Interfacial interaction induced synergistic lubricating performance of MoS2 and SiO2 composite nanofluid

Abstract

SiO 2 was employed as an auxiliary lubricant for MoS 2 nanofluid to gain superior lubricating effect. Tribological properties and cold rolling lubrication performance of pure SiO 2 nanofluid, pure MoS 2 nanofluid and the MoS 2 +SiO 2 composite nanofluid were investigated to reveal the synergistic lubrication of MoS 2 nanosheets and SiO 2 nanoparticles. The results of tribological tests indicated that the composite nanofluid with κ (mass ratio of MoS 2 and SiO 2 ) ≥1 showed more excellent tribological properties than pure MoS 2 nanofluid depended on a low shear composite lubricating film formed on steel surface. The formation mechanism of the composite lubricating film was investigated through both experimental characterization and molecular dynamics simulation. During cold rolling process, SiO 2 nanoparticles which did not readily adsorb to steel surface firstly absorbed on the surface of MoS 2 . And then adsorb on the steel surface together with MoS 2 in virtue of the adsorption between MoS 2 and steel surface. A pressurized interlayer slip theory was creatively provided to explain the synergistic lubrication mechanism of the low shear composite lubricating film. The SiO 2 adsorbed on MoS 2 nanosheets changed the contact type between MoS 2 nanosheets from surface contact to point contact. Thus, the normal pressure on the surface of MoS 2 nanosheets was increased. According to the results of molecular dynamics simulation, the increase of normal pressure promoted the interlayer slip and reduced the friction coefficient between MoS 2 nanosheets. The relationship between lubrication mechanism and the mass ratio of MoS 2 and SiO 2 was also investigated to provide a systemic understanding of the synergistic lubrication performance. • SiO 2 could be used as an auxiliary lubricant for MoS 2 nanofluid. • The formation mechanism of the composite lubricating film was investigated. • A pressurized interlayer slip mechanism was creatively provided. • Sustainable lubrication mechanism of the composite nanofluid was studied.