Characteristics of wear particles produced during friction tests of conventional and unconventional disc brake materials

Recent attention to the improvement of line-haul truck brake effectiveness, to compensate for lowered aerodynamic drag and to increase road safety, has prompted the US Department of Energy to support several projects aimed at the development of lightweight, high-performance friction materials. Using a specially designed, sub-scale disc brake testing system, a series of experiments was conducted to study the friction, wear, and frictional heating characteristics of both conventional and unconventional candidate disc brake materials. The selected sliding speed (11.0 m/s) was comparable to that experienced by a commercial disc brake surface on a truck travelling 60 miles/h (96.6 km/h). Material combinations included a commercial friction material on a gray cast iron disc, a commercial friction material on an aluminum metal matrix composite disc, a commercial friction material on a cast iron aluminide (Fe3Al) alloy disc, and a carbon/silicon carbide material pad on a disc of similar composition. An adhesive extraction method was used to remove the loose wear particles from the surfaces of the test discs. The characteristics of brake material wear particles differed significantly between the four sliding material combinations studied and are correlated with both surface roughness changes and wear modes.