Evolution in friction and wear of Mg-SiC_p composites: Influence of fretting duration

摘要

In the effort toward achieving lightweight, wear-resistant, composite materials, considerable effort, in recent times, has been put forward to develop Mg-SiC composites. The detailed wear mechanism of these newly developed composites is still unclear, and most of the work on metal matrix composites (MMC) to date has concentrated on evaluating the wear behavior of Al-based MMCs. In the present work, the influences of fretting test duration on the evolution of frictional behavior as well as wear properties were studied. The experimental results revealed that fluctuations in friction curve are significantly suppressed with highest reinforcement content (26.3 wt percent) in composites while considerable fluctuations continue to exist even after achieving steady state condition in base Mg. In all the fretting contacts, tribochemical reactions were observed to be dominant wear mechanisms. In the early stage of fretting, oxidative wear dominates due to formation of MgO. As the fretting continues, MgO undergoes tribochemical reaction and forms soft, viscous hydrated magnesia. For base Mg, surface fatigue cracks were observed after a threshold number of cycles. In composites, the soft, viscous triboproducts (hydrated MgO and dense hydrous magnesium silicate) smear on the worn surfaces and decrease the friction coefficient.