Influence of electric fields on the tribological behaviour of electrodynamical copper/steel contacts

The crossing of the electric current in rail lines through a copper/steel sliding contact is associated with an electric field between the sliding surfaces. The electric field increases with the current intensity, the sliding speed and the contact resistance, and it decreases with an applied normal load. An electric field enhances the oxidation of surfaces, and the growth of such an oxide layer increases the electric field. Mechanical wear removes the oxide film and then decreases the electric field. The process of wear in an electrical sliding contact is continuously modified by the electric field according to the current intensity. Surfaces can be damaged by abrasive wear, by oxidation, or by an electric arc through the contact. This paper presents the results of an experimental study of the wear behaviour of an electrical sliding contact and its variation in the presence of an electric field. We discuss the effects of the electric field on surfaces, mechanical properties and tribological behaviour.