Influence of particle content and porosity on the wear behaviour of cast in situ Al(Mn)–Al2O3(MnO2) composite

Aluminium-based tribological materials may reduce the weight of components, leading to significant fuel economy. The aim of the present study is to investigate the wear and friction in cast in situ Al(Mn)–Al2O3(MnO2) composites synthesized by dispersing MnO2 particles in molten aluminium, which get reduced to form Al2O3 particles. Wear tests have been conducted at four normal loads of 9.8, 19.6, 29.4 and 39.2 N and at a constant sliding speed of 1.05 m/s using a pin-on-disc wear testing machine, under dry sliding conditions. The results of the investigation indicate that the cumulative volume loss and wear rate of in situ composites are significantly lower than those observed in either the commercial aluminium or Al–Mn base alloy, under similar loading and sliding conditions. The influences of both reinforcing particle and porosity contents on the tribological behaviour of in situ composites were evaluated. It has been found that at a given particle content, the wear rate increases with increasing porosity content due to its combined effect on real area of contact and subsurface cracking. The wear rate of in situ composites with relatively lower porosity decreases with increasing particle content, but does not appear to change significantly or even increases a little with increasing particle content when the composites have relatively higher porosity. In view of large fluctuations in coefficient of friction during sliding, no effect of particle or porosity contents on the coefficient of friction could be determined unambiguously for different in situ composites.