High Temperature Tribological Behavior of W-Doped Diamond-like Carbon Films

In this study, W-doped diamond-like carbon films(W-DLC)were deposited by anode layer ion source combined with unbalanced magnetron sputtering. The structure, micro morphology and high temperature tribological properties were investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and an UMT-3 tribometer. The results show that nanometer sized tungsten carbide crystals were dispersedly embedded in the amorphous carbon matrix. The high temperature tribological behaviors of W-DLC films were systematically studied ranging from 25 ℃ to 500 ℃. The incorporation of W atoms into the DLC film improved the high temperature tribological stability and toughness as well. The structure and tribological properties were stable up to 200 ℃. The graphitization and oxidation of carbon were observed at 300 ℃, which deteriorated the wear resistance of as-deposited DLC films. The formation of WO₃ was detected on the worn surface above 400 ℃. The coefficient of friction was as low as 0.15 at 500 ℃ while the wear rate was much higher than that under 200 ℃.