Analysis of the influence quantities on the adhesion of CVD diamond layers on carbide tools

• Applicant: Professor Dr.-Ing. Eckart Uhlmann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 267184104

During the first funding period of this project, the functional profile of cobalt- and nickel-bonded, novel niobium carbide (NbC) cutting materials was developed, which were produced using different sintering processes. The material properties of these NbC nuances were tested and compared with a commercially available tungsten carbide cobalt (WC-6Co, submicron grain). Furthermore, the NbC hard metal nuances were used in the machining of various materials and the wear behavior was compared with the WC-6Co-tools.It could be shown that the new cutting material achieves longer tool life compared to WC-6Co in dry turning of hardened steel 42CrMo4 + QT and also in turning of carbon steel C45E using the same process parameters. It was found that during the machining of C45E with a high cutting speed of vc = 150 m/min, significantly less crater wear occurs, which is due to the lower solubility of NbC in solid metals such as iron. The tool life advantages of the NbC grades increase with increasing cutting speed. Despite the lower hardness of the NbC cutting tool at room temperature (RT), higher cutting time was achieved during the machining of hardened steel, which is attributable to a higher hot hardness of the NbC compared to WC-6Co. During the milling of the aluminum alloy AlSi9Cu4Mg, similar tool lifetime as with WC-6Co could be achieved, although the NbC nuances so far still have a lower toughness.Up to now, the NbC nuances have been produced in the laboratory scale as well as for the most part by means of the sintering method Spark Plasma Sintering (SPS), which is not customary in the industry. In the application for continuation, therefore, the industrially relevant production methods of the NbC cutting materials are increasingly focussed with a further increase in hardness, strength and toughness values as well as prevention of grain growth. By adapting the micro- and macro-geometry of the tools to the wear behavior per workpiece material, the NbC nuances are used in the turning and milling processing of a wide range of materials analyzing the behavior in cutting process. A parameter study is carried out for each material and the influence of different cooling methods on the tool life is investigated. The causes of wear are determined using different analytical methods. Finally, an analytical model for the description of the application and wear behavior is prepared, taking into account different production methods and binder materials of the NbC nuances.

• DFG Programme: Research Grants