The charm of coatings lies in the fact that they take over the entire tribological function of any base material. If the coating is very hard and therefore abrasive wear-resistant and also exhibits low friction coefficients under almost all tribological conditions, this coating is a candidate for demanding applications, such as found in bearings, gears, guideways, chains and so on. Hard diamond-like carbon coatings are predestined in this context and have therefore been used for a long time on highly loaded moving components in machines and vehicles, for example.

The DLC variant tetrahedral amorphous carbon (ta-C) even shows an additional feature: the ability to extremely low coefficients of friction in the superlubricity range (µ<0.01) in combination with certain fluids. This phenomenon was reproduced in laboratory tribometers with various fluids and has now also been clarified as an atomistic friction mechanism by using molecular dynamic simulations. The Fraunhofer SupraSlide project is aimed at utilizing the superlubricity of ta-C for sliding bearing applications and investigating practical aspects such as long-term stability, dependence on load and temperature, etc.

The results of the SupraSlide project show above all that the phenomenon of superlubricity with ta-C coatings is very robust and occurs in a wide load and temperature range. There is a high sensitivity with regard to the required roughness, i.e. very smooth initial surfaces must be present. Superlubricity is also observed with doped ta-C:X coatings, which enables the additional possibility of coating functionalization (mechanical, electrical, chemical).

Overall, there is a very high potential to use ta-C-based coatings for industrial superlubricated sliding bearing applications.