Sliding tribological properties of 0.45% carbon steel lubricated with Fe3O4 magnetic nano-particle additives in baseoil

Approximately 10 nm Fe3O4 magnetic nano-particles (MNPs), modified by oleic acid, were used as lubricant additives and dispersed into base oil. The tribological properties of 0.45% carbon steel were investigated in sliding contact against 440C stainless steel lubricated with various concentrations of Fe3O4 MNPs. Wear tests were carried out on a ball-on-flat contact at various loads (10, 30, and 50 N) for 1 h. The results show that the coefficient of friction and wear-loss-volume can be reduced efficiently with addition of Fe3O4 MNPs. The average coefficient of friction is reduced with the increase of the concentrations of Fe3O4 MNPs, and the difference was particularly evident at a load of 10 N. The wear-loss-volume decreased as the concentration of Fe3O4 MNPs increased, e.g. the wear-loss-volume was reduced by 41.8%, 51.5%, and 64.7% when lubricated with concentration 0.5, 1and 2 g/L magnetic lubricants at the load of 10 N, respectively. It is believed that the reduction of friction and wear must come from the addition of Fe3O4 MNPs in the base oil which can offer protection between the rubbing surfaces.