Effect of pre-existing surface crack morphology on the interfacial thermal fracture of thermal barrier coatings: a numerical study

The interfacial fracture of thermal barrier coatings (TBCs) at the ceramic-bond coat interface occurs during the cooling period following exposure to high temperatures. Previous studies showed that, the presence of multiple vertical surface precracks that span over the entire coating thickness, was beneficial in reducing the propagation of interface cracks. In this paper, the effect of different surface precrack morphologies, such as precrack length and precrack density, on an interface crack during a thermal shock caused by a high heat flux is presented. The results show that shorter surface precracks and a larger precrack density can delay the interfacial fracture. In particular, this behavior is shown to be more prominent in thicker TBCs.