Synergistic friction-reduction and wear-resistance mechanism of 3D graphene and SiO2 nanoblend at harsh friction interface

Developing nano-materials as lubricating anti-wear additives is an effective way to reduce wear and friction of mechanical equipments for significantly improving their energy conservation and service life. Herein, the tribological properties (friction-reduction and wear-resistance properties) friction-reduction and wear-resistance mechanism of 3D graphene nanosheets (GNS), SiO2 nanoparticles and their nanoblend as additives in castor oil at steel/steel (SUS304 stainless steel) contact interface are comprehensively investigated under varied load and speed. And two main wear forms, adhesive wear and abrasive wear, under different experimental conditions are analyzed in detail. The friction and wear of the corresponding friction interface can be effectively reduced by these nano additives, the nanoparticles' mechanism of action is closely related to the load and speed applied, in particular under low speed and heavy load. The SiO2/3D GNS nanoblend demonstrates the best tribological performance with the maximum reduction of reducing wear and friction by 46.1% and 22.4%. By comparison, the tribological performance of pure GNS and SiO2 are much lower than that of the GNS and SiO2 hybrid nanoparticles. The origin of such high anti-wear mechanism is rooted from the formation of the protective film formed by 3D GNS and SiO2 as well as the synergistic effect between 3D GNS and SiO2. Besides, the easy-shear nature between the layers of graphene and the rolling-bear effect of SiO2 together reduce the friction at the steel/steel contact friction interface.