Effect of FeSi₂ content on tribological properties of C/C–SiC–FeSi₂ composites

In this work, tribological properties of different FeSi₂-modified C/C–SiC composites have been studied using disk-on-disk type laboratory scale dynamometer. Results indicated that line wear rate decreased significantly with the introduction of FeSi₂ in C/C–SiC. In addition, when C/C–SiC is modified with FeSi75, linear wear rate decreased obviously and reduced to 10% of C/C–SiC wear rate at high braking speeds. However, coefficient of friction (CoF) attenuated seriously due to excess introduction of Fe–Si alloy and this attenuation can be solved by reducing the content of FeSi₂ in C/C–SiC–FeSi₂. In order to have simultaneous advantages of low wear rate and high CoF, appropriate FeSi₂ content in C/C–SiC was identified (such as, using FeSi95). Furthermore, the development of friction surface of C/C–SiC–FeSi₂ through microstructural image registration of the surface after a range of braking stops is reported. It has been found that the introduction of FeSi₂ can reduce the roughness of friction surface after braking stops and increase the integrity of friction films. This continuous friction film that covers C/C region can effectively reduce wear rate. However, excessive alloy friction film will reduce surface roughness and weaken the effect of plough. Therefore, high CoF is hard to maintain at high braking speeds. From this study, three types of friction films are identified, which are generated by different FeSi₂ contents in C/C–SiC. Additionally, their morphologies are characterized to illustrate the effect of FeSi₂ content on tribological performance of the composites.