Temperature stability of C-N/NbN nanocomposite multilayers

Nanostructured C-N/NbNx coatings were deposited by radio-frequency magnetro n sputtering when two cathodes of carbon and niobium were operating concurr ently in an argon/nitrogen mixture in the side-by-side configuration. The c omposite coatings, typically 1-3 mu m thick, were deposited at a substrate temperature not exceeding 200 degrees C. Various substrates such as highly polished tungsten carbide and silicon were used. The friction coefficient a nd wear rate for Si3N4 and 52100 steel balls were measured at room temperat ure and after heat treatment of the coatings to 500 degrees C in air, on a reciprocating ball-on-disc tribometer. We investigated the structure of the multilayer by means of low-angle X-ray reflection and high-angle X-ray dif fraction after isochronal annealing at temperatures from room temperature t o 500 degrees C in air. From the low-angle reflection we determined the mul tilayer period and thickness of a surface oxide layer. The high-angle diffr action data revealed the polycrystalline structure of the multilayer, which has a grain sine comparable to the multilayer period. Multilayer nanocompo sites can be deposited at low substrate temperatures in conventional physic al vapour deposition coaters and can offer a number of prospective industri al applications. (C) 2000 Elsevier Science S.A. All rights reserved.