An investigation on the wear resistance and mechanism of Fe60-Co20Mo Ni20 (x=10, 15, 20) high-entropy alloy reinforced by μ-phase

Fe–Co–Ni face-centered cubic (FCC) alloy has been one of the most extensively investigated alloys due to its potential ductility and toughness, while its low yield strength and wear resistance limit the engineering application. In this study, the different Mo content is added in the Fe–Co–Ni based alloy to solve this problem. The microstructure, wear resistance and tribological mechanism of Fe60-xCo20MoxNi20 (x = 10, 15, 20) high-entropy alloys after different annealing treatments are systematically investigated. The results reveal that the content of the μ phase increases with the addition of Mo element when annealed at 600 °C, and the highest amount of the μ phase is observed in the Mo20 alloy. The formation of the μ phase enhances the hardness of the Mo20 alloy, reduces the surface roughness during the wear process compared to Mo10 and Mo15 alloys, thereby improving the wear resistance. Furthermore, increasing annealing temperature also affects the content and distribution of the μ phase. The Mo20 alloy annealed at 600 °C exhibits the best wear resistance. However, as the annealing temperature increases to 1000 °C, the wear resistance deteriorates due to the spalling of the μ phase. In contrast, the wear resistance of the Mo15 alloy is optimized due to the uniform distribution of the μ phase. Additionally, when the sliding force increases from 2 N to 10 N, the wear resistance of the Mo20 alloy initially deteriorates before improves. This is mainly due to the increase in abrasive wear when the load is increased from 2 N to 5 N, while as the sliding force further increases to 10 N, a glaze layer is formed on the wear surface, which produces a lubricating effect. Furthermore, the better wear resistance of Mo20 and Mo15 alloys compared with others can also be attributed to the friction subsurface with nano-scale structure.