| 摘要 |
PURPOSE:To obtain a sintered material of Si3N4 base having both high toughness and high strength, exhibiting excellent cutting performances as a cutting tool, by press molding a powder mixture of raw material of Si3N4, ZrN, SiO2 and MgO and burning in a nitrogen atmosphere at two stages by heating under pressure. CONSTITUTION:Mixed powder comprising (A) 1-27wt.% ZrN powder, (B) 0.1-5wt.% SiO2 powder, (C) 1-10wt.% MgO powder and (D) the rest of Si3N4 (preferably consisting essentially of alpha type) powder is molded into pressed powder, primarily sintered in a N2 gas atmosphere at 1,500-2,000 deg.C under 1-50atm. Successively the sintered material is secondarily sintered in a N2 gas atmosphere at 1,700-2,000 deg.C under 100-2,000atm. once or twice continuously or intermittently. By the secondary sintering, ZrO2 is formed as a dispersed phase, needle formation of Si3N4 as a hard layer is promoted to improve toughness and O content in a bonded phase of Mg-Si-O-N or Mg-Si-Zr-O-N is reduced and N content is increased to improve heat resistance. |
