, self-assembled, nacre-mimetic brick-walls as fire barrier coatings on textiles

    PubMed Central

    Das, Paramita; Thomas, Helga; Moeller, Martin; Walther, Andreas

    2017-01-01

    Highly loaded polymer/clay nanocomposites with layered structures are emerging as robust fire retardant surface coatings. However, time-intensive sequential deposition processes, e.g. layer-by-layer strategies, hinders obtaining large coating thicknesses and complicates an implementation into existing technologies. Here, we demonstrate a single-step, water-borne approach to prepare thick, self-assembling, hybrid fire barrier coatings of sodium carboxymethyl cellulose (CMC)/montmorillonite (MTM) with well-defined, bioinspired brick-wall nanostructure, and showcase their application on textile. The coating thickness on the textile is tailored using different concentrations of CMC/MTM (1–5 wt%) in the coating bath. While lower concentrations impart conformal coatings of fibers, thicker continuous coatings are obtained on the textile surface from highest concentration. Comprehensive fire barrier and fire retardancy tests elucidate the increasing fire barrier and retardancy properties with increasing coating thickness. The materials are free of halogen and heavy metal atoms, and are sourced from sustainable and partly even renewable building blocks. We further introduce an amphiphobic surface modification on the coating to impart oil and water repellency, as well as self-cleaning features. Hence, our study presents a generic, environmentally friendly, scalable, and one-pot coating approach that can be introduced into existing technologies to prepare bioinspired, thick, fire barrier nanocomposite coatings on diverse surfaces. PMID:28054589

  20. Large-scale, thick, self-assembled, nacre-mimetic brick-walls as fire barrier coatings on textiles.

    PubMed

    Das, Paramita; Thomas, Helga; Moeller, Martin; Walther, Andreas

    2017-01-05

    Highly loaded polymer/clay nanocomposites with layered structures are emerging as robust fire retardant surface coatings. However, time-intensive sequential deposition processes, e.g. layer-by-layer strategies, hinders obtaining large coating thicknesses and complicates an implementation into existing technologies. Here, we demonstrate a single-step, water-borne approach to prepare thick, self-assembling, hybrid fire barrier coatings of sodium carboxymethyl cellulose (CMC)/montmorillonite (MTM) with well-defined, bioinspired brick-wall nanostructure, and showcase their application on textile. The coating thickness on the textile is tailored using different concentrations of CMC/MTM (1-5 wt%) in the coating bath. While lower concentrations impart conformal coatings of fibers, thicker continuous coatings are obtained on the textile surface from highest concentration. Comprehensive fire barrier and fire retardancy tests elucidate the increasing fire barrier and retardancy properties with increasing coating thickness. The materials are free of halogen and heavy metal atoms, and are sourced from sustainable and partly even renewable building blocks. We further introduce an amphiphobic surface modification on the coating to impart oil and water repellency, as well as self-cleaning features. Hence, our study presents a generic, environmentally friendly, scalable, and one-pot coating approach that can be introduced into existing technologies to prepare bioinspired, thick, fire barrier nanocomposite coatings on diverse surfaces.

  1. Deposition Kinetics of Bioinspired Phenolic Coatings on Titanium Surfaces.

    PubMed

    Geißler, Sebastian; Barrantes, Alejandro; Tengvall, Pentti; Messersmith, Phillip B; Tiainen, Hanna

    2016-08-16

    Polyphenols can form functional coatings on a variety of different materials through auto-oxidative surface polymerization in a manner similar to polydopamine coatings. However, the mechanisms behind the coating deposition are poorly understood. We report the coating deposition kinetics of the polyphenol tannic acid (TA) and the simple phenolic compound pyrogallol (PG) on titanium surfaces. The coating deposition was followed in real time over a period of 24 h using a quartz crystal microbalance with dissipation monitoring (QCM-D). TA coatings revealed a multiphasic layer formation: the deposition of an initial rigid layer was followed by the buildup of an increasingly dissipative layer, before mass adsorption stopped after approximately 5 h of coating time. The PG deposition was biphasic, starting with the adsorption of a nonrigid viscoelastic layer which was followed by layer stiffening upon further mass adsorption. Coating evaluation by ellipsometry and AFM confirmed the deposition kinetics determined by QCM-D and revealed maximum coating thicknesses of approximately 50 and 75 nm for TA and PG, respectively. Chemical characterization of the coatings and polymerized polyphenol particles indicated the involvement of both physical and chemical interactions in the auto-oxidation reactions.

  2. Next Generation Thermal Barrier Coatings for the Gas Turbine Industry

    NASA Astrophysics Data System (ADS)

    Curry, Nicholas; Markocsan, Nicolaie; Li, Xin-Hai; Tricoire, Aurélien; Dorfman, Mitch

    2011-01-01

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings.

  3. Failure Mechanism for Thermal Fatigue of Thermal Barrier Coating Systems

    NASA Astrophysics Data System (ADS)

    Giolli, C.; Scrivani, A.; Rizzi, G.; Borgioli, F.; Bolelli, G.; Lusvarghi, L.

    2009-06-01

    Thick thermal barrier coatings (TBCs), consisting of a CoNiCrAlY bond coat and yttria-partially stabilized zirconia top coat with different porosity values, were produced by air plasma spray (APS). The thermal fatigue resistance limit of the TBCs was tested by furnace cycling tests (FCT) according to the specifications of an original equipment manufacturer (OEM). The morphology, residual stresses, and micromechanical properties (microhardness, indentation fracture toughness) of the TBC systems before and after FCT were analyzed. The thermal fatigue resistance increases with the amount of porosity in the top coat. The compressive in-plane stresses increase in the TBC systems after thermal cycling; nevertheless the increasing rate has a trend contrary to the porosity level of top coat. The data suggest that the spallation happens at the TGO/top coat interface. The failure mechanism of thick TBCs was found to be similar to that of conventional thin TBC systems made by APS.

  4. Thermal Cycling Behavior of Quasi-Columnar YSZ Coatings Deposited by PS-PVD

    NASA Astrophysics Data System (ADS)

    Yang, Jiasheng; Zhao, Huayu; Zhong, Xinghua; Shao, Fang; Liu, Chenguang; Zhuang, Yin; Ni, Jinxing; Tao, Shunyan

    2017-01-01

    Columnar-structured thermal barrier coatings, owing to their high strain tolerance, are expected for their potential possibilities to substantially extend turbine lives and improve engine efficiencies. In this paper, plasma spray-physical vapor deposition (PS-PVD) process was used to deposit yttria partially stabilized zirconia (YSZ) coatings with quasi-columnar structures. Thermal cyclic tests on burner rigs and thermal shock tests by heating and water-quenching method were involved to evaluate the thermal cycling and thermal shock behaviors of such kind of structured thermal barrier coatings (TBCs). Evolution of the microstructures, phase composition, residual stresses and failure behaviors of quasi-columnar YSZ coatings before and after the thermal tests was investigated. The quasi-columnar coating obtained had an average life of around 623 cycles when the spallation area reached about 10% of the total coating surface during burner rig tests with the coating surface temperature of 1250 °C. Failure of the coating is mainly due to the break and pull-out of center columnar segments.

  5. Colloidal spray method for low cost thin coating deposition

    DOEpatents

    Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

    2002-01-01

    A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

  6. Colloidal spray method for low cost thin coating deposition

    DOEpatents

    Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

    2005-01-25

    A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

  7. Thermal barrier coating life prediction model development, phase 2

    NASA Technical Reports Server (NTRS)

    Meier, Susan Manning; Sheffler, Keith D.; Nissley, David M.

    1991-01-01

    The objective of this program was to generate a life prediction model for electron-beam-physical vapor deposited (EB-PVD) zirconia thermal barrier coating (TBC) on gas turbine engine components. Specific activities involved in development of the EB-PVD life prediction model included measurement of EB-PVD ceramic physical and mechanical properties and adherence strength, measurement of the thermally grown oxide (TGO) growth kinetics, generation of quantitative cyclic thermal spallation life data, and development of a spallation life prediction model. Life data useful for model development was obtained by exposing instrumented, EB-PVD ceramic coated cylindrical specimens in a jet fueled burner rig. Monotonic compression and tensile mechanical tests and physical property tests were conducted to obtain the EB-PVD ceramic behavior required for burner rig specimen analysis. As part of that effort, a nonlinear constitutive model was developed for the EB-PVD ceramic. Spallation failure of the EB-PVD TBC system consistently occurred at the TGO-metal interface. Calculated out-of-plane stresses were a small fraction of that required to statically fail the TGO. Thus, EB-PVD spallation was attributed to the interfacial cracking caused by in-plane TGO strains. Since TGO mechanical properties were not measured in this program, calculation of the burner rig specimen TGO in-plane strains was performed by using alumina properties. A life model based on maximum in-plane TGO tensile mechanical strain and TGO thickness correlated the burner rig specimen EB-PVD ceramic spallation lives within a factor of about plus or minus 2X.

  8. Thermal expansion mismatch and plasticity in thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Chang, George C.; Phucharoen, Woraphat; Miller, Robert A.

    1987-01-01

    The basic objective of this investigation is the quantitative determination of stress states in a model thermal barrier coating (TBC) as it cools in the air to 600 C from an assumed stress-free state at 700 C. This model is intended to represent a thin plasma-sprayed zirconia-yttria ceramic layer with a nickel chromium-aluminum-yttrium bond coat on a cylindrical substrate made of nickel-based superalloys typically found in gas turbines.

  9. Anisotropic Thermal Diffusivities of Plasma-Sprayed Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Akoshima, Megumi; Takahashi, Satoru

    2017-09-01

    Thermal barrier coatings (TBCs) are used to shield the blades of gas turbines from heat and wear. There is a pressing need to evaluate the thermal conductivity of TBCs in the thermal design of advanced gas turbines with high energy efficiency. These TBCs consist of a ceramic-based top coat and a bond coat on a superalloy substrate. Usually, the focus is on the thermal conductivity in the thickness direction of the TBC because heat tends to diffuse from the surface of the top coat to the substrate. However, the in-plane thermal conductivity is also important in the thermal design of gas turbines because the temperature distribution within the turbine cannot be ignored. Accordingly, a method is developed in this study for measuring the in-plane thermal diffusivity of the top coat. Yttria-stabilized zirconia top coats are prepared by thermal spraying under different conditions. The in-plane and cross-plane thermal diffusivities of the top coats are measured by the flash method to investigate the anisotropy of thermal conduction in a TBC. It is found that the in-plane thermal diffusivity is higher than the cross-plane one for each top coat and that the top coats have significantly anisotropic thermal diffusivity. The cross-sectional and in-plane microstructures of the top coats are observed, from which their porosities are evaluated. The thermal diffusivity and its anisotropy are discussed in detail in relation to microstructure and porosity.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  11. Monitoring Local Strain in a Thermal Barrier Coating System Under Thermal Mechanical Gas Turbine Operating Conditions

    NASA Astrophysics Data System (ADS)

    Manero, Albert; Sofronsky, Stephen; Knipe, Kevin; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M.; Raghavan, Seetha; Bartsch, Marion

    2015-07-01

    Advances in aircraft and land-based turbine engines have been increasing the extreme loading conditions on traditional engine components and have incited the need for improved performance with the use of protective coatings. These protective coatings shield the load-bearing super alloy blades from the high-temperature combustion gases by creating a thermal gradient over their thickness. This addition extends the life and performance of blades. A more complete understanding of the behavior, failure mechanics, and life expectancy for turbine blades and their coatings is needed to enhance and validate simulation models. As new thermal-barrier-coated materials and deposition methods are developed, strides to effectively test, evaluate, and prepare the technology for industry deployment are of paramount interest. Coupling the experience and expertise of researchers at the University of Central Florida, The German Aerospace Center, and Cleveland State University with the world-class synchrotron x-ray beam at the Advanced Photon Source in Argonne National Laboratory, the synergistic collaboration has yielded previously unseen measurements to look inside the coating layer system for in situ strain measurements during representative service loading. These findings quantify the in situ strain response on multilayer thermal barrier coatings and shed light on the elastic and nonelastic properties of the layers and the role of mechanical load and internal cooling variations on the response. The article discusses the experimental configuration and development of equipment to perform in situ strain measurements on multilayer thin coatings and provides an overview of the achievements thus far.

  12. Development of oxide based diffusion barrier coatings for CFC components applied in modern furnaces

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Zhao, Lidong; Schlaefer, Thomas; Warda, Thomas

    2011-12-01

    Carbon fibre reinforced carbon (CFC) materials show a high potential for usage in furnaces as sample carriers for example, which is due to their excellent thermal stability compared to steel carriers. Only their tendency to react with different metals at high temperatures by Cdiffusion is a disadvantage, which can be solved by application of diffusion barriers. In order to enable the utilization of CFC-carriers for e.g. brazing furnaces, within the frame of this study thermally sprayed diffusion barrier coatings were developed. Coatings of mullite and ZrO2-7% Y2O3 (YSZ) were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure and thermal shock behaviour. In order to prove the suitability of the coatings for the application in brazing furnaces, the wettability of the coating surfaces by a Ni-based brazing alloy was investigated. The results showed that both mullite and YSZ could be deposited on CFC substrates with a bond coat of W or SiC. Both coatings exhibited good thermal shock behaviour and an excellent non-wetting behaviour against the used Ni-based braze alloy.

  13. Thermal barrier coatings: Burner rig hot corrosion test results

    NASA Technical Reports Server (NTRS)

    Hodge, P. E.; Stecura, S.; Gedwill, M. A.; Zaplatynsky, I.; Levine, S. R.

    1978-01-01

    A Mach 0.3 burner rig test program was conducted to examine the sensitivity of thermal barrier coatings to Na and V contaminated combustion gases simulating potential utility gas turbine environments. Coating life of the standard ZrO2-12Y2O3/Ni-16.2Cr-5.6Al-0.6Y NASA thermal barrier coating system which was developed for aircraft gas turbines was significantly reduced in such environments. Two thermal barrier coating systems, Ca2SiO4/Ni-16.2Cr-5.6Al-0.6Y and ZrO2-8Y2O3/Ni-16.4Cr-5.1Al-0.15Y and a less insulative cermet coating system, 50 volume percent MgO-50 volume percent Ni-19.6Cr-17.1Al-0.97Y/Ni-16.2Cr-5.6Al-0.6Y, were identified as having much improved corrosion resistance compared to the standard coating.

  14. Thermal Properties, Thermal Shock, and Thermal Cycling Behavior of Lanthanum Zirconate-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-06-01

    Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.

  15. Apparatus and method for laser deposition of durable coatings

    DOEpatents

    Veligdan, J.T.; Vanier, P.; Barletta, R.E.

    1995-08-15

    Method and apparatus are disclosed for depositing durable coatings onto the surface of a substrate without heating the entire substrate to high temperatures by using lasers to heat the substrate and dissociate a deposition gas. The apparatus comprises a deposition chamber for enclosing the substrate upon which a coating is to be deposited, gas delivery means for directing a flow of deposition gas on the substrate, a first laser for heating the substrate, and a second laser for irradiating the deposition gas to dissociate the gas. The method includes placing a substrate within a vacuum deposition chamber and directing a flow of deposition gas on the substrate. Then the substrate is heated with a first laser while the deposition gas is irradiated with a second laser to dissociate the deposition gas. 1 fig.

  16. Apparatus and method for laser deposition of durable coatings

    DOEpatents

    Veligdan, James T.; Vanier, Peter; Barletta, Robert E.

    1995-08-15

    Method and apparatus for depositing durable coatings onto the surface of a substrate without heating the entire substrate to high temperatures by using lasers to heat the substrate and dissociate a deposition gas. The apparatus comprises a deposition chamber for enclosing the substrate upon which a coating is to be deposited, gas delivery means for directing a flow of deposition gas on the substrate, a first laser for heating the substrate, and a second laser for irradiating the deposition gas to dissociate the gas. The method includes placing a substrate within a vacuum deposition chamber and directing a flow of deposition gas on the substrate. Then the substrate is heated with a first laser while the deposition gas is irradiated with a second laser to dissociate the deposition gas.

  17. Heat-barrier coatings for combustion chambers

    NASA Technical Reports Server (NTRS)

    Carpenter, H. W.

    1970-01-01

    Arc-plasma-sprayed layered coating of graded Inconel and zirconia protects film-coolant ring below injector plate of rocket engine combustion chamber. Interfacial temperature is designed for minimum buildup of stress and to avoid melting of the metal phase in the graded layers.

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  19. ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating

    DTIC Science & Technology

    2003-04-02

    roger.johnson@pnl.gov, 509-375-6906 ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating (SERDP Project 1147) Report Documentation...3. DATES COVERED 00-00-2003 to 00-00-2003 4. TITLE AND SUBTITLE ElectroSpark Deposited Coatings for Replacement of Chrome Electroplating 5a...ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 ELECTROSPARK DEPOSITION (ESD) Process

  20. Investigation of Amorphous/Nanocrystalline Iron-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Königstein, T.

    2017-02-01

    Because of their favorable thermophysical properties, good machinability and low material costs, iron-based coatings which exhibit a highly amorphous/nanocrystalline microstructure are currently in the focus of research. Considering the crystallization temperature of the material, iron-based coatings might be the next generation of thermal barrier coatings (TBCs) for low-temperature systems, reducing thermal losses. The objective of this research project is the development of highly amorphous, iron-based coatings. For this purpose, amorphous feedstock materials with different chromium contents have been developed and characterized regarding their microstructures, phase compositions, crystallization temperatures and amorphous content. The results show that the amorphous content is reduced with increasing particle size and chromium content. The coatings were deposited by air plasma spraying (APS) and high-velocity oxygen fuel spraying (HVOF). It is shown that all coatings exhibit amorphous structures. HVOF coatings show a smaller amount of amorphous content compared to the feedstock materials, indicating crystallization occurring in not fully melted particles or insufficient rapid cooling. The APS process can increase the amount of amorphous content compared to the feedstock material, as shown for x Cr = 15%. All coatings proof good thermal shock behavior. Lowest thermal diffusivity values were determined for APS coatings, which confirms the potential of iron-based TBCs.

  1. Depth-Penetrating Luminescence Thermography of Thermal- Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey

    2005-01-01

    A thermographic method has been developed for measuring temperatures at predetermined depths within dielectric material layers . especially thermal-barrier coatings. This method will help satisfy a need for noncontact measurement of through-the-thickness temperature gradients for evaluating the effectiveness of thermal- barrier coatings designed to prevent overheating of turbine blades, combustor liners, and other engine parts. Heretofore, thermography has been limited to measurement of surface and near-surface temperatures. In the thermographic method that is the immediate predecessor of the present method, a thermographic phosphor is applied to the outer surface of a thermal barrier coating, luminescence in the phosphor is excited by illuminating the phosphor at a suitable wavelength, and either the time dependence of the intensity of luminescence or the intensities of luminescence spectral lines is measured. Then an emissivity-independent surface-temperature value is computed by use of either the known temperature dependence of the luminescence decay time or the known temperature dependence of ratios between intensities of selected luminescence spectral lines. Until now, depth-penetrating measurements have not been possible because light of the wavelengths needed to excite phosphors could not penetrate thermal-barrier coating materials to useful depths. In the present method as in the method described above, one exploits the temperature dependence of luminescence decay time. In this case, the phosphor is incorporated into the thermal-barrier coat at the depth at which temperature is to be measured. To be suitable for use in this method, a phosphor must (1) exhibit a temperature dependence of luminescence decay time in the desired range, (2) be thermochemically compatible with the thermal-barrier coating, and (3) exhibit at least a minor excitation spectral peak and an emission spectral peak, both peaks being at wavelengths at which the thermal-barrier coating is

  2. Thermal expansion mismatch and oxidation in thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Chang, G. C.; Phucharoen, W.; Miller, R. A.

    1985-01-01

    Thermal barrier coatings (TBC) for advanced gas turbine blades have been under intensive development during the last several years. This investigation is intended to achieve a clearer understanding of the mechanical behavior of plasma sprayed zirconia-yttria TBCs, involving a nickle-chromium-aluminum bond coat. The near term objectives are to study the stress states in a relatively simple model TBC subjected to steady state thermal loading. The resulting thermal expansion mismatch and oxidation have been primary targets for the study. The finite element approach and the effects of thermal mismatch and oxidation are described. A proposed mechanism for oxidation induced coating failure is also presented.

  3. Monoclinic zirconia distributions in plasma-sprayed thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Lance, M. J.; Haynes, J. A.; Ferber, M. K.; Cannon, W. R.

    2000-03-01

    Phase composition in an air plasma-sprayed Y2O3-stabilized ZrO2 (YSZ) top coating of a thermal barrier coating (TBC) system was characterized. Both the bulk phase content and localized pockets of monoclinic zirconia were measured with Raman spectroscopy. The starting powder consisted of ˜15 vol.% monoclinic zirconia, which decreased to ˜2 vol.% in the as-sprayed coating. Monoclinic zirconia was concentrated in porous pockets that were evenly distributed throughout the TBC. The pockets resulted from the presence of unmelted granules in the starting powder. The potential effect of the distributed monoclinic pockets on TBC performance is discussed.

  4. Effect of La2O3 addition on interface chemistry between 4YSZ top layer and Ni based alloy bond coat in thermal barrier coating by EB PVD.

    PubMed

    Park, Chan-Young; Yang, Young-Hwan; Kim, Seong-Won; Lee, Sung-Min; Kim, Hyung-Tae; Jang, Byung-Koog; Lim, Dae-Soon; Oh, Yoon-Suk

    2014-11-01

    The effect of a 5 mol% La2O3 addition on the forming behavior and compositional variation at interface between a 4 mol% Yttria (Y2O3) stabilized ZrO2 (4YSZ) top coat and bond coat (NiCrAlY) as a thermal barrier coating (TBC) has been investigated. Top coats were deposited by electron beam physical vapor deposition (EB PVD) onto a super alloy (Ni-Cr-Co-Al) substrate without pre-oxidation of the bond coat. Top coats are found to consist of dense columnar grains with a thin interdiffusion layer between metallic bond coats. In the as-received 4YSZ coating, a thin interdiffusion zone at the interface between the top and bond coats was found to consist of a Ni-Zr intermetallic compound with a reduced quantity of Y, Al or O elements. On the other hand, in the case of an interdiffusion area of 5 mol% La2O3-added 4YSZ coating, it was found that the complicated composition and structure with La-added YSZ and Ni-Al rich compounds separately. The thermal conductivity of 5 mol% La2O3-added 4YSZ coating (- 1.6 W/m x k at 1100 degrees C) was lower than a 4YSZ coating (- 3.2 W/m x k at 1100 degrees C) alone.

  5. Modeling Oxidation Induced Stresses in Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ferguson, B. L.; Freborg, A. M.; Petrus, G. J.; Brindley, William J.

    1998-01-01

    The use of thermal barrier coatings (TBC's) in gas turbines has increased dramatically in recent years, due mainly to the need for component protection from ever increasing service temperatures. Oxidation of the bond coat has been identified as an important contributing factor to spallation of the ceramic top coat during service. Additional variables found to influence TBC thermal cycle life include bond coat coefficient of thermal expansion, creep behavior of both the ceramic and bond coat layers, and modulus of elasticity. The purpose of this work was to characterize the effects of oxidation on the stress states within the TBC system, as well as to examine the interaction of oxidation with other factors affecting TBC life.

  6. High temperature solar selective absorber coating deposited by laser cladding

    NASA Astrophysics Data System (ADS)

    Pang, Xuming

    2017-09-01

    In order to prepare high temperature stability cermets solar selective absorbing coating, single- layer Ni/Mo–TiC cermets coatings were firstly deposited on stainless steel substrate using laser cladding method and surface coating method. The result shows that the performance of the laser cladding coating is far superior to the coating fabricated by the surface coating method with thermal emittance decreased from 44.6% to 5.5%. Furthermore, the spectrally selective coating fabricated by laser cladding shows the excellent thermal stability. The solar absorptance and thermal emittance of the coating are 80.7% and 6.0% at 600 °C, 80% and 5.5% at room temperature, respectively. This result indicates that TiC-based cermets are more propitious solar selective absorber materials. More importantly, laser cladding, as a representative of new techniques, could be applied to the field of the solar selective absorber coating.

  7. Acoustic Emission Analysis of Damage Progression in Thermal Barrier Coatings Under Thermal Cyclic Conditions

    NASA Technical Reports Server (NTRS)

    Appleby, Matthew; Zhu, Dongming; Morscher, Gregory

    2015-01-01

    Damage evolution of electron beam-physical vapor deposited (EBVD-PVD) ZrO2-7 wt.% Y2O3 thermal barrier coatings (TBCs) under thermal cyclic conditions was monitored using an acoustic emission (AE) technique. The coatings were heated using a laser heat flux technique that yields a high reproducibility in thermal loading. Along with AE, real-time thermal conductivity measurements were also taken using infrared thermography. Tests were performed on samples with induced stress concentrations, as well as calcium-magnesium-alumino-silicate (CMAS) exposure, for comparison of damage mechanisms and AE response to the baseline (as-produced) coating. Analysis of acoustic waveforms was used to investigate damage development by comparing when events occurred, AE event frequency, energy content and location. The test results have shown that AE accumulation correlates well with thermal conductivity changes and that AE waveform analysis could be a valuable tool for monitoring coating degradation and provide insight on specific damage mechanisms.

  8. Thermomechanical Behavior of Developmental Thermal Barrier Coating Bond Coats

    NASA Astrophysics Data System (ADS)

    Pandey, Amit; Tolpygo, Vladimir K.; Hemker, Kevin J.

    2013-04-01

    Thermal expansion, microtensile, and stress relaxation experiments have been performed to contrast and compare the thermal and mechanical response of two experimental (L1 and H1) coatings provided by Honeywell Corporation (Morristown, NY). Thermal expansion experiments reveal that both coatings have coefficients of thermal expansion (CTE) that vary with temperature and that the CTE mismatch between the coatings and superalloy substrate is significant in the case of L1 as compared to H1. Values of the 0.2% offset yield stress (YS), Young's modulus ( E), and hardening exponent ( n) are reported. Room-temperature microtensile experiments show higher strain hardening and a very low value of failure strain for L1 as compared to H1. At elevated temperatures, there is a significant decrease in the YS of as-received L1 for (924 MPa at room temperature to 85 MPa at 1000°C) as compared to H1. Finally, a power law creep description for high-temperature stress relaxation is developed and the measured values of the stress exponent ( n = 3) and activation energies ( Q creep = 200-250 kJ/mol) are shown to be consistent with power law creep.

  9. Electrophoretic deposition of composite hydroxyapatite-silica-chitosan coatings

    SciTech Connect

    Grandfield, K.; Zhitomirsky, I.

    2008-01-15

    Electrophoretic deposition (EPD) method has been developed for the fabrication of nanocomposite silica-chitosan coatings. Cathodic deposits were obtained on various conductive substrates using suspensions of silica nanoparticles in a mixed ethanol-water solvent, containing dissolved chitosan. Co-deposition of silica and hydroxyapatite (HA) nanoparticles resulted in the fabrication of HA-silica-chitosan coatings. The deposition yield has been studied at a constant voltage mode at various deposition durations. The method enabled the formation of coatings of different thickness in the range of up to 100 {mu}m. Deposit composition, microstructure and porosity can be varied by variation of HA and silica concentration in the suspensions. It was demonstrated that EPD can be used for the fabrication of HA-silica-chitosan coatings of graded composition and laminates. The method enabled the deposition of coatings containing layers of silica-chitosan and HA-chitosan nanocomposites using suspensions with different HA and silica content. Obtained coatings were studied by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The mechanism of deposition is discussed.

  10. Chemical vapor deposited fiber coatings and chemical vapor infiltrated ceramic matrix composites

    SciTech Connect

    Kmetz, M.A.

