A criterion for compressive failure of a continuous, protective surface film

Abstract

Surface coatings (e.g. oxides and deposited coatings) are susceptible to failure in compression during quenches, due to differences in coefficients of thermal expansion between the base metal and the surface coating. In addition, the compressive stresses generated during the growth of some oxide films can also lead to failure. The development of hillocks before extensive delamination suggests that buckling plays an important role in the failure of coatings in compression. Therefore, elastic buckling theory was modified to account for coating/metal adhesion and applied to the failure of coatings in compression. It is found that buckling cannot occur without an interfacial defect where coating/metal adhesion has been lost. Buckling is shown to be a pre-requisite for extensive coating failure, which occurs by the unstable growth of the buckled region. Simple criteria are derived for the onset of buckling, as well as for extensive coating failure. © 1984.