Study on in-situ synthesis of ZrB2 whiskers in ZrB2–ZrC matrix powder for ceramic cutting tools

The composite powder of ZrB2 whisker-toughened ZrB2–ZrC matrix ceramic tool materials was synthesized by in-situ synthesis process combined with the carbothermal reduction method. The product contained ZrB2 as the major phase and ZrC/Ni2B as the minor phases. When increasing the synthesis temperature from 1400°C to 1700°C, the lattice parameters of ZrB2 (a and c) decreased linearly, meanwhile, ZrC exhibited a non-stoichiometric property through the variation of the lattice parameter. The ZrB2 whiskers showed an aspect ratio of 10–30 and a diameter of 1–3μm. The agglomeration of the ZrB2–ZrC matrix powder and the morphology of bonding particles in the whiskers were also observed. The solid–liquid–solid (S–L–S) mechanism and the anisotropic Ostwald ripening were found to govern the growth of the ZrB2 whiskers during the in-situ synthesis process.