Saarbrücken, Univ., Diplomarb., 1996.

Zugl.: Stuttgart, Univ., Diss., 2006. / Druckausg. bei Jost-Jetter, Heimsheim erschienen.

Zugl.: Cottbus, Techn. Univ., Diss., 2009

Techn. Hochsch., Diss., 2003--Aachen.

Techn. Hochsch., Diss., 2003--Aachen.

Universiẗat, Diss., 2004--Stuttgart.

The present thesis focuses on characterisation of microstructure and the resulting mechanical and tribological properties of CVD and PVD coatings used in metal cutting applications. These thin and hard coatings are designed to improve the tribological performance of cutting tools which in metal cutting operations may result in improved cutting performance, lower energy consumption, lower production costs and lower impact on the environment.  In order to increase the understanding of the tribological behaviour of the coating systems a number of friction and wear tests have been performed and evaluated by post-test microscopy and surface analysis. Much of the work has focused on coating cohesive and adhesive strength, surface fatigue resistance, abrasive wear resistance and friction and wear behaviour under sliding contact and metal cutting conditions. The results show that the CVD deposition of accurate crystallographic phases, e.g. α-Al2O3 rather than κ-Al2O3, textures and multilayer structures can increase the wear resistance of Al2O3. However, the characteristics of the interfaces, e.g. topography as well as interfacial porosity, have a strong impact on coating adhesion and consequently on the resulting properties.  Through the deposition of well designed bonding and template layer structures the above problems may be eliminated. Also, the presence of macro-particles in PVD coatings may have a significant impact on the interfacial adhesive strength, increasing the tendency to coating spalling and lowering the surface fatigue resistance, as well as increasing the friction in sliding contacts. Finally, the CVD-Al2O3 coating topography influences the contact conditions in sliding as well as in metal cutting. In summary, the work illuminates the importance of understanding the relationships between deposition process parameters, composition and microstructure, resulting properties and tribological performance of CVD and PVD coatings and how this knowledge can be used to develop the coating materials of tomorrow.

The aim of this master's thesis is to deal with main thread production methods and to study the influence of coatings on tap cutting performance. The high-speed steel cutting taps with different PVD coatings (Physical Vapour Deposition) were tested, while the same cutting conditions were set. Cutting torques were measured and analysed, which together with the results of evaluation of tool wear led to conclusion.

This dissertation treats of the influence of PVD coats to a change of tool lifetime. The theoretical part of the dissertation describes the adjustment of tools before the process of coating. Following part describes the specific properties of deposited layers of the coating and its measuring. There is also the enumeration and specification of selected ways of depositing PVD coats and brief description of its advantages and disadvantages. Second part of the dissertation is focused on an experiment with measuring of the tool force loading and its change depending to the tool wear. There are compared four short four-edged milling cutters with a coat and as well without it. Those tools were made of high speed steel by the conventional way and also by the powder metallurgy. Milling operation was done by down and up milling technique. The evaluation of the experimental results for powder metallurgy tools confirmed that these tools are advantageous compared to the standard high speed steel tools.

This work is focused to the cutting tests. There is a description of cutting test designed for PVD coated cemented carbide end mills. Cutting conditions are chosen according to orders, other subjects of choice are cutting tool geometry and workpiece material.