Photo-Stimulated Luminescence Piezo-Spectroscopy Measurement on a EB-PVD 7YSZ/(Ni, Pt)Al/CMSX-4 TBC System

Photo-stimulated luminescence piezo-spectroscopy (PLPS) is being developed as a non-destructive technique for thermal barrier coatings (TBC). In this study, the evolution of photo-stimulated luminescence with 1 hour at 1121 °C thermal cycling was systematically investigated from the thermally grown oxide (TGO) in a production TBC system which consists of electron beam physical vapor deposited 7wt% Y2O3-ZrO2, (Ni,Pt)Al bond coat and CMSX-4 superalloy substrate. The change of compressive stress in the TGO layer with thermal cycling was calculated from the wavelength shift of luminescence spectrum. It consists of an increase from 1.5 to 2.5 Gpa at as received state to 2.5 to 3.5 Gpa at 10 cycles, a gradual decrease to 1.0 to 2.0 Gpa until 500 cycles, then a plateau at this level until TBC spallation. Some other information, such as change of peak width and relative intensity of R1 and R2 peak with thermal cycling, was also analyzed. The Physical basis of the photo-stimulated luminescence evolution was examined using scanning electron microscopy (SEM).