    1992-01-01

    Conventional Chemical Vapor Deposition (CVD) and Organometallic Chemical Vapor Deposition (MOCVD) were employed to deposit a series of interfacial coatings on SiC and carbon yarn. Molybdenum, tungsten and chromium hexacarbonyls were utilized as precursors in a low temperature (350[degrees]C) MOCVD process to coat SiC yarn with Mo, W and Cr oxycarbides. Annealing studies performed on the MoOC and WOC coated SiC yarns in N[sub 2] to 1,000[degrees]C establish that further decomposition of the oxycarbides occurred, culminating in the formation of the metals. These metals were then found to react with Si to form Mo and W disilicide coatings. In the Cr system, heating in N[sub 2] above 800[degrees]C resulted in the formation of a mixture of carbides and oxides. Convention CVD was also employed to coat SiC and carbon yarn with C, Bn and a new interface designated BC (a carbon-boron alloy). The coated tows were then infiltrated with SiC, TiO[sub 2], SiO[sub 2] and B[sub 4]C by a chemical vapor infiltration process. The B-C coatings were found to provide advantageous interfacial properties over carbon and BN coatings in several different composite systems. The effectiveness of these different coatings to act as a chemically inert barrier layer and their relationship to the degree of interfacial debonding on the mechanical properties of the composites were examined. The effects of thermal stability and strength of the coated fibers and composites were also determined for several difference atmospheres. In addition, a new method for determining the tensile strength of the as-received and coated yarns was also developed. The coated fibers and composites were further characterized by AES, SEM, XPS, IR and X-ray diffraction analysis.

  11. Spectral Properties of Dy-Doped Thermal Barrier Sensor Coatings

    SciTech Connect

    Allison, Stephen W; Moore, Danielle; Heyes, Andrew; Nichols, John R.

    2009-01-01

    We have obtained the excitation (484, 497 and 585 nm) and emission (355, 367 and 385 nm) spectra and measured the fluorescence decay lifetimes for partially Y2O3 stabilized ZrO2 thermal barrier coatings doped with 2mol% Dy2O3, as a function of coating depth for thicknesses ranging from 30 to 200 μm. In principle, these coatings can function not only as thermal protection barriers for turbomachinery blades and vanes, but also as remotely interrogated self-sensors for use in determining in situ wear rates during operation. This is done by varying the excitation wavelength and observing the fluorescence decay times and related parameters.

  12. Advanced thermal barrier coatings for operation in high hydrogen content fueled gas turbines.

    SciTech Connect

    Sampath, Sanjay

    2015-04-02

    and resulted in improved TBC lifetimes. Processing based approaches of identifying optimal processing regimes deploying advanced in-situ coating property measurements and in-flight diagnostic tools were used to develop process maps for bond coats. Having established a framework for the bond coat processing using the HVOF process, effort were channeled towards fabrication of APS and VPS bond coats with the same material composition. Comparative evaluation of the three deposition processes with regard to their microstrcuture , surface profiles and TBC performance were carried out and provided valuable insights into factors that require concurrent consideration for the development of bond coats for advanced TBC systems. Over the course of this program several advancements were made on the development of durable thermal barrier coatings. Process optimization techniques were utilized to identify processing regimes for both conventional YSZ as well as other TBC compositions such as Gadolinium Zirconate and other Co-doped materials. Measurement of critical properties for these formed the initial stages of the program to identify potential challenges in their implementation as part of a TBC system. High temperature thermal conductivity measurements as well as sintering behavior of both YSZ and GDZ coatings were evaluated as part of initial efforts to undersand the influence of processing on coating properties. By effectively linking fundamental coating properties of fracture toughness and elastic modulus to the cyclic performance of coatings, a durability strategy for APS YSZ coatings was developed. In order to meet the goals of fabricating a multimaterial TBC system further research was carried out on the development of a gradient thermal conductivity model and the evaluation of sintering behavior of multimaterial coatings. Layer optimization for desired properties in the multimaterial TBC was achieved by an iterative feedback approach utilizing process maps and in-situ and

  13. Environmental Barrier Coatings for the Energy Efficient Heat Engines Program

    SciTech Connect

    Katherine Faber

    2004-10-31

    This program aimed to develop a fundamental understanding of the microstructural, mechanical, and chemical properties of Ta{sub 2}O{sub 5}-based coatings for Si{sub 3}N{sub 4} (AS800) substrates and optimize such coatings for environmental barriers. The program consisted of three tasks: processing of Ta{sub 2}O{sub 5} coatings, phase and microstructural development, and life-limiting phenomena. Northwestern University formed a cross-functional team with Lehigh University, Honeywell Inc., and Oak Ridge National Laboratory. The major accomplishments are: (1) Conditions for the plasma spray of Ta{sub 2}O{sub 5} and its alloys were optimized to provide maximum density and thickness. (2) Adherent small particle plasma spray coatings of Ta{sub 2}O{sub 5} can be routinely prepared. (3) Ta{sub 2}O{sub 5} can be stabilized against its disruptive phase transformation to 1400 C by the addition of one or more oxides of Al, La, and/or Nb. (4) Residual stresses in the Ta{sub 2}O{sub 5} coatings were measured using X-rays and changed with thermal exposure. (5) Properly doped coatings are more resistant against thermal cycling than undoped coatings, and can be cycled many thousand times without spallation. (6) Water vapor testing in the ORNL Keiser Rig of adherent coatings showed that undoped Ta{sub 2}O{sub 5} is not an effective barrier at preventing chemical changes to the AS800. (7) Limited water vapor testing of doped and adherent coatings, which had successfully survived many thermal cycles, showed that in the water vapor environment, de-cohesion may occur.

  14. Therma1 Conductivity and Durability of Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2003-01-01

    Thermal barrier coatings (TBCs) will play a crucial role in advanced gas turbine engines because of their ability to further increase engine operating temperature and reduce cooling, thus helping to achieve engine emission and efficiency goals. Future TBCs must be designed with increased phase stability, lower thermal conductivity, and improved sintering and thermal stress resistance in order to effectively protect engine hot-section components. Advanced low conductivity TBCs are being developed at NASA by incorporating multi-component oxide dopants into zirconia-yttria or hafnia-yttria to promote the formation of thermodynamically stable defect clusters within the coating structures. This presentation will primarily focus on thermal conductivity and durability of the novel defect cluster thermal barrier coatings for turbine airfoil and combustor applications, determined by a unique CO2 laser heat-flux approach. The laser heat-flux testing approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity under simulated engine temperature and thermal gradient conditions. The conductivity increase due to coating sintering (and/or phase change) and the conductivity decrease due to coating delamination have been determined under steady-state, cyclic, uniform or non-uniform heat-flux conditions. The coating radiation flux resistance has been evaluated by varying coating thermal gradients, and also by using a laser-heated radiative-flux source. Advanced multi-component TBC systems have been shown to have significantly reduced thermal conductivity and improved high temperature stability due to the nano-sized, low mobility defect clusters associated with the paired rare earth dopant additions. The effect of oxide defect cluster dopants on coating thermal conductivity, thermal stability and furnace cyclic durability will also be discussed. The current low conductivity TBC systems have demonstrated long-term cyclic durability at very high

  15. Therma1 Conductivity and Durability of Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2003-01-01

    Thermal barrier coatings (TBCs) will play a crucial role in advanced gas turbine engines because of their ability to further increase engine operating temperature and reduce cooling, thus helping to achieve engine emission and efficiency goals. Future TBCs must be designed with increased phase stability, lower thermal conductivity, and improved sintering and thermal stress resistance in order to effectively protect engine hot-section components. Advanced low conductivity TBCs are being developed at NASA by incorporating multi-component oxide dopants into zirconia-yttria or hafnia-yttria to promote the formation of thermodynamically stable defect clusters within the coating structures. This presentation will primarily focus on thermal conductivity and durability of the novel defect cluster thermal barrier coatings for turbine airfoil and combustor applications, determined by a unique CO2 laser heat-flux approach. The laser heat-flux testing approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity under simulated engine temperature and thermal gradient conditions. The conductivity increase due to coating sintering (and/or phase change) and the conductivity decrease due to coating delamination have been determined under steady-state, cyclic, uniform or non-uniform heat-flux conditions. The coating radiation flux resistance has been evaluated by varying coating thermal gradients, and also by using a laser-heated radiative-flux source. Advanced multi-component TBC systems have been shown to have significantly reduced thermal conductivity and improved high temperature stability due to the nano-sized, low mobility defect clusters associated with the paired rare earth dopant additions. The effect of oxide defect cluster dopants on coating thermal conductivity, thermal stability and furnace cyclic durability will also be discussed. The current low conductivity TBC systems have demonstrated long-term cyclic durability at very high

  16. Thermal barrier coating life-prediction model development. Annual report no. 2

    SciTech Connect

    Strangman, T. E.; Neumann, J.; Liu, A.

    1986-10-01

    The program focuses on predicting the lives of two types of strain-tolerant and oxidation-resistant thermal barrier coating (TBC) systems that are produced by commercial coating suppliers to the gas turbine industry. The plasma-sprayed TBC system, composed of a low-pressure plasma-spray (LPPS) or an argon shrouded plasma-spray (ASPS) applied oxidation resistant NiCrAlY or (CoNiCrAlY) bond coating and an air-plasma-sprayed yttria partially stabilized zirconia insulative layer, is applied by both Chromalloy, Klock, and Union Carbide. The second type of TBS is applied by the electron beam-physical vapor deposition (EB-PVD) process by Temescal. The second year of the program was focused on specimen procurement, TMC system characterization, nondestructive evaluation methods, life prediction model development, and TFE731 engine testing of thermal barrier coated blades. Materials testing is approaching completion. Thermomechanical characterization of the TBC systems, with toughness, and spalling strain tests, was completed. Thermochemical testing is approximately two-thirds complete. Preliminary materials life models for the bond coating oxidation and zirconia sintering failure modes were developed. Integration of these life models with airfoil component analysis methods is in progress. Testing of high pressure turbine blades coated with the program TBS systems is in progress in a TFE731 turbofan engine. Eddy current technology feasibility was established with respect to nondestructively measuring zirconia layer thickness of a TBC system.

  17. Further industrial tests of ceramic thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.; Levine, S. R.

    1982-01-01

    The NASA Lewis Research Center made technical assistance arrangements (contracts) with several commercial organizations under which Lewis designed plasma-sprayed thermal-barrier coatings (TBC) for their products. Lewis was then furnished with the test conditions and evaluations of coating usefulness. The coating systems were developed and sprayed at Lewis. All of the systems incorporated a two-layer, ceramic-bond coating concept. Coating thickness and chemical composition were varied to fit three applications: the leading edges of first-stage turbine vanes for an advanced gas turbine engine; the flame impingement surfaces of a combustor transition section; and diesel engine valves and head surfaces. The TBC incorporated yytria-stabilized zirconia, which lowered metal temperatures, protected metal parts, and increased metal part life. In some cases metal burning, melting, and warping were eliminated. Additional benefits were realized from these endeavors: hands-on experience with thermal-barrier coatings was provided to industry; the success of these endeavors encourages these and other organizations to accelerate the implementation of TBC technology.

  18. Impact Resistance of Environmental Barrier Coated SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Choi, Sung R.; Cosgriff, Laura M.; Fox, Dennis S.; Lee, Kang N.

    2008-01-01

    Impact performance of 2D woven SiC/SiC composites coated with 225 and 525 microns thick environmental barrier coating (EBC) was investigated. The composites were fabricated by melt infiltration and the EBC was deposited by plasma spray. Impact tests were conducted at room temperature and at 1316 C in air using 1.59 mm diameter steel-balls at projectile velocities ranging from 110 to 375 m/s . Both microscopy and non-destructive evaluation (NDE) methods were used to determine the extent of damage in the substrate and coating with increasing projectile velocity. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. At projectile velocities less than 125 m/s , no detectable internal damage was noticed in the MI SiC/SiC composites coated with 525 microns EBC. With increase in projectile velocity beyond this value, spallation of EBC layers, delamination of fiber plies, and fiber fracture were detected. At a fixed projectile velocity, the composites coated with 525 microns EBC showed less damage than those coated with 225 microns EBC. Both types of coated composites retained a large fraction of the baseline properties of the as-fabricated composites and exhibited non-brittle failure after impact testing. Furnace exposure of impacted specimens in a moisture environment at 1316 C for 500 h indicated that the through-the-thickness cracks in the coating and delamination cracks in the substrate generated after impact testing acted as conduits for internal oxidation.

  19. Impact Resistance of Environmental Barrier Coated SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Choi, Sung R.; Cosgriff, Laura M.; Fox, Dennis S.; Lee, Kang N.

    2008-01-01

    Impact performance of 2D woven SiC/SiC composites coated with 225 and 525 microns thick environmental barrier coating (EBC) was investigated. The composites were fabricated by melt infiltration and the EBC was deposited by plasma spray. Impact tests were conducted at room temperature and at 1316 C in air using 1.59 mm diameter steel-balls at projectile velocities ranging from 110 to 375 m/s . Both microscopy and non-destructive evaluation (NDE) methods were used to determine the extent of damage in the substrate and coating with increasing projectile velocity. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. At projectile velocities less than 125 m/s , no detectable internal damage was noticed in the MI SiC/SiC composites coated with 525 microns EBC. With increase in projectile velocity beyond this value, spallation of EBC layers, delamination of fiber plies, and fiber fracture were detected. At a fixed projectile velocity, the composites coated with 525 microns EBC showed less damage than those coated with 225 microns EBC. Both types of coated composites retained a large fraction of the baseline properties of the as-fabricated composites and exhibited non-brittle failure after impact testing. Furnace exposure of impacted specimens in a moisture environment at 1316 C for 500 h indicated that the through-the-thickness cracks in the coating and delamination cracks in the substrate generated after impact testing acted as conduits for internal oxidation.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  1. Environmental Barrier Coatings for Ceramic Matrix Composites - An Overview

    NASA Technical Reports Server (NTRS)

    Lee, Kang; Zhu, Dongming; Wiesner, Valerie Lynn; van Roode, Mark; Kashyap, Tania; Zhu, Dongming; Wiesner, Valerie

    2016-01-01

    Ceramic Matrix Composites (CMCs) are increasingly being considered as structural materials for advanced power generation equipment. Broadly speaking the two classes of materials are oxide-based CMCs and non-oxide based CMCs. The non-oxide CMCs are primarily silicon-based. Under conditions prevalent in the gas turbine hot section the water vapor formed in the combustion of gaseous or liquid hydrocarbons reacts with the surface-SiO2 to form volatile products. Progressive surface recession of the SiC-SiC CMC component, strength loss as a result of wall thinning and chemical changes in the component occur, which leads to the loss of structural integrity and mechanical strength and becomes life limiting to the equipment in service. The solutions pursued to improve the life of SiC-SiC CMCs include the incorporation of an external barrier coating to provide surface protection to the CMC substrate. The coating system has become known as an Environmental Barrier Coating (EBC). The relevant early coatings work was focused on coatings for corrosion protection of silicon-based monolithic ceramics operating under severely corrosive conditions. The development of EBCs for gas turbine hot section components was built on the early work for silicon-based monolithics. The first generation EBC is a three-layer coating, which in its simplest configuration consists of a silicon (Si) base coat applied on top of the CMC, a barium-strontium-aluminosilicate (BSAS) surface coat resistant to water vapor attack, and a mullite-based intermediate coating layer between the Si base coat and BSAS top coat. This system can be represented as Si-Mullite-BSAS. While this baseline EBC presented a significant improvement over the uncoated SiC-SiC CMC, for the very long durations of 3-4 years or more expected for industrial operation further improvements in coating durability are desirable. Also, for very demanding applications with higher component temperatures but shorter service lives more rugged EBCs

  2. Microstructure Evolution and Durability of Advanced Environmental Barrier Coating Systems for SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Evans, Laura J.; McCue, Terry R.; Harder, Bryan

    2016-01-01

    Environmental barrier coated SiC-SiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. Advanced HfO2 and rare earth silicate environmental barrier coatings (EBCs), along with multicomponent hafnium and rare earth silicide EBC bond coats have been developed. The coating degradation mechanisms in the laboratory simulated engine thermal cycling, and fatigue-creep operating environments are also being investigated. This paper will focus on the microstructural and compositional evolutions of an advanced environmental barrier coating system on a SiC-SiC CMC substrate during the high temperature simulated durability tests, by using a Field Emission Gun Scanning Electron Microscopy, Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS). The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will also be discussed. The detailed analysis results help understand the EBC-CMC system performance, aiming at the durability improvements to achieve more robust, prime-reliant environmental barrier coatings.

  3. Thermal-barrier-coated turbine blade study

    NASA Technical Reports Server (NTRS)

    Siemers, P. A.; Hillig, W. B.

    1981-01-01

    The effects of coating TBC on a CF6-50 stage 2 high-pressure turbine blade were analyzed with respect to changes in the mean bulk temperature, cooling air requirements, and high-cycle fatigue. Localized spallation was found to have a possible deleterious effect on low-cycle fatigue life. New blade design concepts were developed to take optimum advantage of TBCs. Process and material development work and rig evaluations were undertaken which identified the most promising combination as ZrO2 containing 8 w/o Y2O3 applied by air plasma spray onto a Ni22Cr-10Al-1Y bond layer. The bond layer was applied by a low-pressure, high-velocity plasma spray process onto the base alloy. During the initial startup cycles the blades experienced localized leading edge spallation caused by foreign objects.

  4. Thermal and stress analysis of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Cassenti, B. N.; Brickley, A. M.; Sinko, G. C.

    1981-01-01

    An analysis has been performed that predicts the thermomechanical behavior of thermal barrier coated specimens. The analysis predicts the behavior during both plasma spray coating application and burner rig testing conditions simulating engine operation. The analysis was accomplished through utilization of one-dimensional through thickness and two-dimensional finite element calculations. The results of these calculations showed that specimens with a substrate control temperature between 300 F and 600 F would be optimum. Controlling substrate temperature was found to have a more dominant effect on the mechanical strains than the ceramic or substrate thicknesses. The predicted stresses and mechanical strains at the bond-coating interface are large enough to cause cracks in this region where post-test observations have determined coating failures originate.

  5. Interfacial bond strength of electrophoretically deposited hydroxyapatite coatings on metals.

    PubMed

    Wei, M; Ruys, A J; Swain, M V; Kim, S H; Milthorpe, B K; Sorrell, C C

    1999-07-01

    Hydroxyapatite (HAp) coatings were deposited onto substrates of metal biomaterials (Ti, Ti6Al4V, and 316L stainless steel) by electrophoretic deposition (EPD). Only ultra-high surface area HAp powder, prepared by the metathesis method 10Ca(NO3)2 + 6(NH4)2HPO4 + 8NH4OH), could produce dense coatings when sintered at 875-1000degreesC. Single EPD coatings cracked during sintering owing to the 15-18% sintering shrinkage, but the HAp did not decompose. The use of dual coatings (coat, sinter, coat, sinter) resolved the cracking problem. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) inspection revealed that the second coating filled in the "valleys" in the cracks of the first coating. The interfacial shear strength of the dual coatings was found, by ASTM F1044-87, to be approximately 12 MPa on a titanium substrate and approximately 22 MPa on 316L stainless steel, comparing quite favorably with the 34 MPa benchmark (the shear strength of bovine cortical bone was found to be 34 MPa). Stainless steel gave the better result since -316L (20.5 microm mK(-1)) > alpha-HAp (approximately 14 microm mK(-1)), resulting in residual compressive stresses in the coating, whereas alpha-titanium (approximately 10.3 microm mK(-1)) < alpha-HAp, resulting in residual tensile stresses in the coating.

  6. Thermal Conductivity of EB-PVD Thermal Barrier Coatings Evaluated by a Steady-State Laser Heat Flux Technique

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.; Nagaraj, Ben A.; Bruce, Robert W.

    2000-01-01

    The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) Zr02-8wt%Y2O3 thermal barrier coatings was determined by a steady-state heat flux laser technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long term test conditions. The thermal conductivity increase due to micro-pore sintering and the decrease due to coating micro-delaminations in the EB-PVD coatings were evaluated for grooved and non-grooved EB-PVD coating systems under isothermal and thermal cycling conditions. The coating failure modes under the high heat flux test conditions were also investigated. The test technique provides a viable means for obtaining coating thermal conductivity data for use in design, development, and life prediction for engine applications.

  7. Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold-Sprayed Nanostructured NiCrAlY Bond Coat

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Li, Chang-Jiu; Li, Yong; Zhang, Shao-Ling; Wang, Xiu-Ru; Yang, Guan-Jun; Li, Cheng-Xin

    2008-12-01

    Nanostructured thermal barrier coatings (TBCs) were deposited by plasma spraying using agglomerated nanostructured YSZ powder on Inconel 738 substrate with cold-sprayed nanostructured NiCrAlY powder as bond coat. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured TBCs. For comparison, the TBC consisting of conventional microstructure YSZ and conventional NiCrAlY bond coat was also deposited and subjected to the thermal shock test. The results showed that nanostructured YSZ coating contained two kinds of microstructures; nanosized zirconia particles embedded in the matrix and microcolumnar grain structures of zirconia similar to those of conventional YSZ. Although, after thermal cyclic test, a continuous, uniform thermally grown oxide (TGO) was formed, cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of nanostructured and conventional TBCs mainly occurred through spalling of YSZ. Compared with conventional TBCs, nanostructured TBCs exhibited better thermal shock resistance.

  8. The effect of bond coat oxidation on the failure of thermal barrier coatings

    SciTech Connect

    Lee, E.Y.; Sisson, R.D. Jr.

    1994-12-31

    The formation of the oxides such as the spinel (Ni(Al,Cr){sub 2}O{sub 4}), Cr{sub 2}O{sub 3}, NiO and CoO in the bond coat oxidation products would accelerate the failure of the EB-PVD thermal barrier coatings during cyclic oxidation. It was found that Al{sub 2}O{sub 3} developed first, followed by the Cr/Ni rich oxides (such as Ni(Al,Cr){sub 2}O{sub 4}, Cr{sub 2}O{sub 3} and NiO) at the interface between the PSZ ceramic coatings and NiCoCrAlY bond coats in a cyclic high temperature environment. For the EB-PVD TBCs, the smooth interface between the PSZ ceramic coating and the bond coat would be also responsible for the failure during cyclic oxidation.

  9. Circulation method for depositing diffusion coatings

    NASA Astrophysics Data System (ADS)

    Arzamasov, B. N.; Simonov, V. N.

    2011-01-01

    The physicochemical fundamentals of directed mass transfer of coating elements with the help of heterogeneous chemical reactions occurring in a circulating gas flow successively washing the source of the coating element and the surface of the saturated part at nonisothermal and isothermal states of the reaction space are considered. Experiments and simulation are used for determining the effect of the process parameters on the thickness and phase composition of coatings on internal and external surfaces of machine parts and on their life.

  10. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  11. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  12. Analysis of Bacterial Deposition on Metal (Hydr)oxide-Coated Sand Filter Media.

    PubMed

    Truesdail; Lukasik; Farrah; Shah; Dickinson

    1998-07-15

    The aim of this study was to investigate the importance of surface potential in microbial deposition onto modified granular surfaces. Recent experimental and theoretical work has indicated that surfaces coated with metal oxides and hydroxide rich oxide/hydroxide mixtures ((hydr)oxides) have the potential to increase the capture efficiencies of commercial filtration systems. This study quantitatively compared different metal (hydr)oxide coatings in their abilities to enhance bacterial deposition. Specifically, the deposition rates of bacterial strains Streptococcus faecalis, Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli were compared for Ottawa sand and surface coatings consisting of aluminum (hydr)oxide, iron (hydr)oxide, and mixed iron and aluminum (hydr)oxide. The metal-(hydr)oxide-modified granular media enhanced bacterial deposition relative to the noncoated Ottawa sand. The electropositive surfaces, the aluminum and the mixed (hydr)oxides, had similar average kinetic rate constants, five times larger than the rate constants observed for the untreated Ottawa sand. The measured kinetic rate constants for the positively charged systems of aluminum (hydr)oxide and mixed (hydr)oxide collectors suggested that the overall rate of deposition was limited by the transport of bacteria to the granular surface rather than the rate of attachment. For systems where the collector surfaces were negatively charged, as in the cases of Ottawa sand and the iron (hydr)oxide coating, large energy barriers to attachment were predicted from DLVO theory but these barriers did not totally inhibit bacterial deposition. The deposition results could not be fully explained by DLVO theory and suggested the importance of other factors such as collector charge heterogeneity, motility, and bacterial surface appendages in enhanced deposition. Copyright 1998 Academic Press.

  13. Thermal barrier coating life-prediction model development

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Neumann, J. F.; Liu, A.

    1987-01-01

    The primary objective of this program was to develop an operative thermal barrier coating (TBC) design model for life prediction. The objective was successfully accomplished with the development, calibration, and demonstration of a mechanistic thermochemical model which rapidly predicts TBC life as a function of engine, mission, and materials system parameters. This thermochemical design model accounts for the three operative TBC damage modes (bond coating oxidation, zirconia toughness reduction, and molten salt film damage), which all contribute to spalling of the insulating zirconia layer.

  14. Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

    SciTech Connect

    Siddiqui, Sanna F.; Knipe, Kevin; Manero, Albert; Raghavan, Seetha; Meid, Carla; Wischek, Janine; Bartsch, Marion; Okasinski, John; Almer, Jonathan; Karlsson, Anette M.

    2013-08-15

    Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

  15. Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

    NASA Astrophysics Data System (ADS)

    Siddiqui, Sanna F.; Knipe, Kevin; Manero, Albert; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M.; Bartsch, Marion; Raghavan, Seetha

    2013-08-01

    Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

  16. Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients.

    PubMed

    Siddiqui, Sanna F; Knipe, Kevin; Manero, Albert; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M; Bartsch, Marion; Raghavan, Seetha

    2013-08-01

    Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

  17. New Barrier Coating Materials for PV Module Backsheets: Preprint

    SciTech Connect

    Barber, G. D.; Jorgensen, G. J.; Terwilliger, K.; Glick, S. H.; Pern, J.; McMahon, T. J.

    2002-05-01

    This conference paper describes the high moisture barrier high resistivity coatings on polyethylene terepthalate (PET) have been fabricated and characterized for use in PV module back sheet applications. These thin film barriers exhibit water vapor transmission rates (WVTR) as low as 0.1 g/m2-day at 37.8 C and have shown excellent adhesion (> 10 N/mm) to both ethylene vinyl acetate (EVA) and PET even after filtered xenon arc lamp UV exposure. The WVTR and adhesion values for this construction are compared to and shown to be superior to candidate polymeric backsheet materials.

  18. Mullite+CAS Bond Coat for Environmental Barrier Coatings for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Opila, Elizabeth J.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Current environmental barrier coatings (EBCs) for silicon-based ceramics consist of a bond coat and a top coat. Mullite bond coat modified by adding low CTE glass ceramics, such as BSAS (xBaO.1xSrO.Al2O3.2SiO2) or CAS (CaO.Al2O3.2SiO2), was developed in the NASA Enabling Propulsion Materials (EPM) Program. EBCs based on mullite+CAS bond coat were characterized using high steam thermal cycling test and high steam isothermal thermogravemitry (TGA) at 1225 C - 13,000 C. The Mullite+CAS bond coat showed far superior durability compared to mullite bond coat, due to enhanced crack resistance. A BSAS top coat provided further improved durability compared to EBCs with a yttria-stabilized zirconia (YSZ) top coat. Still further improvement in the durability was achieved by adding a silicon bond coat between the mullite and the substrate. However, the silicon/mullite+CAS/BSAS EBC showed inferior long-term durability compared to the current state-of-the art EBC (silicon/mullite+BSAS/BSAS EBC), presumably due to the higher CAS-silica chemical reactivity.

  19. TiC-based coatings deposition using electric discharged plasma

    NASA Astrophysics Data System (ADS)

    Rahmatullin, I.; Sivkov, A.; Gerasimov, D.; Ivashutenko, A.; Shanenkova, J.

    2017-05-01

    The aim of this work was to research the possibility of using coaxial magneto plasma accelerator for TiC-coatings deposition on steel substrates. As a result, coatings with 0.01 m2 area was deposited. They were researched using XRD, SEM; also, the nanohardness on cross section of coating was measured. The influence of energy and carbon load on phase content, average hardness and microstructure is shown. It is established that the finest microstructure and average nanohardness is 15.3 GPa are achieved at energy W = 46.7 kJ and carbon load of 2.0 grams.

  20. Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat

    SciTech Connect

    Shillington, E.A.G.; Clarke, D.R.

