Friction and wear behavior of diamond films against steel and ceramics

Friction and wear tests were conducted at room temperature on diamond films deposited on silicon substrates by a microwave plasma-assisted chemical vapor deposition technique. Three different diamond film morphologies ( i.e. faceted, cauliflowered and smooth) were evaluated in sliding contact with steel, α-alumina, silicon nitride and magnesia-stabilized zirconia balls. In addition to the uncoated balls, a few tests were also conducted with silicon nitride balls coated with either a cauliflower-type or a smooth diamond film. All the material combinations, except for diamond films sliding against diamond films, exhibited friction coefficients in the range 0.38–0.90. The average friction coefficient for diamond films sliding against diamond films was 0.10. The faceted films exhibited higher friction coefficients and higher wear rates of the counterface materials than those for the smooth films. Examination of the worn surfaces of the diamond films and steel counterfaces revealed that the diamond films wore primarily by fracturing the tips of crystals. A secondary wear mechanism of delamination within the diamond films was also observed. The wear of the steel counterface occurred by abrasion.