Reliability of laser flash thermal diffusivity measurements of the thermal barrier coatings |
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Authors: | H Wang R B Dinwiddie |
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Affiliation: | (1) High Temperature Materials Laboratory, Oak Ridge National Laboratory, 37831-6064 Oak Ridge, TN |
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Abstract: | The thermal diffusivity of free standing thermal barrier coatings (TBCs) was measured by the laser flash technique. The combination
of low thermal conductivity (1 to 2 W/m K) and small TBC thickness (300 to 600 μm thick) can cause errors in the measurements.
Back surface (opposite the laser) temperatures of free standing plasma-sprayed TBCs were measured as a function of time and
laser power. The front surface temperatures were calculated using thermal transport equations. In the high power region, thermal
diffusivity decreased significantly with increasing laser power. In the moderate power region, thermal diffusivity remained
constant. In the low power region, measurement became unreliable because of noise. The detector nonlinearity was believed
to be a possible cause of deviation in the high power region. Measurements at different laser power levels should be conducted
in order to obtain reliable thermal diffusivity values for TBCs. |
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Keywords: | TBC thermal diffusivity thermal conductivity laser flash |
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