Effect of the electric current on the friction and wear properties of the CNT–Ag–G composites

In this paper, CNT–Ag–G composite brushes were fabricated by means of powder metallurgy method. The friction coefficient, wear volume loss and contact voltage drop of composites with and without current were investigated and worn surface were observed using SEM. The results showed that the wear volume loss of composites with current was greater than that without current. The primary cause of the unfavourable influence of an electric current on brush was the increase in the roughness and intensification of the abrasive properties of the metal counterbody surface. Because of oxidation reaction and weakening of the bond between the grains in the materials of the brush surface layer, the wear volume loss of positive brush was larger than that of negative brush. Due to the forming of continuous lubrication film between brush and ring under mechanical wear, the friction coefficient of composites without current was smaller than that with current. The contact voltage drop of composites was low in the initial state of wear and then rises to a certain level and remained constant.