Superhard nanocrystalline composites:: Present status of the research and possible industrial applications.

After the first reports on the concept for the design of superhard nanocrystalline composites nc-MnN/a-Si3N4 (M = Ti, V, W) few years ago [1], several research groups reproduced the results and extended them to other material combinations including, for example, superhard nc-TiN/BN, TiN-TiB2, nc-TiN/CNx and overstoichiometric carbides. The predicted [1] universality of the design principle which - by forming an interface with a high cohesive energy - avoids the usual softening due to the grain boundary sliding in the crystallite size range of less than or equal to 2-3 nm appears to be strongly supported by these results. Also the preparation techniques were extended from the originally used plasma chemical vapor deposition to industrially more compatible techniques, such as vacuum are evaporation and reactive sputtering. In the present paper we shall briefly review the present status of the research and of the understanding of the properties of these materials. The second part concentrates on the progress towards the industrialization of these coatings. Preliminary results of cutting tests are briefly mentioned as well.