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

Studies using advanced analytical techniques indicated that the reactive el ements (RE) segregate along the oxide grain boundaries and at the oxide-all oy interface during oxidation of alpha-Al2O3 forming alloys. The segregatio n results in inward oxygen diffusion along the oxide grain boundaries as th e predominant transport process in the oxide growth. The present work estab lishes a mathematical model based on the mechanisms of inward oxygen diffus ion along the grain boundaries and oxide grain coarsening. This model has b een 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 gr ain coarsening of alumina scales during oxidation was calculated to be simi lar to 3. The activation energy for oxygen diffusing along the grain bounda ries was 450 kJ/mol. They are also in good agreement with values reported i n the literatures.