Tribological properties of ultrananocrystalline diamond films in various test atmosphere

Transformation from higher to ultra low friction coefficient was observed in ultrananocrystalline diamond film (UNCD) while changing the test atmospheric conditions. High friction coefficients were observed in dry argon and nitrogen atmosphere, however, low and ultra low friction coefficients were obtained in dry oxygen and in ambient atmospheric conditions, respectively. Wear rates follow the same trends as the friction coefficients. This fascinating behavior of friction and wear of UNCD film is explained by the chemical changes of sliding surfaces and extent of passivation of dangling covalent bonds.

Graphical AbstractFriction coefficients for the various samples under the various test conditions.Figure optionsDownload high-quality image (76 K)Download as PowerPoint slideHighlights
► High to ultra low friction coefficient of UNCD film depends on atmospheric conditions.
► High friction coefficient was obtained in dry argon and nitrogen atmosphere.
► Ultra low friction coefficient was measured in ambient atmospheric condition.
► Chemical changes in wear track influence tribological properties of UNCD film.