Assessing condition of turbine engine ceramic components through NDE technology.

Thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) are under development for hot-gas path components to allow higher gas-firing temperatures in advanced (high-efficiency, low-emission) gas turbines. Increasing dependence on the reliability of TBC and EBC components has driven the need for nondestructive evaluation (NDE) methods to assess the condition, or ''health status,'' of these coatings. NDE methods based on elastic optical scatter and thermal imaging have been applied to TBC-coated test specimens that were thermally cycled and to EBC-coated SiC/SiC components that were run in 4.5 MW(e) field-test turbines. One primary interest is to develop NDE methods that can predict a prespall condition. Resulting data suggest a correlation between laser scatter data and thermal cycles for TBC-coated specimens, and thermal imaging results have demonstrated prespall detection for an EBC-coated SiC/SiC combustor liner