Preparation of polycrystalline cBN containing nanodiamond

Abstract

Abstract Polycrystalline cubic boron nitride (PcBN) was prepared with Ti-coated cBN at 5.5 GPa 1200 °C for 500 s. Nanodiamond, aluminum and silicon were used as additives to bind components. The structures and phases of prepared PcBN were analyzed by SEM and XRD and the density and heat endurance of prepared PcBN were also tested. Our results showed that Ti coating led to formation of a series of compounds such as TiB and TiN and atomic bonding was formed among the gradient layers. We also demonstrated that nanodiamond reacted, as the carbon source, with silicon, titanium and aluminum to form various compounds with super hardness, high heat resistance and high stability. These compounds improved the structure consistency and eliminated the extra residual stress between substances. The un-reacted residual nanodiamonds in PcBN kept their diamond structure and there was no graphitizing during the sintering process when silicon was present, but graphitizing occurred in the absence of silicon, suggesting silicon inhibited nanodiamond graphitizing. The presence of nanodiamond not only increased the density and strength of PcBN, but also reduced the ‘bridging effect’. Because there was no obvious borderline between different components, the heat endurance of PcBN was improved.