Effect of wettability on lubricity of DLC films

Abstract

DLC films show the excellent tribological properties under the lubrication with humid air or water. However, environmental effect for lubricity of DLC films not fully understood. In this paper, we investigated effect of wettability and humidity for lubricity of DLC films. Several types of DLC films were deposited on Si substrate by CVD technique. Surface energy of DLC films was controlled by ratio of C_2F_6 and CH4 gases and O_2 or Ar plasma treatment after deposition. Sliding experiment was carried out by pin on plate type tribotester. In case of RH30%, fluorine rich DLC and pure DLC shows 0.4 of friction coefficient. Friction coefficient of plasma treatment DLC was 0.5. On the other hand, in case of RH55%, all DLC shows about 0.4 of friction coefficient. These results indicate friction property of low surface energy DLC don't affected by relative humidity. In contrast, friction property of high surface energy DLC was dependent on relative humidity.