A study on the tool wear of PCD micro end mills in ductile milling of ZrO2 ceramics

This paper investigates the performance of self-developed polycrystalline diamond (PCD) micro end mills in ductile milling of fully sintered zirconia ceramic. Experiments are conducted on a precision milling machine center. The influence of cutting parameters, including axial depth of cut (ap), feed per tooth (fz), and the PCD particle size on the achievable surface quality is studied by experimental design. Further tests are also conducted to study the tool wear during a milling process. The tool wear characteristics are observed and tool wear mechanism is discussed. The results show that average surface roughness Ra below 70 nm can be achieved on the machined samples. The factor of feed per tooth affects Ra value the most. The maximum tool tip wear VC can be used to indicate the severity of tool wear. According to the results, the PCD micro end mill with bigger particle size possesses longer tool life. The mainly tool wear mechanism of the PCD micro end mill in ductile milling ceramics is the periodic peeling off of diamond particles during the interaction between the workpiece and end mill. Zirconia ceramics can deform in a plastic way and adhere to the cutting edge in the milling process. The adhesion and spalling of zirconia would induce the peeling off of PCD particles.