Abstract: Tribological properties of five lubricating additives, T306, T307, T301, T202, T203, were investigated on a modified tribo-tester under electromagnetic field. Their lubrication mechanisms were analyzed from physical effect and chemical effect of electromagnetic field based on the results of surface analysis. In terms of physical effects, the force of electromagnetic field on wear particles is mainly considered. In terms of chemical effects, the structural relationship between active elements and molecular structure of lubricating oil is mainly considered. The results indicated that the electromagnetic effect facilitates the anti-wear properties of T306-doped oils but impairs that of T307-doped oils. The electromagnetic effect was not beneficial for the friction-reducing capacity of T306 and T307. Moreover, the anti-wear and friction-reducing abilities of T301/T202/T203 are improved by the electromagnetic effect.

Key words: electromagnetic effect, lubricating additive, lubrication mechanism, physical effect, chemical effect