The role of tribochemistry on fretting wear of Mg-SiC particulate composites

The objective of the present research is to analyze the role of SiC addition and load on the fretting wear of Mg-SiCp composites. The friction and wear properties of Mg-SiCp/steel contacts are studied with variation of SiC particulate volume fraction and load and compared to those of pure Mg/steel contacts. The wear mechanisms are investigated in detail using analytical techniques such as EDX, EPMA and Raman spectroscopy. In all the fretting contacts, the tribochemical reactions are observed to be dominant. In the early stage of fretting, abrasive wear dominates due to formation of MgO. In composites, the presence of harder SiC particulates causes severe abrasion. As the fretting continues, MgO undergoes tribochemical reaction and forms soft, viscous hydrated magnesia. In composites, hydrated silica formed from SiC, reacts with hydrated MgO and forms a dense hydrous magnesium silicate (DHMS), clinoenastatite. These soft, viscous triboproducts (hydrated MgO and DHMS) smear on the worn surfaces and decrease the friction coefficient. The experimental results reveal that the effect of SiC particulate loading (especially higher volume fractions) on friction coefficient is more significant compared to the normal load applied during fretting.