Sintering of Fine Grained Polycrystalline Cubic Boron Nitride Compacts without Binder

Cubic boron nitride (cBN) is a excellent super hard materials with superior mechanical properties that has been widely used in different industrial applications. Conventional cBN was sintered with binder in the cBN powder, and the binder affect the mechanical properties of cBN. Here we report that we sinter the polycrystalline cBN on WC-16wt% Co substrates without any sintering agent at the pressure 5.5 GPa and temperatures of 1300-1600 degrees C for 10 min. In the sintering, we used 1-2 mu m fine grained cBN powder as the starting materials, also, liquid substance infiltrated from the substrates and occurred chemical reactions with cBN powder. Reaction contents were investigated at different temperatures according to X-ray diffraction(XRD). Plenty of direct BN-BN bonding was formed in the scanning electron microscopy(SEM) observation. The hardness of best samples reach 38.5 GPa under the loading force of 5 kg, which have high hardness for the formation of direct BN-BN fine grains in the sample.