Modelling high temperature oxidation in iron–chromium systems : combined kinetic and thermodynamic calculation of the long-term behaviour and experimental verification

The oxidation of two industrial steels with different chromium content (9 and 12 wt%), oxidised for up to 120 h at 750 °C in air has been investigated experimentally and by means of two-dimensional theoretical methods. The numerical model approach, which we call Applied Simulations of Thermodynamic Reactions and Interphase Diffusion (ASTRID), links the thermodynamic library ChemApp (GTT-Technologies, Germany) to the numerical programme COMSOL (COMSOL Inc., USA). This allows convenient implementations of complex geometries and to probe the oxidation behaviour in “real-life” microstructures under given conditions. Satisfying agreements with experimental findings for the total oxidation depth and local oxide composition have been obtained. Enhancements in the computing speed, as compared to the initial programme InCorr, enable a better resolution of the spatial phase distribution and allow the consideration of different diffusion coefficients corresponding to the newly formed (oxide) phases within the same calculation time