VACUUM-ARC DEPOSITION OF METAL CERAMIC COATINGS ON POLYMER SUBSTRATES/

Thin metal/ceramic coatings were deposited onto polysulfone S2010 subs trates using a triple-cathode vacuum are plasma source connected to a magnetized plasma duct in order to improve the tribological properties of the surface. Various combinations of multi-layer coatings having T i, Zr, or Nb sub-layers, and nitrides of Ti, Zr, and multi-component ( Ti,Zr)N as wear-resistant layers, were deposited and evaluated. The de position parameters (are current, magnetic field strengths, deposition time) were optimized (1) to obtain the required deposition rate and c oating thickness, while preventing substrate damage under the high-ene rgy ion flux exposure, and (2) to obtain good adhesion of the coating to the substrate at low substrate temperatures. The structure and comp osition of the coatings were studied using XRD, AES, and SEM. Scratch tests were used to evaluate the adhesive strength between the substrat e and the coating, and reciprocating wear tests against a steel ball w ere used to study the friction and wear rates of the coated samples. T he wear tracks were examined by SEM. It was shown that TiN layers poss essed a nanocrystalline structure or a mixture of an amorphous and a n anocrystalline structure with random orientation, whereas the ZrN and (Ti,Zr)N had a more defined crystalline nature. The lowest wear rate w as observed for Ti/TiN bilayer coatings. The Zr/ZrN coatings failed co mpletely because of poor adhesion to the substrate. It was observed th at carbide formed at the interface of the Ti coating and the substrate . In contrast, Zr intermediate layers did not form a carbide, and the coatings had poor adhesion and wear resistance. The results suggest th at the formation of a carbide interface improves the coating adhesion. (C) 1998 Elsevier Science S.A. All rights reserved.