Structural transformations in the HP-HT formation of monophase superhard materials based on carbon and boron nitride dense phases

Abstract

The known data on the mechanisms of structural transformations in the formation of bulk monophase materials based on diamond and cubic boron nitride at high pressures and temperatures have been briefly summarized. Two groups of materials have been defined: those based on the initial micron powders of diamond, cBN, and graphite-like BN as powder and pyrolytic deposits. The structure formation of the first group materials has been shown to be governed by the development of the lattice plastic deformations (by translational slip and twinning) and rotational deformation, while the structure formation of the cBN-based materials is governed by the primary recrystallization occurring at T > 1900°C and p = 7.7 GPa. The rotational deformation governs a plastic fragmentation of grains in materials. The formation of materials based on the initial graphite-like BN has been found to depend on the crystal-oriented phase transformation into BN dense (wurtzitic and sphaleritic) phases and recrystallization of the forming cBN phase. The mechanisms of the cBN primary recrystallization have been discussed.