Frictional properties of MoS2 on a multi-level rough wall under starved lubrication

Abstract

Owing to nano-MoS₂'s excellent anti-friction and anti-wear properties, nano-MoS₂, which can act as a nano-additive in lubricating oil or solid lubricants, is believed to have great potential in the lubrication of power machinery and moving parts of a spacecraft. The molecular dynamics method was used to construct a rough surface and a multi-level asperity structure to simulate starved lubrication before oil film breakdown, and the lubrication mechanism of MoS₂ as a nano-additive or directly coated on the textured surface could reduce the friction coefficient and wear was explained from the atomic perspective. Simulations showed that the multilayer MoS₂ played a role of load-bearing at light load or low velocity, and slipped into the grooves to repair the surface under heavy load or high velocity. Even if local asperity contact occurs, MoS₂ nanoparticles could accelerate the detachment of the initial asperity contact to prevent large-scale adhesion. The MoS₂ nanoparticles transformed the pure liquid oil film into a liquid–solid composite oil film, which was more suitable for lubrication under heavy load and high velocity because it increased the contact area, protected the friction surface and prevented asperity contact. The proposed lubrication mechanism contributes to understanding the frictional properties of layered nanomaterials under extreme conditions and provides a reference for further application of MoS₂ materials in the field of lubrication.