Tribological mechanisms of modified C/C-SiC composite discs: A comparison of copper-containing semi-metallic and copper-free friction pads

Investigating the tribological behavior of C/C-SiC against various friction linings is crucial for their advancement. In this study, SiC and graphite hybrid fillers were incorporated into C/C-SiC composites using slurry infiltration (SI) and precursor infiltration and pyrolysis (PIP) methods to modify the matrix and optimize the composition and microstructure. A full-scale dynamometer was used to investigate the tribological behavior of a C/C-SiC disc against copper-containing semi-metallic and copper-free pads. The results indicated that the average coefficient of friction (COF) for semi-metallic-based pads is 0.46, while that for copper-free pads is 0.38. The analysis of the worn surfaces revealed that the infiltrated micro-SiC and reaction-formed nano-SiC forming a multiscale SiC-phase substructure exhibit a "synergistic plowing effect" during friction. Copper-containing semi-metallic pads exhibit a combination of abrasive and adhesive wear, with metal oxidation being the primary cause of fading. The main oxidation products are CuO, Cu₂O, and Fe₂O₃. In contrast, copper-free pads primarily experience abrasive wear. The smaller debris form dense contact plateaus, which result in reduced wear loss.