Effect of SiC content on the microstructure and high-temperature tribological properties of laser-cladded AlCoCrFeNi coatings

In this study, SiC nanoparticle-reinforced AlCoCrFeNi high-entropy alloy composite coatings (AlCoCrFeNi + x wt% SiC, x = 0, 10, 20, and 30) were fabricated on 316L stainless steel substrates by laser cladding. Their tribological behavior under dry sliding at 600 ℃ and 800 ℃ was systematically investigated. Among the tested coatings, the 20 wt% SiC coating exhibited the best overall performance, with average friction coefficients of 0.28 and 0.40, and wear volumes of 0.3997 mm³ and 0.1575 mm³ at 600 ℃ and 800 ℃, respectively, corresponding to reductions of 60.91% and 78.32% relative to the SiC-free coating. The corresponding wear rates were 8.65×10⁻⁵ and 3.41×10⁻⁵ mm³/(N·m). Microhardness measurements indicate that SiC addition improves the load-bearing capability of the coating, whereas excessive SiC increases brittleness and promotes spallation. Multi-scale characterizations suggest that the superior performance of the 20 wt% SiC coating is associated with the formation of a relatively continuous tribo-reaction layer composed mainly of Cr–Fe-rich oxides together with Si–O-related species. In addition, a heterogeneous subsurface structure consisting of Cr-enriched banded regions and Ni/Al-enriched island-like regions was observed after sliding at 800 ℃, which is likely related to enhanced shear accommodation and load support. These results indicate that an appropriate SiC content can improve the high-temperature tribological performance of laser-cladded AlCoCrFeNi coatings by stabilizing the interfacial reaction layer and reducing material removal.