Microstructural and tribological characterization of MoS2-Ti composite solid lubricating films

Sputtered MoS2 thin films provide lubrication and wear improvements for vac uum and space applications. When exposed to humid environments, however, th e MoS2 films are prone to rapid deterioration by oxidation. In this study, we synthesized a composite coating, which consists of titanium metal and so lid lubricating MoS2 layers by the unbalanced magnetron sputtering process. Experimental results indicate that the Ti interlayers among the MoS2-Ti co mposite films effectively enhance the density and stability of the film str ucture. Transmission electron microscopy, X-ray diffractometry, and Raman a nalyses reveal the amorphous nature of the MoS2-Ti coating, which contains only a short-range order within the Ti interlayers. Ball-on-disc tribotests of the MoS2-Ti composite films show a higher friction coefficient, increas ed wear life and microhardness, and reduced wear debris as Ti interlayers i ncreased in thickness. In addition to its densification and strengthening e ffect, the Ti interlayer also reacts preferentially with oxygen to form TiO 2 and thus effectively suppresses adverse oxidation of MoS2. Thus, in humid environments, the MoS2-Ti composite film is highly promising as a solid lu bricant, as evidenced by its prolonged wear life and resistance to oxidatio n. (C) 1999 Elsevier Science S.A. All rights reserved.