INFLUENCE OF THE COMPOSITION AND PROPERTIES OF DIAMOND POWDERS SYNTHESIZED IN THE Mg–Zn–C SYSTEM ON THE FORMATION OF POLYCRYSTALS FROM THEM DURING HIGH PRESSURE SINTERING

Abstract

An MgZn alloy was obtained in a steel high-pressure apparatus. Diamond powders were synthesized in the Mg–Zn–C system at a pressure of 8 GPa and a temperature of 1700 ° C. The synthesis product was chemically purified, and the obtained diamond powder was classified by grain size. The morphometric properties of the obtained powders, the effect of the ratio of coarse-grained and fine fractions of diamond powder and sintering parameters on the structure and physicomechanical properties of sintered diamond polycrystals have been investigated. It has been shown that sintering a mixture of synthesized diamond powders - with a grain size of 100/80 (40 %) and a finely dispersed one with a diamond particle size of less than 40 μm at a temperature of 1800 ° C and a pressure of 8 GPa makes it possible to reduce the residual porosity by 2.46 times compared to sintering with such the same pressure of diamond powders synthesized in systems based on metals of the iron group. The hardness of the obtained polycrystal, determined with a load on the Knoop indenter of 9.8 N, is 50.7 GPa, which is 67 % of the hardness of a single crystal of natural diamond of type Ia (face (100)).