Effects of oxidation temperature on the microstructure and tribological performance of Cu-based brake pad for high-speed train

Abstract

The braking process of different speeds causes varying degrees of oxidation of the Cu-based brake pad, which will significantly affect its tribological performance. To simulate the process, Cu-based brake pads for high-speed trains were oxidized in atmospheric conditions at 25, 200, 400, and 600 °C, respectively. The microstructure and composition of the oxide layers were analyzed, and the tribological properties of the oxidized surfaces were investigated. The results show that, as the oxidation temperature rises, the surface oxides change from Cu2O + Fe3O4 to CuO + Fe3O4, along with the increase in the thickness and hardness of the oxide layer. The ablation of graphite particles is aggravated. The formed oxides and ablated graphite result in high friction coefficient and wear rate. Due to the loss of plastic deformation ability, the dominant wear mechanism of Cu-based brake pad transforms from delamination wear to abrasive wear with the increase of oxidation temperature.