Effect of interfacial delamination on coating crack in thick diamond-like carbon coatings under indentation

Coating crack and interfacial delamination are recognized as two critical factors inducing spallation of thick diamond-like carbon (DLC) coatings. The effect of the two factors is found to dramatically accelerate the failure of thick DLC coatings. However, there are few reports on the effect of interfacial delamination on coating crack. In this work, in order to investigate the evolution of the coating crack and interfacial delamination, as well as the effect of interfacial delamination on coating crack, a finite element model that combines the bilinear cohesive zone model and the extended finite element method (XFEM) is established. It is found that the occurrence of interfacial delamination triggers a second expansion of coating crack. Factors influencing the degree of interfacial delamination on coating crack can be modulated by coating thickness and coating elastic modulus. As the coating thickness increases, the length of interfacial delamination increases, and thus the propagation of coating crack is accelerated. In contrast, the increase of coating elastic modulus could reduce the length of interfacial delamination, which consequently weakens its influence on the propagation of coating crack.