Verbesserung des tribologischen Systems Kolben-Buchse in Axialkolbenmaschinen durch Verwendung konturierter und beschichteter Kolben

The Collaborative Research Centre 442 (CRC 442) ,,Environmentally Friendly Tribological Systems" deals with components of tribological systems in machine tools, e. g. bearings, guidings, gears, tools and hydraulic components. These tribe-systems are commonly realized with biologically questionable lubricants. The CRC 442 aims at the application of biologically fast degradable and environmentally friendly fluids and the development of capable combinations of materials without increasing wear and friction. The task for the application of biofluids will be accomplished in different subprojects. Fundamental work focuses on the development of new coating systems and biofluids and classifies their features in consideration of ageing behaviour and their environmental compatibility. Results of these examinations are transferred to the tribo-systems in machine tools and are tested close to operational conditions. Conclusions, results and knowledge from all examinations are summarized in a data base and will be used to develop guidelines for the construction of machine tools and their tribo-systems. The subproject ,,Tribological Systems in Hydrostatic Displacement Units", which is carried out at the Institute for Fluid Power Drives and Controls of RWTH Aachen University, Germany, is focused on replacing mineral oil based fluids in axial piston machines with environmentally friendly fluids. Mineral oil based fluids feature highly developed, but biologically slow degradable additives and have an excellent extreme-pressure- and anti-wear-behaviour. It has been shown that, due to the weaker properties of biofluids, these features have to be realized by surface coatings on the components of tribe-systems. While using coatings on the surface of components the loads and surface pressures in the contact area have to be reduced by changing the macro-geometry. This is realized by using pistons with a spherical profile to enlarge the contact area. Furthermore the micro-geometry can be optimized by varying the surface roughness and its structure. It will be shown that an optimization of the micro- and macro-geometry of pistons and bushings in axial piston machines can be used in combination with biologically fast degradable fluids without increasing wear and friction.