Microstructural evolution and surface hardening of Fe-Mn-Al alloy through atmospheric pressure plasma jet nitriding

Abstract

Plasma nitriding, a surface-hardening technique, enhances the properties of metallic materials by diffusing nitrogen into their surfaces, thereby increasing wear resistance and reducing friction. This study explores the mechanical properties and corrosion behavior of Fe-Mn-Al alloy following nitriding via an atmospheric pressure plasma jet (APPJ). Utilizing an Hi/Ni gas mixture, the APPJ process facilitated the formation of iron nitride on the alloy surface. Initially, the Fe-Mn-Al alloy exhibited a uniform, single-phase, face-centered cubic (FCC) structure. Post-nitriding, a dual-phase structure emerged, consisting of retained FCC and a newly formed ordered L1i phase. The APPJ nitriding significantly improved the alloy's surface hardness, abrasion resistance, dynamic load performance, and corrosion resistance. These enhancements were more pronounced with increased APPJ power, indicating a strong correlation between APPJ power levels and the effectiveness of nitrogen diffusion and nitride formation on the alloy surface. APPJ nitriding at 500 W forms AlsMn and FeaN, while higher powers (550 W and 600 W) yield FeaN and Al, indicating progressive alloy decomposition.