Microstructure and wear behavior of CoCrFeNi high-entropy alloy reinforced copper-based friction materials at different sintering temperatures

Purpose As trains evolve toward high-speed and heavy-load capabilities, friction materials are prone to severe wear and matrix softening at high temperatures, making it difficult for brake pads to meet long-term, safe and stable service requirements. To address these issues, this paper uses CoCrFeNi high-entropy alloys as reinforcement phases and systematically investigates the effects of sintering temperature on the microstructure, mechanical properties and tribological behavior of copper-based friction materials. The results indicate that, as the sintering temperature increases, the density of copper-based friction materials remains essentially unchanged (approximately 4.96 g/cm3), while the hardness decreases, with the highest hardness achieved at 860°C (23.38 HB). With varying braking speeds, under sintering conditions at 920°C, the material exhibits a relatively stable friction coefficient. Specifically, at a braking speed of 350 km/h, the friction coefficient is 0.379 and the wear loss is 133 mg. The wear mechanism is primarily oxidative wear and fatigue wear, resulting in the best comprehensive performance. Design/methodology/approach In this study, CoCrFeNi high-entropy alloy copper-based friction materials were prepared by powder metallurgy at different temperatures. The specific steps are as follows: powder treatment, cold pressing molding, vacuum sintering and testing. The influence of sintering temperature on the properties of CoCrFeNi high-entropy alloy copper-based friction materials was analyzed by regulating the sintering temperature. Findings From the experimental results, it can be seen that with the increase of sintering temperature, the density of copper-based friction materials remains basically unchanged (about 4.96 g/cm3), while the hardness decreases, reaching the highest hardness (23.38 HB) at 860°C. With the change of braking speed, the material exhibits a relatively stable friction coefficient under the sintering condition of 920°C. Specifically, at a braking speed of 350 km/h, the friction coefficient is 0.379 and the wear amount is 133 mg. The wear mechanism is mainly oxidative wear and fatigue wear, resulting in the best overall performance. Originality/value This study reveals the influence of sintering temperature on copper-based friction materials by designing different sintering temperatures, significantly improving braking performance. Its innovation lies in revealing the influence of sintering temperature, providing a new solution for the preparation process of copper-based friction materials and having high engineering value.