Extensively validated numerical model for the time-dependent simulation of high-temperature oxidation of stainless steels in natural gas and hydrogen combustion atmospheres

Accurate prediction of high-temperature oxidation in Fe–Cr–Ni alloys is essential for assessing material performance in technical combustion environments. In this work, a fully coupled numerical model was developed that integrated multicomponent diffusion, CALPHAD-based phase equilibria and a moving oxide/alloy interface. Interdiffusion coefficients were calculated from thermodynamic factors and mobility data, enabling a physically consistent description of mass transport inside both the growing oxide scale and the alloy substrate. An adaptive boundary condition for the oxygen influx allowed the model to dynamically transition between surface-reaction and solid-diffusion-controlled kinetics. For the first time, an oxidation model directly incorporates the resulting concentrations of the combustion products O 2 , H 2 O, and CO 2 at the gas/oxide interface through gas transport and phase-boundary reactions. The simulations were performed for 1.4307 (X2CrNi18-9) stainless steel at 1200 °C and 1300 °C under air-fuel and oxy-fuel natural gas and hydrogen combustion atmospheres. The predicted specific mass gains, oxide growth rates and concentration profiles exhibited excellent agreement with experimental and literature findings. Its numerically efficient structure facilitates extension to other alloys through parallelization, more complex multi-layer oxide systems, and transient operating scenarios.