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Results for “CERAMIC COATING”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Experimental and analytical study of ceramic-coated turbine-tip shroud seals for small turbine engines

The results of an experimental and analytical evaluation of ceramic turbine tip shrouds within a small turbine engine operating environment are presented. The ceramic shrouds were subjected to 1001 cycles between idle and high power and steady-state conditions for a total of 57.8 engine hr. Posttest engine inspection revealed mud-flat surface cracking, which was attributed to microcracking under tension with crack penetration to the ceramic and bond coat interface. Sections and micrographs tend to corroborate the thesis. The engine test data provided input to a thermomechanical analysis to predict temperature and stress profiles throughout the ceramic gas-path seal. The analysis predicts cyclic thermal stresses large enough to cause the seal to fail. These stresses are, however, mitigated by inelastic behavior of the shroud materials and by the microfracturing that tensile stresses produce. Microfracturing enhances shroud longevity during early life but provides the failure mechanism during life but provides the failure mechanism during extended life when coupled with the time dependent inelastic materials effects.

Biesiadny, T. J.↗
NASA NTRS1976

Potential use of ceramic coating as a thermal insulation on cooled turbine hardware

An analysis was made to determine the potential benefits of using a ceramic thermal insulation coating of calcia-stabilized zirconia on cooled engine parts. The analysis was applied to turbine vanes of a high temperature and high pressure core engine and a moderate temperature and low pressure research engine. Measurements made during engine operation showed that the coating substantially reduced vane metal wall temperatures. Evaluation of the durability of the coating on turbine vanes and blades in a furnace and engine were encouraging.

Liebert, C. H.↗
NASA NTRS1989

Static tensile and tensile creep testing of four boron nitride coated ceramic fibers at elevated temperatures

Six types of uncoated ceramic fibers were static tensile and tensile creep tested at various elevated temperatures. Three types of boron nitride coated fibers were also tested. Room temperature static tensile tests were initially performed on all fibers, at gage lengths of 1, 2, and 4 inches, to determine the magnitude of end effects from the gripping system used. Tests at one elevated temperature, at gage lengths of 8 and 10 inches, were also conducted, to determine end effects at elevated temperatures. Fiber cross sectional shapes and areas were determined using scanning electron microscopy. Creep testing was typically performed for 4 hours, in an air atmosphere.

Coguill, Scott L.↗
NASA NTRS1970

Simple bonding technique for high-temperature ceramic coatings

Coatings, consisting of zirconia powder bonded with orthophosphoric acid and a small amount of hydrofluoric acid, are hard, strong, and refractory, resist thermal shock, and provide good thermal protection. After the aqueous coating is applied to a metallic surface, only a 600 deg F cure is required before service.

Accountius, O. E.↗
NASA NTRS1978

Investigation of the effect of ceramic coatings on rocket thrust chamber life

Cylindrical rocket thrust chamber cylinders were coated with a 0.203 mm (0.008 in.) layer of zirconium oxide using a process that employed electrodeposition of metal to a spray coated mandrel. The cylinders were cyclically tested using hydrogen oxygen propellants at a nominal chamber pressure of 4.14 MN/sq m (600 psia) to show the effect of the coating on life. Both cylinders failed prematurely due to causes unrelated to the coatings. Post destructive analysis showed no cooling passage wall deformation. Where erosion of the coating occurred, the coating thickness stabilized at 0.061 mm (0.0024 in.) within 80 cycles and remained well adhered throughout the tests.

Quentmeyer, R. J.↗
NASA NTRS1978

Investigation of the effect of ceramic coatings on rocket thrust chamber life

Two cylindrical rocket thrust chamber cylinders were coated with a 0.203 mm layer of zirconium oxide using a process that employed electrodeposition of metal to a spray-coated mandrel. The cylinders were cyclically tested using hydrogen-oxygen propellants at a nominal chamber pressure of 4.14 MN/sq m to show the effect of the coating on life. Both cylinders failed prematurely due to causes unrelated to the coatings. Post destructive analysis showed no cooling passage wall deformation. Where erosion of the coating occurred, the coating thickness stabilized at 0.061 mm within 80 cycles and remained well adhered throughout the tests. The hot-gas-side metal wall temperature and the theoretical maximum effective strain were reduced by 80 and 92%, respectively, where the coating was 0.203 mm thick and by 40 and 50%, respectively, where the coating was 0.061 mm thick compared to an uncoated cylinder. The 50 and 92% reductions in maximum effective strain resulted in theoretical lives of 1900 cycles and greater than 10,000 cycles, respectively, compared to 300 cycles for the uncoated cylinder.

Quentmeyer, R. J.↗
NASA NTRS1984

Catalytic surface effect on ceramic coatings for an aeroassisted orbital transfer vehicle

Surface catalytic efficiencies of glassy coatings were determined from a reaction boundary layer computation and arc-jet data. The catalytic efficiencies of the various coatings examined are discussed in terms of their reaction-rate constants. These constants are a function of the wall temperature (1290 K to 2000 K). In addition, the advantage of a thermal protection system for a bent biconic, aeroassisted orbital transfer vehicle with a low surface catalytic efficiency is discussed.

Steward, D. A.↗
NASA NTRS1987

Interface roughness effect on stresses in ceramic coatings

This paper presents an analysis of the interface stress in plasma-sprayed zirconia coatings. The stress distributions along smooth and rough interfaces were calculated for perfectly bonded materials. The effect of mechanial interlock along the interface was also calculated. The interface stresses for noninterlocking interfaces were consistently higher; the interlocking interfaces showed high stresses in small regions only.

Mullen, Robert L.↗
NASA NTRS1988

Effect of surface catalysis on heating to ceramic coated thermal protection systems for transatmospheric vehicles

This paper describes the effect of surface catalysis on the heat transfer rate to the heat shield of a typical Transatmospheric Vehicle (TAV) during ascent and atmospheric entry. Surface kinetics and optical properties obtained from arc-jet tests on candidate thermal protection systems (coated metals) were used in a reacting boundary layer code to estimate the heating distribution along the surface of a TAV. Thermochemical stability of the coatings is described in terms of reduction in emittance and loss of opacifiers from the coatings during the arc-jet tests.

Stewart, David A.↗
NASA NTRS1989

Failure processes within ceramic coatings at high temperatures

Plasma sprayed coatings have a complex structure which is produced by the overlaying of many molten or semi-molten particles in the diameter range of 20 to 120 microns. The failure behavior of coatings has been characterized by using acoustic emission (AE) methodology. Coatings of NiCrAlY bond coat with a zirconia-12 wt pct yttria overlay were applied to disk-shaped specimens of U-700 alloy. A waveguide of 1-mm diameter platinum was TlG welded to the specimen and allowed it to be suspended in a tubular furnace. The specimen was thermally cycled to 1150 C and the AE monitored. Analyses have been carried out with the aim of establishing parameters which are related to the crack size population. These studies have been used to postulate types of cracking mechanisms which may occur in plasma sprayed coatings during thermal cycling. It is shown that microcracking gave rise to a large amount of AE. However, this coating still survived more thermal cycles than a coating which exhibited macrocracking events.

Berndt, Christopher↗
NASA NTRS2004

Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

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.

Zhu, Dong-Ming↗
NASA NTRS2004

Development and Testing of Ceramic Thermal Barrier Coatings

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.

Zhu, Dongming↗