Improved tribological behaviour of MoS2 thin solid films alloyed with WC

J. I. Oñate*, M. Brizuela, A. Garcia-Luis, I. Braceras, J. L. Viviente, J. Gomez-Elvira

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

16 Citations (Scopus)

Abstract

MoS2 is a broadly accepted solid lubricant for space mechanisms. However, the tribological properties can be affected by the deposition parameters that can in turn influence structure and composition of the films. One important drawback of MoS2 is its sensitivity to atmospheric water vapour which renders the film unsuitable for use under high humidity levels and forces the taking of precautions during ground qualification testing and storage of solid lubricated space mechanisms. Recently, and with developments made in magnetron sputtering PVD technology an interest has arisen in the production of more wear and moisture resistant MoS2 films. This has been evaluated by alloying the film by co-depositing a range of metallic and non-metallic elements. This paper follows a previous report in which Ti metal was co-deposited with MoS2 and a low friction under vacuum and atmospheric conditions was demonstrated. However, it was felt that extended durability was still needed for the benefit of space community. In this work, preliminary results on the deposition of WC-MoSx films by magnetron sputtering are presented. Vacuum tribology of these films, at 0.75 and 0.95 GPa contact stresses, shows that the friction coefficients are similar to those obtained in conventional MoS2 films, but there is a significant improvement in durability. When evaluating the performance of these films under atmospheric conditions and at various humidity levels (from 40 to 60 % RH), the tribological response has also been very good, with average friction coefficients as low as 0.07 and a durability as high as 450.000 wear cycles. XPS analyses have shown that the films consist mainly of a MoSx lubricating matrix in which a carbidic wear resistant WC phase is embedded. This combination ensures a low friction behaviour while providing a higher resistance to wear.

Original languageEnglish
Pages (from-to)257-262
Number of pages6
JournalEuropean Space Agency, (Special Publication) ESA SP
Issue number480
Publication statusPublished - 2001
Event9th European Space Mechanisms and Tribology Symposium - Liege, Belgium
Duration: 19 Sept 200121 Sept 2001

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