Residual stress trend in thermal barrier coatings in through thickness direction measured by photoluminescence piezospectroscopy

Photoluminescence piezospectroscopy (PLPS) has been used to determine residual stresses in sapphire, alumina in the yttria stablised zirconia (YSZ)/Al₂O₃ composite and alumina in thermal barrier coatings (TBCs). The TBC of YSZ containing 0·5 wt-% alumina has been produced using electron beam physical vapour deposition. The stress profile through the TBC thickness was measured using a depth sensing method. Reasonable residual stress profiles have been obtained using PLPS with the confocal system for all three material systems. Measurements of TBCs suggest that stress distribution in a TBC system is not uniform in general. However, uniform stress distribution has been found in some positions where damage in TBCs might occur.