Friction behaviour of a graphite-graphite dynamic electric contact in the presence of argon

Friction coefficient mu of graphite-graphite at low dynamical load (P = 5 N, nu < 0.04 m s(-1)) under argon gas at 1.4 X 10(5) Pa is very low (mu = 0.06). Above the critical value of sliding speed (nu = 0.04 m s(-1)) mu is around 0.7. The transition from the low friction state (mu = 0.06) to high friction state (mu = 0.7) depends on the historic of friction, particularly on the revolutions number of disc with speed lower than 0.04 m s(-1). According to the sliding speed and the sliding time, there appears an hysteresis phenomenon. The aim of this paper is to report those results and to discuss the influence of electrical current on this friction behaviour. The passing of an electrical current through the dynamical contact leads to an increase in the friction coefficient, but only above a critical intensity.