Oxidation Resistance of High Aluminum Austenitic Stainless Steel

A new type of austenitic stainless steel has been developed containing 5pct Al and forming a protective Al2O3 film. This steel is free from oxide film spalling and exhibits a greater oxidation resistance than any other conventional austenitic stainless steel. Formation of the Al2O3 film requires the removal of the internal oxidation zone, caused by hot-working, prior to being subjected to high temperatures. The application of a special Al paint is also effective in eliminating the internal oxidation zone. Abnormal oxidation also takes place in this steel, but has less effect than in conventional ferritic Cr-Al steels. The oxidation behavior of this steel can be explained by the low diffusion rates of Al and N in the austenitic phase and also by the reduction in the oxidation rate by Ni.