    1999-03-10

    Although thermal barrier coatings (TBCs) are already being widely used in a variety of gas turbine and diesel engine applications, greater benefits are expected to accrue with TBCs that can be used in critical applications, namely those in which a loss of the coating would expose the underlying metal to a temperature in excess of its design specifications. A plasma-sprayed thermal barrier coating is observed to spall after oxidation at 1121 C from a CoNiCrAlY bond-coated superalloy at the interface between the thermally grown oxide (TGO) and the Zirconia thermal barrier coating (TBC). Phase characterization by photostimulated luminescence and X-ray diffraction, as well as microstructural characterization by scanning electron microscopy, indicates that the spalling is associated with the conversion of the initially formed {alpha}-alumina thermally grown oxide to {alpha}-chromia and a (CoNi)(CrAl) spinel. It is proposed that the phase conversion occurs after the alumina TGO has cracked on thermal cycling and the underlying bond-coat alloy is depleted of aluminum with concurrent enrichment of the oxide by Cr, Co and Ni. The observations suggest that monitoring the luminescence intensity as a function of oxidation time might form the basis of a nondestructive tool for detecting the onset of failure based on the disappearance of {alpha}-alumina.

  1. Initial Assessment of Environmental Barrier Coatings for the Prometheus Project

    SciTech Connect

    M. Frederick

    2005-12-15

    Depending upon final design and materials selections, a variety of engineering solutions may need to be considered to avoid chemical degradation of components in a notional space nuclear power plant (SNPP). Coatings are one engineered approach that was considered. A comprehensive review of protective coating technology for various space-reactor structural materials is presented, including refractory metal alloys [molybdenum (Mo), tungsten (W), rhenium (Re), tantalum (Ta), and niobium (Nb)], nickel (Ni)-base superalloys, and silicon carbide (Sic). A summary description of some common deposition techniques is included. A literature survey identified coatings based on silicides or iridium/rhenium as the primary methods for environmental protection of refractory metal alloys. Modified aluminide coatings have been identified for superalloys and multilayer ceramic coatings for protection of Sic. All reviewed research focused on protecting structural materials from extreme temperatures in highly oxidizing conditions. Thermodynamic analyses indicate that some of these coatings may not be protective in the high-temperature, impure-He environment expected in a Prometheus reactor system. Further research is proposed to determine extensibility of these coating materials to less-oxidizing or neutral environments.

  2. Optimizing thermally grown oxide for thermal barrier coatings on TiAl components via fluorine treatment

    NASA Astrophysics Data System (ADS)

    Donchev, A.; Braun, R.; Schütze, M.

    2010-01-01

    Titanium aluminides suffer from non-protective mixed-oxide scale formation during high-temperature exposure in oxidizing environments, so that they cannot be used at temperatures above approximately 800° C for longer times without additional treatment. A fluorine treatment on γ-TiAl alloys leads to the formation of a pure protective alumina scale and allows their use at service temperatures above 800°C. This thermally grown aluminum oxide layer can be used for bonding ceramic thermal barrier coatings to the TiAl substrate. Zirconia topcoats deposited by electron-beam physical vapor deposition were very adherent to F-treated TiA samples during cyclic oxidation tests at 900 to 1,000°C. A separate bond coat is not needed in this case.

  3. Coating Layer Characterization of Laser Deposited AlSi Coating over Laser Weld Bead

    NASA Astrophysics Data System (ADS)

    Gu, Hongping; Van Gelder, Aldo

    Corrosion protection of steel components is an important topic in automotive industry. Laser beam welding makes a narrow weld bead, thus minimizing the damage to the original coating on the steel material. However, the weld bead loses its original coating and is vulnerable to corrosive attack. It was demonstrated in this study that laser beam generated AlSi coating is an effective way to apply a protective coating on the weld bead. Coatings with different thickness and topography have been deposited under different laser power and processing speed. The microstructure of the as-deposited coating and its evolution after heat treatment has been studied. EDS was employed to analyze the distribution of chemical compositions of the laser generated coatings. Several metallic compounds of Al and iron have been identified. It was found that the type of metallic compounds can be influenced by the laser processing parameters.

  4. Prolonging thermal barrier coated specimen life by thermal cycle management

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Mcdonald, G.; Poolos, N. P.

    1981-01-01

    Thermal barrier coatings applied to the heated side of engine components such as seals, combustor, and blades of a gas turbine offer a potential increase in efficiency through the use of higher gas temperatures or less cooling air or benefits arising from extended component life by reducing component metal temperatures. The considered investigation has the objective to show that while a thermal barrier coated (TBC) specimen can be brought to a fixed temperature using various fuel-air ratio (F/A) values, lower calculated stresses are associated with lower (F/A) values. This implies that control of (F/A) values (i.e., rates of heat input) during the starting transient and to a lesser extent during shutdown and operation, offers a potential method of improving TBC lifetime through thermal cycle management.

  5. Low conductivity and sintering-resistant thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming (Inventor); Miller, Robert A. (Inventor)

    2007-01-01

    A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

  6. Low conductivity and sintering-resistant thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming (Inventor); Miller, Robert A. (Inventor)

    2006-01-01

    A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

  7. Low conductivity and sintering-resistant thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming (Inventor); Miller, Robert A. (Inventor)

    2004-01-01

    A thermal barrier coating composition comprising a base oxide, a primary stabilizer oxide, and at least one dopant oxide is disclosed. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. The base oxide is selected from the group consisting of zirconia and hafnia and combinations thereof. The primary stabilizing oxide is selected from the group consisting of yttria, dysprosia, erbia and combinations thereof. The dopant or group A and group B cluster-promoting oxide dopants are selected from the group consisting of rare earth metal oxides, transitional metal oxides, alkaline earth metal oxides and combinations thereof. The dopant or dopants preferably have ionic radii different from those of the primary stabilizer and/or the base oxides.

  8. Deposition and Evaluation of Protective PVD Coatings on Ferritic Stainless Steel SOFC Interconnects

    SciTech Connect

    Gorokhovsky, Vladimir I.; Gannon, Paul; Deibert, Max; Smith, Richard J.; Kayani, Asghar N.; Kopczyk, M.; Van Vorous, D.; Yang, Z Gary; Stevenson, Jeffry W.; Visco, s.; jacobson, c.; Kurokawa, H.; Sofie, Stephen W.

    2006-09-21

    Reduced operating temperatures (600-800°C) of Solid Oxide Fuel Cells (SOFCs) may enable the use of inexpensive ferritic steels as interconnects. Due to the demanding SOFC interconnect operating environment, protective coatings are gaining attention to increase longterm stability. In this study, large area filtered arc deposition (LAFAD) and hybrid filtered arc assisted electron beam physical vapor deposition (FA-EBPVD) technologies were used for deposition of two-segment coatings with Cr-Co-Al-O-N based sublayer and Mn-Co-O top layer. Coatings were deposited on ferritic steel and subsequently annealed in air for various time intervals. Surface oxidation was investigated using RBS, SEM and EDS analyses. Cr volatilization was evaluated using a transpiration apparatus and ICP-MS analysis of the resultant condensate. Electrical conductivity (Area Specific Resistance) was studied as a function of time using the four-point technique with Ag electrodes. The oxidation behavior, Cr volatilization rate, and electrical conductivity of the coated and uncoated samples are reported. Transport mechanisms for various oxidizing species and coating diffusion barrier properties are discussed.

  9. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    SciTech Connect

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; Esvan, Jerome; Lafont, Marie-Christine; Scheid, Emmanuel; Veith, Gabriel M.; Vahlas, Constantin

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties but an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.

  10. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    DOE PAGES

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; ...

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties butmore » an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.« less

  11. Ion beam assisted deposition of tribological coatings. Quarterly summary

    SciTech Connect

    Sartwell, B.D.

    1993-04-01

    TiN coatings 5 micrometers thick were deposited in UHV IBAD chamber onto M50 and Si substrates over a wide range of R (Ar-ion-to-Ti-atom ratio) values. Sputtering reduced the actual thickness at high R values, with two out of every three deposited Ti atoms being removed at R = 0.7. Because of charge exchange neutralization, it was possible to obtain coatings in the UHV IBAD system with properties equivalent to those deposited in the high vacuum IBAD system by using a higher apparent R value. Unless the extent of the charge exchange neutralization is known, it will not be possible to duplicate coating properties. Adhesion of the thick TiN coating deposited at R - 0.5 was equivalent to a magnetron sputtered TiN coating. Thick Cr{sub 2}O{sub 3} coatings were deposited onto M50 and Si substrates and wear testing was initiated. At high R values, sputtering prevented chemisorption of oxygen at surface. The wear process eliminated most of the surface topography.

  12. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Durmazuçar, Hasan H.; Gündüz, Güngör

    2000-12-01

    Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

  13. Study on the behavior of atomic layer deposition coatings on a nickel substrate at high temperature.

    PubMed

    Heidary, Damoon Sohrabi Baba; Randall, Clive A

    2016-06-17

    Although many techniques have been applied to protect nickel (Ni) alloys from oxidation at intermediate and high temperatures, the potential of atomic layer deposition (ALD) coatings has not been fully explored. In this paper, the application of ALD coatings (HfO2, Al2O3, SnO2, and ZnO) on Ni foils has been evaluated by electrical characterization and transmission electron microscopy analyses in order to assess their merit to increase Ni oxidation resistance; particular consideration was given to preserving Ni electrical conductivity at high temperatures. The results suggested that as long as the temperature was below 850 °C, the ALD coatings provided a physical barrier between outside oxygen and Ni metal and hindered the oxygen diffusion. It was illustrated that the barrier power of ALD coatings depends on their robustness, thicknesses, and heating rate. Among the tested ALD coatings, Al2O3 showed the maximum protection below 900 °C. However, above that temperature, the ALD coatings dissolved in the Ni substrate. As a result, they could not offer any physical barrier. The dissolution of ALD coatings doped on the NiO film, formed on the top of the Ni foils. As found by the electron energy loss spectroscopy (EELS), this doping affected the electronic transport process, through manipulating the Ni(3+)/Ni(2+) ratio in the NiO films and the chance of polaron hopping. It was demonstrated that by using the ZnO coating, one would be able to decrease the electrical resistance of Ni foils by two orders of magnitude after exposure to 1020 °C for 4 min. In contrast, the Al2O3 coating increased the resistance of the uncoated foil by one order of magnitude, mainly due to the decrease in the ratio of Ni(3+)/Ni(2+).

  14. Study on the behavior of atomic layer deposition coatings on a nickel substrate at high temperature

    NASA Astrophysics Data System (ADS)

    Sohrabi Baba Heidary, Damoon; Randall, Clive A.

    2016-06-01

    Although many techniques have been applied to protect nickel (Ni) alloys from oxidation at intermediate and high temperatures, the potential of atomic layer deposition (ALD) coatings has not been fully explored. In this paper, the application of ALD coatings (HfO2, Al2O3, SnO2, and ZnO) on Ni foils has been evaluated by electrical characterization and transmission electron microscopy analyses in order to assess their merit to increase Ni oxidation resistance; particular consideration was given to preserving Ni electrical conductivity at high temperatures. The results suggested that as long as the temperature was below 850 °C, the ALD coatings provided a physical barrier between outside oxygen and Ni metal and hindered the oxygen diffusion. It was illustrated that the barrier power of ALD coatings depends on their robustness, thicknesses, and heating rate. Among the tested ALD coatings, Al2O3 showed the maximum protection below 900 °C. However, above that temperature, the ALD coatings dissolved in the Ni substrate. As a result, they could not offer any physical barrier. The dissolution of ALD coatings doped on the NiO film, formed on the top of the Ni foils. As found by the electron energy loss spectroscopy (EELS), this doping affected the electronic transport process, through manipulating the Ni3+/Ni2+ ratio in the NiO films and the chance of polaron hopping. It was demonstrated that by using the ZnO coating, one would be able to decrease the electrical resistance of Ni foils by two orders of magnitude after exposure to 1020 °C for 4 min. In contrast, the Al2O3 coating increased the resistance of the uncoated foil by one order of magnitude, mainly due to the decrease in the ratio of Ni3+/Ni2+.

  15. Coating of nanoporous membranes: atomic layer deposition versus sputtering.

    PubMed

    Grigoras, K; Airaksinen, V M; Franssila, S

    2009-06-01

    Nanoporous anodic alumina membranes and silicon samples with plasma etched nanopores have been coated with zinc oxide or gold layer using atomic layer deposition (ALD) or sputtering, respectively. In the case of ALD process, the precursor pulses were extended, compared with planar substrate coating. Thick (60 microm) anodic alumina membranes have been conformally coated with zinc oxide ALD layer. Metal sputtering technique was used just for opposite purpose--to minimize the penetration of gold into the pores during gold-coating of the top and bottom surfaces of the membrane. Scanning electron microscopy (SEM) has been used to investigate the layer thickness, uniformity and conformality inside the nanopores.

  16. Biased deposition of nanocrystalline Be1-x Cux coatings

    SciTech Connect

    Jankowski, A

    2000-11-03

    Coatings of Be{sub 1-x}Cu{sub x} are prepared by magnetron sputter deposition onto spherical polymer mandrels. The application of an applied bias during deposition refines the columnar morphology of the coating and surface finish to the nanoscale. A mechanical testing technique is developed to load the thin-walled spherical capsules under uniaxial tension at constant strain to fracture. The bias-deposited material exhibits an increase in strength by a factor of three or more following a Hall-Petch type relationship with surface roughness.

  17. Surface pre-treatment for barrier coatings on polyethylene terephthalate

    NASA Astrophysics Data System (ADS)

    Bahre, H.; Bahroun, K.; Behm, H.; Steves, S.; Awakowicz, P.; Böke, M.; Hopmann, Ch; Winter, J.

    2013-02-01

    Polymers have favourable properties such as light weight, flexibility and transparency. Consequently, this makes them suitable for food packaging, organic light-emitting diodes and flexible solar cells. Nonetheless, raw plastics do not possess sufficient barrier functionality against oxygen and water vapour, which is of paramount importance for most applications. A widespread solution is to deposit thin silicon oxide layers using plasma processes. However, silicon oxide layers do not always fulfil the requirements concerning adhesion and barrier performance when deposited on films. Thus, plasma pre-treatment is often necessary. To analyse the influence of a plasma-based pre-treatment on barrier performance, different plasma pre-treatments on three reactor setups were applied to a very smooth polyethylene terephthalate film before depositing a silicon oxide barrier layer. In this paper, the influence of oxygen and argon plasma pre-treatments towards the barrier performance is discussed examining the chemical and topological change of the film. It was observed that a short one-to-ten-second plasma treatment can reduce the oxygen transmission rate by a factor of five. The surface chemistry and the surface topography change significantly for these short treatment times, leading to an increased surface energy. The surface roughness rises slowly due to the development of small spots in the nanometre range. For very long treatment times, surface roughness of the order of the barrier layer's thickness results in a complete loss of barrier properties. During plasma pre-treatment, the trade-off between surface activation and roughening of the surface has to be carefully considered.

  18. A study on thermal barrier coatings including thermal expansion mismatch and bond coat oxidation

    NASA Technical Reports Server (NTRS)

    Chang, George C.; Phucharoen, Woraphat; Miller, Robert A.

    1986-01-01

    The present investigation deals with a plasma-sprayed thermal barrier coating (TBC) intended for high temperature applications to advanced gas turbine blades. Typically, this type of coating system consists of a zirconia-yttria ceramic layer with a nickel-chromium-aluminum bond coat on a superalloy substrate. The problem on hand is a complex one due to the fact that bond coat oxidation and thermal mismatch occur in the TBC. Cracking in the TBC has also been experimentally illustrated. A clearer understanding of the mechanical behavior of the TBC is investigated. The stress states in a model thermal barrier coating as it cools down in air is studied. The powerful finite element method was utilized to model a coating cylindrical specimen. Four successively refined finite element models were developed. Some results obtained using the first two models have been reported previously. The major accomplishment is the successful development of an elastic TBC finite element model known as TBCG with interface geometry between the ceramic layer and the bond coat. An equally important milestone is the near-completion of the new elastic-plastic TBC finite element model called TBCGEP which yielded initial results. Representative results are presented.

  19. Thermal and Environmental Barrier Coatings for Advanced Turbine Engine Applications

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2005-01-01

    Ceramic thermal and environmental barrier coatings (T/EBCs) will play a crucial role in advanced gas turbine engine systems because of their ability to significantly increase engine operating temperatures and reduce cooling requirements, thus help achieve engine low emission and high efficiency goals. Advanced T/EBCs are being developed for the low emission SiC/SiC ceramic matrix composite (CMC) combustor applications by extending the CMC liner and vane temperature capability to 1650 C (3000 F) in oxidizing and water vapor containing combustion environments. Low conductivity thermal barrier coatings (TBCs) are also being developed for metallic turbine airfoil and combustor applications, providing the component temperature capability up to 1650 C (3000 F). In this paper, ceramic coating development considerations and requirements for both the ceramic and metallic components will be described for engine high temperature and high-heat-flux applications. The underlying coating failure mechanisms and life prediction approaches will be discussed based on the simulated engine tests and fracture mechanics modeling results.

  20. Internal Radiation Effects in Zirconia Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Siegel, Robert

    1996-01-01

    Using thermal barrier coatings on combustor liners, turbine vanes, and rotating blades is important for reducing metal temperatures in current and advanced aircraft engines. Zirconia is a common coating material, and it is partially transparent to thermal radiation. Radiation becomes more significant as temperatures are raised for higher efficiency in advanced engines. Calculations are often made with radiation effects neglected inside the coating. The effect of radiation is illustrated here, where an analytical procedure is provided by using the two-flux method for the radiative contribution. A detailed study was made of ceramic thermal barrier coatings for diesel engines, and a two-flux analysis was developed for radiation in semitransparent multilayer composites. These efforts provide the basis for the present analysis where illustrative solutions are obtained for typical conditions in an aircraft engine. The formulation and solution of the exact spectral radiative transfer equations including large scattering, as is characteristic of zirconia, are rather complicated. The two-flux method is used here to provide a simplified method.

  1. Method for depositing an oxide coating

    NASA Technical Reports Server (NTRS)

    Mcdonald, G. E. (Inventor)

    1982-01-01

    A metal oxide coating is plated onto a metal substrate at the cathode from an acid solution which contains an oxidizing agent. The process is particularly useful for producing solar panels. Conventional plating at the cathode avoids the presence of oxidizing agents. Coatings made in accordance with the invention are stable both at high temperatures and while under the influence of high photon flux in the visible range.

  2. Deposition of copper coatings in a magnetron with liquid target

    SciTech Connect

    Tumarkin, A. V. Kaziev, A. V.; Kolodko, D. V.; Pisarev, A. A.; Kharkov, M. M.; Khodachenko, G. V.

    2015-12-15

    Copper coatings were deposited on monocrystalline Si substrates using a magnetron discharge with a liquid cathode in the metal vapour plasma. During the deposition, the bias voltage in the range from 0 V to–400 V was applied to the substrate. The prepared films were investigated by a scanning electron microscope, and their adhesive properties were studied using a scratch tester. It was demonstrated that the adhesion of the deposited films strongly depends on the bias voltage and varies in a wide range.

  3. Electro-Spark Deposited Coatings for Replacement of Chrome Electroplating

    DTIC Science & Technology

    2005-06-01

    Wear and Corrosion: the Electrospark Deposition Process", published in Proceedings, American Electroplaters and Surface Finishers Society, Jan. 2002. 6...Johnson, R.N., " ElectroSpark Deposition : Principals and Applications", Society of Vacuum Coaters 45th Annual Technical Conference Proceedings, Apr...AD AD-E403 050 Contractor Report ARAET-CR-05002 ELECTRO-SPARK DEPOSITED COATINGS FOR REPLACEMENT OF CHROME PLATING R. N. Johnson J. A. Bailey Pacific

  4. Modified drug release using atmospheric pressure plasma deposited siloxane coatings

    NASA Astrophysics Data System (ADS)

    Dowling, D. P.; Maher, S.; Law, V. J.; Ardhaoui, M.; Stallard, C.; Keenan, A.

    2016-09-01

    This pilot study evaluates the potential of atmospheric plasma polymerised coatings to modify the rate of drug release from polymeric substrates. The antibiotic rifampicin was deposited in a prototype multi-layer drug delivery system, consisting of a nebulized layer of active drug between a base layer of TEOS deposited on a plastic substrate (polystyrene) and an overlying layer of plasma polymerised PDMS. The polymerised TEOS and PDMS layers were deposited using a helium atmospheric plasma jet system. Elution of rifampicin was measured using UV-VIS spectroscopy, in addition to a antimicrobial well diffusion assay with an established indicator organism. The multi-layered plasma deposited coatings significantly extended the duration of release of the rifampicin from 24 h for the uncoated polymer to 144 h for the coated polymer.

  5. The use of electrophoretically deposited diamond powder coatings as a precursor for chemically vapor deposited diamond

    SciTech Connect

    Panitz, J.K.G.

    1991-12-31

    It has generally been observed that in order in expedite the formation of chemical vapor deposited (CVD) diamond coatings, it is desirable to prepare a substrate by ``seeding`` it with diamond powder. We have determined that thick, stress free, shaped, diamond powder coatings can be electrophoretically deposited in a relatively short amounts of time. These diamond powder precursor coatings are then densified in a hot filament assisted CVD reactor to produce good quality CVD diamond/diamond powder composites. This combination of deposition techniques avoids many potential problems associated with predominantly CVD diamond.

  6. Laser drilling of thermal barrier coated jet-engine components

    NASA Astrophysics Data System (ADS)

    Sezer, H. K.

    Aero engine hot end components are often covered with ceramic Thermal Barrier Coatings (TBCs). Laser drilling in the TBC coated components can be a source of service life TBC degradation and spallation. The present study aims to understand the mechanisms of TBC delamination and develop techniques to drill holes without damaging the TBC, Nimonic 263 workpieces coated with TBC are used in the experiments. Microwave non-destructive testing (NDT) is employed to monitor the integrity of the coating /substrate interfaces of the post-laser drilled materials. A numerical modelling technique is used to investigate the role of melt ejection on TBC delamination. The model accounts for the vapour and the assist gas flow effects in the process. Broadly, melt ejection induced mechanical stresses for the TBC coating / bond coating and thermal effects for the bond coating / substrate interfaces are found the key delamination mechanisms. Experiments are carried out to validate the findings from the model. Various techniques that enable laser drilling without damaging the TBC are demonstrated. Twin jet assisted acute angle laser drilling is one successful technique that has been analysed using the melt ejection simulation. Optimisation of the twin jet assisted acute angle laser drilling process parameters is carried out using Design of Experiments (DoE) and statistical modelling approaches. Finally, an industrial case study to develop a high speed, high quality laser drilling system for combustor cans is described. Holes are drilled by percussion and trepan drilling in TBC coated and uncoated Haynes 230 workpieces. The production rate of percussion drilling is significantly higher than the trepan drilling, however metallurgical hole quality and reproducibility is poor. A number of process parameters are investigated to improve these characteristics. Gas type and gas pressure effects on various characteristics of the inclined laser drilled holes are investigated through theoretical

  7. Corrosion resistant thermal barrier coating. [protecting gas turbines and other engine parts

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Miller, R. A.; Hodge, P. E. (Inventor)

    1981-01-01

    A thermal barrier coating system for protecting metal surfaces at high temperature in normally corrosive environments is described. The thermal barrier coating system includes a metal alloy bond coating, the alloy containing nickel, cobalt, iron, or a combination of these metals. The system further includes a corrosion resistant thermal barrier oxide coating containing at least one alkaline earth silicate. The preferred oxides are calcium silicate, barium silicate, magnesium silicate, or combinations of these silicates.

  8. Growth and properties of W-B-N diffusion barriers deposited by chemical vapor deposition

    SciTech Connect

    Fleming, J.G.; Roherty-Osmun, E.; Custer, J.; Smith, P.M.; Reid, J.S.; Nicolet, M.A.

    1995-10-01

    The authors have used chemical vapor deposition to grow ternary tungsten-based diffusion barriers to determine if they exhibit properties similar to those of sputter-deposited ternaries. A range of different W-B-N compositions in a band of compositions roughly between 20 and 40% W were produced. The deposition temperature was low, 350 C, and the precursors used are well accepted by the industry. Deposition rates are high for a diffusion barrier application. Resistivities range from 200 to 20,000 {micro}{Omega}-cm, the films with the best barrier properties having {approximately}1,000 {micro}{Omega}-cm resistivities. Adhesion to oxides is sufficient to allow these films to be used as the adhesion layer in a tungsten chemical mechanical polishing plug application. The films are x-ray amorphous as-deposited and have crystallization temperatures of up to 900 C. Barrier performance against Cu has been tested using diode test structures. A composition of W{sub .23}B{sub .49}N{sub .28} was able to prevent diode failure up to a 700 C, 30 minute anneal. These materials, deposited by CVD, display properties similar to those deposited by physical deposition techniques.

  9. Thermal Barrier Coatings Chemically and Mechanically Resistant to High Temperature Attack by Molten Ashes

    NASA Astrophysics Data System (ADS)

    Gledhill, Andrew

    Thermal barrier coatings (TBCs) are ceramic coatings used on component in the hottest sections of gas turbine engines, used for power generation and aviation. These coatings insulate the underlying metal components and allow for much higher engine operating temperatures, improving the engine efficiency. These increase temperatures engender a new set of materials problems for TBCs. Operating temperatures in engines are now high enough for silicate impurities, either present in the fuel or ingested into the engines, to melt and adhere to the surface of the TBCs. The effects of four such impurities, two coal fly ashes, a petroleum coke-fly ash blend, and volcanic ash from the Eyjafjallajokull volcano were tested with conventional yttria-stabilized zirconia (YSZ) coatings, and found to penetrate through the entire thickness of the coating. This penetration reduces the strain tolerance of the coatings, and can result in premature failure. Testing on a newly built thermal gradient burner rig with simultaneous injection of ash impurities has shown a reduction of life up to 99.6% in these coatings when ash is present. Coatings of an alternative ceramic, gadolinium zirconate (Gd2Zr 2O7), were found to form a dense reaction layer with each of these impurities, preventing further penetration of the molten ash. This dense layer also reduces the strain tolerance, but these coatings were found to have a significantly higher life than the YSZ coatings. Testing with a small amount of ash baked onto the samples showed thirteen times the life of YSZ coatings. When the ash is continuously sprayed onto the hot sample, the life of the Gd2Zr2O7 coatings was nearly twice that of the YSZ. Finally, a delamination model was employed to explain the degradation of both types of coatings. This elastic model that takes into account the degree of penetration, differential cooling in thermal gradient testing, and thermal expansion mismatch with the underlying substrate, predicted the failure of

  10. Process for depositing hard coating in a nozzle orifice

    DOEpatents

    Flynn, P.L.; Giammarise, A.W.

    1991-10-29

    The present invention is directed to a process for coating the interior surfaces of an orifice in a substrate that forms a slurry fuel injection nozzle. In a specific embodiment, the nozzle is part of a fuel injection system for metering a coal-water slurry into a large, medium-speed, multi-cylinder diesel engine. In order to retard erosion of the orifice, the substrate is placed in a chemical vapor deposition (CVD) reaction chamber. A reaction gas is passed into the chamber at a gas temperature below its reaction temperature and is directed through the orifice in the substrate. The gas reaction temperature is a temperature at and above which the reaction gas deposits as a coating, and the reaction gas is of a composition whereby improved resistance to erosion by flow of the particulates in the slurry fuel is imparted by the deposited coating. Only the portion of the substrate in proximity to the orifice to be coated is selectively heated to at least the gas reaction temperature for effecting coating of the orifice's interior surfaces by the vapor deposited coating formed from the reaction gas. 2 figures.

  11. Process for depositing hard coating in a nozzle orifice

    DOEpatents

    Flynn, Paul L.; Giammarise, Anthony W.

    1991-01-01

    The present invention is directed to a process for coating the interior surfaces of an orifice in a substrate that forms a slurry fuel injection nozzle. In a specific embodiment, the nozzle is part of a fuel injection system for metering a coal-water slurry into a large, medium-speed, multi-cylinder diesel engine. In order to retard erosion of the orifice, the substrate is placed in a chemical vapor deposition (CVD) reaction chamber. A reaction gas is passed into the chamber at a gas temperature below its reaction temperature and is directed through the orifice in the substrate. The gas reaction temperature is a temperature at and above which the reaction gas deposits as a coating, and the reaction gas is of a composition whereby improved resistance toerosion by flow of the particulates in the slurry fuel is imparted by the deposited coating. Only the portion of the substrate in proximity to the orifice to be coated is selectively heated to at least the gas reaction temperature for effecting coating of the orifice's interior surfaces by the vapor deposited coating formed from the reaction gas.

