Effect of adding Sn to graphite on electrical contact resistance between sliding surfaces of graphite and Cu

Sliding experiments associated with electrical contact resistance were conducted with sintered graphite or graphite containing Sn (5.30%) pin samples on a copper disk at a constant speed (0.75 m/s), load (2.7 N), and sliding distance (1.5 km) with and without electric current (0.05-5 A). Air and argon atmospheres, including moisture ranging from 4 to 95% relative humidity, were tested. It was found that with increasing humidity the thickness of transferred graphite gradually increased, and its film oriented preferentially parallel to the (001) plane on the sliding surface. The electrical contact resistance increased as the preferred orientation was formed. By adding a suitable content of Sn to graphite, the increase of electrical contact resistance tended to be controlled depending on the humidity