The effect of Al 2O 3 on the friction performance of automotive brake friction materials

Abstract

This study consists of two stages. In the first stage, bronze-based break linings were produced and friction-wear properties of them were investigated. In the second stage, 0.5%, 1%, 2% and 4% alumina (Al 2O 3) powders were added to the bronze-based powders and Al 2O 3 reinforced bronze-based break linings were produced. Friction–wear properties of the Al 2O 3 reinforced samples were aslo investigated and compared to those of plain bronze-based ones. For this purpose, friction coefficient and wear behaviour of the samples were tested on the grey cast iron disc. The hardness and density of the samples were also determined. Microstructures of the samples before and after the sintering and the worn surfaces of the wear specimens were examined using a scanning electron microscope (SEM). The sample compacted at 350 MPa and sintered at 820 °C exhibited the optimum friction–wear behaviour. With increase in friction surface temperature, a reduction in the friction coefficient of the samples was observed. The lowest reduction in the friction coefficient with increasing temperature was for the 2% and 4% Al 2O 3 reinforced samples. The SEM images of the sample indicated that increase in Al 2O 3 content resulted in adhesive wear. With increase in Al 2O 3 content, a reduction in mass loss of the samples was also observed. Overall, the samples reinforced with 2% and 4% Al 2O 3 exhibited the best results.