  12. Apparatus for depositing hard coating in a nozzle orifice

    DOEpatents

    Flynn, P.L.; Giammarise, A.W.

    1995-02-21

    The present invention is directed to a process for coating the interior surfaces of an orifice in a substrate that forms a slurry fuel injection nozzle. In a specific embodiment, the nozzle is part of a fuel injection system for metering a coal-water slurry into a large, medium-speed, multi-cylinder diesel engine. In order to retard erosion of the orifice, the substrate is placed in a chemical vapor deposition (CVD) reaction chamber. A reaction gas is passed into the chamber at a gas temperature below its reaction temperature and is directed through the orifice in the substrate. The gas reaction temperature is a temperature at and above which the reaction gas deposits as a coating, and the reaction gas is of a composition whereby improved resistance to erosion by flow of the particulates in the slurry fuel is imparted by the deposited coating. Only the portion of the substrate in proximity to the orifice to be coated is selectively heated to at least the gas reaction temperature for effecting coating of the orifice`s interior surfaces by the vapor deposited coating formed from the reaction gas. 2 figs.

  13. Apparatus for depositing hard coating in a nozzle orifice

    DOEpatents

    Flynn, Paul L.; Giammarise, Anthony W.

    1995-01-01

    The present invention is directed to a process for coating the interior surfaces of an orifice in a substrate that forms a slurry fuel injection nozzle. In a specific embodiment, the nozzle is part of a fuel injection system for metering a coal-water slurry into a large, medium-speed, multi-cylinder diesel engine. In order to retard erosion of the orifice, the substrate is placed in a chemical vapor deposition (CVD) reaction chamber. A reaction gas is passed into the chamber at a gas temperature below its reaction temperature and is directed through the orifice in the substrate. The gas reaction temperature is a temperature at and above which the reaction gas deposits as a coating, and the reaction gas is of a composition whereby improved resistance to erosion by flow of the particulates in the slurry fuel is imparted by the deposited coating. Only the portion of the substrate in proximity to the orifice to be coated is selectively heated to at least the gas reaction temperature for effecting coating of the orifice's interior surfaces by the vapor deposited coating formed from the reaction gas.

  14. Hafnia-Based Nanostructured Thermal Barrier Coatings for Advanced Hydrogen Turbine Technology

    SciTech Connect

    Ramana, Chintalapalle; Choudhuri, Ahsan

    2013-01-31

    Thermal barrier coatings (TBCs) are critical technologies for future gas turbine engines of advanced coal based power generation systems. TBCs protect engine components and allow further increase in engine temperatures for higher efficiency. In this work, nanostructured HfO{sub 2}-based coatings, namely Y{sub 2}O{sub 3}-stabilized HfO{sub 2} (YSH), Gd{sub 2}O{sub 3}-stabilized HfO{sub 2} (GSH) and Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}-HfO{sub 2} (YSZH) were investigated for potential TBC applications in hydrogen turbines. Experimental efforts are aimed at creating a fundamental understanding of these TBC materials. Nanostructured ceramic coatings of YSH, GSH and YSZH were grown by physical vapor deposition methods. The effects of processing parameters and ceramic composition on the microstructural evolution of YSH, GSH and YSZH nanostructured coatings was studied using combined X-ray diffraction (XRD) and Electron microscopy analyses. Efforts were directed to derive a detailed understanding of crystal-structure, morphology, and stability of the coatings. In addition, thermal conductivity as a function of composition in YSH, YSZH and GSH coatings was determined. Laboratory experiments using accelerated test environments were used to investigate the relative importance of various thermo-mechanical and thermo-chemical failure modes of TBCs. Effects of thermal cycling, oxidation and their complex interactions were evaluated using a syngas combustor rig.

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

    SciTech Connect

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

    1996-05-01

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

  16. Electrophoretic deposition of zinc-substituted hydroxyapatite coatings.

    PubMed

    Sun, Guangfei; Ma, Jun; Zhang, Shengmin

    2014-06-01

    Zinc-substituted hydroxyapatite nanoparticles synthesized by the co-precipitation method were used to coat stainless steel plates by electrophoretic deposition in n-butanol with triethanolamine as a dispersant. The effect of zinc concentration in the synthesis on the morphology and microstructure of coatings was investigated. It is found that the deposition current densities significantly increase with the increasing zinc concentration. The zinc-substituted hydroxyapatite coatings were analyzed by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. It is inferred that hydroxyapatite and triethanolamine predominate in the chemical composition of coatings. With the increasing Zn/Ca ratios, the contents of triethanolamine decrease in the final products. The triethanolamine can be burnt out by heat treatment. The tests of adhesive strength have confirmed good adhesion between the coatings and substrates. The formation of new apatite layer on the coatings has been observed after 7days of immersion in a simulated body fluid. In summary, the results show that dense, uniform zinc-substituted hydroxyapatite coatings are obtained by electrophoretic deposition when the Zn/Ca ratio reaches 5%.

  17. Barrier properties to surrogates of hydrogenated carbon nano-films deposited on PET by plasma-enhanced chemical vapour deposition.

    PubMed

    Oliveira, Éder C; Echegoyen, Yolanda; Nerin, Cristina; Cruz, Sandra A

    2014-01-01

    Poly(ethylene terephthalate) resin was contaminated with a series of surrogates using a US Food and Drug Administration protocol. The contaminated samples were coated with two different kinds of hydrogenated amorphous carbon thin films (a-C:H): one with diamond-like hydrogenated amorphous carbon and another with polymer-like hydrogenated carbon (PLCH) phases. To evaluate the barrier properties of the a-C:H films, migration assays were performed using food simulants. After the tests, analysis by gas chromatography with different detectors was carried out. The appearance of the films before and after the migration experiments was studied by field emission scanning electron microscopy. The results showed that a-C:H films have good barrier properties for most of the evaluated compounds, mainly when they are deposited as PLCH phase.

  18. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  19. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  20. Microcracks Characterization for Thermal Barrier Coatings at High Temperature

    NASA Astrophysics Data System (ADS)

    Hua, J. J.; Wu, W.; Lin, C. C.; Zeng, Y.; Wang, H.; Zheng, X. B.

    2013-06-01

    Thermal barrier coatings (TBCs), used in gas turbine blades, are exposed to oxidation and thermal fatigue conditions. The characterization of TBCs was often performed in laboratory experiments, therefore, its detail failure mechanism is not quite obvious. For better understanding of the phenomenon, it is recommended to observe it under the condition simulating the real service conditions of gas turbines. In the present work, ZrO2 coatings were prepared by air plasma spraying (APS). Scanning electron microscope (SEM), equipped with a heating system, was used to study the in situ microstructure change of TBCs at service temperature at which the aircraft is operated. The bond coat (BC) layer's thickening process and thermally grown oxide (TGO) generation along with the cracks growth are revealed. Moreover, the influence of the service temperature and holding time on the failure mechanism of TBCs is discussed. The crack healing produced during the coating re-melting reaction is observed, and it is the key factor to increase the thermal conductivity of the coating.

  1. Microwave plasma deposition of diamond like carbon coatings

    NASA Astrophysics Data System (ADS)

    Patil, D. S.; Ramachandran, K.; Venkataramani, N.; Pandey, M.; D'Cunha, R.

    2000-11-01

    he promising applications of the microwave plasmas have been appearing in the fields of chemical processes and semiconductor manufacturing. Applications include surface deposition of all types including diamond/diamond like carbon (DLC) coatings, etching of semiconductors, promotion of organic reactions, etching of polymers to improve bonding of the other materials etc. With a 2.45 GHz, 700 W, microwave induced plasma chemical vapor deposition (CVD) system set up in our laboratory we have deposited diamond like carbon coatings. The microwave plasma generation was effected using a wave guide single mode applicator. We have deposited DLC coatings on the substrates like stainless steel, Cu--Be, Cu and Si. The deposited coatings have been characterized by FTIR, Raman spectroscopy and ellipsometric techniques. The results show that we have achieved depositing ~ 95% sp3 bonded carbon in the films. The films are uniform with golden yellow color. The films are found to be excellent insulators. The ellipsometric measurements of optical constant on silicon substrates indicate that the films are transparent above 900 nm.

  2. Performance Evaluation and Modeling of Erosion Resistant Turbine Engine Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming; Kuczmarski, Maria

    2008-01-01

    The erosion resistant turbine thermal barrier coating system is critical to the rotorcraft engine performance and durability. The objective of this work was to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and thermal gradient environments, thus validating a new thermal barrier coating turbine blade technology for future rotorcraft applications. A high velocity burner rig based erosion test approach was established and a new series of rare earth oxide- and TiO2/Ta2O5- alloyed, ZrO2-based low conductivity thermal barrier coatings were designed and processed. The low conductivity thermal barrier coating systems demonstrated significant improvements in the erosion resistance. A comprehensive model based on accumulated strain damage low cycle fatigue is formulated for blade erosion life prediction. The work is currently aiming at the simulated engine erosion testing of advanced thermal barrier coated turbine blades to establish and validate the coating life prediction models.

  3. Vacuum-deposited optical coatings experiment (A0138-4)

    NASA Technical Reports Server (NTRS)

    Malherbe, A.

    1984-01-01

    The stability of various vacuum deposited optical coatings exposed to the space environment were analyzed. A wide range of optical components manufactured by vacuum deposition, such as metallic and multidielectric reflective coatings in the UV range, metal dielectric interference filtes in the UV and IR ranges, narrow-bandpass filters int he near-UV and visible ranges, selective metallic mirrors in the range from 1500 to 2500 A. antireflective and reflective IR coatings, beam splitters in the visible and IR ranges, and optical surface reflection (OSR) coatings were developed. Many of these components were incorporated into scientific and technical experiments flown on balloons and rockets as well as on Symphonie, Meteosate, OTS, D2-B, TIROS n, and others. It appears that these components operate successfully in flight.

  4. Tantalum oxide-based plasma-sprayed environmental barrier coatings

    NASA Astrophysics Data System (ADS)

    Weyant, Christopher M.

    Energy efficiency in gas turbine engines is linked to the high temperature capabilities of materials used in the hot section of the engine. To facilitate a significant increase in engine efficiency, tough structural ceramics have been developed that can handle the thermo-mechanical stresses that gas turbine components experience. Unfortunately, the high-temperature, high-pressure, and high-velocity combustion gases in a gas turbine contain water vapor and/or hydrogen which have been shown to volatilize the protective silica layer on silicon-based ceramics. This degradation leads to significant surface recession in ceramic gas turbine components. In order to maintain their structural integrity, an environmental barrier coating (EBC) could be used to protect ceramics from the harsh gas turbine environment. Due to its coefficient of thermal expansion and phase stability at elevated temperatures, tantalum oxide (Ta2O5) was examined as the base material for an air plasma-sprayed EBC on Si3N 4 ceramics. As-sprayed pure Ta2O5 was comprised of both low-temperature beta-Ta2O5 and high-temperature alpha-Ta 2O5 that was quenched into the structure. Residual stress measurements via X-ray diffraction determined the as-sprayed coating to be in tension and extensive vertical macrocracks were observed in the coating. Heat treatments of the pure coating led to conversion of alpha-Ta2 O5 to beta-Ta2O5, conversion of tensile stresses to compressive, localized buckling of the coating, and significant grain growth which caused microcracking in the coating. The pure coating was found to be an inadequate EBC. Al2O3 was investigated as a solid solution alloying addition designed to enhance the stability of beta-Ta2O 5, and reduce grain growth by slowing grain boundary diffusion. La 2O3 was investigated as an alloying addition designed to form second phase particles which would reduce grain growth through pinning. Al2O3 was successful at both stabilizing beta-Ta 2O5 and reducing grain

  5. Design and Characterization of High-strength Bond Coats for Improved Thermal Barrier Coating Durability

    NASA Astrophysics Data System (ADS)

    Jorgensen, David John

    High pressure turbine blades in gas turbine engines rely on thermal barrier coating (TBC) systems for protection from the harsh combustion environment. These coating systems consist of a ceramic topcoat for thermal protection, a thermally grown oxide (TGO) for oxidation passivation, and an intermetallic bond coat to provide compatibility between the substrate and ceramic over-layers while supplying aluminum to sustain Al2O 3 scale growth. As turbine engines are pushed to higher operating temperatures in pursuit of better thermal efficiency, the strength of industry-standard bond coats limits the lifetime of these coating systems. Bond coat creep deformation during thermal cycling leads to a failure mechanism termed rumpling. The interlayer thermal expansion differences, combined with TGO-imposed growth stresses, lead to the development of periodic undulations in the bond coat. The ceramic topcoat has low out-of-plane compliance and thus detaches and spalls from the substrate, resulting in a loss of thermal protection and subsequent degradation of mechanical properties. New creep resistant Ni3Al bond coats were designed with improved high-temperature strength to inhibit this type of premature failure at elevated temperatures. These coatings resist rumpling deformation while maintaining compatibility with the other layers in the system. Characterization methods are developed to quantify rumpling and assess the TGO-bond coat interface toughness of experimental systems. Cyclic oxidation experiments at 1163 °C show that the Ni3Al bond coats do not experience rumpling but have faster oxide growth rates and are quicker to spall TGO than the (Pt,Ni)Al benchmark. However, the Ni 3Al coatings outperformed the benchmark by over threefold in TBC system life due to a higher resistance to rumpling (mechanical degradation) while maintaining adequate oxidation passivation. The Ni3Al coatings eventually grow spinel NiAl2O4 on top of the protective Al2O3 layer, which leads to the

  6. Durability and CMAS Resistance of Advanced Environmental Barrier Coatings Systems for SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2015-01-01

    Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. This paper will emphasize advanced environmental barrier coating developments for SiCSiC turbine airfoil components, by using advanced coating compositions and processing, in conjunction with mechanical and environment testing and durability validations. The coating-CMC degradations and durability in the laboratory simulated engine fatigue-creep and complex operating environments are being addressed. The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will be discussed. The results help understand the advanced EBC-CMC system performance, aiming at the durability improvements of more robust, prime-reliant environmental barrier coatings for successful applications of the component technologies and lifing methodologies.

  7. Combined Thermomechanical and Environmental Durability of Environmental Barrier Coating Systems on SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan; Bhatt, Ramakrishna

    2016-01-01

    Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) will play a crucial role in next generation turbine engines for hot-section component applications. The development of prime-reliant environmental barrier coatings is essential to the EBC-CMC system durability, ensuring the successful implementations of the high temperature and lightweight engine component technologies for engine applications.This paper will emphasize recent NASA environmental barrier coating and CMC developments for SiC/SiC turbine airfoil components, utilizing advanced coating compositions and processing methods. The emphasis has been particularly placed on thermomechanical and environment durability evaluations of EBC-CMC systems. We have also addressed the integration of the EBCs with advanced SiC/SiC CMCs, and studied the effects of combustion environments and Calcium-Magnesium-Alumino-Silicate (CMAS) deposits on the durability of the EBC-CMC systems under thermal gradient and mechanical loading conditions. Advanced environmental barrier coating systems, including multicomponent rare earth silicate EBCs and HfO2-Si based bond coats, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

  8. Deposition of Wear and Corrosion Resistant Coatings onto Landing Gear Components Via Directed Vapor Deposition

    DTIC Science & Technology

    2007-01-01

    Multilayer coatings • Combinatorial synthesis • Reactive deposition of oxides and nitrides • Supersonic gas jet focuses vapor flux onto substrate...velocity oxy -fuel (HVOF) process cannot be used. 3) Demonstrate that the coating is viable for sealing surfaces, where a surface finish of 8 to 12 micro

  9. Characterization of the WC coatings deposited by plasma spraying

    NASA Astrophysics Data System (ADS)

    Benea, M. L.; Benea, L. P.

    2015-06-01

    Tungsten monocarbide (WC) is deposited using a plasma jet on the martensitic noncorrosive steel support (Z12CNDV12), in three different thicknesses.The characteristics of the coatings are determined by: its chemical composition, optical microscopy, RX analysis, tensile adhesion strength, Vickers hardness, the nature and the processing degree of the substrate and the deposition conditions.The method used for determining the behaviour in a corrosive environment of the WC coatings deposited by plasma spraying consists in measuring the electrochemical potential difference between the coating and the substrate, which are immersed in a solution containing NaCl as a corrosive agent. The experimental results are then mathematically processed in order to determine a law and the mechanisms involved.

  10. Optical Diagnostics for High-Temperature Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.

    2009-01-01

    Thermal barrier coatings (TBCs) are typically composed of translucent ceramic oxides that provide thermal protection for metallic components exposed to high-temperature environments, such as in jet turbine engines. Taking advantage of the translucent nature of TBCs, optical diagnostics have been developed that can provide an informed assessment of TBC health that will allow mitigating action to be taken before TBC degradation threatens performance or safety. In particular, rare-earth-doped luminescent sublayers have been integrated into the TBC structure to produce luminescence that monitors TBC erosion, delamination, and temperature gradients. Erosion monitoring of TBC-coated specimens is demonstrated by utilizing visible luminescence that is excited from a sublayer that is exposed by erosion. TBC delamination monitoring is achieved in TBCs with a base rare-earth-doped luminescent sublayer by the reflectance-enhanced increase in luminescence produced in regions containing buried delamination cracks. TBC temperature monitoring is demonstrated using the temperature-dependent decay time for luminescence originating from the specific coating depth associated with a rare-earth-doped luminescent sublayer. The design and implementation of these TBCs with integrated luminescent sublayers is discussed, including co-doping strategies to produce more penetrating near-infrared luminescence. It is demonstrated that integration of the rare-earth-doped sublayers is achieved with no reduction in TBC life. In addition, results for multilayer TBCs designed to also perform as radiation barriers are also presented.

  11. Low Conductive Thermal Barrier Coatings Produced by Ion Beam Assisted EB-PVD with Controlled Porosity, Microstructure Refinement and Alloying Additions for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Wolfe, Douglas E.; Singh, Jogender

    2005-01-01

    Various advanced Hafnia-based thermal barrier coatings (TBC) were applied on nickel-based superalloy coupons by electron beam physical vapor deposition. In addition, microstructural modifications to the coating material were made in an effort to reduce the thermal conductivity of the coating materials. Various processing parameters and coating system modifications were made in order to deposit the alloyed TBC with the desired microstructure and thus coating performance, some of which include applying coatings at substrate temperatures of 1150 C on both PtAl and CoNiCrAlY bond coated samples, as well as using 8YSZ as a bond layer. In addition, various characterization techniques including thermal cyclic tests, scanning electron microscopy, x-ray diffraction, thermal conductivity, and reflectivity measurements were performed. Although the coating microstructure was never fully optimized due to funding being cut short, significant reductions in thermal conductivity were accomplished through both chemistry changes (composition) and microstructural modifications.

  12. Graphene Oxide Bionanocomposite Coatings with High Oxygen Barrier Properties

    PubMed Central

    Uysal Unalan, Ilke; Boyacı, Derya; Ghaani, Masoud; Trabattoni, Silvia; Farris, Stefano

    2016-01-01

    In this work, we present the development of bionanocomposite coatings on poly(ethylene terephthalate) (PET) with outstanding oxygen barrier properties. Pullulan and graphene oxide (GO) were used as main polymer phase and nanobuilding block (NBB), respectively. The oxygen barrier performance was investigated at different filler volume fractions (ϕ) and as a function of different relative humidity (RH) values. Noticeably, the impermeable nature of GO was reflected under dry conditions, in which an oxygen transmission rate (OTR, mL·m−2·24 h−1) value below the detection limit of the instrument (0.01 mL·m−2·24 h−1) was recorded, even for ϕ as low as 0.0004. A dramatic increase of the OTR values occurred in humid conditions, such that the barrier performance was totally lost at 90% RH (the OTR of coated PET films was equal to the OTR of bare PET films). Modelling of the experimental OTR data by Cussler’s model suggested that the spatial ordering of GO sheets within the main pullulan phase was perturbed because of RH fluctuations. In spite of the presence of the filler, all the formulations allowed the obtainment of final materials with haze values below 3%, the only exception being the formulation with the highest loading of GO (ϕ ≈ 0.03). The mechanisms underlying the experimental observations are discussed. PMID:28335372

  13. FeS-coated sand for removal of arsenic(III) under anaerobic conditions in permeable reactive barriers

    USGS Publications Warehouse

    Han, Y.-S.; Gallegos, T.J.; Demond, A.H.; Hayes, K.F.

    2011-01-01

    Iron sulfide (as mackinawite, FeS) has shown considerable promise as a material for the removal of As(III) under anoxic conditions. However, as a nanoparticulate material, synthetic FeS is not suitable for use in conventional permeable reactive barriers (PRBs). This study developed a methodology for coating a natural silica sand to produce a material of an appropriate diameter for a PRB. Aging time, pH, rinse time, and volume ratios were varied, with a maximum coating of 4.0 mg FeS/g sand achieved using a pH 5.5 solution at a 1:4 volume ratio (sand: 2 g/L FeS suspension), three days of aging and no rinsing. Comparing the mass deposited on the sand, which had a natural iron-oxide coating, with and without chemical washing showed that the iron-oxide coating was essential to the formation of a stable FeS coating. Scanning electron microscopy images of the FeS-coated sand showed a patchwise FeS surface coating. X-ray photoelectron spectroscopy showed a partial oxidation of the Fe(II) to Fe(III) during the coating process, and some oxidation of S to polysulfides. Removal of As(III) by FeS-coated sand was 30% of that by nanoparticulate FeS at pH 5 and 7. At pH 9, the relative removal was 400%, perhaps due to the natural oxide coating of the sand or a secondary mineral phase from mackinawite oxidation. Although many studies have investigated the coating of sands with iron oxides, little prior work reports coating with iron sulfides. The results suggest that a suitable PRB material for the removal of As(III) under anoxic conditions can be produced through the deposition of a coating of FeS onto natural silica sand with an iron-oxide coating. ?? 2010 Elsevier Ltd.

  14. Electrophoretic deposition of composite hydroxyapatite-chitosan coatings

    SciTech Connect

    Pang Xin; Zhitomirsky, Igor . E-mail: zhitom@mcmaster.ca

    2007-04-15

    Cathodic electrophoretic deposition has been utilized for the fabrication of composite hydroxyapatite-chitosan coatings on 316L stainless steel substrates. The addition of chitosan to the hydroxyapatite suspensions promoted the electrophoretic deposition of the hydroxyapatite nanoparticles and resulted in the formation of composite coatings. The obtained coatings were investigated by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning and transmission electron microscopy, potentiodynamic polarization measurements, and electrochemical impedance spectroscopy. It was shown that the deposit composition can be changed by a variation of the chitosan or hydroxyapatite concentration in the solutions. Experimental conditions were developed for the fabrication of hydroxyapatite-chitosan nanocomposites containing 40.9-89.8 wt.% hydroxyapatite. The method enabled the formation of adherent and uniform coatings of thicknesses up to 60 {mu}m. X-ray studies revealed that the preferred orientation of the hydroxyapatite nanoparticles in the chitosan matrix increases with decreasing hydroxyapatite content in the composite coatings. The obtained coatings provided the corrosion protection for the 316L stainless steel substrates00.

  15. Osteogenic responses to zirconia with hydroxyapatite coating by aerosol deposition.

    PubMed

    Cho, Y; Hong, J; Ryoo, H; Kim, D; Park, J; Han, J

    2015-03-01

    Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. © International & American Associations for Dental Research 2015.

  16. Osteogenic Responses to Zirconia with Hydroxyapatite Coating by Aerosol Deposition

    PubMed Central

    Cho, Y.; Hong, J.; Ryoo, H.; Kim, D.; Park, J.

    2015-01-01

    Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. PMID:25586588

  17. Development Status and Performance Comparisons of Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan

    2016-01-01

    Environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft turbine engine systems, because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. This paper presents current NASA EBC-CMC development emphases including: the coating composition and processing improvements, laser high heat flux-thermal gradient thermo-mechanical fatigue - environmental testing methodology development, and property evaluations for next generation EBC-CMC systems. EBCs processed with various deposition techniques including Plasma Spray, Electron Beam - Physical Vapor Deposition, and Plasma Spray Physical Vapor Deposition (PS-PVD) will be particularly discussed. The testing results and demonstrations of advanced EBCs-CMCs in complex simulated engine thermal gradient cyclic fatigue, oxidizing-steam and CMAS environments will help provide insights into the coating development strategies to meet long-term engine component durability goals.

  18. Chemical vapor deposition coatings for oxidation protection of titanium alloys

    NASA Technical Reports Server (NTRS)

    Cunnington, G. R.; Robinson, J. C.; Clark, R. K.

    1991-01-01

    Results of an experimental investigation of the oxidation protection afforded to Ti-14Al-21Nb and Ti-14Al-23Nb-2V titanium aluminides and Ti-17Mo-3Al-3Nb titanium alloy by aluminum-boron-silicon and boron-silicon coatings are presented. These coatings are applied by a combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes. The former is for the application of aluminum, and the latter is for codeposition of boron and silicon. Coating thickness is in the range of 2 to 7 microns, and coating weights are 0.6 to 2.0 mg/sq cm. Oxidation testing was performed in air at temperatures to 1255 K in both static and hypersonic flow environments. The degree of oxidation protection provided by the coatings is determined from weight change measurements made during the testing and post test compositional analyses. Temperature-dependent total normal emittance data are also presented for four coating/substrate combinations. Both types of coatings provided excellent oxidation protection for the exposure conditions of this investigation. Total normal emittances were greater than 0.80 in all cases.

  19. Mechanisms and Mitigation of CMAS Attack on Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Zaleski, Elisa Marie

    As gas turbine engines are driven to operate at higher temperatures to maximize efficiency, components become susceptible to attack by deposits of calcium magnesium alumino-silicate (CMAS) ingested with the intake air. Of particular interest to this work is the degradation of thermal barrier coatings (TBCs) by CMAS. Molten CMAS is known to interact with TBCs both thermochemically, by dissolving the ceramic and reprecipitating it as a new or modified phase, and thermomechanically, by infiltrating the porosity and degrading the strain tolerance. The thermochemical degradation of TBCs was investigated using primarily differential scanning calorimetry (DSC) by comparing the endotherms and exotherms recorded for pure, model silicates to those observed for silicates mixed with various TBC materials including YSZ and GZO. The five ternary silicates studied (CaO-AlO1.5-SiO2) began melting over a relatively narrow range (˜1125-1145°C). Introducing magnesium to the ternary results in higher melting temperatures and only minor changes to the crystallization behavior. Iron decreases the melting temperature, and markedly improves the crystallization kinetics of pure silicate systems, especially absent magnesium. Modification of the crystallization behavior of pure silicates has been proposed in the literature as a mitigation strategy for CMAS. This work utilizes DSC to look for characteristic changes as described above to probe potentially effective TBCs. The addition of YSZ to a quaternary CMAS results in little change to the melting or crystallization in the DSC, despite the dissolution of YSZ into the silicate. In stark contrast, GZO with CMAS generates a significant crystallization exotherm that appears in the DSC immediately after the silicate melts. As the fraction of GZO is increased, the melting endotherm begins to shrink due to the thermal overlap of the melting and crystallization processes. This signifies a rapid reaction, and a potentially useful TBC material for

  20. Thermal barrier coatings for gas-turbine engine applications.

    PubMed

    Padture, Nitin P; Gell, Maurice; Jordan, Eric H

    2002-04-12

    Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities.

  1. Sol-gel deposited electrochromic coatings

    SciTech Connect

    Ozer, N.; Lampert, C.M.

    1995-06-01

    Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

  2. Tribological performance of hybrid filtered arc-magnetron coatings - Part I: Coating deposition process and basic coating properties characterization

    SciTech Connect

    Gorokhovsky, Vladimir; Bowman, C.; Gannon, Paul E.; VanVorous, D.; Voevodin, A. A.; Rutkowski, A.; Muratore, C.; Smith, Richard J.; Kayani, Asghar N.; Gelles, David S.; Shutthanandan, V.; Trusov, B. G.

