Preparation and tribological properties of thin oxide coatings on an Al383/SiO2 metallic matrix composite

A new Al383/SiO2 metal matrix composites (MMC) was designed to improve the wear properties of the aluminium (Al) alloys with manufacturing cost much lower than the hypereutectic Al–Si alloys. However, like the hypereutectic Al alloys, the MMC was also subject to large plastic deformation of the soft Al matrix under high contact stress during lubricated sliding wear tests. As a result, the reinforced SiO2 particles detached from the matrix and promoted the third-body wear. In this paper, to improve the wear performance of the MMC under high contact stress but also to avoid the honing process, a new proprietary approach based on a modified Plasma Electrolytic Oxidation (PEO) process was used to produce oxide coatings on the MMC. The effect of both oxide coating thickness and the volume content of SiO2 particles on the wear behaviour of the MMC was investigated. It was found that with a proper combination of the volume content of SiO2 and coating thickness, the coated MMC presented a much higher wear resistance and lower friction coefficient than the uncoated MMC.