Eco-friendly brake-pads using ferritic stainless-steel particles of varying sizes: Influence on performance properties

Metallic particles in brake-friction materials (FMs) play a vital role in improving mainly strength, friction level, thermal conductivity and hence resistance to fade during braking operations. Although Copper was the most efficient and popular metallic ingredient in FMs, it is being phased out because of its proven threat to the aquatic life in the form of wear debris. Hardly any successful efforts are reported in open literature barring few on in the authors' laboratory. It is well-known that the size and shape of particles affect the performance of composites apart from their type, concentration, etc. In this paper, Ferritic stainless steel (SS 434) particles were selected as a theme ingredient in two forms, first particulate (SSP) with two sizes, larger (30-45 micron) and smaller (10-20 micron) and also in the form of swarf. The aim was to investigate the size and shape effect of these ingredients when used to manufacture the brake-pads on the performance properties. A series of three multi-ingredient brake-pads with identical composition but differing in the type of SS particles and swarf. The theme ingredients were SS 434 particles (10-20 and 30-45 micron) and SS 434 swarf (Length:1-2 mm, diameter-50 micron). The developed brake-pads were characterised for physical, mechanical, chemical and thermal properties as per standards. Tribological performance was evaluated on full-scale inertia dynamometer by following JASO C406 standards. Results indicated that most of the tribological properties best for pads with smaller sized SSPs and the poorest with swarf (SSS). The topography of worn brake-pads was studied using a scanning electron microscopy (SEM). Finally, overall performance was analyzed by using the âMultiple Objective Optimizations by Ratio Analysis (MOORA) technique.'