ホウ化物系硬質セラミックスの焼結および摩擦摩耗に関する研究 Sintering and Tribology of Boride Hard Materials
An experimental and analytical studies for obtaining high performance ceramics of TiB<SUB>2</SUB>-and B<SUB>4</SUB>C-based hard materials are inclusively presented in this paper. An improvement of sinterability and mechanical properties of TiB<SUB>2</SUB> and B<SUB>4</SUB>C hard materials are achieved by using ultra-fine powders and sintering aids. First results obtained showed that the ultra-fine and size-controlled powders of TiB<SUB>2</SUB> can be produced by magnesium-thermic reduction method. Fabrication processing of TiB<SUB>2</SUB> using pressureless sintering was also investigated with special emphasis on the effect of doping Ni<SUB>7</SUB>Zr<SUB>2</SUB>, Ni<SUB>3</SUB>B, NiB, and Co. The pore-free sintered compacts can be obtained by the addition of extreme small amount of Ni<SUB>7</SUB>Zr<SUB>2</SUB>. Moreover, sintering behavior and mechanical properties of B<SUB>4</SUB>C-TiB<SUB>2</SUB> composites were investigated by pressureless sintering up to 2100°C in vacuum, resulting in a maximum density of 99% of the theoretical density. Tailored microstructures may be obtained in composites on the B<SUB>4</SUB>C-TiB<SUB>2</SUB> system. The importance of microstructural features, resulting from precipitation phases from supersaturated solid solutions, for the improvement of sinterability and mechanical properties, is also addressed. Finally, sliding friction experiments were conducted on hard materials. A friction coefficient of B<SUB>4</SUB>C-TiB<SUB>2</SUB> as low as 0.1 can be obtained because the oxidation of btmde produces a trapped-lubricating, glassy phase of boron oxide on the sliding surfaces.
粉体および粉末冶金 43(4), 464-471, 1996-04-15
Japan Society of Powder and Powder Metallurgy