Braking behaviors of Cu-based PM brake pads mating with C/C-SiC and 30CrMnSi steel discs under high-energy braking

Exploring braking behaviors of powder metallurgy (PM) brake pads mating with different brake discs is conducive to promoting the development of high-speed trains. In this study, the braking behaviors and wear mechanisms of Cu-based PM brake pads mating with C/C-SiC and 30CrMnSi steel disc, respectively, under high-energy braking condition have been investigated. Results show that compared with PM-30CrMnSi brake pair, the coefficient of friction (COF) and stability coefficient of PM-C/C-SiC brake pair are increased by 28.9% and 13.9%, respectively, and the PM pad wear rate and braking time are reduced by 31.0% and 29.5%. Moreover, PM-C/C-SiC brake pair does not exist obvious tail warping in braking curve, which can be attributed to the formation of dense tribo-layer and the lubrication of carbon fibers. TEM analysis shows that the tribo-layer of PM-C/C-SiC brake pair is composed of nanostructured oxide layer and plastic deformation layer. Besides, a similar to 600 nm thick oxide layer containing nano-sized Cu/Fe oxides and ZrSiO4 particles greatly improves COF and wear resistance of PM pad. The dominant wear mechanisms of PM-C/C-SiC brake pair are delamination and oxidation wear, whilst those of PM-30CrMnSi brake pair are abrasive and adhesive wear.