    2006-12-04

    Aircraft propulsion applications require low-friction and wear resistant surfaces that operate under high contact loads in severe environments. Recent research on supertough and low friction nanocomposite coatings produced with hybrid plasma deposition processes was demonstrated to have a high potential for such demanding applications. However, industrially scalable hybrid plasma technologies are needed for their commercial realization. The Large area Filtered Arc Deposition (LAFAD) process provides atomically smooth coatings at high deposition rates over large surface areas. The LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different metal ion vapors. Further advancement can be realized through a combinatorial process using a hybrid filtered arc-magnetron deposition system. In the present study, multilayer and nanostructured TiCrCN/TiCr +TiBC composite cermet coatings were deposited by the hybrid filtered arc-magnetron process. Filtered plasma streams from arc evaporated Ti and Cr targets, and two unbalanced magnetron sputtered B4C targets, were directed to the substrates in the presence of reactive gases. A multiphase nanocomposite coating architecture was designed to provide the optimal combination of corrosion and wear resistance of advanced steels (Pyrowear 675) used in aerospace bearing and gear applications. Coatings were characterized using SEM/EDS, XPS and RBS for morphology and chemistry, XRD and TEM for structural analyses, wafer curvature and nanoindentation for stress and mechanical properties, and Rockwell and scratch indentions for adhesion. Coating properties were evaluated for a variety of coating architectures. Thermodynamic modeling was used for estimation of phase composition of the top TiBC coating segment. Correlations between coating chemistry, structure and mechanical properties are discussed.

  3. Highly defective oxides as sinter resistant thermal barrier coating

    DOEpatents

    Subramanian, Ramesh

    2005-08-16

    A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

  4. NON-DESTRUCTIVE THERMAL BARRIER COATING SPALLATION PREDICTION BY A LOADBASED MICRO-INDENTATION TECHNIQUE

    SciTech Connect

    J. M. Tannenbaum; K. Lee; B. S.-J. Kang; M.A. Alvin

    2010-11-18

    Currently, the durability and life cycle of thermal barrier coatings (TBC) applied to gas turbine blades and combustor components are limiting the maximum temperature and subsequent efficiency at which gas turbine engines operate. The development of new materials, coating technologies and evaluation techniques is required if enhanced efficiency is to be achieved. Of the current ceramic coating materials used in gas turbine engines, yttria stabilized zirconia (YSZ) is most prevalent, its low thermal conductivity, high thermal expansion coefficient and outstanding mechanical strength make it ideal for use in TBC systems. However, residual stresses caused by coefficients of thermal expansion mismatches within the TBC system and unstable thermally grown oxides are considered the primary causes for its premature and erratic spallation failure. Through finite element simulations, it is shown that the residual stresses generated within the thermally grown oxide (TGO), bond coat (BC), YSZ and their interfaces create slight variations in indentation unloading surface stiffness response prior to spallation failure. In this research, seven air plasma sprayed and one electron beam physical vapor deposition yttria partially stabilized zirconia TBCs were subjected to isothermal and cyclic loadings at 1100°C. The associated coating degradation was evaluated using a non-destructive multiple partial unloading micro-indentation procedure. The results show that the proposed non-destructive micro-indentation evaluation technique can be an effective and specimenindependent TBC failure prediction tool capable of determining the location of initial spallation failure prior to its actual occurrence.

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

    SciTech Connect

    Helminiak, Yanar NM

    2009-12-01

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

  6. Role of atomic layer deposited aluminum oxide as oxidation barrier for silicon based materials

    SciTech Connect

    Fiorentino, Giuseppe Morana, Bruno; Forte, Salvatore; Sarro, Pasqualina Maria

    2015-01-15

    In this paper, the authors study the protective effect against oxidation of a thin layer of atomic layer deposited (ALD) aluminum oxide (Al{sub 2}O{sub 3}). Nitrogen doped silicon carbide (poly-SiC:N) based microheaters coated with ALD Al{sub 2}O{sub 3} are used as test structure to investigate the barrier effect of the alumina layers to oxygen and water vapor at very high temperature (up to 1000 °C). Different device sets have been fabricated changing the doping levels, to evaluate possible interaction between the dopants and the alumina layer. The as-deposited alumina layer morphology has been evaluated by means of AFM analysis and compared to an annealed sample (8 h at 1000 °C) to estimate the change in the grain structure and the film density. The coated microheaters are subjected to very long oxidation time in dry and wet environment (up to 8 h at 900 and 1000 °C). By evaluating the electrical resistance variation between uncoated reference devices and the ALD coated devices, the oxide growth on the SiC is estimated. The results show that the ALD alumina coating completely prevents the oxidation of the SiC up to 900 °C in wet environment, while an oxide thickness reduction of 50% is observed at 1000 °C compared to uncoated devices.

  7. Global and local planarization of surface roughness by chemical vapor deposition of organosilicon polymer for barrier applications

    NASA Astrophysics Data System (ADS)

    Coclite, Anna Maria; Gleason, Karen K.

    2012-04-01

    Particulates and asperities on the surface of plastic substrates limit the performance of the current protective barrier coatings for flexible electronics. By applying a smoothing layer to the substrate, prior to barrier deposition, permeation is reduced. While application of smoothing layers from the liquid-phase application and curing of acrylate monomers is well known, reports of planarization achieved by vapor deposition are quite limited. In the current work, the chemical vapor deposition (CVD) of a flexible smoothing layer, requiring no curing, is implemented in the same reactor chamber and from the same organosilicon monomer used for depositing the multilayer barrier stack. The process similarity between the smoothing and barrier layer deposition steps has the potential to lower the overall cost of the process and to improve interfacial properties, such as adhesion between the smoothing layer and the barrier stack. The current methods adapts and combines features of two well established methods for CVD of organic layers, plasma enhancement (PECVD) and the specific use of an initiator species (iCVD). The novel, initiated plasma enhanced chemical vapor deposition (iPECVD) method achieves a far greater degree of planarization of flexible organic layer than either of its predecessors. Polystyrene microspheres serve as model defects and allow the degree of planarization to be quantitatively measured. Both cross-sectional scanning electron micrographs and atomic force micrographs demonstrate that when the iPECVD organic layer is 1.8 µm thick, the degree of global planarization is 99%. A model demonstrates that the planarization is achieved as a result of the coating viscosity and the surface tension. Finally, the water vapor barrier performance of a 20-nm-thick SiOx layer is two orders of magnitude improved when it is deposited on a planarized substrate.

  8. Global and local planarization of surface roughness by chemical vapor deposition of organosilicon polymer for barrier applications

    SciTech Connect

    Coclite, Anna Maria; Gleason, Karen K.

    2012-04-01

    Particulates and asperities on the surface of plastic substrates limit the performance of the current protective barrier coatings for flexible electronics. By applying a smoothing layer to the substrate, prior to barrier deposition, permeation is reduced. While application of smoothing layers from the liquid-phase application and curing of acrylate monomers is well known, reports of planarization achieved by vapor deposition are quite limited. In the current work, the chemical vapor deposition (CVD) of a flexible smoothing layer, requiring no curing, is implemented in the same reactor chamber and from the same organosilicon monomer used for depositing the multilayer barrier stack. The process similarity between the smoothing and barrier layer deposition steps has the potential to lower the overall cost of the process and to improve interfacial properties, such as adhesion between the smoothing layer and the barrier stack. The current methods adapts and combines features of two well established methods for CVD of organic layers, plasma enhancement (PECVD) and the specific use of an initiator species (iCVD). The novel, initiated plasma enhanced chemical vapor deposition (iPECVD) method achieves a far greater degree of planarization of flexible organic layer than either of its predecessors. Polystyrene microspheres serve as model defects and allow the degree of planarization to be quantitatively measured. Both cross-sectional scanning electron micrographs and atomic force micrographs demonstrate that when the iPECVD organic layer is 1.8 {mu}m thick, the degree of global planarization is 99%. A model demonstrates that the planarization is achieved as a result of the coating viscosity and the surface tension. Finally, the water vapor barrier performance of a 20-nm-thick SiO{sub x} layer is two orders of magnitude improved when it is deposited on a planarized substrate.

  9. Two-layer thermal barrier coating for turbine airfoils - furnace and burner rig test results

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1976-01-01

    A simple, two-layer plasma-sprayed thermal barrier coating system was developed which has the potential for protecting high temperature air-cooled gas turbine components. Of those coatings initially examined, the most promising system consisted of a Ni-16Cr-6Al-0.6Y (in wt%) thermal barrier coating (about 0.005 to 0.010 cm thick) and a ZrO2-12Y2O3 (in wt%) thermal barrier coating (about 0.025 to 0.064 cm thick). This thermal barrier substantially lowered the metal temperature of an air-cooled airfoil. The coating withstood 3,200 cycles (80 sec at 1,280 C surface temperature) and 275 cycles (1 hr at 1,490 C surface temperature) without cracking or spalling. No separation of the thermal barrier from the bond coating or the bond coating from the substrate was observed.

  10. The Development of Erosion and Impact Resistant Turbine Airfoil Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2007-01-01

    Thermal barrier coatings are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments and extend component lifetimes. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Advanced erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the doped thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion and impact damage mechanisms of the thermal barrier coatings will also be discussed.

  11. Ion Assisted Deposition of Optical Coatings.

    DTIC Science & Technology

    1986-08-01

    comparable to the value of 2.15 for e-team evaporated Ta205 reported by Herrmann. 49 Demiryont, Sites and Geib reported a value of 2.18 for ion-beam...243 (1982). 156 15. H. Demiryont, J. R. Sites and Kent Geib , "Effects of oxygen content on the optical properties of tantalum oxide films deposited by

  12. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials.

  13. Strain response of thermal barrier coatings captured under extreme engine environments through synchrotron X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Knipe, Kevin; Manero, Albert; Siddiqui, Sanna F.; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M.; Bartsch, Marion; Raghavan, Seetha

    2014-07-01

    The mechanical behaviour of thermal barrier coatings in operation holds the key to understanding durability of jet engine turbine blades. Here we report the results from experiments that monitor strains in the layers of a coating subjected to thermal gradients and mechanical loads representing extreme engine environments. Hollow cylindrical specimens, with electron beam physical vapour deposited coatings, were tested with internal cooling and external heating under various controlled conditions. High-energy synchrotron X-ray measurements captured the in situ strain response through the depth of each layer, revealing the link between these conditions and the evolution of local strains. Results of this study demonstrate that variations in these conditions create corresponding trends in depth-resolved strains with the largest effects displayed at or near the interface with the bond coat. With larger temperature drops across the coating, significant strain gradients are seen, which can contribute to failure modes occurring within the layer adjacent to the interface.

  14. Strain response of thermal barrier coatings captured under extreme engine environments through synchrotron X-ray diffraction.

    PubMed

    Knipe, Kevin; Manero, Albert; Siddiqui, Sanna F; Meid, Carla; Wischek, Janine; Okasinski, John; Almer, Jonathan; Karlsson, Anette M; Bartsch, Marion; Raghavan, Seetha

    2014-07-31

    The mechanical behaviour of thermal barrier coatings in operation holds the key to understanding durability of jet engine turbine blades. Here we report the results from experiments that monitor strains in the layers of a coating subjected to thermal gradients and mechanical loads representing extreme engine environments. Hollow cylindrical specimens, with electron beam physical vapour deposited coatings, were tested with internal cooling and external heating under various controlled conditions. High-energy synchrotron X-ray measurements captured the in situ strain response through the depth of each layer, revealing the link between these conditions and the evolution of local strains. Results of this study demonstrate that variations in these conditions create corresponding trends in depth-resolved strains with the largest effects displayed at or near the interface with the bond coat. With larger temperature drops across the coating, significant strain gradients are seen, which can contribute to failure modes occurring within the layer adjacent to the interface.

  15. The failure of thermal barrier coatings at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Yanar, Nazik Meltem

    In this study, the current state of the art thermal barrier coating (TBC) systems (heavy grit blasted Pt aluminide and NiCoCrAlY Bond Coats with EBPVD TBCs) were investigated first followed by TBC systems which were modified based upon the results obtained on the failure of the state of the art TBC systems. The specimens were subjected to cyclic oxidation testing, mostly at 1100°C in a bottom loading furnace in laboratory air. Optical and scanning electron microscopy (SEM) were used for characterization of the as-processed and failed specimens. The state of the art TBC systems with NiCoCrAlY bond coats failed in the presence of defects which were identified as TBC defects, transient oxides, surface defects and reactive element (RE) rich oxide protrusions. On the other hand, the failure of the state of the art TBC systems with Pt aluminide bond coats were due to deformation of the bond coat by a mechanism known as ratcheting. The stored strain energy in the TGO was also a factor that contributed to the failure of both systems. Most of the modifications performed on the state of the art TBC systems improved their lives to some extent. In the case of NiCoCrAlY systems, elimination or at least minimization of the identified defects was responsible for the improvements whereas the prevention of the ratcheting type of failure was the main reason for the improvement in lives in the case of Pt alumimde systems. On the other hand, other issues such as slower growth of the TGO as well as improved interfacial toughnesses with some of the modifications were observed to be contributing factors in the improved lives. Based on the observations on the failure of both the state of the art as well as the modified TBC systems, the surface condition of the bond coats as well as the morphology of the TBCs close to the TGO were found to have a first order effect on the failure of TBC systems. The characteristics of the TGO, such as composition, growth rate and adherence both to the

  16. Polymer derived ceramic composites as environmental barrier coatings on steel

    NASA Astrophysics Data System (ADS)

    Torrey, Jessica D.

    Polymer derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as fibers and coatings. They offer advantages over traditional ceramic processing routes including lower pyrolysis temperatures and the ability to employ polymeric processing techniques. The main drawback to preceramic polymers is that they undergo a shrinkage during pyrolysis that can be greater than 50-volume%. One way to overcome this shrinkage is to add filler particles, usually elemental or binary metals, which will expand upon reaction with the pyrolysis atmosphere, thereby compensating for the shrinkage of the polymer. The aim of this study is to develop a polymer derived ceramic composite coating on steel as a barrier to oxidation and carburization, while concurrently gaining insight as to the fundamental mechanisms for compositional and microstructural evolution within the system. A systematic approach to selecting the preceramic polymer and expansion agents was taken. Six commercially available poly(silsesquioxane) polymers and a polysiloxane were studied. Several metals and an intermetallic were considered as potential expansion agents. The most desirable polymer/expansion agent combination was achieved with poly(hydridomethylsiloxane) as the matrix and titanium disilicide as the filler. Processing parameters have been optimized and a relationship derived to predict final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals an amorphous composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating-steel interface, indicating good bonding. The optimized coatings are ˜18mum thick, have some residual porosity and a density of 2.57g/cm3. A systematic study of the phase transformations and microstructural changes in the coating and its components during pyrolysis in air is also presented. The system evolves from a polymer filled with a binary metal at

  17. Parametric Studies Of Failure Mechanisms In Thermal Barrier Coatings During Thermal Cycling Using FEM

    NASA Astrophysics Data System (ADS)

    Srivathsa, B.; Das, D. K.

    2015-12-01

    Thermal barrier coatings (TBCs) are widely used on different hot components of gas turbine engines such as blades and vanes. Although, several mechanisms for the failure of the TBCs have been suggested, it is largely accepted that the durability of these coatings is primarily determined by the residual stresses that are developed during the thermal cycling. In the present study, the residual stress build-up in an electron beam physical vapour deposition (EB-PVD) based TBCs on a coupon during thermal cycling has been studied by varying three parameters such as the cooling rate, TBC thickness and substrate thickness. A two-dimensional thermomechanical generalized plane strain finite element simulations have been performed for thousand cycles. It was observed that these variations change the stress profile significantly and the stress severity factor increases non-linearly. Overall, the predictions of the model agree with reported experimental results and help in predicting the failure mechanisms.

  18. Mechanical Properties of Air Plasma Sprayed Environmental Barrier Coating (EBC) Materials

    NASA Technical Reports Server (NTRS)

    Richards, Bradley; Zhu, Dongming; Ghosn, Louis; Wadley, Haydn

    2015-01-01

    Development work in Environmental Barrier Coatings (EBCs) for Ceramic Matrix Composites (CMCs) has focused considerably on the identification of materials systems and coating architectures to meet application needs. The evolution of these systems has occurred so quickly that modeling efforts and requisite data for modeling lag considerably behind development. Materials property data exists for many systems in the bulk form, but the effects of deposition on the critical properties of strength and fracture behavior are not well studied. We have plasma sprayed bulk samples of baseline EBC materials (silicon, ytterbium disilicate) and tested the mechanical properties of these materials to elicit differences in strength and toughness. We have also endeavored to assess the mixed-mode fracture resistance, Gc, of silicon in a baseline EBC applied to SiCSiC CMC via four point bend test. These results are compared to previously determined properties of the comparable bulk material.

  19. Crack prediction in EB-PVD thermal barrier coatings based on the simulation of residual stresses

    NASA Astrophysics Data System (ADS)

    Chen, J. W.; Zhao, Y.; Liu, S.; Zhang, Z. Z.; Ma, J.

    2016-07-01

    Thermal barrier coatings systems (TBCs) are widely used in the field of aerospace. The durability and insulating ability of TBCs are highly dependent on the residual stresses of top coatings, thus the investigation of the residual stresses is helpful to understand the failure mechanisms of TBCs. The simulation of residual stresses evolution in electron beam physical vapor deposition (EB-PVD) TBCs is described in this work. The interface morphology of TBCs subjected to cyclic heating and cooling is observed using scanning electron microscope (SEM). An interface model of TBCs is established based on thermal elastic-plastic finite method. Residual stress distributions in TBCs are obtained to reflect the influence of interfacial roughness. Both experimental and simulation results show that it is feasible to predict the crack location by stress analysis, which is crucial to failure prediction.

  20. Failure of thick, low density air plasma sprayed thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Helminiak, Michael Aaron

    This research was directed at developing fundamental understandings of the variables that influence the performance of air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC). Focus was placed on understanding how and why each variable influenced the performance of the TBC system along with how the individual variables interacted with one another. It includes research on the effect of surface roughness of NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying, the interdiffusion behavior of bond coats coupled to commercial superalloys, and the microstructural and compositional control of APS topcoats to maximize the coating thicknesses that can be applied without spallation. The specimens used for this research were prepared by Praxair Surface Technologies and have been evaluated using cyclic oxidation and thermal shock tests. TBC performance was sensitive to bond coat roughness with the rougher bond coats having improved cyclic performance than the smoother bond coats. The explanation being the rough bond coat surface hindered the propagation of the delamination cracks. The failure mechanisms of the APS coatings were found to depend on a combination of the topcoat thickness, topcoat microstructure and the coefficient of thermal expansion (CTE) mismatch between the superalloy and topcoat. Thinner topcoats tended to fail at the topcoat/TGO interface due to bond coat oxidation whereas thicker topcoats failed within the topcoat due to the strain energy release rate of the thicker coating exceeding the fracture strength of the topcoat. Properties of free-standing high and conventional purity YSZ topcoats of both a lowdensity (LD) and dense-vertically fissure (DVF) microstructures were evaluated. The densification rate and phase evolution were sensitive to the YSZ purity and the starting microstructure. Increasing the impurity content resulted in enhanced sintering and phase decomposition rates, with the exception of the

  1. Thermal Conductivity Measurement of an Electron-Beam Physical-Vapor-Deposition Coating.

    PubMed

    Slifka, A J; Filla, B J

    2003-01-01

    An industrial ceramic thermal-barrier coating designated PWA 266, processed by electron-beam physical-vapor deposition, was measured using a steady-state thermal conductivity technique. The thermal conductivity of the mass fraction 7 % yttria-stabilized zirconia coating was measured from 100 °C to 900 °C. Measurements on three thicknesses of coatings, 170 μm, 350 μm, and 510 μm resulted in thermal conductivity in the range from 1.5 W/(m·K) to 1.7 W/(m·K) with a combined relative standard uncertainty of 20 %. The thermal conductivity is not significantly dependent on temperature.

  2. The Use of Feature Parameters to Asses Barrier Properties of ALD coatings for Flexible PV Substrates

    NASA Astrophysics Data System (ADS)

    Blunt, Liam; Robbins, David; Fleming, Leigh; Elrawemi, Mohamed

    2014-03-01

    This paper reports on the recent work carried out as part of the EU funded NanoMend project. The project seeks to develop integrated process inspection, cleaning, repair and control systems for nano-scale thin films on large area substrates. In the present study flexible photovoltaic films have been the substrate of interest. Flexible PV films are the subject of significant development at present and the latest films have efficiencies at or beyond the level of Si based rigid PV modules. These flexible devices are fabricated on polymer film by the repeated deposition, and patterning, of thin layer materials using roll-to-roll processes, where the whole film is approximately 3um thick prior to encapsulation. Whilst flexible films offer significant advantages in terms of mass and the possibility of building integration (BIPV) they are at present susceptible to long term environmental degradation as a result of water vapor transmission through the barrier layers to the CIGS (Copper Indium Gallium Selenide CuInxGa(1-x)Se2) PV cells thus causing electrical shorts and efficiency drops. Environmental protection of the GIGS cell is provided by a thin (40nm) barrier coating of Al2O3. The highly conformal aluminium oxide barrier layer is produced by atomic layer deposition (ALD) where, the ultra-thin Al2O3 layer is deposited onto polymer thin films before these films encapsulate the PV cell. The surface of the starting polymer film must be of very high quality in order to avoid creating defects in the device layers. Since these defects reduce manufacturing yield, in order to prevent them, a further thin polymer coating (planarization layer) is generally applied to the polymer film prior to deposition. The presence of surface irregularities on the uncoated film can create defects within the nanometre-scale, aluminium oxide, barrier layer and these are measured and characterised. This paper begins by reporting the results of early stage measurements conducted to characterise

  3. Oxidation-resistant coatings on titanium alloys by ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Bedell, C. J.; Bishop, H. E.; Dearnaley, G.; Desport, J. E.; Romary, H.; Romary, J.-M.

    1991-07-01

    The high strength and creep resistance of modern titanium alloys makes them potentially attractive for aero engine compressor blades operating at temperatures above 500° C, to improve thermal efficiency and performance. However, all these alloys suffer from oxidation at such elevated temperatures and the in-diffusing oxygen stabilizes the more brittle alpha-phase of the alloy making it prone to crack under stress. There is thus a need for protective highly adherent coatings. In the present work, chromium was deposited with simultaneous ion bombardment using 60 keV nitrogen ions, to a thickness of 1 μm. Ion assisted deposition provides excellent adhesion and a very compact, pore-free coating with a small grain size. However, at high temperatures titanium diffuses into the chromium and impairs its protectiveness. To combat this, a diffusion barrier of silicon nitride was deposited first, by evaporating silicon and matching the rate of arrival of Si atoms with a 0.5 keV nitrogen ion beam from a Kaufman source to produce Si 3N 4 to thicknesses from 0.1 to 0.3 μm. As an added protection, in some experiments an overlay coating of about 0.3 μm of silicon nitride was deposited after the chromium layer. Oxidation was carried out in air at temperatures between 600 and 800° C and for periods up to 100 h. Subsequent analysis by SIMS showed excellent protection up to at least 700° C but diffusion across the barrier occurred at 800° C. Titanium nitride was less successful than silicon nitride for barrier purposes.

  4. Sputtering - A vacuum deposition method for coating material.

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1972-01-01

    The sputtering method is discussed in terms of the unique features which sputter offers in depositing coatings. These features include versatility, momentum transfer, configuration of target, precise controls, and a relatively slow deposition rate. Sputtered films are evaluated in terms of adherence, coherence, and the internal stresses. The observed strong adherence is attributed to the high kinetic energies of the sputtered material, sputter etched surface, and the submicroscopic particle size. Film thickness can be controlled to a millionth of a centimeter. Very adherent films of sputtered PTFE (teflon) can be deposited in a single operation on any type of material and on any geometrical configuration.

  5. Sputtering - A vacuum deposition method for coating material.

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1972-01-01

    The sputtering method is discussed in terms of the unique features which sputter offers in depositing coatings. These features include versatility, momentum transfer, configuration of target, precise controls, and a relatively slow deposition rate. Sputtered films are evaluated in terms of adherence, coherence, and the internal stresses. The observed strong adherence is attributed to the high kinetic energies of the sputtered material, sputter etched surface, and the submicroscopic particle size. Film thickness can be controlled to a millionth of a centimeter. Very adherent films of sputtered PTFE (teflon) can be deposited in a single operation on any type of material and on any geometrical configuration.

  6. Property Evaluation and Damage Evolution of Environmental Barrier Coatings and Environmental Barrier Coated SiC/SiC Ceramic Matrix Composite Sub-Elements

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Halbig, Michael; Jaskowiak, Martha; Hurst, Janet; Bhatt, Ram; Fox, Dennis S.

    2014-01-01

    This paper describes recent development of environmental barrier coatings on SiC/SiC ceramic matrix composites. The creep and fatigue behavior at aggressive long-term high temperature conditions have been evaluated and highlighted. Thermal conductivity and high thermal gradient cyclic durability of environmental barrier coatings have been evaluated. The damage accumulation and complex stress-strain behavior environmental barrier coatings on SiCSiC ceramic matrix composite turbine airfoil subelements during the thermal cyclic and fatigue testing of have been also reported.

  7. Effect of an Opaque Reflecting Layer on the Thermal Behavior of a Thermal Barrier Coating

    NASA Technical Reports Server (NTRS)

    Spuckler, Charles M.

    2007-01-01

    A parametric study using a two-flux approximation of the radiative transfer equation was performed to examine the effects of an opaque reflective layer on the thermal behavior of a typical semitransparent thermal barrier coating on an opaque substrate. Some ceramic materials are semitransparent in the wavelength ranges where thermal radiation is important. Even with an opaque layer on each side of the semitransparent thermal barrier coating, scattering and absorption can have an effect on the heat transfer. In this work, a thermal barrier coating that is semitransparent up to a wavelength of 5 micrometers is considered. Above 5 micrometers wavelength, the thermal barrier coating is opaque. The absorption and scattering coefficient of the thermal barrier was varied. The thermal behavior of the thermal barrier coating with an opaque reflective layer is compared to a thermal barrier coating without the reflective layer. For a thicker thermal barrier coating with lower convective loading, which would be typical of a combustor liner, a reflective layer can significantly decrease the temperature in the thermal barrier coating and substrate if the scattering is weak or moderate and for strong scattering if the absorption is large. The layer without the reflective coating can be about as effective as the layer with the reflective coating if the absorption is small and the scattering strong. For low absorption, some temperatures in the thermal barrier coating system can be slightly higher with the reflective layer. For a thin thermal barrier coating with high convective loading, which would be typical of a blade or vane that sees the hot sections of the combustor, the reflective layer is not as effective. The reflective layer reduces the surface temperature of the reflective layer for all conditions considered. For weak and moderate scattering, the temperature of the TBC-substrate interface is reduced but for strong scattering, the temperature of the substrate is increased

  8. Atomic Layer Deposition for the Conformal Coating of Nanoporous Materials

    DOE PAGES

    Elam, Jeffrey W.; Xiong, Guang; Han, Catherine Y.; ...

    2006-01-01

    Amore » tomic layer deposition ( ALD ) is ideal for applying precise and conformal coatings over nanoporous materials. We have recently used ALD to coat two nanoporous solids: anodic aluminum oxide ( AAO ) and silica aerogels. AAO possesses hexagonally ordered pores with diameters d ∼ 40 nm and pore length L ∼ 70 microns. The AAO membranes were coated by ALD to fabricate catalytic membranes that demonstrate remarkable selectivity in the oxidative dehydrogenation of cyclohexane.dditional AAO membranes coated with ALD Pd films show promise as hydrogen sensors. Silica aerogels have the lowest density and highest surface area of any solid material. Consequently, these materials serve as an excellent substrate to fabricate novel catalytic materials and gas sensors by ALD .« less

  9. Preparation of sol-gel coatings by electrophoretic deposition

    SciTech Connect

    Hirashima, Hiroshi; Obu, Yusuke; Nagai, Takayuki; Imai, Hiroaki

    1994-12-31

    Thin films of ZrO{sub 2} and lead zirconate-titanate, PZT, about 100 to 1,000 nm in thickness, were prepared by electrophoretic deposition from transparent sols obtained by hydrolysis of metal alkoxides. Stainless steel plates and Pt-coated glass plates were used as substrates/electrodes. The applied field was up to 20 V/cm. The refractive indices of as dried films were higher than those of dip-coated films. High temperature oxidation of stainless steel plates was suppressed by the ZrO{sub 2} coatings. Uniformity of the chemical composition of the as-dried PZT films, determined by Auger electron spectroscopy, was better than the dip-coated PZT films.

