Nanocomposite TiC/a-C : H hard coatings deposited by reactive PVD

Thin films of titanium carbide and amorphous hydrogenated carbon at various compositions have been deposited by unbalanced reactive magnetron sputteri ng from a metallic titanium target in the presence of argon and acetylene. XRD probed the presence of nanocrystalline TiC and, at high titanium concen trations, of metallic titanium. The XPS examinations allowed one to determi ne the amount of TiC produced at any concentration of titanium. Raman spect roscopy proved the presence of a-C:H up to 38 at.% of titanium. The coating s have a pronounced hardness maximum of 35 GPa at a composition of approxim ately 80% TiC and 20% a-C:H. The hardness at 60% TiC and 40% a-C:H as well as that of 100% TiC does not exceed 18 GPa. The mean separation of the crys tallites, whose diameter is approximately 4 nm, amounts to a few atomic dis tances. At the maximum hardness a coefficient of friction of 0.25-0.3 is ob tained. The coatings thus provide, at the optimum composition, high hardnes s at low friction. (C) 2000 Elsevier Science B.V. All rights reserved.