Fabrication And Performance Evaluation Of The Brazed Diamond Thin-wall Drills Of Small Diameter

The diamond abrasive grains are widely used in making various consolidation abrasive tools due to their distinguished properties of extremely high hardness, high wear resistance, superior thermal stability and excellent thermal conductivity etc. At present, the traditional sintered and electroplated diamond abrasive tools are occupying the large market share. However, there are generally lots of defects to manufacture the small diameter high precision thin-walled drills by sintering or electroplating process, such as the low holding strength for grains and limited storage space for chips. These will restrict the application of diamond abrasives tools in the precision holes processing areas. To avoid these deffects, such kind of drills will be maked by high temperature brazing process. The holding strength for grains grits will be improved by the chemical and metallurgical behavior among the filler alloy, grains and the stainless steel, and the problems that the traditional process cannot handle will be sovled.The main contents in this paper are as follows:(1) The brazed diamond core drill of 3 mm diameter substrate is successfully maked respectively by vacuum furnace and high frequency inductive heating device.(2) The micro-structure of the diamond core drill was observed by scanning electron microscopy (SEM), and the similarities and differences between the vacuum furnace brazing samples and argon protection high-frequency brazing samples was analyzed. The results show that both of the heating modes are applicative.(3) The relationship between the abrasive wear mode and the height of abrasive outcoming was analyzed through comparing the grits wear conditions before and after drilling test. The results show that the diamond grit outcoming height should be 50%~60% of its own height by considering the drilling efficiency; chips discharge effect and failure modes, etc.(4) With initial drilling efficiency as the test index, carried on the orthogonal experiment design. Then made nine groups brazed diamond core drill bit samples and carried out the silicate flat glass drilling test according to the test plan. Achieve the optimal process parameter: the diamond abrasive grains size for 60/70 #, the outcoming height of diamond grits (filler-alloy dosage) approximately 50%, diamond abrasive grains area concentration (diamond dosage) is about 30%, the filler-alloy particle size for - 200 #.