Efficient drilling of holes in Al2O3 armor ceramic using impregnated diamond bits

This study aims at achieving a high efficient mode of hole-drilling in Al2O3 armor ceramic by using impregnated diamond bits. First, the most suitable diamond segment for the armor ceramic is selected by using higher quality diamonds and varying the composition of the metal matrix, as well as combining to the drilling test and SEM examination. Bit structure parameters such as grain size, diamond concentration, number of slots and wall thickness are optimized then by an orthogonal test. Experiments for analyzing the influence of the axial force and spindle speed to the efficiency are also carried out. Then hole quality is discussed. Finally, the ground surface integrity of Al2O3 armor ceramic is analyzed under SEM examination. The results show: (1) the bit with diamond type of SMD40 and metal matrix of Cu50Co25Sn18Ti7 (wt%) presents the best self-dressing capability among the four kind of different matrix bits; (2) the bit with wall thickness of 2.5 mm, grain size of 35/40 US mesh, diamond concentration of 100% and number of slots of 2 achieves a higher efficient mode; (3) the increased axial force and spindle speed could increase the drilling efficiency but overlarge axial force and too high spindle speed also lower the efficiency; (4) hole quality can be improved by using an prepress exerted device; (5) the ground surface of Al2O3 armor ceramic is composed of fractured area and ductile streak area which indicate that the material removal mode is contributed by both brittle fracture and ductile cutting, and the brittle fracture removal is dominant.