Micromilling of Sintered ZrO2 Ceramic via cBN and Diamond Coated Tools

This paper presents an experimental investigation on micromilling of fully sintered Zirconia ceramics by means of advanced cutting tools, including cBN and diamond coated mills. Zirconium oxide is selected because of its high hardness, resistance to wear, heat and chemicals.Two-flute end mills of nominal diameter 1 mm and negative rake angle were used. The effect of the coating and tool material, along with the cutting parameters, were investigated by means of a one-factor variation experimental design; and the responses of interest, including tool wear and sample surface quality, were monitored over the machining time. The worn tools and the machined surfaces were also analyzed on a SEM to investigate the type of material removal mechanisms (MRM). The diamond coated tools provide the best performance in terms of life time, however delamination of the diamond coating followed by wear of the underlying hardmetal is identified as the prevailing tool wear mechanism. A ductile type of material removal mechanism could be observed, inducing an achievable surface roughness below 60 nm. On the contrary, cBN tools exhibited fast breakage. A combined ductile-brittle material removal mechanism occurs, resulting in a surface roughness around 300 nm.