Environmental effects on the friction of hydrogenated DLC films |
| |
Authors: | HI Kim JR Lince OL Eryilmaz A Erdemir |
| |
Affiliation: | (1) Tribology Section, The Aerospace Corporation, El Segundo, CA 90245, USA;(2) Argonne National Laboratories, Argonne, IL 60439, USA |
| |
Abstract: | We have investigated environmental effects on hydrogenated diamond-like carbon (H-DLC) films under various pressures of H2O, O2, and N2 by ultrahigh vacuum (UHV) tribometry. The H-DLC film exhibits an ultralow coefficient of friction (μ = 0.004 in UHV). The
μ value increases with increasing pressure of H2O and O2. Specifically, μ increases up to 0.07 under 10 Torr of H2O, and up to 0.03 under 150 Torr of O2; these are typical H2O and O2 contents respectively in ambient air. Our results are consistent with similar environmental effects previously reported.
But, we have also discovered that these friction changes are reversible, returning to the ultralow value when UHV is restored.
The reversibility of the friction behavior in both environments, coupled with the lack of evidence of tribochemical changes
by Auger electron spectroscopy, suggest that the observed friction changes are due to the weakly adsorbed gas molecules that
influence the friction property by physically separating the H-DLC interface. Speed-dependent tribometry also supports this
argument. In addition, two DLC films with different hydrogen contents and with widely different friction coefficients in UHV
are shown to exhibit identical μ values under humid environments, further demonstrating that the frictional properties of
these DLC films are essentially determined by the surface layer of adsorbed gas molecules. |
| |
Keywords: | friction mechanisms diamond-like carbon coatings friction-reducing unlubricated Friction vapor phase lubrication water |
本文献已被 SpringerLink 等数据库收录! |
|