Effects of combined additions of SiO2and MoS2nanoparticles as lubricant additive on the tribological properties of AZ31 magnesium alloy

The tribological properties of combinative addition of nano-MoS2and nano-SiO2to the base oil have been investigated with a reciprocating ball-on-plate tribotester for magnesium alloy–steel contacts. The results demonstrate that the optimum mass ratio of nano-SiO2to nano-MoS2is 0.25:0.75. The optimum combinative addition into the base oil reduces the friction coefficient by 43.8% and the surface roughness (Sa) by 31.7% when compared to that found with the base oil. Meanwhile, the combinative addition of nano-MoS2and nano-SiO2, in comparison with single nanoparticles addition, is more pronounced in terms of the lubrication film stability. The excellent tribological properties of the SiO2/MoS2combinations are attributed to the formation of physical adsorption films and tribochemical products during the rubbing process and the micro-cooperation of various nanoparticles with different shapes and lubrication mechanisms.