Tribological Properties of Abrasives (Alumina, Silica, Zircon) for Brake Friction Materials

Automotive brake friction materials are multi-component composites composed of functional materials such as fibers (reinforcements), binder, solid lubricants, friction modifiers, abrasives and space fillers. Abrasives are the ingredients that have higher Mohs hardness and play important roles on tribological properties of brake friction materials. Most commonly used abrasives in commercial brake friction materials are alumina (Al2O3), silica (SiO2), silicon carbide (SiC), zircon (ZrSiO4) and zirconia (ZrO2). In this study, six brake lining samples were produced using abrasives of three types viz. silica, alumina and zircon (5 and 10 wt.%) and investigated its friction properties. The samples were produced by a conventional procedure for a dry formulation following dry-mixing, pre-forming and hot pressing. Friction and wear characteristics of the specimens were examined using a pad-on-disc-type wear tester. The physical and mechanical properties such as hardness, density, porosity, tensile strength, compressive strength of samples and morphological properties via Scanning Electron Microscope (SEM) were investigated. The results of tests showed that the friction coefficients of the composites increased with increasing abrasive amount. The results also indicated that specific wear ratio of the composites decreased with increasing abrasive amount. The sample containing 10 wt. % alumina exhibited the better friction performance