Development of Low Particle Emission Brake Rotors

Brake wear has been recognized as one of the most significant non-exhaust traffic-related particulate matter emission sources. Conventional cast iron brake rotors/discs experience substantial wear during the braking and contribute largely to the brake wear debris emissions. To tackle this issue, surface coating on the cast iron rotors represents a trending approach. In this study, a plasma electrolytic aluminating (PEA) process was used for preparing an alumina-based ceramic coating with metallurgical bonding to the cast iron brake rotors. Three different types of brake pads (ceramic, semi-metallic and non asbestos organic (NAO)) were used as the counterparts for tribological tests. The PEA coating with a dimple-like surface promotes the formation of a thin layer transferred from the pad materials to protect the rotor from wear. Compared with uncoated cast iron rotors in the same laboratory test conditions, the coated ones also resulted in a reduced wear rate of the brake pad. The wear debris is likely transported between the secondary plateaus regenerated through compacting wear debris on the pads and the transfer layer on the PEA-coated rotors before the debris is worn off, which would reduce the brake wear emission. The dynamic formation and detachment of the secondary plateaus are responsible to the variation of COFs. The PEA coating could be a promising solution to reduce wear and emission issues and increase longevities of brake rotors for both conventional and electrical vehicles