CAVITATION OF INTERPHASE INTERFACES AT ELEVATED TEMPERATURES

Abstract
Intergranular fracture in high temperature structural materials, for example, stainless steels and superalloys, is often precipitated by the nucleation of microcavities between the metal and the ceramic particles such as oxides and carbides that are present at grain boundaries. A thermodynamic model for the nucleation of cavities is presented. The most critical parameter is the interfacial energy of the metal ceramic interface. The work is extended to the stability of thin films of one material on a substrate of another material where poor wetting is shown to lead to the breakdown of the film by cavity nucleation and by mass transport through solid state diffusion. Examples include thin films of zirconia on sapphire and copper on sapphire.