Abrasive cubic boron nitride - from hexagonal boron nitride using metal borides

摘要

Initiator consisting of alkali(ne earth) metal boride, pref. Mg- or Be boride, promotes conversion of hexagonal to cubic BN above 1000 degrees C and 40 kbar press. B content of initiator, calc. as elemental B, is such as to raise total B content of reaction mixt. by >=10% w.r.t. stoichiometric content in hexagonal BN. Pref. hexagonal BN and initiator mixt. is pre-heated to >=1000 degrees C to form an alloy, which is cooled and used as reaction mixt. Abrasive prod. pref. contains 90 - 98% cubc BN, =9% non-hydrolysable borides, nitrides and free B and consists of >=80% polycrystalline granular aggregates. It is useful for grinding tools, e.g. wheels, -stone, -cloth, abrasive paper and emergy pastes and withsands moisture.