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 c hemical vapor deposition technique. Three different diamond film morph ologies (i.e. faceted, cauliflowered and smooth) were evaluated in sli ding contact with steel, alpha-alumina, silicon nitride and magnesia-s tabilized zirconia balls. In addition to the uncoated balls, a few tes ts were also conducted with silicon nitride balls coated with either a cauliflower-type or a smooth diamond film. All the material combinati ons, except for diamond films sliding against diamond films, exhibited friction coefficients in the range 0.38-0.90. The average friction co efficient for diamond films sliding against diamond films was 0.10. Th e faceted films exhibited higher friction coefficients and higher wear rates of the counterface materials than those for the smooth films. E xamination of the worn surfaces of the diamond films and steel counter faces revealed that the diamond films wore primarily by fracturing the tips of crystals. A secondary wear mechanism of delamination within t he diamond films was also observed. The wear of the steel counterface occurred by abrasion.