Direktstrukturierte, netzwerkmodifizierte DLC-Schichten

Die Beschichtung von Bauteilen mit diamantähnlichen Schichten (DLC: Diamond Like Carbon) ist ein Schlüssel zur Lösung vieler tribologischer Probleme, da DLC den Verschleiß und die Reibung drastisch reduzieren kann. In Anwendungen, in denen die Schichten bei Schmierstoffverlust oder Überlast Notlaufeigenschaften garantieren sollen, müssen die Schichten zusätzlich dem geschmierten Normalbetrieb angepasst werden.

The coating of components with Diamondlike Carbon (DLC) layers is a key to the solution of many tribological problems because DLC can drastically reduce wear and friction. In applications in which the coatings are expected to guarantee against lubricant loss or overload emergency conditions, the coatings must in addition be adjusted to normal lubricated operating conditions. In the simplest case this means that the DLC coating is well wetted by the lubricant to build on the lubrication clearance and achieve a separation between the two moving surfaces. The wettability can be changed by the introduction of network modifying elements because thereby a defined surface energy/surface chemistry is possible. The atomic density of the available network structure influences the disperse fraction of the free surface energy which is lower the fewer the number of covalent bonding pairs per volume element in the coating matrix. While the disperse fraction depends basically on the d egree of cross-linking of the surface, the polar fraction is influenced by the different types of functional groups and their number. For the further optimization of lubricated systems with participation of carbon-based layers and for the developing of new applications, the hydrodynamics of the lubricating film must also be considered. Lasers, electron radiation, and lithographic techniques, for example, applied to drastically reduce the use of lubricants, have not produced this effect for geometrically complex parts. These costly techniques are also not in the situation to generate structures in the nano range or they damage the coating or the substrate. At the Fraunhofer-Institut für Werkstoffmechanik IWM a plasma supported process technology was developed that enables a separate control of inherent and topographical properties of coatings from the family of amorphous hydrocarbons. This original PACVD technique enables the sought for structuring of DLC coatings directly from the process.