TRIBOLOGICAL STUDY OF CNX FILMS PREPARED BY REACTIVE DC MAGNETRON SPUTTERING

The effects of both substrate bias voltage during fabrication and coun tersurface materials during sliding, on the tribology of CNx films are reported. Amorphous CNx films (12-24 at.% N), about 1 mu m thick, wer e deposited onto Si(100) substrates at 600 degrees C by d.c. magnetron sputtering of graphite in a nitrogen plasma. Tribological behaviour o f the CNx films was evaluated in continuous, unidirectional sliding ag ainst different materials (Al2O3, 52100 steel, and diamond film-coated Si3N4 balls) in pin-on-disk tests. Low friction coefficient values (m u=0.1-0.25) were found for soft, but rougher, films prepared at lower bias voltage (-300 V). Such films exhibited a relatively high wear rat e (greater than or equal to 1.3 X 10(-13)m(3)N(-1)m(-1)), partial tran sfer to the alumina ball, but the wear debris acted as a lubricant dur ing sliding. Harder CNx films prepared at higher bias voltage (-700 V) resulted in lower wear but higher friction levels (mu=0.25-0.5) when sliding against alumina, The hardest film (23 GPa) prepared at a press ure of 0.5 Pa also showed lower wear, but relatively high and variable friction, behaviour when sliding against 52100 steel (mu=0.4-0.5). Sl iding against the rough, polycrystalline diamond coated countersurface eventually led to film delamination. Friction coefficients calculated from scratch test measurements are also compared with previous result s obtained for diamond-like carbon films. (C) 1997 Elsevier Science S. A.