Experimental Investigation On The Drilling Of Brittle Materials With Brazed Diamond Grains

Because of the high rigidity and brittleness, form machining of engineering ceramics is difficulty especially in the drilling of holes. The tools used for drilling of engineering ceramics were mainly electroplated diamond bits or sintered diamond bits in previous studies. But the life of a sintered bit is relatively short because of it's lower height of protrusion and chip storage space; Although an electroplated bit has a higher protrusion, the bit will lose machining ability due to the pop-outs of diamonds or the splits of electroplated coatings under higher loads, because it doesn't achieved chemical metallurgy combination for diamond grains and matrix substrate. Therefore, it is very important to develop new technologies of efficiently shaped drilling of engineering ceramics for further exploiting and utilizing engineering ceramics.Chemical metallurgy combination for diamond grains, bond and matrix substrate can be achieved in brazing tools. The height of grit protrusion can be up to 70%~80%; The chip storage space is increased greatly; The utilization ratio of the grains are improved, and decreased the clogging. So, brazed diamond tools are considered to be the ideal tools for efficiently and costly machining brittle materials. And that is why brazed diamond thin-wall bits were studied in this thesis. By high-frequency induction, brazed thin-wall diamond bits were fabricated and were used to drill alumina engineering ceramics. In drilling experiments, both the axial force and the torque are measured. Statuses of grains on bit were also observed. Compared with electroplated bits, performances of brazed thin-wall bits were studied. Additionally, experiments of drilling other hard and brittle materials such as stone and glass were also carried out.The main work achievements and results of this thesis can be summarized as follows:1. Compared with electroplated bits, brazed diamond thin-wall bits are superior of steadily machining process, long life and high quality of the workpiece especially under conditions of high rotary speed and big feeding.2. The effect of feeding speed to axial force and torque is evidently larger than that of the rotary speed.3. The bit's performances are evidently influenced by the thinness of bit. Neither too thin nor too thick is fit for efficiently machining.