Novel routes to process cubic boron nitride and its composite for extreme environments

Cubic boron nitride (cBN) is well known for its super hardness, the second-hardest material after diamond, and also exhibits high temperature stability, thermal conductivity, and chemical stability, which are desirable for applications in extreme environments such as grinding, cutting, and friction welding. However, its widespread applications have been hindered since it has been synthesized by high-pressure high-temperature processing, which in turn limits its size availability. In this talk, we introduce a novel route that can reduce the processing conditions to process superhard bulk nanocrystalline cBN, which combines the use of emulsion detonation and high-pressure high-temperature transformation-assisted consolidation. Emulsion detonation process activates BN powder to have unique structure and chemistry, i.e. wurtzite BN nanograins in hexagonal BN matrix with enhanced structural disordering and Oxygen impurity, which combined together enhances the nucleation rate of cBN and its densification leading to the formation of superhard bulk nanocrystalline cBN at reduced conditions. In addition, we also present preliminary results of a new approach for low-pressure processing cBN composites, which is designing binder that forms liquid wetting cBN and reacts with cBN forming hard compounds.