Modeling of oxidation kinetics of Y-doped Fe-Cr-Al alloys

Studies using advanced analytical techniques indicated that the reactive elements (RE) segregate along the oxide grain boundaries and at the oxide-alloy interface during oxidation of alpha-Al2O3 forming alloys. The segregation results in inward oxygen diffusion along the oxide grain boundaries as the predominant transport process in the oxide growth. The present work establishes a mathematical model based on the mechanisms of inward oxygen diffusion along the grain boundaries and oxide grain coarsening. This model has been used to describe the oxidation kinetics of Y-doped Fe-Cr-Al alloys. The results showed a much better agreement with the experimental data than the parabolic rate law. By using this model, the exponential number for the grain coarsening of alumina scales during oxidation was calculated to be similar to 3. The activation energy for oxygen diffusing along the grain boundaries was 450 kJ/mol. They are also in good agreement with values reported in the literatures.