Composition design of corrosion resistant Fe40Mn40Co10Cr10 HEA by “dissolution-diffusion-deposition” model

Abstract

Fe₄₀Mn₄₀Co₁₀Cr₁₀ high-entropy alloy (HEA) is known for the outstanding mechanical properties. However, the poor corrosion resistance severely inhibits its popularization. To remove the corrosion problem obstructing the application of Fe₄₀Mn₄₀Co₁₀Cr₁₀ HEA, the “dissolution-diffusion-deposition” model was used to optimize its composition. Since increasing pH value significantly enhanced the corrosion resistance, the N alloying approach, which could remit the acidification of solution environment, was proposed according to the modelling calculation results. The verify experiments on the HEAs with similar compositions as those in modelling calculation show that N alloying increased the pitting potential and optimized the passive film. The oxide content and the ratio of Cr₂O₃ in passive film improved with N addition, which clarified the enhancement of protectivity. During the passivation process, N suppressed the acidification of solution mainly by the dissolving process of N, and the hydrolyzation reaction of NH₃. The alkaline environment created by N provided a favorable condition for passivation. Additionally, the CrN layer existing on the interface of matrix/passive film also played an important role in the repassivation process of matrix. The “dissolution-diffusion-deposition” model could be a powerful tool when design the corrosion resistant alloy, since it is qualified to provide a quantitative description for the influence of element addition on passivation process.