Machinability and properties of zirconia ceramics prepared by gelcasting method

The machinability of newly developed zirconia ceramics for computer numerically controlled milling (CNC) was investigated. The zirconia blanks were prepared by the gelcasting method and tested in the green and two pre-sintered states. All blanks exhibited uniform sintering shrinkage in all directions. The blanks were investigated from the viewpoint of surface milling roughness, quality of milled edges and sharp tips, and machinability of thin structures. The best milling results were obtained for the blanks pre-sintered at 900?C/1?h. Mechanical properties of zirconia blanks, such as biaxial flexural strength, microhardness, indentation elastic modulus, and fracture toughness were determined in the green and pre-sintered states (900 and 1100?C/1?h) and the correlation with the milling results was discussed. The biaxial strength tests of sintered discs showed the advantage of optimised surface milling over conventional polishing.