Fumihiro Ueda

Synthesis of polycrystalline diamond compact with magnesium carbonate and its physical properties

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.