NDLI: Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions

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Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions

Content Provider	Semantic Scholar
Author	Zhu, Dongming Miller, Robert A.
Copyright Year	2000
Abstract	Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser-simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8% Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m K to 1.15, 1.19, and 1.5 W/m K after 30 h of testing at surface temperatures of 990, 1100, and 1320 °C, respectively, Hardness and elastic modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and microindentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface and to 7.5 GPa at the ceramic coating surface after 120 h of testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced microporosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various TBC applications.
Starting Page	175
Ending Page	180
Page Count	6
File Format	PDF HTM / HTML
DOI	10.1361/105996300770349890
Volume Number	9
Alternate Webpage(s)	https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990047263.pdf
Alternate Webpage(s)	https://doi.org/10.1361/105996300770349890
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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