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 μm particle sizes) and cBN content (up to 50 vol%) were selected for this study. Near-full densification was obtained at temperatures between 1100° and 1200°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 _{I C} measured by Vickers indentation), and a moderate decrease of mechanical strength (determined by three-point bending).