The effects of TGO growth stress and creep rate on TC/TGO interface cracking in APS thermal barrier coatings

Abstract To design reliable thermal barrier coatings (TBCs), it is essential to elucidate the interface failure mechanism and establish a better life-prediction model. Up to now, how the variations of thermally grown oxide (TGO) growth stresses and creep rates affect the interfacial cracking behavior between top coat (TC) and TGO has not been clearly studied. In this work, the thermos-mechanical model with simplified cosine curve interface morphology in TBCs is developed utilizing numerical simulation software (ABAQUS). According to the calculated stress states of TC/TGO interface, the possible damage scenarios are inferred. On this basis, the interface crack nucleation and propagation is simulated by the surface-based cohesive behavior. General features of the interface crack are in good coincidence with previous conjectures. Furthermore, large TGO growth stresses will trigger off premature cracking, conversely, the formation of TC/TGO interface crack can be postponed due to large TGO creep rates. In addition, the dominant fracture mode of TC/TGO interface is impacted by the variations of TGO growth stresses as well as its creep rate. The position of interface fracture mode transition has been shifted to a certain extent.