A novel CoCrNi-based medium-entropy alloy self-lubricating composite with superior wear performance

CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties, suggesting its potential as a structural material. Nevertheless, the challenge lies in achieving an elusive combination of high hardness and inherent self-lubrication on the worn surface, which is crucial for attaining exceptional tribological performance in medium-entropy alloy (MEA). This study reports the preparation of a novel CoCrNi-based self-lubricating composite by powder metallurgy, which is reinforced simultaneously with Ag solid lubricating phase and SiC ceramic particles. During the sintering process, SiC decomposes to form high hardness in situ Cr₂₃C₆, enabling the composite to achieve high load-bearing capacity. During the sliding process, thick and dense Ag self-lubricating film is successfully achieved due to the mechanical and thermal effects. The protective tribo-layer effectively mitigates surface stress concentration induced by wear, thereby inhibiting surface coarsening and substantially enhancing the tribological performance. The results showed that compared with CoCrNi MEA, the wear rate and friction coefficient of CoCrNi/SiC/Ag composite are reduced by 88.1% and 32.8%, respectively, showing superior tribological properties over most MEA-based self-lubrication composites. This study further elucidates the wear mechanism of CoCrNi/SiC/Ag composite, providing a new strategy for developing self-lubricating materials with excellent comprehensive performance, which overcomes the inherent trade-off between wear resistance and lubrication.