Residual stresses in thermal barrier coatings measured by photoluminescence piezospectroscopy and indentation technique

Residual stresses in electron beam physical vapour deposition (EB-PVD) thermal barrier coatings (TBCs) have been measured by photoluminescence piezospectroscopy (PLPS). It was found that the macro-stress, caused by the thermal mismatch between the substrate and the coating, decreases from the TBC/TGO interface to the top surface. The Young's modulus, measured on the cross-section of EB-PVD coating by nano-indentation, was also found to decrease from TBC/TGO interface to top surface. The variation of Young's modulus can be explained by change in the contact area of TBC under macro-stress. A model was employed to examine the contact area in relation to the stresses. And the stresses estimated based on results from nano-indentation measurements showed the same trend as that obtained from PLPS.