Precise cutting of cemented carbide with nanopolycrystalline diamond in ductile regime

Today's demands on technical applications require the precise machining of high-performance materials. Cemented carbide is used as a wear-resistant material in a wide range of industrial applications, e.g. tool and mould making, mobility and medical engineering. Due to the brittle material characteristics and the resulting high hardness and wear resistance, the machining of the cemented carbide is severely limited. Long machining times and high tool wear are remaining challenges at state of the art. A novel approach for the machining of cemented carbide is the application of binderless nanopolycrystalline diamond (NPD) as cutting material for precise turning. Based on investigated fundamental cutting phenomena, within the scope of this work, the application of the novel cutting material was further investigated by comprehensive turning experiments. Turning tests were carried out with cemented carbide samples with a tungsten carbide content of CC = 88 %, a cobalt content of CCo = 12 % and a grain size of dg = 0.5 μm. Prior to the turning tests, the brittle-ductile transition as well as the minimum chip thickness were determined by dedicated spiral cutting tests as a function of the feed. In subsequent turning tests, the influence of the cutting speed, feed velocity and depth of cut were investigated. Process forces were evaluated and specimens were analysed regarding surface roughness and topography. In the course of the investigations, it could be shown that a dedicated set of process parameters enable cutting in ductile regime with great chip formation. Thus, the great potential of the novel cutting material NPD in turning of cemented carbide could be demonstrated.