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.