Law of crushing of diamond powders by ultra-high pressure extrusion

Abstract

In order to understand the law of super-high pressure extrusion fragmentation of diamond powders, a simulation experiment was designed for the polycrystalline diamond (PCD) synthesis of raw diamond powders with different particle sizes, crystal types, and particle size ratios at 5.5 GPa without heating for a short time (30 s). Crushing and plastic deformation of diamond powders with different grain sizes, crystal shapes, and grain sizes ratios were observed and analysed using scanning electron microscopy. The variation in the particle size composition of diamond powders with different particle sizes and particle size ratios before and after the action of high pressure was analysed quantitatively by a grain-size distribution tester. The results showed that the coarser the grain size and the more incomplete the crystal shape of a raw diamond, the more likely high-pressure extrusion and crushing occurred, and vice versa. A diamond with a fine size of smaller than 1 μm and a mixed diamond powder with high density ratio did not easily crush under high pressure, but the density ratio was not high after the high-pressure action. On this basis, the effect of high-pressure extrusion crushing and plastic deformation of diamond powders on the properties of sintered PCDs was further discussed. The design idea of high density ratio after the high-pressure effect was put forward, and the theoretical analysis and the experimental basis were provided for the design of the optimum particle size ratio of raw diamonds and the synthesis of high-performance PCD materials.