Hardness effect of stainless steel substrates on tribological properties of water-lubricated DLC films against AISI 440C ball

Diamond-like carbon (DLC) films were deposited on stainless steel substrates with different hardness by thermal electron excited plasma CVD method, and their tribological properties in water-lubricated conditions were investigated. EDS was used to estimate the wear of the films. The results show that the hardness of the substrates has little effect on the friction and, the wear loss of the films is much smaller than that measured by an optical interferometer. The deep wear track is mainly due to the plastic deformation of the substrates and the films but not due to wear. However, the failure of the films is closely related to the hardness of their substrates. The harder the substrate, the higher the failure-resistant capability. The film deposited on a soft substrate is easy to crack and fail due to the low deformation resistance of the substrate and rubbing at a high contact-pressure. On the other hand, the wear of the counter balls increases with the hardness of the substrates.