Fading behavior and wear mechanisms of C/C–SiC brake disc during cyclic braking

In this work, the performances of C/C–SiC brake discs under extreme operating conditions, including cyclic high-temperature and emergency braking of heavy-duty tracked vehicles, were investigated. The friction interface evolution and anti-fading mechanism of C/C–SiC brake discs during cyclic braking were also revealed. The maximum temperature of the C/C–SiC brake discs contact surface during cyclic high-temperature braking reached 663.7 °C, while the maximum decay rate was only 9.55%. Compared with the iron-based brake discs, the average coefficient of friction (COF) of the C/C–SiC increased by 14.70% and the wear rate decreased by 306.68% after the 10th braking cycle. A “C + SiC + SiO2” continuous friction film generated during the late stage of braking slowed down the diffusion of oxygen into the matrix, resulting in an excellent performance of the brake discs at high temperatures. Furthermore, the average COF of the C/C–SiC brake discs was maintained at 0.45–0.50 during cyclic emergency braking. When the friction film was not generated or was destroyed, the COF mainly depended on the surface asperities. However, when the friction film was completely covered, the COF decreased and tended to be stable and consistent, suggesting that C/C–SiC brake discs can provide a sufficient and stable braking force at different speeds.