Cutting performance of nano-polycrystalline diamond

Nano-polycrystalline diamond (NPD) synthesized by the direct conversion sintering process from graphite under ultra-high pressure and high temperature (15–18 GPa, 2100–2300 °C) has a very fine texture consisting of small diamond grains (10–50 nm in size) bonded directly without any binder materials. NPD has extremely high hardness, high wear resistance, no anisotropic mechanical properties, no cleavage feature, and high thermal stability, and so has high potential for precise cutting tools. To clarify this potential, we conducted cutting tests for various work materials under different conditions and compared the results with those for conventional polycrystalline diamond (PCD) and single crystal diamond (SCD) tools.The results of the cutting tests were as follows: approximately 10–20 times higher than the PCD tool on turning of Al–Si alloy, 3–5 times higher than the PCD tool on turning of cemented carbide, and more than two times higher than the SCD tool on ultra-precision cutting for binderless cemented carbide. Detailed observations of the cutting edge after the cutting tests indicated that the excellent cutting performance of the tool was the result of its isotropic feature and fine texture without any binder. These results revealed that nano-polycrystalline diamond has outstanding potential for various cutting and processing applications.

► We evaluate cutting performance of the nano-polycrystalline diamond (NPD).
► NPD is synthesized from graphite directly under HPHT.
► NPD tools have high cutting performance for various work materials.
► NPD has outstanding potential for various cutting and processing applications.