Excellent adhesion of protective α-Al2O3 layer formed on ODS FeCrAl alloys

The growth of α-Al2O3 layer on ODS FeCrAl alloys NF12 (Fe-12Cr-6Al-0.5Ti-0.4Y-0.4Zr-0.25Ex.O) and SP10 (Fe-15Cr-7Al-0.5Ti-0.4Y-0.4Zr-0.24Ex.O) was investigated by means of the oxidation tests under air atmosphere at 1273 K up to 10 h. The inward oxygen diffusion was promoted through the oxides of reactive elements (i.e., Ti, Y and Zr) formed along the grain boundaries of α-Al2O3 layer, and the inward growth of the layer was accelerated. The shearing stress required for the layer exfoliation was quantitatively evaluated by micro-scratch tests. The adhesion of α-Al2O3 layer formed on the ODS alloys was reinforced by so-called anchoring and pegging effects.