Abrasion resistant low friction diamond-like multilayers

Over the past few years, we have investigated plasma deposited amorphous hydrogenated carbon (DLC) films modified with B, N and Si dopants. Whereas, all three elements have the advantage to induce stress relief in the films (combined with hardness reduction), Si appeared to be the most interesting alloying element for tribological applications (friction and wear). Following this work, multilayer coatings consisting of a stack of DLC layers alternated with Si-doped DLC films and more recently, diamond-like nanocomposite (Dylyn®, a-C:H/a-Si:O) films were developed. A major advantage of the multilayer structure is the stress relief enabling the deposition of thick layers (10 μm) without any loss of good adhesion properties. These thick multilayers show improved abrasion resistance as well as extremely low friction properties (friction coefficient <0.1 independent of the relative humidity). This paper discusses the mechanical and tribological properties of these multilayer coatings and presents a comparison to various other layer systems (TiN, CrN and hard Cr).