Dependence of static strength of large crystals of synthetic diamond type ib of octaedric habitus, after chemical-thermal time and time

Abstract

Increasing demands on the quality of drilling tools are forcing us to revise the traditional methods of their production and develop new alternative technologies. Some issues related to the possibility of increasing the efficiency of a drilling tool using diamond single crystals are considered. It has been suggested that a further reserve for improving the quality of drill bits lies in the use of large, high-strength, non-magnetic diamonds. Scientific research in this area has shown that the efficiency of the drilling process largely depends on the mechanical properties of single crystals, such as tensile strength and hardness. The grains operate under a load close to critical, which can lead to the complete destruction of single crystals instead of gradual chipping with the formation of new cutting edges. The results of an experimental study of the influence of individual stages of the drilling tool manufacturing process, namely, chemical-thermal treatment and annealing at 1150°C, on the static strength of large type Ib synthetic diamond crystals with an octahedral habit are presented. The dependence of this quantity on the geometric dimensions of single crystals was obtained for the first time. The achieved maximum value of static strength was 8750 N. It was experimentally confirmed that with an increase in the breaking load, the size of the fragments decreases. In order to ensure sufficient strength of the cutting part of the drilling tool, it is advisable to limit the size of single crystals to 1000–1200 µm, since the critical load values ​​for them are higher than for crystals whose size is 1300 µm or more, which, according to the theory, is associated with an increase in the number of defects and inclusions in proportion to size. The performed analysis made it possible to make adjustments to aspects of the manifestation of the scale effect when testing the strength properties of diamond single crystals.