High-Pressure Synthesis of High-Purity and High-Performance Diamond and cBN Ceramics

Abstract:

High-purity, single-phase polycrystalline diamond and cBN have been successfully synthesized by direct conversion sintering from graphite and hBN, respectively, under static high pressure and high temperature. The high-purity polycrystalline diamond synthesized directly from graphite at ≧15 GPa and 2300-2500 °C has a mixed texture of a homogeneous fine structure (grain size : 10-30 nm, formed in a diffusion process) and a lamellar structure (formed in a martensitic process). The polycrystalline diamond has very high hardness equivalent to or even higher than that of diamond crystal. The high-purity polycrystalline cBN synthesized from high-purity hBN at 7.7 GPa and 2300 °C consists of homogeneous fine-grained particles (<0.5 μm, formed in a diffusion process). The hardness of the fine-grained high-purity polycrystalline cBN is obviously higher than that of single-crystal cBN. The fine microstructure features without any secondary phases and extremely high hardness of the nano-polycrystalline diamond and the fine-grained polycrystalline cBN are promising for applications in next-generation high-precision and high-efficiency cutting tools.

• Periodical: Advances in Science and Technology (Volume 45)
• Pages: 885-892
• DOI: https://doi.org/10.4028/www.scientific.net/AST.45.885
• Online since: October 2006
• Authors: Hitoshi Sumiya
• Keywords: Cubic Boron Nitride (CBN), Diamond, Direct Conversion, High-Pressure

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DOI: 10.1038/421599b

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