Drilling of alumina and zirconia ceramics using diamond-coated carbide drill

Abstract

The drilling characteristics and availability of a diamond-coated carbide drill for drilling holes in ceramics were investigated and verified. An alumina and yttria-stabilized zirconia ceramics were used as workpiece materials. The drilling characteristics were evaluated based on the cutting-edge behavior, thrust force, integrity of the inner surface of the drilled hole, and chip morphologies. Alumina drilling had appropriate drilling conditions under which the diamond coating did not flake; under these conditions, extremely long tool life was obtained. Even when the diamond coating flaked off, the thrust force was reduced owing to the sharp cutting edges on the remaining coating ridgelines on the flank face. This flaking occurred around the corner edge region and expanded toward the thinning and chisel edge region with an increase in the number of holes drilled. In addition, the diamond flaking on the rake face occurred earlier when the feed rate of the drill was increased. In drilling alumina, the surface roughness of the inner surface deteriorated as the feed rate increased but improved as the diamond coating flaked off. Whereas in drill zirconia, a considerably better inner surface was obtained, regardless of the flaking of the diamond coating and drilling conditions. In both ceramics, thinning the diamond coating from 20 to 10 μm resulted in premature flaking of the coating. The drill life was reached when the flaking region reached the chisel edge from the corner side. The results of this investigation will assist with the drilling of holes in brittle ceramics using a diamond-coated carbide drill.