Untersuchungen zum Fräsen mit CVD-diamantbeschichteten Werkzeugen

CVD-diamond coatings on cemented carbide substrates have undergone significant developments in recent years. Former CVD-diamond coated tools failed in metal cutting applications due to severe flaking of the diamond layer. Thus, first industrial applications had been restricted to machining of graphite, fibre reinforced plastics and green compacts made of cemented carbide respectively of ceramics. The field of application is widened nowadays towards machining of non ferrous metallic materials like aluminium and magnesium alloys. This is mainly related to the superb mechanical and thermal properties of binderless multicrystalline diamond, such as extremely high hardness, low tendency to adhere to Aluminium and good thermal conductivity. Such lightweight materials will increasingly replace steel and iron based castings in automotive products. CVD-diamond coatings are usually produced in a multiple step process chain. The substrate (either inserts or shaft tools) will be cleaned, etched and finally coated. Etching removes the cobalt binder from the rim zone of the carbide. This supports the diamond formation and the adhesion to the substrate. But the removal of the cobalt binder causes also a brittle tungsten carbide skeleton in the rim zone of the substrate which includes the sensitive cutting edge. This inevitably causes a weak cutting edge. Although multiple pre-treatment procedures are described in literature and even patented the chemical etching as described above is nowadays still the most common technology. Therefore, the tooling system coating-substrate-interface-geometry must be carefully balanced. Until now, most of the research work has been performed on the subject materials science of diamond coating and cemented carbide adhesion. This does not cover the entiere system "cutting tool". The main goal of this PhD-thesis is the systematic analysis of the interactions in the system in order to improve the design of CVD-diamond milling tools for high performance as well as dry cutting processes. The influence of the manufacturing of the cutting tool, the cemented carbide grade and the cutting edge properties are analysed and referred to the in-process behaviour of the cutting tool. The analysis is a basis for the definition of tool requirements concerning morphology, thickness of the coating, cutting tool pre-treatment and cemented carbide grade. The verification of the results has been done based on specific machining operations. This includes the influence of the workpiece material and the interruptions of the cut