Chemical and microstructural changes induced by friction and wear of brakes

The chemical and microstructural changes occurring during braking simulatio n tests at the surface of a conventional brake pad material were investigat ed mainly by scanning and transmission electron microscopy and surface anal ytical techniques. It can be shown that patches of a third body material de velop, comprising a compositional mix of all constituents of the pad and ir on oxides from the disk. Milled debris particles still have the crystal str ucture of barite, the major phase of the pad material, but the grain size i s reduced drastically to the nanometer scale. The major wear mechanism is d elamination of filler particles from the organic binder, supported by local degradation of the phenolic resin during asperity heating. Quartz crystals are preserved thereby adopting the function of primary contact areas. (C) 2001 Elsevier Science B.V. All rights reserved.