Substrate Depletion Analysis and Modeling of the High Temperature Oxidation of Binary Alloys

To predict concentration changes in binary alloy due to preferential oxidation during high temperature oxidation, a model based on the flux balance of the oxidized element at the moving oxide/alloy interface has been developed. These changes are driven by the alloy oxidation rate k c . The model is numerically solved considering different initial alloy concentration profiles and a possible diffusion enhancement effect close to the alloy surface. After validating the model by comparison with Wagner’s analytical solution for Ni30wt%–Pt alloy oxidised at 850 °C, we show that the effects of an initial alloy depletion due to the presence of a passive oxide layer are cancelled after very short oxidation times. We also show that a diffusion acceleration due to work-hardening in the vicinity of the alloy surface induces an inflexion point in the depletion profile.