Preparation of superhard cubic boron nitride sintered from commercially available submicron powders Available to Purchase

Using submicron cubic boron nitride (cBN) powder as a starting material, polycrystalline cBN (PcBN) samples without additives were sintered from 8.0–14.0 GPa at 1750 °C, and their sintering behaviour and mechanical properties were investigated. Transmission electron microscopy analysis showed that high-density nanotwins could be generated from common submicron cBN grains during high pressure and high temperature treatment. The dislocation glide and (111) mechanical micro-twinning are the main mechanisms that underlie plastic deformation in the sintering process, and this contributes to the grain refinement. A refinement in the grain size (∼120 nm), micro-defect (nanotwin and stacking faults), and strong covalent bonding between the grains are crucial for improving the sample mechanical properties. The PcBN sintered at 11.0 GPa/1750 °C possessed outstanding mechanical properties, including a high Vickers hardness (∼72 GPa), fracture toughness (∼12.4 MPam^1/2), and thermal stability (∼1273 °C in air).