Tribological and mechanical behavior of multilayer Cu/SiC + Gr hybrid composites for brake friction material applications

In this paper, we study the wear resistance of multi-layered composites of Cu/SiC + Gr hybrid composites prepared by layer compaction and pressure sintering. The tribological behavior and wear resistance of the composites were evaluated at a range of sliding speeds (5, 10, 30 and 35 m/s) in a laboratory scale inertia brake dynamometer for brake friction material applications. The wear surface morphology and mechanisms were studied using scanning electron microscopy (SEM), XRD, and stereoscopy. The microstructure of the composites was also characterized using SEM and optical microscopy and the mechanical response in compression and flexure was evaluated. The results of these tests indicate that the density, wear resistance, braking behavior and mechanical response can be significantly improved by the presence of a layer of copper away from the sliding surface. The presence of the layer also improved friction and wear resistance significantly. The formation of mechanically mixed tribolayer and oxides (Fe3O4) reduced the wear rate and stabilized the friction coefficient at 30 and 35 m/s. Finally, crack deflection and branching at the interface between the composite and Cu layers improved the flexural strength of the layered composites. The fractography analysis indicates a quasi-cleavage intergranular fracture in the composite layer and a purely ductile fracture in the Cu layer.