Investigation of the relation between structure and mechanical properties of hydrogenated diamond-like carbon coatings prepared by PECVD

The mechanical properties, such as scratch, friction, and fretting behavior of hydrogenated diamond-like carbon (DLC) coatings prepared by rf PECVD, are investigated in terms of influences of the coating characterization (the sp3 fraction, surface roughness, and hardness) and testing conditions (the applied load and relative humidity). In general, as the thickness of the DLC coatings increases, both the percentage of sp3 and the surface roughness decrease; however, the hardness increases. The critical load (Lc) in scratch test increases with increasing the coating thickness and decreasing the surface roughness. The steady-state coefficient of friction decreases with the increase of hardness as well as the decrease of sp3 fraction and applied load in the sliding friction test. It decreases with the increase of relative humidity in fretting wear test.