Effect of Surface Modification on the Tribological Properties of Friction Blocks in High-Speed Train Brake Systems

Commercial high-speed train friction blocks with a hole in the middle of the surface and perforated blocks filled with additive materials are introduced in drag brake experiments conducted on a customized small-scaled braking dynamometer. These additive materials include Cu-based powder metallurgy material, composite material, and a Mn-Cu damping alloy. The results indicate that the filling materials significantly influence the wear behavior of a braking interface and the characteristics of friction-induced vibration. Under the same experimental conditions, the perforated blocks filled with different materials produce different types of wear debris and exhibit different wear evolutions, markedly changing the wear debris distribution and surface morphology. These changes lead to variations in thermal distribution on the surfaces of both the friction block and brake disc. The study also shows that as a filling material, the Mn-Cu damping alloy can suppress the friction-induced vibration of the brake system, resulting in the lowest level of brake noise among all brake systems. However, the original friction block (i.e., the block without any filling material) can trap wear debris because of its perforated structure. The structure produces less friction-induced vibration and noise, compared with the block filled with powder metallurgy material. The noise performance of the composite material block is superior to the noise performance of the block without any filling material (i.e., the original block) and the block with powder metallurgy material but inferior to that of the block filled with the Mn-Cu damping alloy. Finite element analysis indicates that the properties of the filling materials exert no effect on the unstable vibration intensity of the brake system. Therefore, the wear debris behavior of the filling materials and the interface wear characteristics influence the friction-induced vibration and noise of the brake system.