PURPOSE: To obtain the subject sintered compact with high fracture toughness by molding a powder mixture comprising silicon nitride, sintering auxiliary, titanium dioxide and liquid carbon source followed by sintering in a nitrogen atmosphere.
CONSTITUTION: A mixture is first prepared, comprising (A) 73.8-87.3wt.% of silicon nitride powder 0.3-1/μm mean particle diameter, (B) 8.2-9.7wt.% of a sintering auxiliary (e.g. yttria powder) 0.5-2μm in mean particle diameter, (C) 3.9-23wt.% of titanium dioxide powder 0.1-1 in mean particle diameter, and (D) 7-14wt.%, based on the titanium dioxide powder, of a liquid carbon source (e.g. phenolic resin with a solid content of 69.1wt.%). Specifically, each specified amount of the powder components is weighed and mixed in a mixer for ca.220hr. The liquid carbon source is then added to the mixture followed by mixing in the mixer for ca.48hr, and the resulting mixture is dried at ca.60°C. Thence, the resulting powder is put to uniaxial pressure molding followed by CID molding into a form. This form is then heated 10 a vacuum at ca.500°C or ca.1hr followed by heating at ca.1200°C for ca.4hr in a nitrogen atmosphere at a pressure of ca.6kgf/cm2 and then sintering in the identical atmosphere at ca.1800-1950°C for ca.4hr.
AKIYAMA KATSUNORI
YAMAMOTO HIROICHI
