Improved High Temperature Oxidation Resistance of REM Added Fe-20Cr-5Al Alloy by Pre-Annealing Treatment

摘要

The effect of pre-annealing on the oxidation behavior of Fe-20mass%Cr-5mass%Al alloy foils containing a small amount of La-Zr or La-Hf was examined in a cyclic oxidation test at 1373 K in air. 1. The oxidation rate of these alloys was reduced by pre-annealing in hydrogen. 2. In the Al_2O_3 scale which formed on the pre-annealed alloys, the outer equiaxed grain layer was thinner and the grain size of the inner columnar grain layer was larger than in the scale which formed on as-cold rolled alloys. 3. The segregation of La, Zr, and/or Hf at the columnar grain boundaries of the Al_2O_3 scale was higher with the pre-annealed alloys than with as-cold rolled alloys. It may be inferred that the low density of grain boundaries in the Al_2O_3 and high segregation of La, Zr, and/or Hf in the Al_2O_3 grain boundaries suppressed oxygen diffusion along these grain boundaries, reducing the growth rate of the Al_2O_3 scale.