Tribological properties and wear mechanisms of hot-pressed sintering mesocarbon microbeads (MCMBs)-SiC composites against different counterparts

Abstract

The sliding tribological properties of dense MCMBs-SiC composites with 30 wt% MCMBs against self-mated counterparts, WC and SSiC were studied through a block-on-ring method under different loads respectively. The dense composites with excellent mechanical properties were fabricated through hot pressed sintering method. The results showed that the tribological properties of MCMBs-SiC composites were affected more by the properties of counterparts than the applied load. Under different loads, compared to WC-mated and SSiC-mated friction pairs, the self-mated pairs showed lower and more stable dry friction coefficient (μ) due to the lubricating film formed on the sliding surfaces. At the same time, the WC-mated friction pairs showed the lowest wear rate due to the highest fracture toughness of WC counterparts. The SSiC-mated friction pairs showed the highest μ and wear rate under both applied loads. The wear mechanisms of different friction pairs were also investigated. The results showed that although the applied loads and counterparts were different, the wear mechanisms of each friction pair can be divided into three stages. For WC-mated and SSiC-mated friction pairs, wear mechanisms were almost the same. The first stage was the mechanical wear of grains, then following by tribochemical reactions (mostly oxide reactions) and finally removal of tribochemical layers. For self-mated friction pairs, during the third stage, the lubricating films was generated on the working surfaces due to a large amount of graphite phase from MCMBs in the composites.