Influence of mechanical and electrical load on a copper/copper-graphite sliding electrical contact

For sliding electrical contacts a combination of satisfactory current transfer and good tribological performance is desired. A complete tribo-electrical study is presented where a mechanical and an electrical load are applied and tribological and electrical properties are evaluated. Stationary copper plated spring steel wires are tested against rotating copper-graphite rings at varying mechanical and electrical load. The focus is on surface modifications of the copper and correlations to the electrical performance are discussed. It is concluded that the tribological action is dominating over any influence from current, resulting in a mechanically mixed layer of Cu2O and Cu, for all currents as well as for the pure mechanical case. A graphitic layer is observed on the very surface of the wire.