Effects of alumina in nonmetallic brake friction materials on friction performance

The effects of alumina (Al₂O₃) as an abrasive on brake friction performance and friction layers of nonmetallic brake friction materials were evaluated. Five experimental compositions containing from 0 to 14.6 vol% alumina were tested (Al₂O₃—0, 3.4, 5.6, 9.0, and 14.6 vol%). The experimental results indicated that alumina enhances friction coefficient and improves wear performance. The formation and development of friction layers were characterized using X-ray fluorescence spectrometry and scanning electron microscopy with energy dispersive X-ray analysis. Phenomena of baryte film and transferred iron-containing film formed on the friction surfaces were observed. Baryte films were detected on specimens containing from 0 to 5.6 vol% alumina. Iron-containing films were detected on surfaces of all alumina-containing specimens but not on the material without alumina. The role of abrasive in nonmetallic friction materials was studied in relation to formulation, friction performance, and friction surfaces.