CBN has higher thermal resistance than diamond. At temperatures exceeding 800F, CBN retains its hardness better than diamond and is able to maintain its cutting edge at temperatures well up to 1000F. In addition, the thermal conductivity of CBN is four and half times better than copper.
CBN is not present in nature. It is produced by the synthesis of hexagonal boron-nitride under static high pressure and high temperature conditions.
CBN has the same crystal structure as diamond, except boron-nitrogen bonds replace the carbon-carbon bonds in diamond. This makes CBN less reactive at high temperatures. Boron atoms in CBN crystal have only three valence electrons. Nitrogen atoms in CBN crystal have five valence electrons, but two of five electrons will form a stable pair on the surface, leaving three valence electrons for bonding with boron. Therefore the surface of CBN contains a reduced amount of free “dangling” electrons, which makes CBN more stable at high temperature.
CBN doesn’t contain the carbon, so it doesn’t react with a metal group the way that diamond does. Strength and resistance to the thermal and chemical attack while maintaining sharp cutting edges during use makes CBN the superior choice when temperature is an issue or when grinding Ferrous metals that diamond cannot efficiently grind.