READILY WORKABLE CERAMICS

摘要

PURPOSE:To obtain the ceramics excellent in oxidation resistance and machinability and from which the vitreous component does not flow out even when used at high temp. in an oxidizing atmosphere by sintering a mixture of hexagonal boron nitride powder, silicon nitride powder and sintering assistant powder in a specified ratio. CONSTITUTION:The ceramics are formed by sintering a powdery composition contg. 20-70 pts.wt. of hexagonal boron nitride powdery 30-80 pts.wt. of silicon nitride powder and 1-10wt.% sintering assistant based on the silicon nitride. A mixture of alumina and yttria is preferably used as the sintering assistant. The ratio of the yttria powder to alumina powder is preferably controlled to (5:5)-(9:1).