Effect of refined boron additives on the microstructure and tribological behavior of automotive brake pads

Abstract This study investigates the effects of refined boron additives on the microstructure, hardness, and wear behavior of brake pads. Conventional materials such as Novolak resin, copper, alumina, graphite, brass, zirconium silicate, and sulfates were combined with boric acid and borax decahydrate at varying weight fractions. Samples were fabricated via pressing, and microstructure, density, hardness, and wear were evaluated. Porosity increased with higher boron content, leading to lower density, while hardness initially increased and then decreased beyond certain concentrations (maximum at 2.5 wt.% for boric acid and 5 wt.% for borax decahydrate). A linear relationship between hardness and wear resistance was observed. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and 3D profilometry analyses revealed microcracks, oxide tribolayers, and plastic deformation at wear track edges. Overall, the incorporation of boron at optimal concentrations significantly improved frictional performance of the brake pads.