Effect of Electric Current on the Friction and Wear Behavior of Carbon Nanotubes-Silver-Graphite Composite

Carbon nanotubes-Ag-graphite (abridged as CNTs-Ag-G) composite was fabricated by means of powder metallurgy. The friction and wear behavior of the CNTs-Ag-G composite sliding against a copper alloy in the presence of electric current was evaluated and compared with that in the absence of the external electric field using a ring-on-block friction and wear tester. The effect of the electric current on the contact drop of the composite electric brush was also examined. Moreover, the worn surface morphologies of the composite at different sliding durations were observed using a scanning electron microscope. It was found that, as compared to the no-electric current condition, the composite sliding against the copper alloy in the presence of 10 A/cm~2 electric current recorded a larger friction coefficient and wear volume loss. This was attributed to the negative effect of the electric current on the uniformity and integrity of the lubricating film formed on the contact surfaces of the frictional pair, owing to the action of the friction-induced heat. Besides, the positive brush had a larger wear volume loss than the negative brush. This was because the water entrapped in the lubricating film was ionized in the presence of the electric current to generate highly active negative oxygen ions, which led to the oxidation of the positive brush and accelerated its wear.