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

Abstract 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 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.