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On the 'dusting' wear regime of graphite sliding against carbon

An examination is made of the influence of the conditions of sliding on the 'dusting' wear of graphitic carbon sliding against non-graphitic carbon. Specific wear rates are essentially independent of load, speed and contact temperature over a wide range, but begin to decrease at speeds above about 10 m s-1. At these high speeds, wear rates increase with increasing environmental pressure and at any one pressure increase with the type of vapour in the order H2, N2, O2, H2O and hydrocarbons. A wear mechanism is proposed in which the adsorption of vapours increases the rate of crack propagation during localised contact by a process analogue to stress-corrosion, and this is supported by an examination of worn surfaces and debris. The existence of a direct relationship between dusting wear rates and the adsorption energies of different gases and vapours on carbons suggests that physical adsorption is primarily involved.