Initial stages of FeMnSiCrNi shape memory stainless steels oxidation mechanism at 800 °C

Abstract FeMnSiCrNi alloys form Mn-rich oxide and Mn/Cr spinel at high temperature. However, studies on the oxidation mechanism are still incipient. Thus, in order to understand the initial oxidation stages of the alloy Fe-17Mn-5Si-10Cr-4Ni-VC at 800 °C, up to 24 h, the oxide scale has been characterized by XR-Diffraction, Raman spectroscopy and TEM-ASTAR. Ferrite expansion during cooling was detected and a new oxidation mechanism was proposed, with simultaneous Mn2O3 (externally) and Mn/Cr spinel (internally) formation since the beginning of oxidation, as also discontinuous Cr2O3 surrounded by spinel. The formation of tetragonal-(Mn,Cr)3O4 was also reinterpreted, highlighting the importance of Mn-diffusion on MnCr2O4.