Prediction of damage and failure in thermal barrier coatings

This paper summarizes the development of a life prediction model for treating failure of thermal barrier coatings (TBC) in gas turbine applications. The model has been formulated based on consideration of the formation of a wing crack at the tip of a shear crack and its propagation near the interface of the TBC and the thermally grown oxide. The effects of thermomechanical fatigue, oxidation, bond coat creep, sintering, curvature, and interface roughness on the propagation of the wing cracks have been treated mechanistically to obtain the form of the TBC life equation. Material constants in the life equation are, however, evaluated from experimental data. Application of the TBC life model to predicting failure of air-plasma-sprayed TBCs indicates that the coating life can be reasonably predicted by the model.