Thermally grown oxide (TGO) layer is grown at the interface between top coating and bond coating when a coating system with thermal barrier coating (top coating) and both coaling is heated. The growth of the TGO layer causes the delamination of top coating from bond coating after heating. The growth of TGO layer had simulated by using finite element analysis model of the interface between top coating and bond coating and it depended on both the geometry of the interface and the temperature at interface in previous paper. In this paper, the fracture mechanism of TBC was examined from the observation at the interface after thermal cycle test. It was found that a lot of cracks were occurred in top coating near convexity of the interface when TGO layer was grown. The location of the occurrence of those cracks coincided with the simulation results.

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