Improving the Anti-corrosion Property of FeCoNi High-Entropy Alloy Using Plasma Nitriding Treatment

A comprehensive analysis focuses on the influence of plasma nitriding on the anti-corrosion performance of FeCoNi high-entropy alloy (HEA) in a simulated alkaline environment utilizing a series of tests. The results indicate that the nitrided HEA possesses more excellent hardness and corrosion resistance than the as-cast HEA by comparing the sectional Vickers hardness, passive current density (i_p), pitting potential (E_p), and corrosion morphology. The significant increase in hardness is related to the infiltration of nitrogen, resulting in the formation of a hard nitrided layer on the HEA. The improvement in the anti-corrosion performance of the HEA is attributed to the compact, uniform, and complete nitrided layer covering the surface of the substrate, and the nitrided layer is mainly composed of anti-corrosion iron nitrides, which can effectively prevent harmful ions in the solution from penetrating the matrix of the HEA. The EIS test result indicates that the nitrided layer possesses high electrochemical stability and protection, which enhances the corrosion resistance of the HEA. Moreover, the substrate of the as-cast HEA mainly experiences the dissolution of nickel element, causing the generation of pit.