Study on milling performances of 3Y-TZP ceramics using PCD and PCBN tools

The 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) is regarded as a superior bioceramic being extensively used in modern denture restoration. However, the material possesses extremely poor machinability and are prone to serious cracking and failure formation due to its exceptionally high hardness and inherent brittleness. Hard milling is a feasible strategy to shape fully-sintered 3Y-TZP to desired quality and target dimensions. The present paper aims to study the milling behaviors and mechanisms of 3Y-TZP ceramics by using superhard PCD and PCBN tools. The fundamental milling responses, including cutting forces, temperatures, and surface morphologies, were all examined. The parametric effects on the 3Y-TZP machinability outputs were addressed. A particular focus is placed on comparing the cutting performances of different tools in milling 3Y-TZP. It is found that the PCD tool outperforms the PCBN tool from the perspective of reducing cutting forces, specific cutting energy consumption, and milling temperatures. To get smooth surface morphologies with minimal damage, the spindle speed lower than 5000 rpm and the feed per tooth lower than 9 mu m/z should be adopted for the PCD tools. However, under large milling parameters, the PCBN tools show advantages in ensuring the stability of machined surface quality for 3Y-TZP ceramics over the PCD ones.