Present and possible future applications of superhard nanocomposite coatings

Recent investigations into the multicomponent (TiAlSi)N and TiBN superhard coatings revealed that the nanostructure, properties and deposition conditions needed for their preparation are in agreement with the known generic concept for the design of novel superhard nanocomposites due to thermodynamically driven phase segregation. All coatings to be reported here were developed on a production scale plasma PVD & CVD equipment consisting of vacuum arc evaporation from a central cathode for the metals in combination with PCVD of non-metals, such as boron, from gaseous reactant. Depending on the composition and deposition conditions the hardness of the coatings is controlled in the range between 35 and 45 GPa or higher. However, for the majority of applications the highest hardness is not the primary goal. More important is the appropriate combination of high hardness with other properties, such as fracture toughness, oxidation resistance, adhesion, etc. The effect of these properties on the resulting utility value of the coated tools will be discussed with respect to the available cutting tools made of cemented carbide and coated with the nanocomposites. Presently, dry milling, drilling and possibly turning are the most important applications of such coated tools. In view of the fairly fast transition from the initial development of these coatings towards their industrial production many further applications are expected. Therefore, future possibilities will be discussed as well.