Dependence of the Static Strength of Type Ib Single Crystal Diamonds with Octahedral Habit on Their Size


Relevance. Scientific and technological progress in diamond drilling is aimed at increasing productivity and reducing the cost of the process. One of the crucial tasks of the last fifty years is to re-equip geological exploration and mining operations with a more efficient tool. This has led to new trends such as the reinforcement of the cutting edge through optimal processing methods, the use of hard alloys based on borides, nitrides and carbides, the use of natural diamond raw materials, and since 1956, the use of synthetic diamonds. Progress in the production of synthetic diamonds allowed making a breakthrough from fine-grained industrial powders consisting of type IIb crystals with a high content of solvent metal inclusions to non-magnetic type Ib crystals of increased strength up to 2 mm in size. Since the main load during operation is directed along the normal to the working surface of the installed crystal, it was decided to use crystals of octahedral habit, which is associated with the anisotropy of the strength properties of diamond.
Purpose. Determination of suitability for the use of non-magnetic type Ib single crystals of octahedral habit as materials for the production of drill bits.
Methods. The method for determination of the static strength for single-crystal substances at a constant load rate is used.
Results. The process of diamond destruction under static load is experimentally studied. It was established that crystals are susceptible to brittle fracture and the decrease in the size of fragments is reduced in proportion to the fracture force. The dependence of the static strength of type Ib single crystals of octahedral habit on the length of the side face is obtained.
Conclusions. Crystals with an edge size greater than 1200 µm have a lower static strength value compared to smaller crystals, the edge size of which varies between 1000...1100 µm. Large single crystals of type Ib synthetic diamond of octahedral µm with size 1100/1600 can be used to make drilling and dressing tools

Keywords: Ib synthetic diamond, diamond drilling tool, geological exploration, physical and mechanical properties, HP-HT temperature gradient method