The Stability of the Coefficient of Friction and Wear Behavior of C/C–SiC

Abstract

To develop a fundamental understanding of the tribological behavior of carbon fiber-reinforced silicon carbide (C/C–SiC) composites as brake pads and discs for high-speed trains, we have studied the brake friction properties of C/C–SiC composites at initial braking speeds ranging from 30 to 63 m/s. The friction mating pairs were fabricated by two methods to obtain composites of different SiC content. The composite with a SiC content of 40.3 % was used as the friction pad, and that with a SiC content of 85.6 % was used as the friction disc. In our experiments, an interesting turning point of 59 m/s was observed: the coefficient of friction (COF) decreased from 0.43 to 0.32 with increases in the braking speed from 30 to 49 m/s, at which braking speed it reached a plateau; the wear rate displayed a cubic curve against initial braking speed and reached a minimum of 315 mm³/MJ at 59 m/s. The topographical observations by scanning electron microscope combined with the residual stress analysis revealed that the limited number tribochemical layers, as well as the mismatch of thermal expansion coefficient between the carbon fiber and matrix, contribute to the unusual tribological characteristics of C/C–SiC composites. The experimental results suggest the good tribological potential of self-mated C/C–SiC composites in high-speed working conditions in terms of a steady COF and low wear rate.