Analysis of interface delamination in thermal barrier coating system with axisymmetric structure based on corresponding normal and tangential stresses

The interface delamination plays an important role in failures of thermal barrier coatings. An axisymmetric finite element model was built for air plasma sprayed thermal barrier coatings. The model incorporated a Fortran subroutine developed for the TGO growth. It is found that the stress conversion happens in the top-coat at high temperature under isothermal exposure. A simple numerical method was proposed to calculate the normal and tangential stresses at the top-coat/TGO interface and the bond-coat/TGO interface. The bond-coat/TGO interface is less likely to separate during thermal exposure because the interfacial stresses are limited mostly by the high-temperature yield strength of the bond-coat. The delamination of the bond-coat/TGO interface happens on cooling, which is supported by the experimental observation. As a result, the delamination of the bond-coat/TGO interface could be appreciated based on the corresponding normal and tangential stresses.