Influence of surface mechanical attrition treatment on the high-temperature oxidation behavior of Fe20Cr25NiNb stainless steel

This study comparatively investigates the effects of surface mechanical attrition treatment (SMAT) on the oxidation performance of Fe20Cr25NiNb stainless steel under static isothermal conditions at 650 °C in air and high-purity CO 2 (3.5 MPa). SMAT modifies the near-surface microstructure by creating a roughened surface with microcracks, a nanocrystalline layer, and an underlying thick hardened zone. These modifications improve the steel's oxidation resistance in air but compromise its performance in high-temperature CO 2 , resulting in significant mass gain, oxide scale spallation, and carburization. This degradation is attributed to microcrack-assisted gas ingress and enhanced elemental diffusivity in the nanocrystalline layer, which accelerated carbide formation and depleted chromium, compromising the integrity of the protective oxide scale.