Cubic boron nitride-containing ceramic matrix composites for cutting tools

Polycrystalline cubic boron nitride (cBN) and cBN-containing composites (CBCCs) are consolidated by the high pressure and high temperature technique, but only small specimens can be made at a high cost. Hot isostatic pressing and spark plasma sintering have been applied to densify CBCCs under various sintering temperatures and moderate pressures. A second phase can decrease the shrinkage temperature and increase the relative density. Mechanical properties are improved by cBN addition. The phase transformation of cBN to hexagonal boron nitride depends on the second phases, sintering aids and sintering parameters. A silica-containing phase can suppress the cBN phase transformation. Future research includes optimization of processing windows, evaluating other properties for applications as cutting tools and characterization of the cBN phase transformation.