Influence of contact parameters on the tribological behaviour of various graphite/graphite sliding electrical contacts

Sliding electrical contacts are used in devices for the conduction of electrical power or the electrical signals between stationary and moving parts. The most widely used electrical-sliding system is still the conventional slip ring and brush assembly. In the last decade, the lifetime of ring-brush contacts was extended through the use of better contact-material combinations and design improvements. However, the extremely rapid electrification of many more components has put severe demands on this extended lifetime. This paper presents a novel, patented design for two sliding discs that allows the use of advantageous graphite/graphite contacts. In the literature there is a serious lack of understanding the performance of sliding electrical contacts with graphite/graphite pairs, which depends on the key contact parameters, as well as the influence and potential of the different available graphite materials. The normal load, the contact velocity, the electric current, and the three self-mated graphite contacts, i.e., hard carbon, electrographite and polymer-bonded graphite, were investigated. The results indicate that the contact conditions influence the performance, which is also very dependent on the graphite materials. The polymer-bonded graphite showed the best results in this study.