Results are presented from studies of the relationship between the friction coefficient and environment, load and sliding velocity for a natural diamond stylus performing reciprocating sliding over a CVD diamond sample. The properties of CVD diamond are not necessarily similar to those of natural diamond. It is thus important to study the tribological properties of the former, both to attempt to understand the friction mechanism and because of its increasing potential applications as a coating material. Traditionally, friction for diamond sliding against diamond has been interpreted principally in terms of the adhesion and surface roughness theories. We put forward, here, a hypothesis based on a chemical transformation occurring during sliding, resulting in the production of graphitic material. The very low friction coefficients that have been measured under certain conditions of load and sliding velocity may thus be partly explained by the lubricating effect of graphite. [References: 43]
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