Kennecott Corporation

The Carborundum Company

Stemcor Corporation

Laurence N Hailey

Carl H McMurtry

Wolfgang D Boecker

John A Coppola

A method of preparing a surface of a silicon carbide article for joining by metal brazing to metal by micro-roughening that surface of the silicon carbide which is to be brazed, applying catalyst consisting essentially of aqueous PdCl.sub.2 directly to the micro-roughened surface, in the absence of pretreatment of said surface with stannous chloride, and electrolessly depositing a thin layer of metal selected from the group consisting of Ni, Cr, Au, Ag and Cu on said catalyst-treated surface.

Silicon carbide-to-metal joint and method of making same

Sintered silicon carbide body having a D.C. electrical resistivity of at least 10.sup.8 Ohm cm at 25.degree. C., a density of at least 2.95 g/cm.sup.3 is formed upon sintering in a nitrogenous atmosphere at a temperature of about 2250.degree. C. or greater, a shaped body composed essentially of carbon or carbon source material in amount sufficient to provide up to 2.5 percent uncombined carbon; from about 0.4 to about 2.0 percent boron carbide; up to 25 percent of temporary binder and a balance of silicon carbide which is predominantly alpha-phase. The shaped body may additionally include other sintering aids such as BN or Al without destruction of desired high electrical resistivity.

Sintered silicon carbide ceramic body of high electrical resistivity

A silicon carbide-to-metal joint includes a thin layer of metal adherent to the ceramic material, a compliant layer of metal overlying the thin metal layer and a brazing alloy in contact with the metal to which the ceramic material is joined. A method for preparing a silicon carbide surface for joining by metallic brazing to a metal includes the steps of applying a thin layer of metal adherent to the ceramic surface followed by application of a compliant layer of metal. Also described is an easily brazable silicon carbide article which includes a silicon carbide substrate, a thin electrically conductive adherent metal layer overlying the substrate and a compliant metal layer overlying the thin metal layer.

Sintered silicon carbide/graphite/carbon composite ceramic body having a homogeneous fine grain microstructure with at least 50 percent of its silicon carbide grains having a size not exceeding about 8 microns and an aspect ratio less than about 3, with graphite grains having an average size not exceeding that of the silicon carbide grains microns uniformly dispersed throughout the matrix of silicon carbide and having a density of at least 75 percent of theoretical can be made by firing of a shaped green body having a density of at least about 45 percent of theoretical, the shaped green body containing graphite of fine particle size, a sintering aid selected from the group consisting of aluminum, beryllium or boron or compounds containing any one or more of these or a mixture of any of the foregoing elements or compounds, silicon carbide having a surface area of from about 5 to about 100 square meters/gram and, optionally, a temporary binder at a sintering temperature of from about 1900.degree. C. to about 2300.degree. C. in an inert atmosphere or vacuum. The process for making such pressureless-sintered composite bodies is relatively undemanding of exact temperature/time control during sintering. Contain embodiments of such composite sintered bodies may electrical-discharge machined.

Sintered silicon carbide/graphite/carbon composite ceramic body having

In accord with the present invention, a composite ceramic article may be produced by joining separate components of ceramic materials with a cement or brazing compound of finely-divided metal borides, such as Mo.sub.2 B.sub.5, MoB.sub.2, TiB.sub.2, GeB.sub.2, ZrB.sub.2, SmB.sub.6, NbB.sub.2, HfB, VB.sub.2, WB.sub.2 or TaB.sub.2. A particularly useful metal boride for use with silicon carbide is Mo.sub.2 B.sub.5. If the metal carbide parts or components to be joined are sintered, the metal boride cement is selected to have a melting point within 150.degree. C., but less than the sintering temperature of the metal carbide. If the metal carbide parts or components to be joined are unsintered, or an unsintered component is to be joined to a sintered component, the metal boride cement is selected to have a melting point slightly higher than the sintering temperature of the metal carbide components to be joined.

Method of producing composite ceramic articles

Pressureless sintered silicon carbide ceramic bodies, having an equiaxed microstructure and an alpha crystalline habit can be produced by firing shaped bodies, containing finely divided silicon carbide, boron source such as boron carbide, carbon source such as phenolic resin and a temporary binder, at a sintering temperature of from about 1900.degree. C. to about 2250.degree. C., depending on the sintering atmosphere, under conditions such that a coating of carbon source is maintained on the finely divided silicon carbide, and sufficient boron is maintained within the shaped body during firing. Boron can be maintained within the shaped body by various techniques, such as the use of a 'seasoned boat' or graphite container for the body being sintered, which has been saturated with boron by exposure to boron at or about the temperature of sintering. There is also disclosed a process for producing a sintered silicon carbide ceramic body, with or without the equiaxed crystal microstructure, from silicon carbide powders of alpha or beta crystal structure, or amorphous noncrystalline silicon carbide, or mixtures thereof.

Sintered alpha silicon carbide ceramic body having equiaxed

Pressureless sintering of silicon carbide to produce ceramic bodies having 75% and greater theoretical densities, can be accomplished by firing shaped bodies, containing finely divided silicon carbide, boron source such as boron carbide, carbon source such as phenolic resin and a temporary binder, at a sintering temperature of from about 1900.degree. C to about 2500.degree. C.

Growing community of inventors

Niagara Falls, NY, United States of America

Laurence N Hailey