Effects and interactions for interface and cutting-edge conditioning in hard micromachining

• Applicants: Professor Dr.-Ing. Dirk Biermann; Professor Dr.-Ing. Wolfgang Tillmann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering ; Coating and Surface Technology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445127534

Machining tempered tool steels with micro tools is an established approach to produce filigree, functional elements and structures in die and mould manufacturing. However, the high hardness of the materials leads to a high tool wear, resulting in a loss of process reliability when machining with conventional tool concepts. The short tool life can be attributed to the missing adaption of cutting edge preparation as well as PVD wear protection coating to the specific load of the hard micromachining process.These challenges of hard micromachining will be evaluated with a multi-scale tool optimization approach in a bilateral project of the Institute of Machining Technology (ISF) and the Institute of Materials Engineering (LWT). The investigations focus, on the one hand, on the model-based modification of the cutting-edge shape of ultrafine grained cemented carbide tools by means of mechanical pre-treatments (wet abrasive jet machining and magneto abrasive finishing) and high-energy plasma-assisted etching processes. On the other hand, for the first time, interactions of the individual pre-treatments with regard to the residual stress state, cutting-edge geometry, and the resulting surface topography are determined. These findings will be transferred to the subsequent coating process and correlated with the properties, which result from the synthesis of the TiAlSiN and TiAlTaN coating. In particular, the chosen approach using a hybrid DC/HiPIMS coating process promises improved properties due to an increased ionization, which results in a finer microstructure. The investigations focus on the system properties such as the film adhesion, which are influenced by the properties of the interface modification.In addition to the structural analysis of the substrate and coating, abstracted wear tests are carried out using a tribometer and an impact tester to analyse dynamic impact loads. The aim is to develop a systematic understanding of the wear behaviour as well as to trace the resulting defects back to the individual pre-treatment steps. The real application behaviour of the tools is finally evaluated in a micromilling of tempered ASP®2023 (1.3344). Tools with selected cutting edges and coating systems (TiAlSiN and TiAlTaN) will be evaluated concerning the surface quality and tool life in a side milling processes designed for roughing as well as finishing. The knowledge gained from this project will help to understand the interaction of individual preparation processes and enable the optimization of the production chain of future tool concepts.

• DFG Programme: Research Grants