Abstract
Cu-based friction materials have better tribological properties, high mechanical strength, and excellent thermal conductivity; therefore, they are widely used as friction materials in high-speed rail brake systems. However, with the remarkable increase in running speed of high-speed trains, a great amount of energy and high temperature are induced in the brake system; therefore, new challenges are generated for brake pad materials. In this paper, Cu-based friction materials were prepared with the addition of various hard particles as the friction phase, in order to obtain a good high temperature tribological performance. The experimental results showed that the Cu-based friction materials with addition of hard particles have moderate mechanical strengths and proper tribological properties. The temperature effects on the tribological behaviors of friction materials were investigated. The coefficient of friction (COF) for friction materials with addition of hard particles increased with temperature, resulting from the integrated effects of friction film, graphite, and material softening. The variation trends of the wear loss and wear rate with temperatures are similar to those of COFs, which are significantly reduced with the addition of hard particles.
Highlights
The brake system is the key safety component of the train
Because of the rapid development of high-speed trains, the reliability of their brake system has attracted much attention,1,2 which is mainly determined by the composition and microstructure of the brake pad material
This study aims to explore the influences of temperature on tribological properties of Cu-based friction materials and provide a basis for further design and fabrication of friction materials to be used in future high-speed trains with excellent braking performance
Summary
The brake system is the key safety component of the train. Because of the rapid development of high-speed trains, the reliability of their brake system has attracted much attention, which is mainly determined by the composition and microstructure of the brake pad material. The ideal brake pad material should have a stable friction coefficient and low wear rate independent of complex operating conditions such as temperature and humidity. Metallic composites, such as Cu-based friction materials, are commonly considered the most promising brake pad material, which are favored because of their good wear and thermal resistance, stable coefficient of friction (COF), and suitable cost. Cu-based friction materials are generally prepared with a substrate, lubricating phase, and friction phase. The substrate is usually Cu due to its good wear resistance and excellent thermal conductivity. Fe is usually added to enhance the mechanical strength and hardness of the Cu matrix. The lubricating phase, such as graphite and MoS2, is added to reduce the friction coefficient and wear rate of the materials. The friction phase is usually hard particles like WC, which is used to reinforce the friction coefficient and wear resistance of the friction materials.. The ideal brake pad material should have a stable friction coefficient and low wear rate independent of complex operating conditions such as temperature and humidity.. The ideal brake pad material should have a stable friction coefficient and low wear rate independent of complex operating conditions such as temperature and humidity.4–7 Metallic composites, such as Cu-based friction materials, are commonly considered the most promising brake pad material, which are favored because of their good wear and thermal resistance, stable coefficient of friction (COF), and suitable cost.. Fe is usually added to enhance the mechanical strength and hardness of the Cu matrix.13 The lubricating phase, such as graphite and MoS2, is added to reduce the friction coefficient and wear rate of the materials..
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