Tribological Properties of Segment-Structured Diamond-Like Carbon Films

Diamond-like carbon (DLC) have been widely recognized as a tribo-coating material with a high wear resistant solid lubricant with a low friction coefficient. The tribological behavior of DLC films depends on the environmental conditions, the nature of the coating, and mechanical properties of a substrate. Particularly, when the DLC films are distorted with the deformation of the soft substrate, it is apparent that fragile DLC films are strongly damaged. In this study DLC films have been deposited by RF-plasma CVD with a methane gas on the soft material substrates, such as a rubber and aluminum, and the friction and wear tests were conducted using a ball-on-disk test. In the case of rubber substrate, DLC films show relatively low friction coefficient from 0.2 to 0.3, despite of large substrate deformation. Observation results of the surface of the rubber substrates suggest that the DLC film forms a "segment structure" automatically, then "segment structure coating" was applied to aluminum substrate. Ball-on-disk test results revealed that wear resistance of the segment-structured DLC film was about two-fold higher than that of a conventional continuous DLC coating.