Friction properties of partially polished CVD diamond films at different sliding speeds

The rate dependence of the friction properties between a partially polished diamond film and metal has been investigated experimentally in the present research. Partially polished diamond films have low friction and low wear properties in air, and it is expected that the friction coefficient becomes very small at high sliding speeds.Polycrystalline diamond films are deposited on SiC substrates by hot filament chemical vapor deposition using a gas mixture of CH4 and H2. Partially polished diamond films of two different surface roughnesses, as well as the as-deposited diamond film, were tested under different sliding speed conditions. The friction properties between the diamond films and an AISI440C pin under dry conditions were determined in ambient atmosphere. For the polished films, a definite reduction in the friction coefficient was observed as the sliding speed increased; the speed at which this reduction began depended on the surface roughness of the film. Extremely low friction and noiseless sliding between films and counter metals were realized on polished diamonds as the sliding speeds increased.

► Diamond films are suitable as sliding materials.
► Surface condition may dominate friction/wear properties of polycrystalline diamonds.
► Super-low friction occurred upon partially polishing the surface of a diamond film.
► Boundary lubrication changes to hydrodynamic lubrication upon partial polishing.