Concomitant oxidation-diffusion-creep processes for stress generation and suppression of oxide-alloy interfacial instabilities

Abstract

Metallic materials under extreme thermo-mechanical-environmental service conditions oftentimes rely on the formation of dense and protective oxide layers, e.g., typically alumina or chromia. Their failures, however, usually emerge from the morphological instability of such layers at the oxide-alloy interface. This work suggests that a tensile, biaxial stress arises in the substrate alloy due to the concomitant oxidation-diffusion-creep processes, which, in contrast to the growth stress in the oxide layer, provides a stabilizing factor that suppresses the rumpling or compositional variation in chromia or alumina interlayers. For rumpling analysis, the substrate tensile stress compensates the growth stress in the oxide layer. The compositional variation is modeled by the stress-domain analysis, which suggests that the substrate tensile stress prefers the growth of high-growth-stress oxide phase at the expense of low-growth-stress one. Our findings have been successfully employed to rationalize recent experiments in superalloys under cyclic oxidation conditions and in carburized or irradiated stainless steels under isothermal oxidation conditions.