AVS 50th International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA4
The Role of the Third Body Processes in the Friction and Wear of MoS2 and MoST Coatings

Monday, November 3, 2003, 3:00 pm, Room 327

Session: Tribology, Adhesion, and Friction
Presenter: G.Y. Lee, U.S. Naval Research Laboratory
Authors: G.Y. Lee, U.S. Naval Research Laboratory
I.L. Singer, U.S. Naval Research Laboratory
K.J. Wahl, U.S. Naval Research Laboratory
Correspondent: Click to Email
The sliding friction behavior of MoST@footnote 1@ (Ti-Mo-S) and MoS@sub 2@ coatings has been investigated by in situ tribometry, which allowed real time observation of third body dynamics. The coatings were deposited by closed field unbalanced magnetron sputtering and contained between 0 to 20 % titanium. Reciprocating tests were performed in both dry (< 4 % RH) and ambient (40-50 % RH) air at a sliding speed of 1 mm/s and 24 N normal load (1.1 GPa mean Hertizan stress) using sapphire hemispheres as counterbodies. All coatings showed similar steady-state friction coefficients: about 0.025 in dry air and 0.06 in ambient air, however titanium containing coatings in ambient air exhibited lower friction coefficients at the beginning of the tests. Titanium containing coatings also showed reduced wear in both dry and ambient conditions. In situ optical microscopy observations identified the formation of a transfer film (third body) on the sapphire hemisphere for all tests. Most of the sliding took place between the transfer film and the wear track indicating that the velocity accommodation was interfacial sliding. The titanium containing coatings exhibited an additional velocity accommodation mode, shearing and extrusion of transfer film, correlated to the higher friction in ambient conditions. The role of the transfer film mobility and mechanical properties in controlling friction behavior will be discussed. @FootnoteText@ @footnote 1@ N.M. Renevier, V.C. Fox, D.G. Teer, and J. Hampshire, Surf. Coat. Tech., 127 (2000) 24-27.