Effect of surface roughness on the development of protective Al 2 O 3 on Fe–10Al (at.%) alloys containing 0–10 at.% Cr

• DOI: 10.1016/j.apsusc.2006.01.027
• Publication Date: 2006-02-15T07:21:04Z
• Authors: Z.G. Zhang; P.Y. Hou; F. Gesmundo; Y. Niu
• Keywords: Surface layer

The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 degrees C in 0.1 MPa oxygen. For alloys that are not strong Al2O3 formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al2O3 Surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al2O3-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al2O3 layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation. (c) 2006 Elsevier B.V. All rights reserved.