Cracking and delamination of coatings

The mechanism by which a coating will fail is governed by a number of parameters. These include not only the properties of the coating, interface, and substrate, but also the distribution of stresses. If the coating is under a residual tensile stress, there are at least three possible mechanisms by which failure can occur. For example, a brittle coating may fracture by the development of cracks through the thickness of the film. Tougher coatings may fail by delamination along the interface or even by the propagation of a crack within the substrate. The failure mechanism associated with a compressive stress in the coating involves simultaneous buckling and delamination. This paper reviews these different modes of failure and discusses the conditions that determine which ones will operate.