Roles of Mn in the High-Temperature Air Oxidation of 9Cr Ferritic–Martensitic Steel After Severe Plastic Deformation

Oxidation resistance of 9Cr ferritic–martensitic steel before and after cold-swaging process in air at 923 K was compared, and the oxide scales were characterized in detail by secondary ion mass spectrometry (SIMS). Both the cold-swaged sample and post-annealed samples showed considerably greater oxidation resistance than the initial as-tempered sample. Mn played a key role in scale formation of the cold-swaged sample and post-annealed sample; although the Mn content was only 0.5 wt% in the matrix, formation of Mn oxide (MnCr2O4 and Mn2O3) was favored. Roles of Mn in the oxidation behaviors of the cold-swaged sample and post-annealed sample were discussed.