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

Abstract

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. 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. 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. 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.