An experimental investigation on milling features of fully-sintered zirconia ceramics using PCD tools

Zirconia ceramics have emerged as a promising restorative material owing to their superior physical properties and excellent biocompatibility. Among the zirconia family, fully-sintered samples show the highest mechanical properties but the poorest machinability compared with those fabricated at pre-sintering temperatures. The current work aims to study the milling characteristics of fully-sintered zirconia ceramics when using polycrystalline diamond (PCD) tools under varying cutting conditions. The machining responses of fully-sintered zirconia ceramics, such as cutting forces, specific cutting energy, milling temperatures, and surface topographies, were carefully addressed. The obtained results were correlated with the applied milling parameters. The tool wear morphologies were eventually characterized to figure out the underlying wear mechanisms governing the performance of PCD tools. The results indicate that increasing the feed per tooth definitely raises the milling forces and temperatures, while increasing the cutting speed elevates the milling temperatures but decreases the cutting forces. The feed per tooth significantly affects the surface topographies of cut zirconia surfaces due to its effects on the ductile-brittle transition of the workpiece. The PCD tool shows the feasibility of carrying out hard milling of fully-sintered zirconia ceramics, which undergoes a minor degree of wear along its cutting edge.