Friction and Wear Mechanics of Fe-Based PM Pad Paired with Carbon Fiber-Reinforced Silicon Carbide (C/C-SiC) Disk Under High-Speed Braking

Powder metallurgy (PM) brake pads pair with carbon fiber-reinforced silicon carbide (C/C-SiC) brake disk have been considered as one of the potential candidates for high-speed train applications. In this work, the braking test for iron-based PM (Fe-PM) pads paired with C/C-SiC brake disk at high speeds was conducted on a full-scale flywheel braking dynamometer. With the increasing of initial brake speed (IBS) to 380 km/h, the mean coefficient of friction (µm) gradually decreased, while the wear rate (Wr) of pad got significant increased. The wear pattern of the Fe-PM pad transitioned from abrasive and adhesive wear to oxidative wear with the increasing of IBS, explaining the variations in µm and Wr. Throughout the braking process, wear debris from Fe-PM pad tended to accumulate, forming a dense transfer film (TF) on the C/C-SiC disk. This TF cracked and peeled off due to thermal stress during the braking process. However, analysis of the interior side of the TF revealed that the peeling only caused slight exfoliation of carbon fibers on the surface of the C/C-SiC disk.