In-situ evolution of thermal barrier coating’s mechanics due to elastic and inelastic deformation via synchrotron X-rays

Abstract

In this study, in-situ synchrotron measurements were conducted on a thermal barrier coating system with a superalloy substrate. The use of high energy X-rays affords real-time monitoring of complex mechanical behavior; when coupled with an integrated high temperature and mechanical loading testing apparatus, variations in realistic representative service loading can be investigated for their influence on each constituent of the multi-layer system. This provides a method for identifying how changes in loading conditions across a turbine blade may play a role in the initiation of failure mechanisms and lifetime expectancy of the coating. Collecting diffraction measurements on a 2D area detector, elastic strain analysis is conducted to elucidate the influence of external thermal loading, applied mechanical loading, and internal cooling on the thermally grown oxide and ceramic zirconia topcoat. Analysis has identified the influence of these loadings on the system. Investigating the texturing and preferred orientation of the diffraction rings, further insight on the influence of plastic strain is discussed including how grains’ lattice plane rotation and subdivision during high temperature loading affect the residual strain state. Together the non-destructive methods of evaluating the multi-layer system shed light on the performance of thermal barrier coatings in operational conditions.