Hubertus Hübsch

Frictional properties of diamondlike carbon layers

Hard diamondlike carbon layers have been deposited on silicon by rf plasma deposition using acetylene as working gas. For the first time the dependence of the sliding friction coefficient μ on the water vapor content of a nitrogen atmosphere was measured. An increase of μ with increasing humidity has been found, with μ ranging from 0.01 to 0.19. A steel ball was employed as the friction partner. The wear of the layers has been assessed by measuring their durability during friction experiments. It has been shown, contrary to other publications, that the durability has a maximum in the range 0.5–5.0% of relative humidity.

Improved tribological properties of sputtered MoSx films by ion beam mixing

Ion beam mixing yielded a distinct enhancement in the sliding life of sputtered MoSx films without any deterioration of the excellent lubrication properties. This effect occurs only at higher ion energies indicating an improved film‐substrate adherence caused by a mixing of the interface, which was confirmed by secondary ion mass spectrometry and topographical investigations. In addition to that a considerable enhancement of the film density was found due to a reorientation of the MoSx platelets which led also to an improvement of the effective film thickness.

Enhanced endurance life of sputtered MoSx films on steel by ion beam mixing

Abstract R.f. sputter-deposited Mosx films (x = 1.6 − 1.9) show excellent lubrication properties. The coefficient of friction under sliding conditions in an inert gas or in vacuum is very low (0.02–0.03), but the endurance life even for optimized sputter parameters depends on the internal mechanical stress and is often insufficient. The method of ion beam mixing was used to increase the film-substrate ahderence and, therefore, to obtain a life enhancement of the lubricating layers. The tribological tests were carried out on a ball-on-disc tribometer under oscillating conditions in a dry nitrogen atmosphere. The mixing experiments were performed with argon and nitrogen ions at various energies (50–400 keV) and fluences ((0.3−5) × 1016 ions cm−2). The film thicknesses ranged from 0.20 to 0.47 μm. A considerable enhancement of the endurance life without any deterioration of the friction behaviour was obtained, depending on the energy and the film thickness. For example, an MoSx layer of 0.36 μm thickness yielded a six-fold increase in the endurance life by implantation with 180 keV nitrogen and 400 keV argon ions. For a thinner film thickness the required energy can be lowered. This indicates a mixing of the interface since the penetration depth and the film thickness have to overlap so that the projected range of the ions falls at the interface. Profilometer traces across the wear tracks indeed show a considerable reduction in flaking after implantation, and with secondary ion mass spectrometry analysis we found a distinctly broadened interface. Additionally, we observed an increased film density of 20%–40% due to nitrogen and argon implantation, depending on the energy and film thickness.

Reibungsarme und verschleißfeste Schichten

Die vorliegende Arbeit gibt eine Darstellung der Ergebnisse, die im Rahmen der Untersuchungen an reibungsarmen und verschleisfesten Schichten gewonnen wurden.