Machinability Investigation on High Speed Hard Turning of ZrO2 with PCD Tools

This paper presents an initial study on the feasibility of machining zirconia ceramics in the hard state. A fully sintered Yttria stabilized tetragonal zirconia poly crystalline ceramic (Y-TZP) was used as work piece material and experiments were performed on a Mori Seiki turn-mill centre. PCD tools with small rake angle (0˚) and large nose radius (0.8 mm) were chosen for the experiments. The study on the influence of process parameters, such as depth of cut, feed and cutting speed (>300 m/min), on the surface quality and tool wear was approached by means of a mixed full factorial experimental design. Machined samples and process chips were also analysed by scanning electron microscope (SEM) to achieve a deep understanding of the occurring material removal mechanisms (MRM) and achievable surface quality; also the PCD inserts were inspected after usage. The findings show that surface roughness (Ra) values below 0.6 μm are easily achievable; the material removal mechanism is mainly based on a combined ductile-brittle material removal. Adhesion of work piece material to the tool is regarded as the most significant tool wear mechanism.