The Arc Caused By The Sliding Friction Effects On The Tribological Properties Under Electric Current

The tests were studied on the HST-100tribo-tester with Copper-graphitecomposite materials/QCr0.5couple under electric current, which simulated workingconditions of the pantograph-wire system used in the electric railway. Influence ofgraphite content, pressure, current, speed and surface roughness on the different typeof arc and friction and wear properties were studied under flexible contact condition.And the worn surface of the pin sample were characterized by SEM, EDS and SurfacePlasmon Resonance Analyzer, the cause of the different type of arc and tribologicalmechanism were discussed under different parameters.According to the experiments, with the increase of the contact pressure，the arcrate and the wear rate decreased at first and then increased, the current-carryingefficiency increased gradually, the friction coefficient declined. Therefore, there is anoptimal contact pressure between the pantograph and overhead contact wires duringthe electric locomotive running. The contact unstable if the load is smaller than theoptimal solution, and the wear loss is big when the load is too big.The experimental results showed that the friction coefficient and wear rise, andthe arc rate increased and the carrying-current quality got worse with increase ofvelocity.The arc rate and the wear rate increased, the friction coefficient and the current-carrying efficiency decreased with increase of the current density. The arc erosion playan important roal in this case.With the graphite content of copper-graphite composite materials increased from5wt%to15wt%, the friction coefficient declined gradually and stability at end, thewear rate and the arc rate decreased at first and then increased, but the current-carryingefficiency increased at first and then decreased. So there is an optimal graphite contentof copper-graphite composite materials.With the reduction of the Surface roughness, the arc rate and the wear rate declined, the friction coefficient decreased at first and then increased, and the current-carrying efficiency increased gradually because the surface contact is better.After analysis of worn surface morphologies, the result showed that with theincreased of load arc erosion was restrained effectively, the arc erosion is more seriousafter the velocity was greater than25m/s, with the increased of the current densityadhesive wear play a major position during the wear process, improving the graphitecontent in a certain range can restrain the occur of arc and reduce the arc erosion, withthe reduce of surface roughness, arc erosion and adhesive wear were reduced duringthe wear process, and the wear mechanism was changed to be particle attrition.