Microstructure and properties of laser-cladded FeCoCrNiMnSix high-entropy alloy coatings with varying Si contents

Abstract

To improve the properties of the FeCoCrNiMn high-entropy alloy (HEA) coatings, FeCoCrNiMnSi_x coatings were fabricated by using laser cladding technology. The influence of Si content on the microstructure, microhardness, tribological properties, and tribocorrosion performance of coatings was systematically investigated. The results revealed that the phase structure of the coatings transformed from a single FCC phase to the FCC + δ dual-phase structure with increasing the Si content. Additionally, the microstructure evolved from strip-like grains to a dense network-like morphology, demonstrating remarkable grain refinement. The microhardness and wear resistance of the coatings were improved significantly with the Si content increased, primarily due to lattice distortion, fine-grained strengthening and second-phase strengthening induced by the Si incorporation. The corrosion resistance of the coating was significantly improved by the Si addition. The newly formed passivation layer (composed of Co₃O₄, NiO, Cr₂O₃, and SiO₂) on the worn surfaces played a role of protection and anti-wear during the corrosive wear process, significantly reduced both COFs and wear rates of the coatings. The Si2.0 coating exhibited the lowest self-corrosion current density (2.671 × 10⁻⁷ A/cm²), the largest impedance arc radius, and the optimal corrosion resistance as well as the lowest wear rate of 0.68 × 10⁻⁷ mm³/(N·m) (two order of magnitude lower than that of the 316 L substrate). The assessment of corrosion-wear interaction indicated that the mechanical wear was the main cause of material loss during corrosive wear.