Co-deposition of titanium/polytetrafluoroethylene films by unbalanced magnetron sputtering

Liu, Chaozong and Fairhurst, R. G. and Ren, L. Q. and Green, S. M. and Tong, J. and Arnell, R. D. (2002) Co-deposition of titanium/polytetrafluoroethylene films by unbalanced magnetron sputtering. Surface and Coatings Technology, 149 (2-3). pp. 143-150. ISSN 0257-8972

Abstract

Graded nanocomposite coatings, consisting of a polytetrafluoroethylene (PTFE)-rich surface layer and functionally graded titanium-titanium carbide-PTFE mixed sublayer, were deposited onto stainless steel substrates using a radio frequence (RF) unbalanced magnetron sputter system with the purpose of improving the tribological performance of the substrate and endowing the surface with hydrophobicity. The results show that decomposition of PTFE during RF plasma sputtering results mainly in the evolution of fluoropolymer species. High incident power results in low F/C ratio in the resulting films, and low incident power results in high F/C ratio films. The tribological performance of the coatings depends on the fluoropolymer content in the film bulk, as well as on the film growth process. The films with high fluoropolymer content, with a gradient multilayer structure, possess good tribological performance especially at the initial stage of testing. During the co-deposition process, the segments were inlaid into the titanium matrix and became strongly mechanically bonded. It is speculated that some of the carbon atoms may react with titanium to form titanium carbide in the coatings. Multilayer structure attributed to the decrease in the stress developed between layers. All these factors attributed to the improvement of the tribological performance of the stainless steel substrate. (C) 2002 Elsevier Science B.V. All rights reserved.