Argon low-pressure plasma treatment to stainless steel particles to augment the wear resistance of Cu-free brake-pads

Nowadays, the usage of Copper in brake friction materials (FMs)/pads is a major concern in the brake industry. Despite some of the earlier attempts for the Cu substitution, an issue with high wear of FMs due to their low adhesion of metal particles with the matrix (i.e., phenolic resin) is still largely unresolved. In the current study, the surface energy (SE) of stainless steels (SS316, SS410) and Cu particles was augmented using the right kind of plasma in optimized dose to improve the wettability/adhesion of metal particles with the matrix. The SE of treated particles increased significantly due to the reduction of oxides from the surfaces. A series of seven types of brake-pads was developed containing 3 vol% of SS and Cu (untreated and treated) particles as the theme ingredients keeping parent composition fixed. A reference pad without metal particles was also developed for benchmarking. The developed pads were characterized for physical properties and then evaluated for the tribological and noise-vibration (NV) performance on a brake-dynamometer following global test standards. The results revealed that the pads with treated SS and Cu particles showed a higher fade resistance (~ 2–3%) and reduced wear by ~ 10% compared to the pads with untreated particles. Overall, based on optimized technique, treated SS316 particles proved the best. The underlying mechanisms were studied through worn surface analysis using a field emission scanning electron microscope attached (FESEM) with an energy dispersive X-ray spectroscopy (EDAX).