Abstract: This application discloses a new powder composition which may be plasma sprayed onto the surface of an article to provide a protective coating therefor. The protective coating may be resistant to heat, wear, and corrosion. The coating may also provide a thermal or radiation barrier.In particular, the coating composition for arc plasma spraying consists of finely divided silicon carbide mixed with finely divided silicon. This coating composition is applied to a substrate by developing a plasma spray, feeding the coating composition to the plasma spray and directing the plasma spray at an exposed surface of the substrate so that the exposed substrate is coated with a coating which consists essentially of beta silicon carbide and silicon.The new article of manufacture disclosed in this application, is a substrate with a tightly adherent coating thereon consisting essentially of beta silicon carbide and silicon. The substrate may be any material, either metallic or non-metallic, to which the coating adheres.

Abstract: A method of making Si.sub.3 N.sub.4 based cutting tools (and the resulting product) is disclosed. A mixture is formed of three powders: a first powder of at least 75% crystalline Si.sub.3 N.sub.4, a second powder selected from the group Y.sub.2 O.sub.3, MgO, CeO.sub.2 and ZrO.sub.2, and a third powder selected from the group consisting of Al.sub.2 O.sub.3, WC, Wsi.sub.2, W and TiC. The mixture is cold pressed to a density of 50-70% of theoretical and then sintered to full density without the application of pressure.

Abstract: This application discloses a new powder composition which may be plasma sprayed onto the surface of an article to provide a protective coating therefor. The protective coating may be resistant to heat, wear, and corrosion. The coating may also provide a thermal or radiation barrier.In particular, the coating composition for arc plasma spraying consists of finely divided silicon carbide mixed with finely divided silicon. This coating composition is applied to a substrate by developing a plasma spray, feeding the coating composition to the plasma spray and directing the plasma spray at an exposed surface of the substrate so that the exposed substrate is coated with a coating which consists essentially of beta silicon carbide and silicon.The new article of manufacture disclosed in this application, is a substrate with a tightly adherent coating thereon consisting essentially of beta silicon carbide and silicon. The substrate may be any material, either metallic or non-metallic, to which the coating adheres.

Abstract: A strong beta silicon carbide article is formed from a moldable mixture including beta silicon carbide particles, from about 1/16% by weight to no more than 1/4% by weight of the total weight of the moldable mixture of niobium carbide particles and a binder for supporting these particles for a molding operation. The mixture is molded to form the shape of an article, and the article is pyrolized so that volatile portions of the binder are driven off and the remaining portions broken down to a carbon phase. The carbon phase is transformed to beta silicon carbide in a siliciding operation. The addition of the small percentage of niobium carbide unexpectedly increases the strength of the finished beta silicon carbide article.

Abstract: A method is taught for making beta silicon carbide in a micro balloon structure, that is, a spherical type structure in which the beta silicon carbide forms only a thin wall of the balloon structure. If desired, the micro balloon structure, which is porous, may be crushed to form beta silicon carbide of a very finely divided size. The method is accomplished by pyrolyzing microballoon structures formed of an organic material so that the material breaks down to leave carbon behind in the microballoon structure. This carbon is reacted with silicon at an appropriate temperature to form the pure beta silicon carbide in the microballoon shape.

Abstract: A method of forming a silicon carbide article is disclosd. Selected weight percentages of silicon carbide particles, graphite particles, if desired, and a thermosetting binder are mixed together and molded into an article by molding techniques which operate on the basis that the thermosetting binder forms a continuous medium about all the particles supported therein. The molded article is heated in the absence of oxygen and the thermosetting binder breaks down to form a low density, vitreous carbon phase. The article is heated in the absence of oxygen to a selected temperature at which the article is maintained for a period of time in a gaseous environment consisting of nitrogen preferably with a small amount of hydrogen therein. The hydrogen-nitrogen treatment is effective to cleanse the article and insure that there is an adequate pore structure through the article for a later siliciding operation to be carried out thereon.

Abstract: A method of forming a silicon carbide article is disclosed. Selected weight percentages of silicon carbide particles, graphite particles, if desired, and a thermosetting binder are mixed together and molded into an article by molding techniques which operates on the basis that the thermosetting binder forms a continuous medium about all the particles supported therein. The molded article is heated in the absence of oxygen and the thermosetting binder breaks down to form a low density, vitreous carbon phase. The article is heated in an oxygen containing environment to remove excess surface carbon. The article is silicided at an elevated temperature by penetration of the article through its pore structure with a reactable form of silicon.