Fracture of thermal barrier coating with multiple surface cracks and delaminations: Interlayer effect

Multiple surface cracks and interfacial delamination are the major failure mechanisms in film/substrate systems. The effect of interlayer upon the failure mechanisms of interfacial delamination concomitant to surface crack was explored. Finite element model was developed to obtain the stress and energy release rate (ERR), which governs the propagation of interface cracks. The dependences of delamination upon the geometry and constitutive properties of interlayer were examined. The results indicate that the effect of elastic modulus of interlayer on the steady state ERR is insignificant. In cases of different geometrical parameters, however, the steady ERR decreases with the increase of the interlayer thickness. These findings lead to the conclusion that the interlayer constraint has significant effect on the ERR and thus coating life, which can be adopted to modify the ceramic top coat.