Copper-free brake-pads: A break-through by selection of the right kind of stainless steel particles

Development of Copper-free friction materials (FMs) with an equivalent or better performance has been a focus of research from the last few years since the Cu-containing wear debris has been proven as a serious threat to the aquatic life. In this work, eco-friendly brake-pads were developed with various types of stainless steel particles (SSPs) to explore the possibility of replacing copper from the brake-pads. A series of six multi-ingredient brake-pads was developed containing 3 vol % SSPs (SS304, SS316, SS410 and SS434), SS swarf (SS434) and copper particles as theme ingredients keeping parent formulation identical. The brake-pads were characterized for physical, mechanical, chemical, and thermal properties. Tribo-performance was evaluated on a full-scale inertia brake-dynamometer by following JASO C406 test standard. Results revealed that almost all the properties were superior to the Cu-containing pads including wear. The average coefficient of friction was almost similar for all pads and wear performance was excellent for SS316 and SS304 based brake-pads since these materials had higher surface energy vis-`a-vis the adhesion improvement with the matrix. Surface analysis of worn brake-pads was done using a scanning electron microscopy (SEM). Finally, overall performance ranking of the brake-pads was done by using `Multiple Objective Optimizations by Ratio Analysis' (MOORA) method.