Hot isostatic pressing of cubic boron nitride-tungsten carbide/cobalt (cBN-WC/Co) composites:: Effect of cBN particle size and some processing parameters on their microstructure and properties

Cubic boron nitride (cBN)-cemented carbide composites have gained attraction over the last few years because of their potential uses as wear parts. The densification behavior of cBN-hard metal composites by glass encapsulation hot isostatic pressing-has been investigated. Composites with different cBN grades (from 0/0.5 to 6/12 mu m particle sizes) and cBN content (up to 50 vol%) were selected for this study. Near-full densification was obtained at temperatures between 1100 degrees and 1200 degrees C, and pressures between 150 and 200 MPa, respectively, while no phase transformation of cBN into the low-hardness hexagonal form has been detected by X-ray diffraction. The addition of cBN to the hard metal base material led to an increase of hardness, a significant increase of fracture toughness (K-IC measured by Vickers indentation), and a moderate decrease of mechanical strength (determined by three-point bending).