Tribological behaviour of lubricated surfaces under application of electric current

The present work discusses the effect of applying external voltage on the sliding of copper, aluminium, and polyethylene (PE) against steel surface lubricated by paraffin oil dispersed by polymeric particles such as PE, polyamide (PA), and polymethylmethacrylate (PMMA). Experiments were carried out to measure friction and wear of the tested materials. Based on the experimental observations, it can be noticed that the friction coefficient and wear are significantly influenced by the generation of electric static charge on the contact surfaces, which causes an attractive force imposed to the normal load. It is found that wear is more influenced by the electric static charge than friction coefficient. Besides, the effect of the external voltage on generating electric static charge is higher than friction. Among the polymeric particles, crystalline polymers such as PE and PA perform more effectively than glassy polymers such as PMMA. Dispersing oil by polymeric particles does not decrease friction coefficient displayed by aluminium sliding against steel, while aluminium as cathode displays minimum wear. PE as cathode shows minimum wear when the oil is dispersed by polymeric particles. For oil free of polymers, wear of PE pins remarkably increases when they are cathodes.