Abstract
Abstract The sintering behavior of natural diamond powder with grain size in the range 6–12 μm was investigated under 7.7 GPa at 1800–2450 °C for 5 or 30 min in the presence of magnesium carbonate. Although diamond powder was not sintered at 1800 °C, a sintered diamond with a high grinding resistance could be synthesized at 7.7 GPa and above 2000 °C for 30 min. A well sintered diamond with a homogeneous microstructure and high hardness was synthesized at 7.7 GPa and above 2150 °C. The thermal resistance of the polycrystalline diamond obtained at 2300 °C and 7.7 GPa for 30 min was investigated at high temperatures of 1000–1500 °C in a vacuum of (1–1.5) × 10 −3 Pa. At 1400 °C, neither graphitization nor cracking were observed inside or on the surface of the polycrystalline diamond after the treatment. A large amount of graphitization was observed in the sintered diamond after the heat treatment at 1500 °C for 30 min in vacuum, but no cracking was detected on the surface of the polycrystalline diamond.
Published Version
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