  10. Strontium-substituted hydroxyapatite coatings deposited via a co-deposition sputter technique.

    PubMed

    Boyd, A R; Rutledge, L; Randolph, L D; Meenan, B J

    2015-01-01

    The bioactivity of hydroxyapatite (HA) coatings can be modified by the addition of different ions, such as silicon (Si), lithium (Li), magnesium (Mg), zinc (Zn) or strontium (Sr) into the HA lattice. Of the ions listed here, strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as Sr has been shown to promote osteoblast proliferation and differentiation, and reduce osteoclast activity. In this study, SrHA coatings were deposited onto titanium substrates using radio frequency (RF) magnetron co-sputtering (and compared to those surfaces deposited from HA alone). FTIR, XPS, XRD, and SEM techniques were used to analyse the different coatings produced, whereby different combinations of pure HA and 13% Sr-substituted HA targets were investigated. The results highlight that Sr could be successfully incorporated into the HA lattice to form SrHA coatings. It was observed that as the number of SrHA sputtering targets in the study were increased (increasing Sr content), the deposition rate decreased. It was also shown that as the Sr content of the coatings increased, so did the degree of preferred 002 orientation of the coating (along with obvious changes in the surface morphology). This study has shown that RF magnetron sputtering (specifically co-sputtering), offers an appropriate methodology to control the surface properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface morphology.

  11. Performance of thermal barrier coatings in high heat flux environments

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Berndt, C. C.

    1984-01-01

    Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8%Y2O3 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12%Y2O3 or ZrO2-20%Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.

  12. Performance of thermal barrier coatings in high heat flux environments

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Berndt, C. C.

    1984-01-01

    Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y203 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-20 percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.

  13. Performance of thermal barrier coatings in high heat flux environments

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Berndt, C. C.

    1984-01-01

    Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y2O3 specimens survived 3000 of the 0.5 sec cycles with falling. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 1 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-2O percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.

  14. A software tool to design thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Petrus, G.; Ferguson, B. L.

    1995-01-01

    This paper summarizes work completed for a NASA Phase 1 SBIR program which demonstrated the feasibility of developing a software tool to aid in the design of thermal barrier coating (TBC) systems. Toward this goal, three tasks were undertaken and completed. Task 1 involved the development of a database containing the pertinent thermal and mechanical property data for the top coat, bond coat and substrate materials that comprise a TBC system. Task 2 involved the development of an automated set-up program for generating two dimensional (2D) finite element models of TBC systems. Most importantly, Task 3 involved the generation of a rule base to aid in the design of a TBC system. These rules were based on a factorial design of experiments involving FEM results, and were generated using a Yates analysis. A previous study has indicated the suitability and benefit of applying finite element analysis to perform computer based experiments to decrease but not eliminate physical experiments on TBC's. This program proved feasibility by expanding on these findings by developing a larger knowledge base and developing a procedure to extract rules to aid in TBC design.

  15. A software tool to design thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Petrus, Gregory; Ferguson, B. Lynn

    1995-01-01

    This paper summarizes work completed for a NASA Phase 1 SBIR program which demonstrated the feasibility of developing a software tool to aid in the design of thermal barrier coating (TBC) systems. Toward this goal, three tasks were undertaken and completed. Task 1 involved the development of a database containing the pertinent thermal and mechanical property data for the top coat, bond coat and substrate materials that comprise a TBC system. Task 2 involved the development of an automated set-up program for generating two dimensional (2D) finite element models of TBC systems. Most importantly, task 3 involved the generation of a rule base to aid in the design of a TBC system. These rules were based on a factorial design of experiments involving FEM results and were generated using a Yates analysis. A previous study had indicated the suitability and benefit of applying finite element analysis to perform computer based experiments to decrease but not eliminate physical experiments on TBC's. This program proved feasibility by expanding on these findings by developing a larger knowledgebase and developing a procedure to extract rules to aid in TBC design.

  16. Crystallographic texture in pulsed laser deposited hydroxyapatite bioceramic coatings

    PubMed Central

    Kim, Hyunbin; Camata, Renato P.; Lee, Sukbin; Rohrer, Gregory S.; Rollett, Anthony D.; Vohra, Yogesh K.

    2008-01-01

    The orientation texture of pulsed laser deposited hydroxyapatite coatings was studied by X-ray diffraction techniques. Increasing the laser energy density of the KrF excimer laser used in the deposition process from 5 to 7 J/cm2 increases the tendency for the c-axes of the hydroxyapatite grains to be aligned perpendicular to the substrate. This preferred orientation is most pronounced when the incidence direction of the plume is normal to the substrate. Orientation texture of the hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups and dehydroxylation effects during deposition all seem to play important roles in the texture development. PMID:18563207

  17. Deposition of antimicrobial coatings on microstereolithography-fabricated microneedles

    NASA Astrophysics Data System (ADS)

    Gittard, Shaun D.; Miller, Philip R.; Jin, Chunming; Martin, Timothy N.; Boehm, Ryan D.; Chisholm, Bret J.; Stafslien, Shane J.; Daniels, Justin W.; Cilz, Nicholas; Monteiro-Riviere, Nancy A.; Nasir, Adnan; Narayan, Roger J.

    2011-06-01

    Microneedles are small-scale needle-like projections that may be used for transdermal delivery of pharmacologic agents, including protein-containing and nucleic acid-containing agents. Commercial translation of polymeric microneedles would benefit from the use of facile and cost effective fabrication methods. In this study, visible light dynamic mask microstereolithography, a rapid prototyping technique that utilizes digital light projection for selective polymerization of a liquid resin, was used for fabrication of solid microneedle array structures out of an acrylate-based polymer. Pulsed laser deposition was used to deposit silver and zinc oxide coatings on the surfaces of the visible light dynamic mask microstereolithography-fabricated microneedle array structures. Agar diffusion studies were used to demonstrate the antimicrobial activity of the coated microneedle array structures. This study indicates that light-based technologies, including visible light dynamic mask microstereolithography and pulsed laser deposition, may be used to fabricate microneedles with antimicrobial properties for treatment of local skin infections.

  18. Synthesis of mullite coatings by chemical vapor deposition

    SciTech Connect

    Mulpuri, R.P.; Sarin, V.K.

    1996-06-01

    Formation of mullite on ceramic substrates via chemical vapor deposition was investigated. Mullite is a solid solution of Al{sub 2}O{sub 3} and SiO{sub 2} with a composition of 3Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2}. Thermodynamic calculations performed on the AlCl{sub 3}{endash}SiCl{sub 4}{endash}CO{sub 2}{endash}H{sub 2} system were used to construct equilibrium chemical vapor deposition (CVD) phase diagrams. With the aid of these diagrams and consideration of kinetic rate limiting factors, initial process parameters were determined. Through process optimization, crystalline CVD mullite coatings have been successfully grown on SiC and Si{sub 3}N{sub 4} substrates. Results from the thermodynamic analysis, process optimization, and effect of various process parameters on deposition rate and coating morphology are discussed. {copyright} {ital 1996 Materials Research Society.}

  19. Enabling Inexpensive Metallic Alloys as SOFC Interconnects: An Investigation into Hybrid Coating Technologies to Deposit Nanocomposite Functional Coatings on Ferritic Stainless Steel

    SciTech Connect

    Gannon, Paul; Gorokhovsky, Vladimir I.; Deibert, Max; Smith, Richard J.; Kayani, Asghar N.; White, P T.; Sofie, Stephen W.; Yang, Z Gary; Mccready, David E.; Visco, S.; Jacobson, C.; Kurokawa, H.

    2007-11-01

    Reduced operating temperatures (600-800°C) of Solid Oxide Fuel Cells (SOFCs) may enable the use of inexpensive ferritic steels as interconnects. Due to the demanding SOFC interconnect operating environment, protective coatings are required to increase long-term stability. In this study, large area filtered arc deposition (LAFAD) and hybrid filtered arc-assisted electron beam physical vapor deposition (FA-EBPVD) technologies were used to deposit two-segment coatings with Cr-Al-Y-O nanocomposite bottom segments and Mn-Co-O spinel-based top segments. Coatings were deposited on ferritic steels and subsequently annealed in air for various times. Surface oxidation was investigated using SEM/EDS, XRD and RBS analyses. Cr-volatilization was evaluated by transpiration and ICP-MS analysis of the resultant condensate. Time dependent Area Specific Resistance (ASR) was studied using the four-point technique. The oxidation behavior, Cr volatilization rate, and ASR of coated and uncoated samples are reported. Significant long-term (>1,000 hours) surface stability, low ASR, and dramatically reduced Cr-volatility were observed with the coated specimens. Improvement mechanisms, including the coating diffusion barrier properties and electrical conductivity are discussed.

  20. Thermal Conductivity of Ceramic Thermal Barrier and Environmental Barrier Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Bansal, Narottam P.; Lee, Kang N.; Miller, Robert A.

    2001-01-01

    Thermal barrier and environmental barrier coatings (TBC's and EBC's) have been developed to protect metallic and Si-based ceramic components in gas turbine engines from high temperature attack. Zirconia-yttria based oxides and (Ba,Sr)Al2Si2O8(BSAS)/mullite based silicates have been used as the coating materials. In this study, thermal conductivity values of zirconia-yttria- and BSAS/mullite-based coating materials were determined at high temperatures using a steady-state laser heat flux technique. During the laser conductivity test, the specimen surface was heated by delivering uniformly distributed heat flux from a high power laser. One-dimensional steady-state heating was achieved by using thin disk specimen configuration (25.4 mm diam and 2 to 4 mm thickness) and the appropriate backside air-cooling. The temperature gradient across the specimen thickness was carefully measured by two surface and backside pyrometers. The thermal conductivity values were thus determined as a function of temperature based on the 1-D heat transfer equation. The radiation heat loss and laser absorption corrections of the materials were considered in the conductivity measurements. The effects of specimen porosity and sintering on measured conductivity values were also evaluated.

  1. Deposition of tantalum carbide coatings on graphite by laser interactions

    NASA Technical Reports Server (NTRS)

    Veligdan, James; Branch, D.; Vanier, P. E.; Barietta, R. E.

    1994-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000 C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing involved the use of a CO2 laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl5 gas near the substrate. The results of preliminary experiments using these techniques are described.

  2. Deposition of Nanocomposite Coatings Employing a Hybrid APS + SPPS Technique

    NASA Astrophysics Data System (ADS)

    Lohia, A.; Sivakumar, G.; Ramakrishna, M.; Joshi, S. V.

    2014-10-01

    A novel approach hybridizing the conventional atmospheric plasma spraying and the solution precursor plasma spraying techniques has been explored to develop nanocomposite coatings. The above hybrid processing route involves simultaneous feeding of an appropriate solution precursor and commercially available spray-grade powder feedstock to realize microstructures comprising nanostructured and micron-sized features, which are unique in thermal spraying. The attractive prospects offered by this hybrid technique for deposition of nanocomposite coatings are specifically highlighted in this paper through a case study. Plasma sprayed Mo-alloy coatings are known for their good tribological characteristics and widely used in many applications. Further augmentation in performance of these coatings is expected through incorporation of distributed nanostructured oxide phases in the microstructure. Successful development of such coatings using a spray-grade Mo-alloy powder and a suitable oxide-forming solution precursor has been demonstrated. Splat formation under varied processing conditions has been comprehensively investigated and related to microstructure and tribological behavior of the coatings to assess the efficacy of the above nanocomposite coatings for wear resistant applications.

  3. Pt and Hf Additions to NiAl Bond Coats and Their Effect on the Lifetime of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Gleeson, B.; Sordelet, D.; Barrett, C. A.

    2003-01-01

    The lifetimes of thermal barrier coatings (TBC's) with various NiAlPt(HfZr) bond coats were determined by cyclic oxidation testing at 1163 C (2125 F). The bond coats were sprayed from powders by low pressure plasma spraying onto Rene N5 superalloy substrates. Yttria stabilized zirconia (8YSZ) top coats were applied by air plasma spraying. Surprisingly, there was not a strong correlation between TBC lifetime and Pt or Hf content although Zr additions decreased lifetimes. TBC failure morphologies and bond coat microstructures were examined and are discussed with respect to the bond coat compositions.

  4. Gas barrier properties of diamond-like carbon films coated on PTFE

    NASA Astrophysics Data System (ADS)

    Ozeki, K.; Nagashima, I.; Ohgoe, Y.; Hirakuri, K. K.; Mukaibayashi, H.; Masuzawa, T.

    2009-05-01

    Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE substrate was modified with a N 2 plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N 2 plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N 2 plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N 2 plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2 μm. The DLC-coated PTFE with the N 2 plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.

  5. Phase evolution and thermal properties of yttria-stabilized hafnia nano-coatings deposited on alumina

    NASA Astrophysics Data System (ADS)

    Rubio, Ernesto Javier

    High-temperature coatings are critical to the future power-generation systems and industries. Thermal barrier coatings (TBCs), which are usually the ceramic materials applied as thin coatings, protect engine components and allow further increase in engine temperatures for higher efficiency. Thus, the durability and reliability of the coating systems have to be more robust compared to current natural gas based engines. While a near and mid-term target is to develop TBC architecture with a 1300 °C surface temperature tolerance, a deeper understanding of the structure evolution and thermal behavior of the TBC-bond coat interface, specifically the thermally grown oxide (TGO), is of primary importance. In the present work, attention is directed towards yttria-stabilized hafnia (YSH) coatings on alumina (α-Al2O 3) to simulate the TBC-TGO interface and understand the phase evolution, microstructure and thermal oxidation of the coatings. YSH coatings were grown on α-Al2O3 substrates by sputter deposition by varying coating thickness in a wide range ˜30-1000 nm. The effect of coating thickness on the structure, morphology and the residual stress has been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (SEM). Thermal oxidation behavior of the coatings has been evaluated using the isothermal oxidation measurements under static conditions. X-ray diffraction analyses revealed the existence of monoclinic hafnia phase for relatively thin coatings indicating that the interfacial phenomena are dominant in phase stabilization. The evolution towards pure stabilized cubic phase of hafnia with the increasing coating thickness is observed. The SEM results indicate the changes in morphology of the coatings; the average grain size increases from 15 to 500 nm with increasing thickness. Residual stress was calculated employing XRD using the variable ψ-angle. Relation between residual stress and structural change is also studied. The results

  6. Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2008-01-01

    Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

  7. On coating adhesion during impulse plasma deposition

    NASA Astrophysics Data System (ADS)

    Nowakowska-Langier, Katarzyna; Zdunek, Krzysztof; Chodun, Rafal; Okrasa, Sebastian; Kwiatkowski, Roch; Malinowski, Karol; Składnik-Sadowska, Elzbieta; Sadowski, Marek J.

    2014-05-01

    The impulse plasma deposition (IPD) technique is the only method of plasma surface engineering (among plasma-based technologies) that allows a synthesis of layers upon a cold unheated substrate and which ensures a good adhesion. This paper presents a study of plasma impacts upon a copper substrate surface during the IPD process. The substrate was exposed to pulsed N2/Al plasma streams during the synthesis of AlN layers. For plasma-material interaction diagnostics, the optical emission spectroscopy method was used. Our results show that interactions of plasma lead to sputtering of the substrate material. It seems that the obtained adhesion of the layers is the result of a complex surface mechanism combined with the effects of pulsed plasma energy impacts upon the unheated substrate. An example of such a result is the value of the critical load for the Al2O3 layer, which was measured by the scratch-test method to be above 40 N.

  8. Thermal barrier coatings (TBC's) for high heat flux thrust chambers

    NASA Astrophysics Data System (ADS)

    Bradley, Christopher M.

    The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot

  9. Conversion Coatings for Aluminum Alloys by Chemical Vapor Deposition Mechanisms

    NASA Technical Reports Server (NTRS)

    Reye, John T.; McFadden, Lisa S.; Gatica, Jorge E.; Morales, Wilfredo

    2004-01-01

    With the rise of environmental awareness and the renewed importance of environmentally friendly processes, the United States Environmental Protection Agency has targeted surface pre-treatment processes based on chromates. Indeed, this process has been subject to regulations under the Clean Water Act as well as other environmental initiatives, and there is today a marked movement to phase the process out in the near future. Therefore, there is a clear need for new advances in coating technology that could provide practical options for replacing present industrial practices. Depending on the final application, such coatings might be required to be resistant to corrosion, act as chemically resistant coatings, or both. This research examined a chemical vapor deposition (CVD) mechanism to deposit uniform conversion coatings onto aluminum alloy substrates. Robust protocols based on solutions of aryl phosphate ester and multi-oxide conversion coating (submicron) films were successfully grown onto the aluminum alloy samples. These films were characterized by X-ray Photoelectron Spectroscopy (XPS). Preliminary results indicate the potential of this technology to replace aqueous-based chromate processes.

  10. The development of chemically vapor deposited mullite coatings for the corrosion protection of SiC

    SciTech Connect

    Auger, M.; Hou, P.; Sengupta, A.; Basu, S.; Sarin, V.

    1998-05-01

    Crystalline mullite coatings have been chemically vapor deposited onto SiC substrates to enhance the corrosion and oxidation resistance of the substrate. Current research has been divided into three distinct areas: (1) Development of the deposition processing conditions for increased control over coating`s growth rate, microstructure, and morphology; (2) Analysis of the coating`s crystal structure and stability; (3) The corrosion resistance of the CVD mullite coating on SiC.

  11. Multilayered thermal barrier coatings by CVD. Final report, September 1996--February 1997

    SciTech Connect

    Fortini, A.J.; Heng, S.; Sherman, A.J.

    1997-05-01

    Turbine engine component life is currently limited by creep, creep-rupture, oxidation/corrosion, and thermomechanical fatigue. The use of protective coatings, such as nickel-chromium-aluminum-yttrium (NiCrAlY) and more recently platinum aluminides and various thermal barrier coatings (TBCs), has enabled higher temperatures and longer component life to be achieved, but component life and temperature capability still limit obtainable engine operating efficiency. Reduction in component temperature through the development and use of improved TBCs can dramatically extend component life, or conversely, allow higher operating temperatures to be used at constant component life. Additionally, lowering oxygen diffusion through the TBC will increase the life of the TBC itself, and reduce or eliminate oxidation and corrosion of the bondcoat and underlying component structure. Extension of TBC technology to increasingly complicated combustor, blade, and vane geometries and cooling passages requires improved application methods. In this project, Ultramet developed and demonstrated the chemical vapor deposition (CVD) of bondcoats and multilayered TBCs. Analytical modeling to quantify performance improvement predicted a 40--80 C drop in turbine blade temperature through the use of these coatings. In addition, burner rig oxidation and salt spray corrosion testing were performed on a coated blade.

  12. Silicon oxide barrier films deposited on PET foils in pulsed plasmas: influence of substrate bias on deposition process and film properties

    NASA Astrophysics Data System (ADS)

    Steves, S.; Ozkaya, B.; Liu, C.-N.; Ozcan, O.; Bibinov, N.; Grundmeier, G.; Awakowicz, P.

    2013-02-01

    A widely used plastic for packaging, polyethylene terephtalate (PET) offers limited barrier properties against gas permeation. For many applications of PET (from food packaging to micro electronics) improved barrier properties are essential. A silicon oxide barrier coating of PET foils is applied by means of a pulsed microwave driven low-pressure plasma. While the adjustment of the microwave power allows for a control of the ion production during the plasma pulse, a substrate bias controls the energy of ions impinging on the substrate. Detailed analysis of deposited films applying oxygen permeation measurements, x-ray photoelectron spectroscopy and atomic force microscopy are correlated with results from plasma diagnostics describing the deposition process. The influence of a change in process parameters such as gas mixture and substrate bias on the gas temperature, electron density, mean electron energy, ion energy and the atomic oxygen density is studied. An additional substrate bias results in an increase in atomic oxygen density up to a factor of 6, although plasma parameter such as electron density of ne = 3.8 ± 0.8 × 1017 m-3 and electron temperature of kBTe = 1.7 ± 0.1 eV are unmodified. It is shown that atomic oxygen densities measured during deposition process higher than nO = 1.8 × 1021 m-3 yield in barrier films with a barrier improvement factor up to 150. Good barrier films are highly cross-linked and show a smooth morphology.

  13. Thick Thermal Barrier Coatings (TTBCs) for Low Emission, High Efficiency Diesel Engine Components

    SciTech Connect

    M. Brad Beardsley, Caterpillar Inc.; Dr. Darrell Socie, University of Illinois; Dr. Ed Redja, University of Illinois; Dr. Christopher Berndt, State University of New York at Stony Brook

    2006-03-02

    The objective of this program was to advance the fundamental understanding of thick thermal barrier coating (TTBC) systems for application to low heat rejection diesel engine combustion chambers. Previous reviews of thermal barrier coating technology concluded that the current level of understanding of coating system behavior is inadequate and the lack of fundamental understanding may impede the application of thermal barrier coating to diesel engines.(1) Areas of TTBC technology examined in this program include powder characteristics and chemistry; bond coating composition, coating design, microstructure and thickness as they affect properties, durability, and reliability; and TTBC "aging" effects (microstructural and property changes) under diesel engine operating conditions. Fifteen TTBC ceramic powders were evaluated. These powders were selected to investigate the effects of different chemistries, different manufacturing methods, lot-to-lot variations, different suppliers and varying impurity levels. Each of the fifteen materials has been sprayed using 36 parameters selected by a design of experiments (DOE) to determine the effects of primary gas (Ar and N2), primary gas flow rate, voltage, arc current, powder feed rate, carrier gas flow rate, and spraying distance. The deposition efficiency, density, and thermal conductivity of the resulting coatings were measured. A coating with a high deposition efficiency and low thermal conductivity is desired from an economic standpoint. An optimum combination of thermal conductivity and disposition efficiency was found for each lot of powder in follow-on experiments and disposition parameters were chosen for full characterization.(2) Strengths of the optimized coatings were determined using 4-point bending specimens. The tensile strength was determined using free-standing coatings made by spraying onto mild steel substrates which were subsequently removed by chemical etching. The compressive strengths of the coatings

  14. Nucleation and growth of combustion flame deposited diamond coatings on silicon nitride

    NASA Astrophysics Data System (ADS)

    Rozbicki, Robert T.

    An investigation has been performed on the kinetics of diamond nucleation on silicon nitride (Si3N4) based materials during oxy-acetylene combustion flame chemical vapor deposition. The deposits were characterized using scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) techniques. Kinetic parameters of the nucleation process, such as nucleation rate (I), period of initial nuclei formation (tng), and maximum nucleation density (Nd) were experimentally determined. It was concluded that at low temperatures (Ts < 875°C), the observed nucleation density is due to epitaxial or pseudo-epitaxial growth on residual particles on the substrate surface. At higher temperatures (Ts > 875°C), heterogeneous nucleation of diamond on Si3N4 occurs with an apparent activation energy ( Eahet ) of ˜ 18 kcal/mol. From an Arrhenius plot of particle growth rate, the activation energy (Ea) for diamond growth was calculated to be ˜ 9 kcal/mol. These results suggest that the energy barrier associated with the heterogeneous nucleation process ( Eahet > Ea) may in fact be responsible for the observed low nucleation densities on Si3N4 substrates. Consequently, nucleation density on Si3N4 is limited by the concentration of available sites for nuclei formation. As surface diffusion to those sites was determined to be negligible, growth of stable nuclei occurs via direct impingement of gas phase species. Based on these conclusions, a multistage deposition technique was developed to deposit continuous diamond coatings on untreated Si3N4 substrates. This two stage technique consisted of (i) an in situ flame pretreatment of the substrate to enhance nucleation through the formation of SiC and (ii) subsequent growth on the flame pretreated surface under optimized parameters. Using a previously developed compression test for brittle coating/substrate systems, the adhesion of multistage deposited coatings was compared

  15. Ion beam assisted deposition of tribological coatings

    SciTech Connect

    Sartwell, B.D.; Dillich, S.A.; Sprague, J.A.; Kant, R.A.; Smidt, F.A.

    1989-01-01

    During this period films prepared under a variety of processing conditions were examined by TEM to explore the relation between hardness and grain boundary porosity. It was found that porosity decreased (and hardness increased) as the Ar[sup +] ion to T atom arrival rate ratio increased. A systematic error in measuring film thickness under varying chamber pressures due to scattering of T atoms near substrate surface by Ar atoms from the ion gun was discovered and the apparatus was modified and recalibrated. Hardness measurements on thick TiN films (1.5-2.5[mu]m) deposited on an M50 steel and Si substrates were performed at 3 loads and compared to a 0.5[mu]m thick film. Effect of increasing R value on hardness was evident at all loads but film thicknesses in excess of 1.5Am were required to produce representative hardness values at 25 gr indent loads. Scratch test adhesion measurements performed on these thick films showed no indication of brittle fracture and no indication of decohesion at loads up to 100N, well above the critical load of 30 Newtons expected for a sputtered TiN film. Additional experiments on effect of residual pressure on film properties were initiated.

  16. Environmental Barrier Coatings for Silicon-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Fox, Dennis S.; Robinson, Raymond C.; Bansal, Narottam P.

    2001-01-01

    Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based ceramics, however, suffer from rapid surface recession in combustion environments due to volatilization of the silica scale via reaction with water vapor, a major product of combustion. Therefore, application of silicon-based ceramic components in the hot section of advanced gas turbine engines requires development of a reliable method to protect the ceramic from environmental attack. An external environmental barrier coating (EBC) is considered a logical approach to achieve protection and CP long-term stability. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 Wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program (5). They consist of three layers, a silicon first bond coat, a mullite or a mullite + BSAS (BaO(1-x)-SrO(x)-Al2O3-2SiO2) second bond coat, and a BSAS top coat. The EPM EBCs were applied on SiC/SiC CMC combustor liners in three Solar Turbines (San Diego, CA) Centaur 50s gas turbine engines. The combined operation of the three engines has accumulated over 24,000 hours without failure (approximately 1,250 C maximum combustor liner temperature), with the engine in Texaco, Bakersfield, CA, accumulating about 14,000 hours. As the

  17. ZrN coatings deposited by high power impulse magnetron sputtering and cathodic arc techniques

    SciTech Connect

    Purandare, Yashodhan Ehiasarian, Arutiun; Hovsepian, Papken; Santana, Antonio

    2014-05-15

    Zirconium nitride (ZrN) coatings were deposited on 1 μm finish high speed steel and 316L stainless steel test coupons. Cathodic Arc (CA) and High Power Impulse Magnetron Sputtering (HIPIMS) + Unbalanced Magnetron Sputtering (UBM) techniques were utilized to deposit coatings. CA plasmas are known to be rich in metal and gas ions of the depositing species as well as macroparticles (droplets) emitted from the arc sports. Combining HIPIMS technique with UBM in the same deposition process facilitated increased ion bombardment on the depositing species during coating growth maintaining high deposition rate. Prior to coating deposition, substrates were pretreated with Zr{sup +} rich plasma, for both arc deposited and HIPIMS deposited coatings, which led to a very high scratch adhesion value (L{sub C2}) of 100 N. Characterization results revealed the overall thickness of the coatings in the range of 2.5 μm with hardness in the range of 30–40 GPa depending on the deposition technique. Cross-sectional transmission electron microscopy and tribological experiments such as dry sliding wear tests and corrosion studies have been utilized to study the effects of ion bombardment on the structure and properties of these coatings. In all the cases, HIPIMS assisted UBM deposited coating fared equal or better than the arc deposited coatings, the reasons being discussed in this paper. Thus H+U coatings provide a good alternative to arc deposited where smooth, dense coatings are required and macrodroplets cannot be tolerated.

  18. Design and Environmental Factors Contributing to the Failure of Thermal Barrier Coating Systems

    NASA Astrophysics Data System (ADS)

    Weeks, Matthew David

    Gas turbine engines are a staple of 21st century air and sea propulsion systems and are also a critical component in large-scale electricity generation. The hot-section components of these engines are protected by a complex ceramic and metal multi-layer coating called a thermal barrier coating (TBC) system. The failure of TBC systems occurs as a result of both thermo-chemical and thermo-mechanical degradation. This research involves exploring both of these mechanisms for two distinctly different issues. The United States Navy is currently making a push to implement the use of alternative fuels by 2012, but the use of these fuels (syngas, high hydrogen content, and alternatives to JP-8) presents significant materials durability challenges. Initial data suggests that high water vapor levels, high sulfur concentrations, and ash deposits from fuel impurities lead to unique, and severe, degradation modes. This research is aimed at addressing the effects of differing combustion environment characteristics on the corrosion and oxidation of TBC systems. On the industrial front, there is a constant driver to better understand and predict coating failure, particularly in air-plasma sprayed (APS) TBC systems. The morphology of the metal-ceramic interface is known to play a key role in the generation of compressive and tensile stresses that eventually cause coating failure in typical engine environments. Experimental evidence and field experience have shown that a tortuous interface is generally beneficial to coating lifetime. Nevertheless, for the past 40 years engineers have struggled to find a functional correlation between BC topology and coating system lifetime. This document also addresses the progress that has been made toward the establishment of this functional correlation.

