Influence of inhomogeneous thermally grown oxide thickness on residual stress distribution in thermal barrier coating system

Residual stress is a significant factor to understand failure mechanism of thermal barrier coating system (TBCs). In this work, the residual stress was studied by finite element method during a thermal cycle load. A complicated model was proposed to study the effect of inhomogeneous thickness of thermally grown oxide (TGO). The top ceramic coating (TC), TGO, bond coating (BC) and substrate were assumed to be viscoelastic and the plastic behavior of BC was taken into consideration. The material parameters of four layers are temperature dependent. The residual stress distributions along TC/TGO and BC/TGO interfaces were determined. The influence of nonuniform TGO thickness on residual stress was discussed by comparing with uniform TGO thickness. Meanwhile, the effect of different TGO roughness was studied. The results show that inhomogeneous TGO thickness has complicated effects on residual stress. The effect on stress values near peak and valley of TC/TGO and BC/TGO interfaces is relatively large. And residual stress distributions of TC/TGO interface vary a lot for most cases. The stress levels of the two interfaces increase obviously with the augment of TGO roughness. These results help to understand the failure mechanism of TBCs.