Effect of the Granular Composition of Diamond Powder Synthesized in the Mg–Zn–C System on the Structure, Physicomechanical Properties, and Performance Characteristics of Crystals Sintered from It under High Pressure

Abstract

The synthesis of diamond was performed at a pressure of 8 GPa and a temperature of 1700°C in the Mg–Zn–C system and, after the product was chemically purified, the resulting diamond powder was classified by grain sizes. The effect produced by the ratio between coarse and fine diamond powder fractions and the sintering parameters on the structure and physicomechanical properties of sintered diamond polycrystals was studied. The wear resistance of synthesized samples was investigated when turning a cylindrical X drillability granite core sample from the Korostyshiv deposit. The high-pressure sintering of a mixture of synthesized coarsely and finely dispersed diamond powders was shown to provide a 2.46-fold decrease in the residual porosity as compared to sintering under the same pressure for the diamond powders synthesized in the systems based on iron group metals. Among the resulting polycrystalline samples, the highest hardness determined at a Knoop indenter load of 9.8 N was 66 GPa to attain 87% from the hardness of natural type Ia diamond single crystal (face (100)). Polycrystalline diamond elements sintered in a Toroid 30 high-pressure autoclave at a pressure of 8 GPa and a temperature of 1780°C from the purified product of synthesis in the Mg–Zn–C system with a diameter of 15 mm and a height of 3 mm demonstrated the highest wear resistance, which was 5.6–10.9 times higher than for the reference specimen sintered from the powder synthesized in the Ni–Mn–C system.