| AVS 56th International Symposium & Exhibition | |
| Tribology Focus Topic | Tuesday Sessions |
| Session TR+SS-TuA |
| Session: | Surface Science for Tribology |
| Presenter: | K.J. Wahl, Naval Research Laboratory |
| Authors: | K.J. Wahl, Naval Research Laboratory S.D. Dvorak, University of Maine G.Y. Lee, Naval Research Laboratory I.L. Singer, Naval Research Laboratory |
| Correspondent: | Click to Email |
Tribological processes that influence friction and wear involve a complex combination of materials science, physics, chemistry, and rheology. Our understanding of these sliding contact phenomena is limited by the fact that all the action takes place in a buried interface. Most often the only evaluation of these interfaces is accomplished through ex situ means after separating the contacts. In situ approaches to studying friction and wear processes are challenging because most engineerin g surfaces are metals or ceramics that have no optical transparency at visible wavelengths. For this reason, most of what is known about interfacial processes occurring during sliding has been learned through optical probes of sliding interfaces.
We have used an in situ tribometer to perform reciprocating sliding tests of Pb-Mo-S and Ti-Mo-S solid lubricant coatings. Experiments were performed in dry and ambient air. The interfacial films formed during sliding were monitored with in situ Raman spectroscopy and optical microscopy through transparent counterfaces. The dominant velocity accommodation mode in both dry and humid conditions was interfacial sliding between the surface of the wear track and the outer surface of the transfer film on the counterbody. Humid air sliding resulted in a second velocity accommodation mode involving shear and/or extrusion of the transfer film. We will demonstrate and discuss how the interface properties – shear strength and transfer film mechanical properties – affect friction behavior of these solid lubricant coatings.