Effects of methane concentration on tribological properties of diamond films prepared on different ceramic substrates

Diamond films were prepared on silicon nitride and zirconia ceramic substrates using hot filament chemical vapor deposition (HFCVD). The surface morphology, friction, and wear properties of the diamond films prepared with different methane concentrations (2%, 4%, and 6%) were compared using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and friction and wear testing machines. The results showed that, with an increase in the methane concentration, the diamond particles gradually changed from micro- to nanodiamonds, and the grain size first increased and then decreased. The diamond films on silicon nitride substrates were of excellent quality, with good wear resistance, strong adhesion, and wear rates of 2.857 x 10-8 mm-3 center dot m-1 center dot N-1, 5.151 x 10-8 mm-3 center dot m-1 center dot N-1, and 1.334 x 10-7 mm-3 center dot m-1 center dot N-1, respectively. The diamond films on zirconia substrates had more impurities on the surface, higher internal stress, poorer wear resistance, and weaker adhesion, with wear rates of 3.789 x 10-8 mm-3 center dot m-1 center dot N-1, 5.899 x 10-8 mm-3 center dot m-1 center dot N-1, and 2.074 x 10-7 mm-3 center dot m-1 center dot N-1, respectively. Hence, the deposition of diamond films on ceramic substrates significantly reduced the friction coefficient, and the performance of diamond films on silicon nitride substrates was excellent.