Preparation and Characterization of Polycrystalline Cubic Boron Nitride (PcBN) Compacts by a Pressureless Sintering Process

A novel cost-effective pressureless sintering method has been developed to prepare polycrystalline cubic boron nitride (PcBN) compacts. The effect of feldspar as sintering aids was analyzed in this paper. Various amounts of feldspar from 5 to 15 wt% were added to cBN powders, and the pressureless sintering was conducted at temperatures ranging from 900C to 1200C under an air atmosphere. The microstructure, phase, density and microhardness of the as-obtained PcBN compacts were measured and correlated to amounts of Si added and to sintering temperatures. The sample showed superior sintering behavior in comparison to those fabricated using hot pressed sintering. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that feldspar diffused homogeneously and tightly bonded with cBN. But hBN appeared when the sintering temperature even at 900C, which dramatically affected the property of PcBN compacts. A PcBN compact with a relative density of 91% was obtained at 1100C and its microhardness was as high as 1000HV.