| 摘要 |
The invention relates to polycrystalline sintered articles comprising at least 50% by weight of crystalline silicon nitride phase of which at least 90% by weight is in the beta -form, and at least one secondary crystalline intergranular silicate phase, and having a density of at least 99% of the theoretically possible density, a modulus of elasticity at room temperature of less than 300 kN/mm2, a short-term bending strength at room temperatue, measured according to the 4-point method, of at least 600 N/mm2 which, up to 1200 DEG C., decreases by less than 50%, and a long-term bending strength, measured according to the 4-point method, which is characterized by a numerical value of more than 40 at 1200 DEG C. for the crack growth resistance parameter n. These polycrystalline sintered articles are manufactured, by sintering with or without the use of pressure, a mixture of silicon nitride powder, crystalline silicates of natural or synthetic origin having melting points in the range of from 1350 DEG C. to 1950 DEG C. as sintering additives and metal carbides having melting points at least from 1500 DEG C. as nucleus formers. |
