Abstract
The Fe-Mn-Al-based alloys have attracted considerable interest for their potential application in stainless steel usage. In this study the oxidation and nitridation behaviour of Fe-31 Mn-9Al-6Cr-0.86C (wt%) alloy is investigated. The effects of a gaseous atmosphere, a pre-existing oxide layer and the alloy phase distribution in the matrix are evaluated with respect to the morphological development and kinetics. The nitridation behaviour of the alloy in air is sensitive to the alloy surface condition, such as the alloy phases in the matrix and the oxides in the scale. For the aged multiphase alloy, oxidation occurs in the ferrite phase and nitridation takes place in the austenite phase due to the higher solubility of nitrogen. The existing interphase boundaries provide an easy path for nitrogen migration and thus promote the nitridation. However, the surface oxide layers act as a diffusion barrier for nitrogen. The effectiveness of the barrier in the retardation of nitridation depends on the amounts of MnAl 2 O 4 and α-Al 2 O 3 in the oxide layer. © 1988 Chapman and Hall Ltd.