A chemical, mechanical, and tribological analysis of DLC coatings deposited by magnetron sputtering

Diamond-like carbon is one of the most studied and used solid lubricants on the market. Despite this large use and its outstanding mechanical and tribological properties, there are still some unclear aspects related to its self-lubricant properties, and some drawbacks in the deposition methods. We deposited soft DLC films on Si(100), iron, and stainless steel substrates by PVD magnetron sputtering technique with a Cr/CrN adhesive interlayer. The DLC films were characterized from a chemical, mechanical, and tribological point of view. Our aim was to connect the coating chemical and mechanical characteristics to the different conditions used for the deposition, such as discharge power and substrate-target distance. We found a stronger sp(3) dependence on the discharge power for DLC deposited closer to the target. The tribological results did not depend on the chosen substrate-target distance, but rather on the hardness of the substrate. This could be ascribed to the better mechanical coupling of soft DLC films on harder substrates.