| 摘要 |
PURPOSE:To obtain the sintered body of Si3N4 which is less degraded in strength even in a high temp. region of 1400 deg.C by mixing sintering assistant powder consisting of a prescribed weight ratio of Sc2O3 powder and mullite powder with Si3N4 powder and molding the mixture, then sintering the molding in a nonoxidative atmosphere. CONSTITUTION:The sintering assistant powder formed by mixing the Sc2O3 powder and the mullite (3Al2O3.2SiO2) powder at 5/2 to 1/2 ratio is mixed at 1 to 6wt.% with 99 to 94wt.% fine powder of the Si3N4 having preferably <=1.0mum average grain size. This powder mixture is molded to a prescribed shape in a metallic mold and thereafter, a high isostatic pressure is loaded to the molding, by which the molding is produced. The molding is then sintered under an atm. pressure or pressurization at 1750 to 1850 deg.C in the nonoxidative atmosphere consisting of N2, etc. The sintered body of the Si3N4 obtd. in such a manner has the above-mentioned characteristics, is less increased in weight by oxidation and is highly resistant to oxidation; therefore, the use of the sintered body as engine parts is attained. |
