Behaviour of graphite in friction under various environments. Connection with the surface reactivity
We have shown that the relative slip under load at an interface of copper/polycrystalline graphite in the presence of a low water vapour pressure, leads to the gradual growth of a superficial boundary of strongly oriented graphite with basal planes parallel to the friction surface. X-ray analysis has shown an analogy with the structure of high oriented pyrolitic graphite (HOPG) and the mechanical properties of this thin boundary are excellent. It is load resistive and the friction coefficient is very low and near 0.1.