Effect of Mo content on microstructural evolution, corrosion behavior, and friction performance of laser cladded (Fe50Mn30Co10Cr10)1−xMox coatings

Abstract

In this study, (Fe₅₀Mn₃₀Co₁₀Cr₁₀)_1−xMo_x (x = 0, 0.1, 0.2, 0.3 at.%) high-entropy alloy (HEA) coatings were fabricated using laser cladding technology and characterized through OM, XRD, SEM, TEM, 3D optical profilometry, microhardness tests, and electrochemical measurements. The results indicate that the addition of Mo causes an initial increase, followed by a decrease, in the martensite content of the (Fe₅₀Mn₃₀Co₁₀Cr₁₀)_1−xMo_x coating microstructure. The Mo content of x = 0.1 promotes HCP martensite phase formation. However, an excessive Mo content will lead to the enrichment of Mo in the IR, causing a large amount of Fe₂Mo phase to start precipitating continuously with the IR as nucleation points. The addition of these Fe₂Mo phases significantly enhances the average microhardness of the coating through second-phase strengthening and solid-solution strengthening. This enables the Mo_0.3 coating to possess the highest microhardness of 711 HV and the lowest coefficient of friction of 0.57. Moreover, the Mo_0.1 coating demonstrates superior corrosion resistance, as evidenced by the lowest self-corrosion current density and the broadest passivation region. This is attributed to the protective MoO₃/MoO₂ oxide film and the low Fe₂Mo precipitate content, which together lower the Cl⁻ erosion rate. When the Mo content is x = 0.2 at.%, the (Fe₅₀Mn₃₀Co₁₀Cr₁₀)_1−xMo_x HEA coating achieves the optimal balance among hardness, wear resistance and corrosion resistance.