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This paper presents a unique tribological system that is able to produce no measurable wear of material combination and that reduces friction markedly in the ultralow regime under boundary lubrication. Ultralow friction (0.03) was obtained by sliding hydrogen-free Diamond-Like-Carbon ta-C against ta-C lubricated with Poly-alpha Olefin base oil containing Glycerol Mono-Oleate (GMO) additive. The origin of ultralow friction in these conditions has been investigated by surface analysis techniques. Results are in agreement with the formation of a OH-terminated carbon surface. This new surface chemistry might be formed by the tribochemical reaction of alcohol function groups with the friction-activated ta-C atoms. The origin of low friction could be due to the very low-energy interaction between OH-terminated surfaces.

The geometry of micro-scale textures and the relative motion of surfaces in contact may affect the performance of an elastohydrodynamic lubrication interface. Reported in this paper are the investigations of the effects of texture bottom shape and surface relative motion on lubrication enhancement using numerically generated textures by means of model-based virtual texturing and numerical simulation. These textures are on one of the interacting surfaces in a triangular distribution and have the same density. The results suggest that the bottom shapes involving a micro-wedge and/or a micro-step bearing tend to yield thicker films. The lubrication of selected textured surfaces was also studied under three different relative motions: texture surface moving, un-textured surface moving, and both moving. The results indicate that textures on the faster moving surface offer stronger film thickness enhancement.

Micro-scale textures may be engineered into surfaces for lubrication performance improvement. It is expected that a carefully chosen texture helps retain lubricant and enhances the hydrodynamic effect at the interface. The concept of model-based virtual texturing enables textured surfaces to be generated and ''tested'' through numerical simulations. This paper reports virtual texturing and simulation of a group of textured surfaces in a lubricated concentrated contact. The focus of the study is on the selection of texture distribution patterns based on their lubrication performance. Patterns of fishbone, sinusoidal, triangular, and honeycomb distributions have been investigated. The effects of texture direction, orientation angle, feature continuity, and aspect ratio are also studied. The results indicate that, for the given material and geometry system under the given conditions in the present work, the textures generating the strongest hydrodynamic lifting are short grooves with a small aspect ratio and sinusoidal waves of a small wavelength/amplitude ratio propagating in the motion direction.

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