Effect of Cr3C2 content on microstructure, mechanical and tribological properties of Ni3Al-based coatings

To broaden the applicability of Cr3C2 -reinforced Ni3Al-based coatings, which possess exceptional high-temperature strength and anti-friction properties for high-temperature solid lubrication, this study examined the influence of varying Cr3C2 concentrations (0 wt%, 10 wt%, 15 wt%, and 20 wt%) on the phase composition, microstructure, mechanical performance, and friction and wear behaviors of Ni3Al-based coatings from 25 °C to 800 °C. The findings indicated that decarburization of Cr3C2 took place during HVOF spraying, forming Cr7C3. The remarkable high-temperature lubricity of all coatings can be attributed to the synergistic lubrication effect resulting from the precipitation of soft metal Ag, the brittle-plastic transformation of MoO3, and high-temperature solid lubricants such as NiCr2O4 and Ag2MoO4, which are induced by high-temperature friction. The second phase strengthening of Cr3C2 and the solute effect in the Ni3Al matrix phase significantly improved the hardness and toughness of the coatings, thereby enhancing their wear resistance. Notably, the coating containing 15 wt% Cr3C2 exhibited the lowest coefficients of friction (COFs) and wear rates (WRs) (10−5 mm3·(N·m)−1), ranging from 0.60 to 0.26 and 14.48 to 2.01 at 25 °C to 800 °C, which can be ascribed to the coordination between lubricity and mechanical strength.