A Triboscopic Investigation of the Wear and Friction of MoS2 in a Reciprocating Sliding Contact
NAVAL RESEARCH LAB WASHINGTON DC
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Reciprocating sliding tests with ball-on-flat geometry were performed on a duplex coating at low speeds in moist air RH60. The coating, 55 nm MoS2 on 35 nm of TiN, was deposited by ion-beam assisted deposition onto a steel substrate. Friction coefficient micro and electrical contact resistance Rc measurements were recorded at 2micrometers intervals along the track these spatially resolved measurements were compared to the more commonly presented cycle-averaged values. The last-cycle tracks of several runs were also analyzed by a variety of microscopies and spectroscopies to identify compositions and determine thicknesses of films on the tracks and balls. Rc measurements, both averaged and spatially resolved, were more sensitive to coating damage and loss than mu measurements. In the averaged data, fluctuations in Rc were observed before fluctuations in mu. Spatially resolved data showed that local drops in Rc could be detected as early as 20 of life. Additionally, recovery of both high mu and low Rc regions, interpreted as healing of damage in the contact, occurs. Friction coefficient data were insensitive to changes in MoS2 coating thickness conversely, Rc followed wear track thickness and consequently may provide an in situ method of monitoring coating wear.
- Inorganic Chemistry
- Electrical and Electronic Equipment
- Properties of Metals and Alloys