To elucidate the mechanisms of the low friction coefficient in diamond-like carbon (DLC) film, a series of pin-on-plate type friction tests was performed in ambient air and in argon. To elucidate the effects of frictional heat on the friction coefficient, tests were conducted by changing the load applied on the pin. As the test piece, a combination of high-speed tool steel JIS-SKH51 pin and DLC-coated plate (SKH51/DLC) was used with a combination of DLC-coated pin and DLC-coated plate (DLC/DLC). In both atmospheres and for both pin and plate combinations, results show that the coefficient of friction decreased with the increase of the applied load. Raman spectroscopy revealed the presence of graphite-like material in wear debris that was formed because of friction. These results demonstrate that the low coefficient of friction resulted from the soft graphite-like material transformed from DLC by frictional heat. The coefficient of friction of DLC/DLC is lower than that of SKH51/DLC because the fraction of graphite-like material in the wear debris is greater than in the former combination. The coefficient of friction in argon is lower than that in air because the graphite-like material is not lost by oxidation in argon.
Fe-Ni-W alloy electrodeposited films were prepared in a plating bath under various concentrations of Na2WO4･2H2O: 0.012 mol/dm3, 0.06 mol/dm3, 0.12 mol/dm3, 0.18 mol/dm3, 0.24 mol/dm3. The film corrosion behavior was evaluated using their polarization curves obtained in 3 wt% NaCl solution. Electrodeposited films with composition ratio of Fe: 37.40 at%, Ni: 23.39 at%, W: 39.17 at% were prepared under concentrations of 0.24 mol/dm3 Na2WO4･2H2O, pH7.8. The plated film showed no passivation behavior from the anodic polarization curve. However, after heat treatment at 220 ℃, 4 h in air, this treated film exhibited distinct passivation behavior.