  19. Nondestructive evaluation of environmental barrier coatings in CFCC combustor liners.

    SciTech Connect

    Sun, J. G.; Benz, J.; Ellingson, W. A.; Kimmel, J. B.; Price, J. R.; Energy Technology; Solar Turbines, Inc

    2007-01-01

    Advanced combustor liners fabricated of SiC/SiC continuous fiber-reinforced ceramic composite (CFCC) and covered with environmental barrier coatings (EBCs) have been successfully tested in Solar Turbines Inc. field engines. The primary goal for the CFCC/EBC liners is to reach a 30,000-h lifetime. Because the EBCs, when applied on the hot surfaces of liners, protect the underlying CFCC from oxidation damage, their performance is critical in achieving the lifetime goal. To determine CFCC/EBC liner condition and assess operating damage, the liners were subjected to nondestructive evaluation (NDE) during various processing stages, as well as before and after the engine test. The NDE techniques included pulsed infrared thermal imaging, air-coupled ultrasonic scanning, and X-ray computerized tomography. It was found that EBC damage and spallation depend on the condition of the CFCC material. The NDE results and correlations with destructive examination are discussed.

  20. Environmental Barrier Coatings (EBC) for Ceramic Matrix Composite (CMC) Materials

    NASA Technical Reports Server (NTRS)

    Lee,Kang

    2001-01-01

    The upper use temperature of current Environmental Barrier Coatings (EBC's) based on mullite and BSAS (EPM EBC's) is limited to -255 F due to silica volatility, chemical reactions, and high thermal conductivity. Therefore, new EBC s having low CTE, good chemical compatibility, and high melting point (greater than 2700 F ) are being investigated. Sinter-resistant, low thermal conductivity EBC s are strongly desired to achieve the UEET EBC goal of 270 F EBC surface temperature and 30 F AT over long exposures (greater than 1000 hr). Key areas affecting the upper temperature limit of current EBC s as well as the ongoing efforts to develop next generation EBC s in the UEET Program will be discussed.

  1. Acoustic emission assessment of interface cracking in thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Yang, Li; Zhong, Zhi-Chun; Zhou, Yi-Chun; Zhu, Wang; Zhang, Zhi-Biao; Cai, Can-Ying; Lu, Chun-Sheng

    2016-04-01

    In this paper, acoustic emission (AE) and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression. The interface failure process can be identified via its AE features, including buckling, delamination incubation and spallation. According to the Fourier transformation of AE signals, there are four different failure modes: surface vertical cracks, opening and sliding interface cracks, and substrate deformation. The characteristic frequency of AE signals from surface vertical cracks is 0.21 MHz, whilst that of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. The energy released of the two types of interface cracks are 0.43 and 0.29 MHz, respectively. Based on the energy released from cracking and the AE signals, a relationship is established between the interface crack length and AE parameters, which is in good agreement with experimental results.

  2. Reliability assessment on interfacial failure of thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Guo, Jin-Wei; Yang, Li; Zhou, Yi-Chun; He, Li-Min; Zhu, Wang; Cai, Can-Ying; Lu, Chun-Sheng

    2016-10-01

    Thermal barrier coatings (TBCs) usually exhibit an uncertain lifetime owing to their scattering mechanical properties and severe service conditions. To consider these uncertainties, a reliability assessment method is proposed based on failure probability analysis. First, a limit state equation is established to demarcate the boundary between failure and safe regions, and then the failure probability is calculated by the integration of a probability density function in the failure area according to the first- or second-order moment. It is shown that the parameters related to interfacial failure follow a Weibull distribution in two types of TBC. The interfacial failure of TBCs is significantly affected by the thermal mismatch of material properties and the temperature drop in service.

  3. FGM (Functionally Graded Material) Thermal Barrier Coatings for Hypersonic Structures - Design and Thermal Structural Analysis

    DTIC Science & Technology

    2007-06-29

    1 AOARD REPORT Contract No. 064043 FGM (Functionally Graded Material) Thermal Barrier Coatings for Hypersonic Structures – Design and...Material) Thermal Barrier Coatings for Hypersonic Structures ? Design and Thermal Structural Analysis 5a. CONTRACT NUMBER FA48690610074 5b. GRANT...modeling. Additionally, the TBCs will be applied to realistic hypersonic structures such as a cylindrical combustor and tested under realistic combustion

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  5. Josephson tunnel junctions with chemically vapor deposited polycrystalline germanium barriers

    SciTech Connect

    Kroger, H.; Jillie, D.W.; Smith, L.N.; Phaneuf, L.E.; Potter, C.N.; Shaw, D.M.; Cukauskas, E.J.; Nisenoff, M.

    1984-03-01

    High quality Josephson tunnel junctions have been fabricated whose tunneling barrier is polycrystalline germanium chemically vapor deposited on a NbN base electrode and covered by a Nb counterelectrode. These junctions have excellent characteristics for device applications: values of V/sub m/ (the product of the critical current and the subgap resistance measured at 2 mV and 4.2 K) ranging between 35--48 mV, ideal threshold curves, a steep current rise at the gap voltage, and Josephson current densities from 100 to 1100 A/cm/sup 2/.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  7. Hot-Corrosion Behavior of Thermal Barrier Coated DZ125 Superalloy Exposed to Atomized Seawater and Kerosene

    NASA Astrophysics Data System (ADS)

    Bai, Zhiming; Zhou, Le; Liang, Tianquan; Guo, Hongbo; Gong, Shengkai

    The bare superalloy DZ 125 alloy, the aluminide coated specimens and electron beam physical vapor deposited (EB-PVD) thermal barrier coating (TBC) consisting of yttria stabilizied zirconia (YSZ) topcoat and NiCoCrAlY bond coat specimens were exposed to atomized seawater and kerosene at 900°C and the cyclic hot-corrosion behaviors of the specimens were investigated. Disastrous spallation of the bare superalloy occurred within 50 h hot-corrosion. In contrast to this, after 100 h hot-corrosion, the average mass change for the aluminized and TBC coated specimens is 0.7 mg/cm2 and 0.63 mg/cm2, respectively, exhibiting excellent hot-corrosion resistance.

  8. Vibration atomic layer deposition for conformal nanoparticle coating

    SciTech Connect

    Park, Suk Won; Woo Kim, Jun; Jong Choi, Hyung; Hyung Shim, Joon

    2014-01-15

    A vibration atomic layer deposition reactor was developed for fabricating a conformal thin-film coating on nanosize particles. In this study, atomic layer deposition of 10–15-nm-thick Al{sub 2}O{sub 3} films was conducted on a high-surface-area acetylene black powder with particle diameters of 200–250 nm. Intense vibration during the deposition resulted in the effective separation of particles, overcoming the interparticle agglomeration force and enabling effective diffusion of the precursor into the powder chunk; this phenomenon led to the formation of a conformal film coating on the nanopowder particles. It was also confirmed that the atomic layer deposition Al{sub 2}O{sub 3} films initially grew on the high-surface-area acetylene black powder particles as discrete islands, presumably because chemisorption of the precursor and water occurred only on a few sites on the high-surface-area acetylene black powder surface. Relatively sluggish growth of the films during the initial atomic layer deposition cycles was identified from composition analysis.

  9. Emittance and absorptance of NASA ceramic thermal barrier coating system. [for turbine cooling

    NASA Technical Reports Server (NTRS)

    Liebert, C. H.

    1978-01-01

    Spectral emittance measurements were made on a two-layer ceramic thermal barrier coating system consisting of a metal substrate, a NiCrAly bond coating and a yttria-stabilized zirconia ceramic coating. Spectral emittance data were obtained for the coating system at temperatures of 300 to 1590 K, ceramic thickness of zero to 0.076 centimeter, and wavelengths of 0.4 to 14.6 micrometers. The data were transformed into total hemispherical emittance values and correlated with respect to ceramic coating thickness and temperature using multiple regression curve fitting techniques. The results show that the ceramic thermal barrier coating system is highly reflective and significantly reduces radiation heat loads on cooled gas turbine engine components. Calculation of the radiant heat transfer within the nonisothermal, translucent ceramic coating material shows that the gas-side ceramic coating surface temperature can be used in heat transfer analysis of radiation heat loads on the coating system.

  10. Synthesis of mullite coatings by chemical vapor deposition

    SciTech Connect

    Mulpuri, R.P.; Auger, M.; Sarin, V.K.

    1996-08-01

    Formation of mullite on ceramic substrates via chemical vapor deposition was investigated. Mullite is a solid solution of Al{sub 2}O{sub 3} and SiO{sub 2} with a composition of 3Al{sub 2}O{sub 3}{circ}2SiO{sub 2}. Thermodynamic calculations performed on the AlCl{sub 3}-SiCl{sub 4}-CO{sub 2}-H{sub 2} system were used to construct equilibrium CVD phase diagrams. With the aid of these diagrams and consideration of kinetic rate limiting factors, initial process parameters were determined. Through process optimization, crystalline CVD mullite coatings have been successfully grown on SiC and Si{sub 3}N{sub 4} substrates. Results from the thermodynamic analysis, process optimization, and effect of various process parameters on deposition rate and coating morphology are discussed.

  11. Thermochromism of sputter-deposited vanadium oxyfluoride coatings

    SciTech Connect

    Khan, K.A.; Granqvist, C.G.

    1990-12-31

    Thermochromism offers interesting possibilities for controlling the radiative throughput through windows, as well as for numerous other applications. The purpose of this brief paper is to point at the potential and prospects of using sputter-deposited vanadium oxyfluoride coatings. A thermochromic coating, suitable for energy-efficient windows, is characterized by a transmittance which drops as the temperature goes above a certain comfort temperature.Thermochromism in VO{sub 2}-based materials is well known; it is connected with a reversible structural transition from a low-temperature monoclinic phase to a high-temperature phase with metallic-like properties. The metallic phase is characterized by a plasma wavelength at {approximately} 1 {mu}m. Hence it is possible to accomplish a temperature-dependent modulation of the near-infrared transmittance. In order to produce a practically useful window coating, the VO{sub 2}-based material must be processed suitably. The authors discuss how magnetron sputtering can be used for (potential) large-area deposition. Among the many alternative approaches for depressing the phase change temperature they note the replacement of oxygen by fluorine and the introduction of stress either from the substrate or from a suitable overlayer. The work reported here deals with fluorination through reactive sputter deposition. A key result, reported below, is that the fluorination leads to a significant decrease of the luminous absorptance. Finally, it may be that a practical window coating must invoke a three-layer design with a VO{sub 2}-based coating embedded between antireflecting dielectric layers; this latter point will not be pursued further here.

  12. Novel Functionally Graded Thermal Barrier Coatings in Coal-Fired Power Plant Turbines

    SciTech Connect

    Zhang, Jing

    2016-11-01

    This project presents a detailed investigation of a novel functionally graded coating material, pyrochlore oxide, for thermal barrier coating (TBC) in gas turbines used in coal-fired power plants. Thermal barrier coatings are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The ultimate goal of this research is to develop a manufacturing process to produce the novel low thermal conductivity and high thermal stability pyrochlore oxide based coatings with improved high-temperature durability. The current standard TBC, yttria stabilized zirconia (YSZ), has service temperatures limited to <1200°C, due to sintering and phase transition at higher temperatures. In contrast, pyrochlore oxide, e.g., lanthanum zirconate (La2Zr2O7, LZ), has demonstrated lower thermal conductivity and better thermal stability, which are crucial to high temperature applications, such as gas turbines used in coal-fired power plants. Indiana University – Purdue University Indianapolis (IUPUI) has collaborated with Praxair Surface Technologies (PST), and Changwon National University in South Korea to perform the proposed research. The research findings are critical to the extension of current TBCs to a broader range of high-temperature materials and applications. Several tasks were originally proposed and accomplished, with additional new opportunities identified during the course of the project. In this report, a description of the project tasks, the main findings and conclusions are given. A list of publications and presentations resulted from this research is listed in the Appendix at the end of the report.

  13. Thermal barrier coatings for thermal insulation and corrosion resistance in industrial gas turbine engines

    NASA Technical Reports Server (NTRS)

    Vogan, J. W.; Hsu, L.; Stetson, A. R.

    1981-01-01

    Four thermal barrier coatings were subjected to a 500-hour gas turbine engine test. The coatings were two yttria stabilized zirconias, calcium ortho silicate and calcium meta titanate. The calcium silicate coating exhibited significant spalling. Yttria stabilized zirconia and calcium titanate coatings showed little degradation except in blade leading edge areas. Post-test examination showed variations in the coating due to manual application techniques. Improved process control is required if engineering quality coatings are to be developed. The results indicate that some leading edge loss of the coating can be expected near the tip.

  14. Atmospheric Plasma Deposition of Diamond-like Carbon Coatings

    SciTech Connect

    Ladwig, Angela

    2008-01-23

    There is great demand for thin functional coatings in the semiconductor, optics, electronics, medical, automotive and aerospace industries [1-13]. As fabricated components become smaller and more complex, the properties of the materials’ surface take on greater importance. Thin coatings play a key role in tailoring surfaces to give them the desired hardness, wear resistance, chemical inertness, and electrical characteristics. Diamond-like carbon (DLC) coatings possess an array of desirable properties, including outstanding abrasion and wear resistance, chemical inertness, hardness, a low coefficient of friction and exceptionally high dielectric strength [14-22]. Diamond-like carbon is considered to be an amorphous material, containing a mixture of sp2 and sp3 bonded carbon. Based on the percentage of sp3 carbon and the hydrogen content, four different types of DLC coatings have been identified: tetrahedral carbon (ta-C), hydrogenated amorphous carbon (a-C:H) hard, a-C:H soft, and hydrogenated tetrahedral carbon (ta-C:H) [20,24,25]. Possessing the highest hardness of 80 GPa, ta-C possesses an sp3 carbon content of 80 to 88u%, and no appreciable hydrogen content whereas a-C:H soft possesses a hardness of less than 10 GPa, contains an sp3 carbon content of 60% and a hydrogen content between 30 to 50%. Methods used to deposit DLC coatings include ion beam deposition, cathodic arc spray, pulsed laser ablation, argon ion sputtering, and plasma-enhanced chemical vapor deposition [73-83]. Researchers contend that several advantages exist when depositing DLC coatings in a low-pressure environment. For example, ion beam processes are widely utilized since the ion bombardment is thought to promote denser sp3-bonded carbon networks. Other processes, such as sputtering, are better suited for coating large parts [29,30,44]. However, the deposition of DLC in a vacuum system has several disadvantages, including high equipment cost and restrictions on the size and shape of

  15. Chemical vapor deposition coating of fibers using microwave application

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Hoover, Gordon (Inventor); Jackson, Henry W. (Inventor)

    2000-01-01

    Chemical vapor deposition coating is carried out in a cylindrical cavity. The fibers are heated by a microwave source that is uses a TM0N0 mode, where O is an integer, and produces a field that depends substantially only on radius. The fibers are observed to determine their heating, and their position can be adjusted. Once the fibers are uniformly heated, a CVD reagent is added to process the fibers.

  16. Residual Stress Analysis of Laser-Drilled Thermal Barrier Coatings Involving Various Bond Coats

    NASA Astrophysics Data System (ADS)

    Guinard, C.; Montay, G.; Guipont, V.; Jeandin, M.; Girardot, J.; Schneider, M.

    2015-01-01

    The gas turbine combustion chamber of aero-engines requires a thermal barrier coating (TBC) by thermal spraying. Further heat protection is achieved by laser drilling of cooling holes. The residual stresses play an important role in the mechanical behaviour of TBC. It could also affect the TBC response to delamination during laser drilling. In this work, studies of the cracking behaviour after laser drilling and residual stress distribution have been achieved for different bond coats by plasma spray or cold spray. From interface crack length measured pulse-by-pulse after laser percussion drilling at 20° angle, the role of the various bond coats on crack initiation and propagation are investigated. It is shown that the bond coat drastically influences the cracking behaviour. The residual stresses profiles were also determined by the incremental hole-drilling method involving speckle interferometry. An original method was also developed to measure the residual stress profiles around a pre-drilled zone with a laser beam at 90°. The results are discussed to highlight the influence of TBCs interfaces on the resulting residual stresses distribution before laser drilling, and also to investigate the modification around the hole after laser drilling. It is shown that laser drilling could affect the residual stress state.

  17. Shear strength of a thermal barrier coating parallel to the bond coat

    SciTech Connect

    Cruse, T.A.; Dommarco, R.C.; Bastias, P.C.

    1998-01-01

    The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard Iosipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.

  18. Pulsed laser deposition of strontium-substituted hydroxyapatite coatings

    NASA Astrophysics Data System (ADS)

    Pereiro, I.; Rodríguez-Valencia, C.; Serra, C.; Solla, E. L.; Serra, J.; González, P.

    2012-09-01

    The growing evidence of the beneficial role of strontium in bone has increased the interest of developing strontium-containing biomaterials for medical applications, and specifically biocompatible coatings that can be deposited on metallic implants to benefit from their load-bearing capabilities. In this work, strontium-substituted hydroxyapatite (Sr-HA) coatings have been fabricated by pulsed laser deposition (PLD) from initial targets obtained after mixing and compacting commercial HA and SrCO3 powders in different proportions. The films thus fabricated were then structurally, morphologically and chemically characterized using scanning electron microscopy, optical profilometry, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The macroscopic morphology of the films presented in all cases equivalent spherical shaped aggregates of typical calcium phosphate coatings. The results reveal, however, the incorporation of Sr2+ and carbonate groups in the coatings as a function of the SrCO3 content in the ablation target, being the incorporation of Sr2+ a linear phenomenon that is accompanied by a similarly linear withdrawal of Ca2+. The role of Sr2+ in the modification of the HA structure and a possible mechanism of substitution of Sr2+ atoms in place of Ca2+ atoms are discussed.

  19. Method of applying a bond coating and a thermal barrier coating on a metal substrate, and related articles

    DOEpatents

    Hasz, Wayne Charles; Borom, Marcus Preston

    2002-01-01

    A method for applying at least one bond coating on a surface of a metal-based substrate is described. A foil of the bond coating material is first attached to the substrate surface and then fused thereto, e.g., by brazing. The foil is often initially prepared by thermally spraying the bond coating material onto a removable support sheet, and then detaching the support sheet. Optionally, the foil may also include a thermal barrier coating applied over the bond coating. The substrate can be a turbine engine component.

  20. Plasma-Sprayed Ceramic Coatings for Barrier Applications Against Molten Uranium Corrosion

    NASA Astrophysics Data System (ADS)

    Ananthapadmanabhan, P. V.; Chakravarthy, Y.; Chaturvedi, Vandana; Thiyagarajan, T. K.; Pragatheeswaran, A.

    2015-07-01

    Ceramic coatings are applied on engineering components for protecting them from large thermal load and hot corrosion. Choices of coating material for protection against hot corrosion by uranium are few, because of its high reactivity. Yttrium oxide has a high melting temperature and is inert towards uranium. Therefore, yttrium oxide coatings are effective as a barrier against hot corrosion by uranium and its alloys. This paper gives a summary of the developmental work on plasma-sprayed yttria coatings for corrosion barrier applications against molten uranium. Results show that plasma-sprayed yttria coatings offer a long-term solution to hot corrosion problems.

  1. Crystalline ha coating on peek via chemical deposition

    NASA Astrophysics Data System (ADS)

    Almasi, D.; Izman, S.; Assadian, M.; Ghanbari, M.; Abdul Kadir, M. R.

    2014-09-01

    Polyether ether ketone (PEEK) has a similar elastic modulus to bone and can be a suitable alternative to metallic implants. However, PEEK is bioinert and does not integrate well with the surrounding tissues. The current commercial method for solving this problem is by coating PEEK substrates with calcium phosphates via plasma spraying. However, this method produces a low bonding strength between the substrate and the coating layer, as well as non-uniform density of the coating. In this study, chemical deposition was used to deposit HA crystalline particles on PEEK substrate without any subsequent crystallisation process therefore producing crystalline treated layer. EDX results confirmed the deposition of HA, and the XRD results confirmed that the treated layer was crystalline HA. FT-IR analysis confirmed the chemical bonding between HA and the substrate. Surface roughness increased from 24.27 nm to 34.08 nm for 3 min immersion time. The water contact angle showed an increase in wettability of the treated sample from 71.6 to 36.4 degrees, which in turn increased its bioactivity. The proposed method is a suitable alternative to other conventional methods as high temperature was not involved in the process which could damage the surface of the substrate.

  2. Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

    2010-01-01

    Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

  3. Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Schmitt, Michael P.; Rai, Amarendra K.; Zhu, Dongming; Dorfman, Mitchell R.; Wolfe, Douglas E.

    2015-01-01

    To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability.

  4. Microstructure and characterization of a novel cobalt coating prepared by cathode plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Quan, Cheng; He, Yedong

    2015-10-01

    A novel cobalt coating was prepared by cathode plasma electrolytic deposition (CPED). The kinetics of the electrode process in cathode plasma electrolytic deposition was studied. The composition and microstructure of the deposited coatings were investigated by SEM, EDS, XRD and TEM. The novel cobalt coatings were dense and uniform, showing a typically molten morphology, and were deposited with a rather fast rate. Different from the coatings prepared by conventional electrodeposition or chemical plating, pure cobalt coatings with face center cubic (fcc) structure were obtained by CPED. The deposited coatings were nanocrystalline structure with an average grain size of 40-50 nm, exhibited high hardness, excellent adhesion with the stainless steels, and superior wear resistance. The properties of the novel cobalt coatings prepared by CPED have been improved significantly, as compared with that prepared by conventional methods. It reveals that cathode plasma electrolytic deposition is an effective way to prepare novel cobalt coatings with high quality.

  5. EVALUATION OF BARRIERS TO THE USE OF RADIATION-CURED AND HOT MELT COATINGS IN COATED AND LAMINATED SUBSTRATE MANUFACTURING

    EPA Science Inventory

    The report gives results of a study to investigate and identify the technical, educational, and economic barriers to the use and implementation of radiation-cured and hot melt coatings in coated and laminated substrate manufacturing. (NOTE: In support of EPA's Source Reduction Re...

  6. EVALUATION OF BARRIERS TO THE USE OF RADIATION-CURED AND HOT MELT COATINGS IN COATED AND LAMINATED SUBSTRATE MANUFACTURING

    EPA Science Inventory

    The report gives results of a study to investigate and identify the technical, educational, and economic barriers to the use and implementation of radiation-cured and hot melt coatings in coated and laminated substrate manufacturing. (NOTE: In support of EPA's Source Reduction Re...

  7. Vapors and Droplets Mixture Deposition of Metallic Coatings by Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Vautherin, B.; Planche, M.-P.; Bolot, R.; Quet, A.; Bianchi, L.; Montavon, G.

    2014-04-01

    In recent years, the very low pressure plasma-spraying (VLPPS) process has been intensely developed and implemented to manufacture thin, dense and finely structured ceramic coatings for various applications, such as Y2O3 for diffusion barriers, among other examples. This paper aims at presenting developments carried out on metallic coatings. Aluminum was chosen as a demonstrative material due to its "moderate" vaporization enthalpy (i.e., 38.23 KJ cm-3) compared to the one of copper (i.e., 55.33 KJ cm-3), cobalt (i.e., 75.03 KJ cm-3), or even tantalum (i.e., 87.18 KJ cm-3). The objective of this work is primarily to better understand the behavior of a solid precursor injected into the plasma jet leading to the formation of vapors and to better control the factors affecting the coating structure. Nearly dense aluminum coatings were successfully deposited by VLPPS at 100 Pa with an intermediate power plasma torch (i.e., Sulzer Metco F4 type gun with maximum power of 45 kW). Optical emission spectroscopy (OES) was implemented to study and analyze the vapor behavior into the plasma jet. Simplified CFD modeling allowed better understanding of some of the thermo-physical mechanisms. The effect of powder-size distribution, substrate temperature and spray distance were studied. The phase composition and microstructural features of the coatings were characterized by XRD and SEM. Moreover, Vickers microhardness measurements were implemented.

  8. SnS thin films deposited by chemical bath deposition, dip coating and SILAR techniques

    NASA Astrophysics Data System (ADS)

    Chaki, Sunil H.; Chaudhary, Mahesh D.; Deshpande, M. P.

    2016-05-01

    The SnS thin films were synthesized by chemical bath deposition (CBD), dip coating and successive ionic layer adsorption and reaction (SILAR) techniques. In them, the CBD thin films were deposited at two temperatures: ambient and 70 °C. The energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and optical spectroscopy techniques were used to characterize the thin films. The electrical transport properties studies on the as-deposited thin films were done by measuring the I-V characteristics, DC electrical resistivity variation with temperature and the room temperature Hall effect. The obtained results are deliberated in this paper.

  9. Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

    1998-01-01

    Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

  10. Optical coatings in microscale channels by atomic layer deposition.

    PubMed

    Gabriel, Nicholas T; Talghader, Joseph J

    2010-03-10

    High-aspect-ratio channels may be coated using atomic layer deposition (ALD) due to the unique self-limiting nature of the process, and this has been often demonstrated using deep reactive-ion etched trenches in silicon. However, for optical and microfluidic applications, many channels are centimeters deep with diameters of tens to hundreds of micrometers, and the relatively large area exposes more difficult problems of temperature and gas flow uniformity. To quantify the uniformity of optical coatings deposited by ALD under those conditions, an air wedge has been created between two square wafers of silicon approximately 7 cm on a side, with the air gap varying linearly from 0-1560 microm. ALD aluminum oxide uniformity is astounding, while hafnium oxide shows a need for process optimization, but still exceeds the capability observed in other deposition techniques. A six-layer Fabry-Perot optical cavity with fixed 500 nm resonance was deposited inside a wedge, and the measured resonant wavelength closely matched predictions, except at the deepest regions of the wedge.

  11. Defect Clustering and Nano-phase Structure Characterization of Multicomponent Rare Earth-Oxide-Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2004-01-01

    Advanced thermal barrier coatings (TBCs) have been developed by incorporating multicomponent rare earth oxide dopants into zirconia-based thermal barrier coatings to promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nanophases within the coating systems. In this paper, the defect clusters, induced by Nd, Gd, and Yb rare earth dopants in the zirconia-yttria thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The TEM lattice imaging, selected area diffraction (SAD), and electron energy-loss spectroscopy (EELS) analyses demonstrated that the extensive nanoscale rare earth dopant segregation exists in the plasma-sprayed and electron-physical-vapor-deposited (EB PVD) thermal barrier coatings. The nanoscale concentration heterogeneity and the resulting large lattice distortion promoted the formation of parallel and rotational defective lattice clusters in the coating systems. The presence of the 5-to 100-nm-sized defect clusters and nanophases is believed to be responsible for the significant reduction of thermal conductivity, improved sintering resistance, and long-term high temperature stability of the advanced thermal barrier coating systems.

  12. Microfibrillated cellulose and borax as mechanical, O₂-barrier, and surface-modulating agents of pullulan biocomposite coatings on BOPP.

