Evaluation of frictional and wear properties of polycrystalline diamond at room temperature

In this paper, the room temperature friction and deformation properties of various polycrystalline diamonds; i.e. aggregates of diamond crystals with a "binder" phase of cobalt and a polycrystalline coating produced by a chemical vapour deposition processes (CVD) were studied when softer metallic and ceramic sliders were used. The experiments were conducted at relatively low sliding speeds (10 mm/min), in a vacuum of 10(-5) mbr after having cleaned the specimen surfaces by out-gassing them for about 30 min at 800 degreesC. As a result of increasing the number of traversals significant wear of the coated diamond by softer metallic sliders (aluminium and mild steel) was observed. With ceramic sliders, it is shown that the multiple traversals result in the formation of wear groove. With diamond silicon carbide, high friction and adhesion lead to significant metal transfer which then pre-empts cumulative deformation of the harder materials. With the diamond-cobalt composite, the friction is surprisingly low, there accumulation of wear debris on the tip of the slider but no permanent transfer of metal and the harder specimen is not damaged even after 5000 traversal.