Effect of the SiC Content on the Tribological Properties of Hybrid Al/Gr/SiC Composites Processed by <i>In Situ</i> Powder Metallurgy (IPM) Method

Abstract

The Al/Gr/SiC hybrid composites have attracted a considerable attention owing to their high wear resistance combined with a low friction coefficient. In these composites graphite acts as a solid lubricating agent and lowers the friction coefficient. However, it reduces the mechanical properties of the composite. The presence of hard SiC particles in these hybrid composites increases the hardness and strength and compensates for the weakening effects of graphite. Powder metallurgy (P/M) is an important processing technique for processing of these MMCs but requires a relatively long mixing time for obtaining a uniform distribution of graphite and SiC particles in the matrix alloy. In the present study for the first time a new method, namely "in situ powder metallurgy (IPM)" is applied for preparation of Al/SiC/Gr hybrid composites. In this work, the effects of different contents (0-40 vol.%) of SiC particles on the morphology and size distribution of the IPM produced Al/Gr/SiC powder mixtures containing 9 vol.% of graphite particles was investigated. Then Al/Gr/SiC compacts were prepared by cold pressing of different powder mixtures and after sintering, the effects of SiC content on the density, microstructure, hardness and wear properties of the resultant hybrid composites was investigated.