Tribological behaviour of A390/Grp metal-matrix composites fabricated using a combination of rheocasting and squeeze casting techniques

The dry sliding wear performance of hypereutectic A390 Al-Si alloy reinforced with graphite particulates (Gr(p)) was investigated. Composites containing 4 and 8 wt% of Gr(p) were produced by rheocasting technique followed by squeeze casting. Pins of the materials were rubbed against a 316 stainless steel disc using pin-on-ring type apparatus under various loads and speeds. It has been observed that both wear rate and the coefficient of friction of the composites decreased considerably with Gr(p) additions. The A390/Gr(p) composites exhibited higher wear resistance than those obtained for the monolithic A390 alloy. The formation of the hard tribo-layer on the surface of the composites assisted in increasing the wear resistance of these materials. It is believed that the reduction of the friction coefficient is attributed the presence of the graphite layers within the tribo-layer.