| 摘要 |
PURPOSE:To enhance wear resistance and defection resistance, and improve cutting performance of casting material in the case of a silicon nitride basis sintered body containing the 3a group elements of the Periodic Table by forming the sintered body made of needle-shaped particles wherein the average short diameter and average aspect ratio of silicone nitride particles are prescribed. CONSTITUTION:A silicon nitride basis sintered body is formed with a chemical compound of the 3a group elements of the Periodic Table and silicon nitride as its nucleuses. These ingredients should preferably contain, for example, the 3a group elements of the Periodic Table in the ratio of about 0.5-5mol percentage when calculated in term of an oxide conversion (RE2O3), and contain excess oxygen in the ratio of not more than 10mol percentage when calculated in term of SiO, and, formation of these silicon nitride particles is set to needle- shaped particles whose average short diameter is not more than 1mum and average aspect ratio is not less than 3%, and the mol ratio shown by SiO2/RE3 should be preferably made in a range from 0.5 to 2.5. |
