Effect of CoCrFeNi high-entropy alloy on the friction and wear properties of copper-based powder metallurgy friction materials

Purpose This experimental paper aims to investigate the effect of “CoCrFeNi high-entropy alloy” as a reinforcing phase on the properties of copper-based powder metallurgy friction materials. By systematically analyzing the influence of different CoCrFeNi contents on the microstructure, hardness, friction coefficient and wear rate of the materials, it seeks to optimize their application performance in high-speed train braking, addressing the issues of large fluctuation in friction coefficient and severe high-temperature wear of traditional materials. Eventually, 4 Wt.% CoCrFeNi is determined as the optimal addition ratio, achieving a balance between high friction coefficient and low wear rate. Design/methodology/approach In this study, the CoCrFeNi-reinforced copper-based friction materials were fabricated via the powder metallurgy method, with the specific procedures as follows: 1. Powder pretreatment and mixing (including Cu, Fe, Sn, CrFe, CoCrFeNi, etc.); 2. Cold pressing forming; 3. Hot-press sintering; 4. Performance testing (density, hardness, friction and wear experiments). By regulating the CoCrFeNi content (0–5 Wt.%), the influence of CoCrFeNi on the microstructure and tribological properties of the materials was analyzed. Findings The study found that the copper-based material with the addition of 4 Wt.% CoCrFeNi exhibits the optimal comprehensive performance: the hardness is increased by 7% (with a peak value of 23.12 HB), the friction coefficient reaches the highest (0.37) at 350 km/h and the wear loss is the lowest (107 mg). Excessive addition (>4 Wt.%) leads to particle agglomeration, which induces fatigue wear. Microscopic analysis shows that the CoCrFeNi has a good interface bonding with the copper matrix, promoting the formation of an oxide film and the wear mechanism shifts from abrasive wear to being dominated by oxidative wear. Originality/value This paper optimizes copper-based friction materials by introducing CoCrFeNi high-entropy alloy, which significantly improves high-speed braking performance (with a friction coefficient of 0.37 and wear loss reduced to 107 mg) and solves the problem of poor high-temperature stability in traditional materials. Its innovation lies in revealing the reinforcement mechanisms of high-entropy alloys (interface diffusion and oxide film regulation), providing new insights for the design of high-speed railway braking materials and thus possessing both academic value and potential for engineering applications. Peer review The peer review history for this article is available at: Link to the cited article.