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

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 phases during the initial stage of fast oxidation. Application of the model to the thermal oxidation of a gamma-Ni-27Cr-9Al (at.%) alloy at 1373 K and a partial oxygen pressure (p(o2)) of 2x10(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. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.