    PubMed

    Cozzolino, Carlo A; Campanella, Gaetano; Türe, Hasan; Olsson, Richard T; Farris, Stefano

    2016-06-05

    Multifunctional composite coatings on bi-oriented polypropylene (BOPP) films were obtained using borax and microfibrillated cellulose (MFC) added to the main pullulan coating polymer. Spectroscopy analyses suggested that a first type of interaction occurred via hydrogen bonding between the C6OH group of pullulan and the hydroxyl groups of boric acid, while monodiol and didiol complexation represented a second mechanism. The deposition of the coatings yielded an increase in the elastic modulus of the entire plastic substrate (from ∼2GPa of the neat BOPP to ∼3.1GPa of the P/B+/MFC-coated BOPP). The addition of MFC yielded a decrease of both static and kinetic coefficients of friction of approximately 22% and 25%, respectively, as compared to the neat BOPP. All composite coatings dramatically increased the oxygen barrier performance of BOPP, especially under dry conditions. The deposition of the high hydrophilic coatings allowed to obtain highly wettable surfaces (water contact angle of ∼18°). Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Gadolinia doped hafnia (Gd2O3- HfO 2) thermal barrier coatings for gas turbine applications

    NASA Astrophysics Data System (ADS)

    Gullapalli, Satya Kiran

    Thermal efficiency of the gas turbines is influenced by the operating temperature of the hot gas path components. The material used for the hot gas path components can only withstand temperature up to a certain limit. Thermal barrier coatings (TBC) provide the additional thermal protection for these components and help the gas turbine achieve higher firing temperatures. Traditionally available yttria stabilized zirconia (YSZ) TBCs have a limitation up to 1200 C due to their phase transformation. The present work focuses on gadolinia based hafnia (GSH) TBCs to study their potential to replace the YSZ coatings. Different compositions of gadolinia doped hafnia coatings have been deposited using electron beam physical vapor deposition (EB-PVD) technique and characterized using x-ray diffraction (XRD) and scanning electron microscope (SEM). The crystal structure analysis performed using XRD confirmed the stabilization of the high temperature cubic phase of hafnia. Cross sectional analysis confirmed the presence of columnar structure in the coatings which is a signature of the EB-PVD coatings. Mechanical properties of the coatings were investigated using nanoindentation and nano impact testing at both room temperature and high temperature. Indentation tests indicate a reduction in hardness with an increase in temperature and gadolinia content in hafnia. Impact testing reveals the fracture resistance of the coatings as a function of stabilizer content and heat treatment. Thermal measurements and impedance testing was performed on the bulk material to study the effect of gadolinia content. Thermal cycling was performed to study the spallation behavior of the as deposited and aged samples. Finite element models were developed to study the interfacial stress development in the coatings subjected to thermal cycling.

  14. Liquid Feedstock Plasma Spraying: An Emerging Process for Advanced Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Markocsan, Nicolaie; Gupta, Mohit; Joshi, Shrikant; Nylén, Per; Li, Xin-Hai; Wigren, Jan

    2017-08-01

    Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.

  15. Application of the dielectric barrier discharge to detect defects in a teflon coated metal surface

    NASA Astrophysics Data System (ADS)

    Ebihara, Kenji; Tanaka, Takahiro; Ikegami, Tomoaki; Yamagata, Yukihiko; Matsunaga, Toru; Yamashita, Kazutaka; Oyama, Yoshifumi

    2003-12-01

    In the semiconductor industry, flexible stainless steel tubes, the inside of which are coated with thick Teflon films, by the splay coating method, have been used to prevent their degradation and erosion by organic solvents. We have developed an inspection system to detect pinholes and cracks in the deposited Teflon films, and the dielectric barrier discharge (DBD) was employed to reduce residual substances and damages to the coated film in the tube. Conducting water contained in the cylinder-like glass pipe was used as a liquid electrode to apply a high voltage at any portion of the tube tested. A defective part with a pinhole was modelled by a point electrode in this experiment, because the uncoated defective part has a lower electric breakdown voltage. High frequency voltage (10 kHz) was applied between the point electrode and the liquid electrode. The level of the liquid electrode was varied to detect the occurrence of a microdischarge. It is found that the number of current pulses due to the microdischarge can be used to estimate the size and location of the defective uncoated point of the sample tube.

  16. Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2005-01-01

    When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

  17. Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

    NASA Astrophysics Data System (ADS)

    Mao, Shoudong; Yang, Hengxiu; Li, Jinlong; Huang, Feng; Song, Zhenlun

    2011-04-01

    Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar+ ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar+ ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.

  18. Investigation into Spectroscopic Techniques for Thermal Barrier Coating Spall Detection

    NASA Technical Reports Server (NTRS)

    deGroot, Wim; Opila, Beth

    2001-01-01

    Spectroscopic methods are proposed for detection of thermal barrier coating (TBC) spallation from engine hot zone components. These methods include absorption and emission of airborne marker species originally embedded in the TBC bond coat. In this study, candidate marker materials for this application were evaluated. Thermochemical analysis of candidate marker materials combined with additional constraints such as toxicity and uniqueness to engine environment, provided a short list of four potential species: platinum, copper oxide, zinc oxide. and indium. The melting point of indium was considered to be too low for serious consideration. The other three candidate marker materials, platinum, copper oxide, and zinc oxide were placed in a high temperature furnace and emission and absorption properties were measured over a temperature range from 800-1400 C and a spectral range from 250 to 18000 nm. Platinum did not provide the desired response, likely due to the low vapor Pressure of the metallic species and the low absorption of the oxide species. It was also found, however. that platinum caused a broadening of the carbon dioxide absorption at 4300 nm. The nature of this effect is not known. Absorption and emission caused by sodium and potassium impurities in the platinum were found in the platinum tests. Zinc oxide did not provide the desired response, again, most likely due to the low vapor pressure of the metallic species and the low absorption of the oxide species. Copper oxide generated two strongly temperature dependent absorption peaks at 324.8 and 327.4 nm. The melting point of copper oxide was determined to be too low for serious consideration as marker material.

  19. Environmental degradation of oxidation resistant and thermal barrier coatings for fuel-flexible gas turbine applications

    NASA Astrophysics Data System (ADS)

    Mohan, Prabhakar

    The development of thermal barrier coatings (TBCs) has been undoubtedly the most critical advancement in materials technology for modern gas turbine engines. TBCs are widely used in gas turbine engines for both power-generation and propulsion applications. Metallic oxidation-resistant coatings (ORCs) are also widely employed as a stand-alone protective coating or bond coat for TBCs in many high-temperature applications. Among the widely studied durability issues in these high-temperature protective coatings, one critical challenge that received greater attention in recent years is their resistance to high-temperature degradation due to corrosive deposits arising from fuel impurities and CMAS (calcium-magnesium-alumino-silicate) sand deposits from air ingestion. The presence of vanadium, sulfur, phosphorus, sodium and calcium impurities in alternative fuels warrants a clear understanding of high-temperature materials degradation for the development of fuel-flexible gas turbine engines. Degradation due to CMAS is a critical problem for gas turbine components operating in a dust-laden environment. In this study, high-temperature degradation due to aggressive deposits such as V2O5, P2O 5, Na2SO4, NaVO3, CaSO4 and a laboratory-synthesized CMAS sand for free-standing air plasma sprayed (APS) yttria stabilized zirconia (YSZ), the topcoat of the TBC system, and APS CoNiCrAlY, the bond coat of the TBC system or a stand-alone ORC, is examined. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. This study demonstrated that the V2O5 melt degrades the APS YSZ through the formation of ZrV2O7 and YVO 4 at temperatures below 747°C and above 747°C, respectively. Formation of YVO4 leads to the depletion of the Y2O 3 stabilizer and the deleterious transformation of the YSZ to the monoclinic ZrO2 phase. The investigation on the YSZ degradation by Na 2SO4 and a Na2SO4 + V2

  20. Calcium-magnesium Aluminosilicate (CMAS) Interactions with Advanced Environmental Barrier Coating Material

    NASA Technical Reports Server (NTRS)

    Wiesner, Valerie L.; Bansal, Narottam P.

    2015-01-01

    Particulates, like sand and volcanic ash, threaten the development of robust environmental barrier coatings (EBCs) that protect next-generation silicon-based ceramic matrix composite (CMC) turbine engine components from harsh combustion environments during service. The siliceous particulates transform into molten glassy deposits of calcium-magnesium aluminosilicate (CMAS) when ingested by an aircraft engine operating at temperatures above 1200C. In this study, a sample of desert sand was melted into CMAS glass to evaluate high-temperature interactions between the sand glass and an advanced EBC material. Desert sand glass was added to the surface of hot-pressed EBC substrates, which were then heated in air at temperatures ranging from 1200C to 1500C. Scanning electron microscopy and X-ray energy-dispersive spectroscopy were used to evaluate microstructure and phase compositions of specimens and the CMASEBC interface after heat treatments.

  1. Atomic-scale insight and design principles for turbine engine thermal barrier coatings from theory

    PubMed Central

    Marino, Kristen A.; Hinnemann, Berit; Carter, Emily A.

    2011-01-01

    To maximize energy efficiency, gas turbine engines used in airplanes and for power generation operate at very high temperatures, even above the melting point of the metal alloys from which they are comprised. This feat is accomplished in part via the deposition of a multilayer, multicomponent thermal barrier coating (TBC), which lasts up to approximately 40,000 h before failing. Understanding failure mechanisms can aid in designing circumvention strategies. We review results of quantum mechanics calculations used to test hypotheses about impurities that harm TBCs and transition metal (TM) additives that render TBCs more robust. In particular, we discovered a number of roles that Pt and early TMs such as Hf and Y additives play in extending the lifetime of TBCs. Fundamental insight into the nature of the bonding created by such additives and its effect on high-temperature evolution of the TBCs led to design principles that can be used to create materials for even more efficient engines.

  2. Thermal and Environmental Barrier Coating Development for Advanced Propulsion Engine Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.; Fox, Dennis S.

    2008-01-01

    Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. Advanced TEBCs that have significantly lower thermal conductivity, better thermal stability and higher toughness than current coatings will be beneficial for future low emission and high performance propulsion engine systems. In this paper, ceramic coating design and testing considerations will be described for turbine engine high temperature and high-heat-flux applications. Thermal barrier coatings for metallic turbine airfoils and thermal/environmental barrier coatings for SiC/SiC ceramic matrix composite (CMC) components for future supersonic aircraft propulsion engines will be emphasized. Further coating capability and durability improvements for the engine hot-section component applications can be expected by utilizing advanced modeling and design tools.

  3. NASA's Advanced Environmental Barrier Coatings Development for SiC/SiC Ceramic Matrix Composites: Understanding Calcium Magnesium Alumino-Silicate (CMAS) Degradations and Resistance

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming

    2014-01-01

    Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is essential to the viability and reliability of the envisioned CMC engine component applications, ensuring integrated EBC-CMC system durability and designs are achievable for successful applications of the game-changing component technologies and lifing methodologies.This paper will emphasize recent NASA environmental barrier coating developments for SiCSiC turbine airfoil components, utilizing advanced coating compositions, state-of-the-art processing methods, and combined mechanical and environment testing and durability evaluations. The coating-CMC degradations in the engine fatigue-creep and operating environments are particularly complex; one of the important coating development aspects is to better understand engine environmental interactions and coating life debits, and we have particularly addressed the effect of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the durability of the environmental barrier coating systems, and how the temperature capability, stability and cyclic life of the candidate rare earth oxide and silicate coating systems will be impacted in the presence of the CMAS at high temperatures and under simulated heat flux conditions. Advanced environmental barrier coating systems, including HfO2-Si with rare earth dopant based bond coat systems, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

  4. Factors Influencing Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    McGrann, Roy T. R.; Rybicki, Edmund F.; Shadley, John R.; Brindley, William J.

    1997-01-01

    To improve gas turbine and diesel engine performance using thermal barrier coatings (TBC's) requires an understanding of the factors that influence the in-service behavior of thermal barrier coatings. One of the many factors related to coating performance is the state of stress in the coating. The total stress state is composed of the stresses due to the in-service loading history and the residual stresses. Residual stresses have been shown to affect TBC life, the bond strength of thermal spray coatings, and the fatigue life of tungsten carbide coatings. Residual stresses are first introduced in TBC's by the spraying process due to elevated temperatures during processing and the difference in coefficients of thermal expansion of the top coat, bond coat, and substrate. Later, the residual stresses can be changed by the in-service temperature history due to a number of time and temperature dependent mechanisms, such as oxidation, creep, and sintering. Silica content has also been shown to affect sintering and the cyclic life of thermal barrier coatings. Thus, it is important to understand how the spraying process, the in-service thermal cycles, and the silica content can create and alter residual stresses in thermal barrier coatings.

  5. Vacuum deposited optical coatings experiment (AO 138-4)

    NASA Technical Reports Server (NTRS)

    Charlier, Jean

    1991-01-01

    The aim of this experiment was to test the optical behavior of 20 components and coatings subjected to space exposure. Most of them are commonly used for their reflective or transmittive properties in spaceborne optics. They consist in several kind of metallic and dielectric mirrors designed for the 0.12 to 10 microns spectrum, UV, and NIR bandpass filters, visible, and IR antireflecting coatings, visible/IR dichroic beam splitters, and visible beam splitter. The coatings were deposited on various substrates such as glasses, germanium, magnesium fluoride, quartz, zinc selenide, and kanigened aluminum. Several coating materials were used such as Al, Ag, Au, MgF2, LaF3, ThF3, ThF4, SiO2, TiO2, ZrO2, Al2O3, MgO, Ge, and ZnSe. Five samples of each component were manufactured. Two flight samples were mounted in such a way that one was directly exposed to space and the other looking backwards. The same arrangement was used for the spare samples stored on ground in a box identical to the flight one and they were kept under vacuum during the LDEF mission. Finally, one set of reference components was stocked in a sealed box under a dry nitrogen atmosphere. By comparing the preflight and postflight optical performances of the five samples of each component, it is possible to detect the degradations due to the space exposure.

  6. Chemical vapor deposited silica coatings for solar mirror protection

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Dever, Therese M.; Banholzer, William F.

    1988-01-01

    A variety of techniques is available to apply protective coatings to oxidation susceptible spacecraft components, and each has associated advantages and disadvantages. Film applications by means of chemical vapor deposition (CVD) has the advantage of being able to be applied conformally to objects of irregular shape. For this reason, a study was made of the oxygen plasma durability of thin film (less than 5000 A) silicon dioxide coatings applied by CVD. In these experiments, such coatings were applied to silver mirrors, which are strongly subject to oxidation, and which are proposed for use on the space station solar dynamic power system. Results indicate that such coatings can provide adequate protection without affecting the reflectance of the mirror. Scanning electron micrographs indicated that oxidation of the silver layer did occur at stress crack locations, but this did not affect the measured solar reflectances. Oxidation of the silver did not proceed beyond the immediate location of the crack. Such stress cracks did not occur in thinner silica flims, and hence such films would be desirable for this application.

  7. Protecting polymers in space with atomic layer deposition coatings.

    PubMed

    Minton, Timothy K; Wu, Bohan; Zhang, Jianming; Lindholm, Ned F; Abdulagatov, Aziz I; O'Patchen, Jennifer; George, Steven M; Groner, Markus D

    2010-09-01

    Polymers in space may be subjected to a barrage of incident atoms, photons, and/or ions. Atomic layer deposition (ALD) techniques can produce films that mitigate many of the current challenges for space polymers. We have studied the efficacy of various ALD coatings to protect Kapton polyimide, FEP Teflon, and poly(methyl methacrylate) films from atomic-oxygen and vacuum ultraviolet (VUV) attack. Atomic-oxygen and VUV studies were conducted with the use of a laser-detonation source for hyperthermal O atoms and a D2 lamp as a source of VUV light. These studies used a quartz crystal microbalance (QCM) to monitor mass loss in situ, as well as surface profilometry and scanning electron microscopy to study the surface recession and morphology changes ex situ. Al2O3 ALD coatings protected the underlying substrates from atomic-oxygen attack, and the addition of TiO2 coatings protected the substrates from VUV-induced damage. The results indicate that ALD coatings can simultaneously protect polymers from oxygen-atom erosion and VUV radiation damage.

  8. Deposition and properties of novel nitride superlattice coatings

    SciTech Connect

    Barnett, S.A.; Sproul, W.D.; Wong, M.S.

    1993-04-01

    We have carried out detailed studies of the processing, structure, and properties of certain polycrystalline superlattice coatings, including TiN/NbN, TiN/VN, TiN/Ni, and TiN/NiCr, which were produced using an opposed, dual-cathode, high-rate, reactive, unbalanced-magnetron sputtering system. The coatings exhibited hardness values as high as 5200 kgf/mm[sup 2] for TiN/NbN, 5100 for TiN/VN, 3500 for TiN/Ni, and 3200 for TiN/NiCr. These hardness values are all twice higher than their corresponding rule-of-mixture hardness values. The structure and properties of the coatings are a strong function of superlattice period, partial pressure of N[sub 2], and energy and flux of ion bombardment during deposition. Possible mechanisms for hardness enhancement in the polycrystalline superlattice appear to be a result of dislocation blocking due to coherency strains, difference in dislocation line energies between layers, and small grain sizes. In response to high interest shown by industry, BIRL formed a 2-year Industrial Group Program, currently with 12 members, to transfer the superlattice coating technology.

  9. Vacuum deposited optical coatings experiment (AO 138-4)

    NASA Technical Reports Server (NTRS)

    Charlier, Jean

    1991-01-01

    The aim of this experiment was to test the optical behavior of 20 components and coatings subjected to space exposure. Most of them are commonly used for their reflective or transmittive properties in spaceborne optics. They consist in several kind of metallic and dielectric mirrors designed for the 0.12 to 10 microns spectrum, UV, and NIR bandpass filters, visible, and IR antireflecting coatings, visible/IR dichroic beam splitters, and visible beam splitter. The coatings were deposited on various substrates such as glasses, germanium, magnesium fluoride, quartz, zinc selenide, and kanigened aluminum. Several coating materials were used such as Al, Ag, Au, MgF2, LaF3, ThF3, ThF4, SiO2, TiO2, ZrO2, Al2O3, MgO, Ge, and ZnSe. Five samples of each component were manufactured. Two flight samples were mounted in such a way that one was directly exposed to space and the other looking backwards. The same arrangement was used for the spare samples stored on ground in a box identical to the flight one and they were kept under vacuum during the LDEF mission. Finally, one set of reference components was stocked in a sealed box under a dry nitrogen atmosphere. By comparing the preflight and postflight optical performances of the five samples of each component, it is possible to detect the degradations due to the space exposure.

  10. Chemical vapor deposited silica coatings for solar mirror protection

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Dever, Therese M.; Banholzer, William F.

    1988-01-01

    A variety of techniques is available to apply protective coatings to oxidation susceptible spacecraft components, and each has associated advantages and disadvantages. Film applications by means of chemical vapor deposition (CVD) has the advantage of being able to be applied conformally to objects of irregular shape. For this reason, a study was made of the oxygen plasma durability of thin film (less than 5000 A) silicon dioxide coatings applied by CVD. In these experiments, such coatings were applied to silver mirrors, which are strongly subject to oxidation, and which are proposed for use on the space station solar dynamic power system. Results indicate that such coatings can provide adequate protection without affecting the reflectance of the mirror. Scanning electron micrographs indicated that oxidation of the silver layer did occur at stress crack locations, but this did not affect the measured solar reflectances. Oxidation of the silver did not proceed beyond the immediate location of the crack. Such stress cracks did not occur in thinner silica films, and hence such films would be desirable for this application.

  11. Influence of deposition parameters on chemical properties of calcium phosphate coatings prepared by using electrostatic spray deposition.

    PubMed

    Leeuwenburgh, S; Wolke, J; Schoonman, J; Jansen, J A

    2005-08-01

    The electrostatic spray deposition (ESD) technique offers the possibility of depositing calcium phosphate (CaP) coatings onto various substrate materials with defined chemical and morphological properties. The relationship between physical, apparatus-related deposition parameters, and the chemical characteristics of ESD coatings was investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy to be able to deposit CaP coatings with tailored chemical properties. The results showed that the chemical characteristics of CaP coatings, deposited with use of the ESD technique, were strongly dependent on the deposition temperature, the nozzle-to-substrate distance, the liquid flow rate, and the geometry of the spraying nozzle. By investigating the influence of the deposition temperature, information could be obtained on the formation mechanism of CaP coatings-and specifically the biologically interesting carbonate apatite phase-using the ESD technique. CaP coatings were not formed merely because of solvent evaporation; a chemical reaction was needed to synthesize the coatings. This reaction involved thermal decomposition of the organic solvent butyl carbitol into carbonate ions via formation of intermediate oxalate ions. The amount of carbonate incorporation, and consequently, the Ca/P ratios of the deposited coatings, was shown 1) to decrease with increasing nozzle-to-substrate distance, 2) to decrease with increasing liquid flow rate, and 3) to decrease by making use of a novel two-component nozzle geometry. (c) 2005 Wiley Periodicals, Inc.

  12. Thermal Shock Behavior of Air Plasma Sprayed CoNiCrAlY/YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Liu, Zi Wei; Wu, Wei; Hua, Jia Jie; Lin, Chu Cheng; Zheng, Xue Bin; Zeng, Yi

    2014-07-01

    The structural changes and failure mechanism of thermal barrier coatings (TBCs) during thermal shock cycling were investigated. TBCs consisting of CoNiCrAlY bond coat and partially yttria-stabilized zirconia (YSZ) top coat were deposited by atmospheric plasma spraying (APS) on a nickel-based alloy substrate and its thermal shock resistance performance was evaluated. TBCs were heated at 1100°C for 15 min followed by cold water quenching to ambient temperature. Microstructural evaluation and elemental analysis of TBCs were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The crack features of YSZ coatings in TBCs during thermal shock cycling, including those of horizontal (parallel to the substrate) and vertical cracks (perpendicular to the substrate), were particularly investigated by means of SEM and image analysis. Results show that horizontal and vertical cracks have different influences on the thermal shock resistance of the coatings. Horizontal cracks that occur at the interface of YSZ and thermally growth oxidation (TGO) cause partial or large-area spalling of coatings. When vertical and horizontal cracks encounter, network segments are formed which lead to partial spalling of the coatings.

  13. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin

    2015-12-01

    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  14. Environmental Barrier Coatings for Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Fox, Dennis; Eldridge, Jeffrey; Robinson, R. Craig; Bansal, Narottam

    2004-01-01

    One key factor that limits the performance of current gas turbine engines is the temperature capability of hot section structural components. Silicon-based ceramics, such as SiC/SiC composites and monolithic Si3N4, are leading candidates to replace superalloy hot section components in the next generation gas turbine engines due to their excellent high temperature properties. A major stumbling block to realizing Si-based ceramic hot section components is the recession of Si-based ceramics in combustion environments due to the volatilization of silica scale by water vapor. An external environmental barrier coating (EBC) is the most promising approach to preventing the recession. Current EBCs are based on silicon, mullite (3A12O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit the durability and temperature capability of current EBCs. Research is underway to develop EBCs with longer life and enhanced temperature capability. Understanding key issues affecting the performance of current EBCs is necessary for successful development of advanced EBCs. These issues include stress, chemical compatibility, adherence, and water vapor stability. Factors that affect stress are thermal expansion mismatch, phase stability, chemical stability, elastic modulus, etc. The current understanding on these issues will be discussed.

  15. Environmental Barrier Coatings for Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Fox, Dennis; Eldridge, Jeffrey; Robinson, R. Craig; Bansal, Narottam

    2004-01-01

    One key factor that limits the performance of current gas turbine engines is the temperature capability of hot section structural components. Silicon-based ceramics, such as SiC/SiC composites and monolithic Si3N4, are leading candidates to replace superalloy hot section components in the next generation gas turbine engines due to their excellent high temperature properties. A major stumbling block to realizing Si-based ceramic hot section components is the recession of Si-based ceramics in combustion environments due to the volatilization of silica scale by water vapor. An external environmental barrier coating (EBC) is the most promising approach to preventing the recession. Current EBCs are based on silicon, mullite (3A12O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit the durability and temperature capability of current EBCs. Research is underway to develop EBCs with longer life and enhanced temperature capability. Understanding key issues affecting the performance of current EBCs is necessary for successful development of advanced EBCs. These issues include stress, chemical compatibility, adherence, and water vapor stability. Factors that affect stress are thermal expansion mismatch, phase stability, chemical stability, elastic modulus, etc. The current understanding on these issues will be discussed.

  16. A Guide to Finite Element Simulations of Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Bäker, Martin; Seiler, Philipp

    2017-08-01

    To understand the stress evolution and failure mechanisms of thermal barrier coatings (TBCs), finite element simulations are an invaluable tool. Simulations are especially useful to unwrap complex interactions of different phenomena at high temperature, including creep, sintering, diffusion, and oxidation. However, the correct setup and evaluation of a finite element model for this problem are difficult. This article reviews critical issues in modelling TBC systems. Some of the most important aspects are as follows: (a) stresses in 3D simulations may differ considerably from 2D models; (b) the interface shape strongly affects the stresses and using an idealized geometry may underestimate stresses; (c) crack propagation requires simulating sufficiently large regions to correctly capture stress redistribution; (d) a correct description of the material behaviour (visco-plasticity, TGO growth, sintering) is crucial in determining the stress state. The article discusses these and other issues in detail and provides guidelines on the choice of model parameters, boundary conditions, etc. The paper also points out open questions in modelling TBC systems and discusses aspects of verification and validation.

  17. Method And Apparatus For Determining Health Of Thermal Barrier Coatings

    DOEpatents

    Srivastava, Alok Mani; Setlur, Anant Achyut; Comanzo, Holly Ann; Devitt, John William; Ruud, James Anthony; Brewer, Luke Nathaniel

    2005-09-13

    A method for determining past-service conditions and/or remaining useful life of a component of a combustion engine and/or a thermal barrier coating ("TBC") of the component comprises providing a photoluminescent ("PL") material in the TBC, directing an exciting radiation at the TBC, measuring the intensity of a characteristic peak in the emission spectrum of the PL material, and correlating the intensity of the characteristic peak or another quantity derived therefrom to an amount of a new phase that has been formed as a result of the exposure of the component to extreme temperatures. An apparatus for carrying out the method comprises a radiation source that provides the exciting radiation to the TBC, a radiation detector for detecting radiation emitted by the PL material, and means for relating a characteristic of the emission spectrum of the PL material to the amount of the new phase in the TBC, thereby inferring the past-service conditions or the remaining useful life of the component.

  18. A Guide to Finite Element Simulations of Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Bäker, Martin; Seiler, Philipp

    2017-07-01

    To understand the stress evolution and failure mechanisms of thermal barrier coatings (TBCs), finite element simulations are an invaluable tool. Simulations are especially useful to unwrap complex interactions of different phenomena at high temperature, including creep, sintering, diffusion, and oxidation. However, the correct setup and evaluation of a finite element model for this problem are difficult. This article reviews critical issues in modelling TBC systems. Some of the most important aspects are as follows: (a) stresses in 3D simulations may differ considerably from 2D models; (b) the interface shape strongly affects the stresses and using an idealized geometry may underestimate stresses; (c) crack propagation requires simulating sufficiently large regions to correctly capture stress redistribution; (d) a correct description of the material behaviour (visco-plasticity, TGO growth, sintering) is crucial in determining the stress state. The article discusses these and other issues in detail and provides guidelines on the choice of model parameters, boundary conditions, etc. The paper also points out open questions in modelling TBC systems and discusses aspects of verification and validation.

  19. Morphology, Composition, and Bioactivity of Strontium-Doped Brushite Coatings Deposited on Titanium Implants via Electrochemical Deposition

    PubMed Central

    Liang, Yongqiang; Li, Haoyan; Xu, Jiang; Li, Xin; Qi, Mengchun; Hu, Min

    2014-01-01

    Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for use in dental applications. In this study, strontium-doped brushite coatings were deposited on titanium by electrochemical deposition. The phase composition of the coating was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy, and the cytocompatibility and bioactivity of the strontium-doped brushite coatings were evaluated using cultured osteoblasts. Osteoblast proliferation was enhanced by the addition of strontium, suggesting a possible mechanism by which strontium incorporation in brushite coatings increased bone formation surrounding the implants. Cell growth was also strongly influenced by the composition of the deposited coatings, with a 10% Sr-doped brushite coating inducing the greatest amount of bone formation among the tested materials. PMID:24901526

  20. Morphology, composition, and bioactivity of strontium-doped brushite coatings deposited on titanium implants via electrochemical deposition.

    PubMed

    Liang, Yongqiang; Li, Haoyan; Xu, Jiang; Li, Xin; Qi, Mengchun; Hu, Min

    2014-06-04

    Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for use in dental applications. In this study, strontium-doped brushite coatings were deposited on titanium by electrochemical deposition. The phase composition of the coating was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy, and the cytocompatibility and bioactivity of the strontium-doped brushite coatings were evaluated using cultured osteoblasts. Osteoblast proliferation was enhanced by the addition of strontium, suggesting a possible mechanism by which strontium incorporation in brushite coatings increased bone formation surrounding the implants. Cell growth was also strongly influenced by the composition of the deposited coatings, with a 10% Sr-doped brushite coating inducing the greatest amount of bone formation among the tested materials.