Effect of Ceramic Reinforcement Type on Friction Stability and Wear Resistance of Cu and Cu–Bronze Matrix Powder Metallurgy Brake Composites

The tribological performance of copper-matrix sintered brake pads for high-speed rail applications is strongly influenced by ceramic reinforcement type. However, a systematic comparison of SiC, ZrO2, and SiO2 within Cu and Cu–Bronze (Cu–Br) matrix systems remains limited. In this study, six powder metallurgy composites were produced by cold pressing and sintering at 900 °C, with each matrix reinforced with 2 wt.% SiC, ZrO2, or SiO2 and containing graphite and MoS2 as solid lubricants. Tribological tests were performed at 25, 100, and 400 °C under an 18 N normal load. Microstructural and thermal characteristics were evaluated using optical microscopy, SEM/EDS, and DTA/TGA. The coefficient of friction (COF) ranged from 0.163 to 0.364 across all formulations and temperatures. The Cu–Br-based composites exhibited a narrower reinforcement-dependent COF range than the Cu-based composites, particularly at elevated temperatures. Cu–SiO2 showed the highest COF within the Cu-based at all test temperatures, whereas Cu–Br–SiC composite exhibited the highest COF among the Cu–Br-based composites at 400 °C. The lowest specific wear rates were obtained for Cu–SiO2 at 25 °C and Cu–SiC at 400 °C. SiC-reinforced composites exhibited the highest hardness within both matrix systems.