An investigation on the lubrication mechanism of MoS2 nanoparticles in unidirectional and reciprocating sliding point contact: The flow pattern effect around contact area

The goal of the work is to investigate the flow pattern of MoS2 nanoparticles, which influences the lubrication properties of the lubricant. The tribological behavior of MoS2 nanoparticles was studied in unidirectional or reciprocating ball-on-disk sliding tribometer. Friction reduction of 0.25 wt% MoS2 nanoparticles in reciprocating mode reached 53.1% compared with that of base oil; whereas the friction coefficient of 0.25 wt% MoS2 nanoparticles in unidirectional mode was similar with that of base lubricant (about 0.18). Flow pattern results of MoS2 nanoparticles around contact area show that particles piled up heavily in the inlet of contact zone in unidirectional mode, leading to starved lubrication. However, loose net-like aggregations were formed in reciprocating mode, benefiting to reduce friction and wear.