Thermal barrier coatings (TBCs) are a critical component in low-emission gas turbines. A reliable method is required to monitor the condition of the TBC and predict coating failure. The condition of the interface between the metallic bond coat and TBC has been shown to be a potential indicator of spallation. The TBC is optically translucent; therefore, the bond coat/TBC interface can be probed using laser light with a wavelength of 0.632 microns or higher. A laser system in an optical backscatter configuration has been used to investigate several yttria-stabilized zirconia (YSZ) TBCs applied with either electron-beam physical vapor deposition (EB-PVD) or air plasma spraying (APS). The TBCs were thermally cycled for one hour increments until failure and investigated by the laser backscatter method after set numbers of thermal cycles. Correlations have been established between laser backscatter data and the number of thermal cycles, suggesting that the laser backscatter method can be used to predict failure. A theoretical model has been used to compare interface topography scatter to experimental results. This paper will discuss the laser backscatter technique and the experimental results and will compare the experimental data and theoretical scatter.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.