XPS and SEM Analyses of Self-Repairing Film Formed by Mineral Particles as Lubricant Additives on the Metal Friction Pairs

The characteristics of the 1045 steel pairs using serpentine particles as oil additive were investigated by an AMSLER friction and wear tester. The surface topographies and composition of the worn surface of 1045 steel rings were identified by SEM and XPS. The results show that the additives can form a self-repairing film with a large number of micro-hole on the worn metal surface, which reduces the wear extent of the friction pairs significantly. The main elemental compositions of the film are Fe, O, Si, C and Mg, which indicates that the additives directly take part in the formation of the self-repairing film. The mechanism is that the rubbing action of the asperities between the two contact surfaces makes the surface of the particles generate a large numbers of dangling bonds during the process of friction. At the same time, the activated surface formed on the contact metal friction pairs make the particles adhered to it. Under the action of shearing stress on the contact surfaces, the particles spread on the worn metal surface to form self-repairing film.