Modelling the thermal oxidation of ternary alloys-compositional changes in the alloy and the development of oxide phases

摘要

A coupled thermodynamic-kinetic oxidation model is presented that describes the thermal oxidation of a single-phase ternary alloy. For given oxide-layer growth kinetics, the model computes composition-depth profiles in the alloy, as well as the amount of each oxide phase developed as a function of oxidation time, including the formation of multiple oxide phase during the initial stage of fast oxidation. Application of the model to the thermal oxidation of a γ-Ni-27Cr-9Al (at.) alloy at 1373 K and a partial oxygen pressure (p_(O_2)) of 2 * 10~4 Pa showed that the phase constitution of the developing oxide layer is predominantly governed by the growth rate and duration of the initial oxidation stage, whereas the eventual, steady-state interface composition of the alloy is mainly determined by the parabolic oxide-layer growth rate.