The deteriorated tribological and noise performances of copper-based brake pads induced by the increased content of flake graphite

Enhancing the lubricity of copper-based brake pads has been viewed as a crucial strategy to boost braking performance. Flake graphite and the oxide film are two substances that are widely concerned with providing lubrication at the friction interface. However, the results from full-scale dynamometer in this work indicate that the increased content of flake graphite with stronger lubrication and iron particles that accelerate the generation of oxide film lead to a deterioration in tribological and noise performance. This is manifested by high sensitivity to clamping force, significant fading behavior, increased sound pressure level and high-frequency noise. The evidence from the worn surface suggests that flake graphite is susceptible to peeling off from the friction surface, thereby amplifying the instability of the friction surface. The unstable existence of both flake graphite and oxide film during emergency braking actually diminishes the lubrication of the friction interface, likely resulting in the degraded braking performance. The indication suggests that the development of high-performance copper-based brake pads should aim to achieve a harmonization of diverse properties, rather than emphasizing only specific aspects.