Analysis of self-repair films on friction surface lubricated with nano-Cu additive

Abstract

The surface modified nanocopper particles were prepared with chemical reduction method. The wear test was carried out on a T-11 ball-on-plate friction and wear tester made in Poland. The material of the upper sample was GCr15 and the counterpart was AISI-1045 steel. The morphologies of the worn surfaces of the samples were observed by optical microscope and scanning electron microscope, while the element distributions on the worn surfaces were determined by means of electron microprobe analysis. As the results, a film mainly made of Cu is formed on the worn surface. The film on the surface of the still upper sample is thicker than that formed on the revolving counterpart. At the edge of the groove of the worn surface made by the milling before test there is Cu element observed obviously, but there is not any Cu element in the bottom of the groove. A possible action mechanism of the film is suggested. The friction movement can induce reactivity of the metal and continuously produce activation surface. It benefits the film formed by nano-Cu in lubricant on the worn surface. Hardness and modulus of nano-Cu films were successfully measured and analyzed by the nanoindentation instrument. The results show that the hardness and modulus of the films are lower than those of the initial surface.

Keywords

nano-Cu / surface analysis / nanoindentation / mechanism of film