Elektroschmelzwerk Kempten Gmbh

Jochen Kriegesmann

Alfred Lipp

Klaus Reinmuth

Klaus Hunold

Karl A Schwetz

The invention is substantially pore-free shaped articles which consist essentially of polycrystalline .alpha.- or .beta.-silicon carbide in the form of a single-phase homogeneous microstructure having grain sizes not exceeding 8 .mu.m, and which are manufactured from SiC powder, without the concomitant use of sintering aides, by isostatic hot-pressing in a vacuum-tight casing at temperatures of from about 1900.degree. C. to 2300.degree. C. and at pressures of from about 100 to 400 MPa. The SiC starting materials have .alpha.- and/or .beta.-SiC powders having a total content of metallic impurities not exceeding 0.1% by weight and a particle size of 4 .mu.m and finer.

Shaped polycrystalline silicon carbide articles and isostatic

The invention relates to dense shaped articles of polycrystalline .alpha.-silicon carbide containing from 0.1 to 0.4%, by weight, of aluminum and optionally, a small amount of nitrogen and/or phosphorus, having a homogeneous virtually single-phase microstructure. The additional constituents are substantially in the form of a solid solution in the .alpha.-SiC lattice. The shaped articles are distinguished by flexural strength of at least 600 N/mm.sup.2 up to 1450.degree. C. and low subcritical crack propagation under mechanical stress. The fracture mechanism is trans granular up to at least 1450.degree. C. The shaped articles are manufactured by simultaneously shaping and hot pressing pulverulent .alpha.-silicon carbide containing a small amount of an aluminum-containing additive, such as aluminum powder, aluminum nitride and/or aluminum phosphide, at temperatures between 1850.degree. C. and 2300.degree. C. under a pressure of at least 100 bar (10 MPa).

Dense shaped articles of polycrystalline .alpha.-silicon carbide and

The invention relates to dense shaped articles of polycrystalline .beta.-silicon carbide containing small amounts of aluminum and optionally, nitrogen and/or phosphorus, having a virtually single-phase microstructure since the additional constituents are substantially in the form of a solid solution in the .beta.-SiC lattice. The shaped articles are characterized by high temperature flexural strengths of at least 600 N/mm.sup.2 at temperatures up to 1450.degree. C. The fracture mechanism is transgranular up to at least 1450.degree. C. The shaped articles are manufactured by hot-pressing and simultaneously shaping pulverulent .beta.-silicon carbide with small amounts of an aluminum-containing additive, such as aluminum powder or aluminum nitride and/or aluminum phosphide, at temperatures between 1750.degree. C. and 2200.degree. C. under a pressure of at least 100 bar (10 MPa).

Growing community of inventors

Durach-Bechen, Germany

Jochen Kriegesmann