Asea Aktiebolag

Allmanna Svenska Elektriska Aktiebolaget

Asea Ab

Abb Cerama Ab

Asea Cerama Ab

Jan Adlerborn

Hans Larker

Jan Nilsson

Bertil Mattsson

Sven-Erik Isaksson

Leif Hermansson

An object is manufactured of a powdered material by isostatic pressing of a body (10), preformed from the powdered material, whereby the preformed body is surrounded by a casing (16) which at least for the main part is transferred to molten phase, before the isostatic pressing is carried out while sintering the powder. As material in the casing there is used glass or a material forming glass when being heated and containing 48-52 percent by weight B.sub.2 O.sub.3, 46-50 percent by weight SiO.sub.2 and 1.5-2.5 percent by weight Al.sub.2 O.sub.3. It can be removed from the finished object by water or water vapor and has a low coefficient of thermal expansion at temperatures below the melting temperature of the glass. To counteract the penetration of molten glass from the casing into the preformed body, a barrier layer (18) may be arranged on the preformed body inside the casing. (FIG. 3)

Method of manufacturing an object of a powdered material by isostatic

When manufacturing an object of powdered material by isostatic pressing of a body (10), preformed from the powdered material, with a gaseous pressure medium, the preformed body is provided with a casing (19) of glass which is made gas-impermeable by heating before carrying out the isostatic pressing. Inside the glass casing there is arranged on the preformed body a barrier layer (11) which counteracts the penetration of melted glass from the enclosure in the preformed body. The barrier layer is built up of at least two layers, of which one layer (12) at least substantially consists of powdered boron nitride and one layer (13) of a mixture of powdered boron nitride and a powdered material with the ability, upon contact with glass from the casing in melted form, to make a layer containing boron nitride tighter.

Method of manufacturing an object of powdered material by isostatic

In the manufacture of an article of ceramic material, for example a bladed turbine wheel of silicon nitride, there is first formed a plurality of article parts, at least one of which is a shaped powder body formed from powder of ceramic material mixed with a plasticizer, after which the plasticizer is driven off by a suitable heating operation. The article parts are then assembled together into a configuration conforming to that of the article to be manufactured, and the assembled article parts are surrounded with a gas-impermeable layer, for example a layer of glass. Finally, the assembled parts are isostatically pressed at elevated temperature to form the assembled article parts into a dense, homogeneous article.

Method of manufacturing articles of ceramic material

An object is manufactured from a powdered material by isostatic pressing of a body, preformed from the powdered material, with a pressure medium, whereby the preformed body, in which at least the surface layer consists of a ceramic material in the form of a nitride, is surrounded by a casing which is rendered impenetrable to the pressure medium, before the isostatic pressing is carried out and the powder sintered. As the material in the casing there is used boron oxide or a glass containing boron oxide or a material forming glass while being heated, in which the content of boron oxide is sufficiently high for the glass--or the glass formed during heating--to be removable by water. The preformed body surrounded by the casing is subjected to a heat treatment for the formation of boron nitride on the surface of the preformed body, before the isostatic pressing is carried out. The casing is removed from the finished product by means of water or water vapor.

Disclosed is a method for manufacturing an object of silicon nitride. In the method, a body preformed from silicon nitride is surrounded with a casing which is permeable to gas. Upon heating, the casing is transformed into a layer which is impermeable to a pressure medium which is used during isostatic pressing of the preformed body while a pressure outside the casing is maintained which is at least as high as the pressure of the gas which is present in the pores of the preformed product. After the casing has been made impermeable to the pressure medium and the preformed body has been enclosed therein, the isostatic pressing is carried out while the body is simultaneously sintered.

Method for manufacturing an object of silicon nitride

An object of ceramic or metallic material is manufactured by isostatic pressing of a body preformed from a powder of the metallic or ceramic material, the preformed body (10) then being embedded in glass, for example in a mass of glass particles (16) in a vessel (15) which is resistant to the temperature at which the sintering of the metallic or ceramic material is carried out, the material embedding the preformed body being transferred to a melt having a surface limited by the walls of the vessel, below which surface the preformed body is located, and a pressure necessary for the isostatic pressing of the preformed body then being applied on the melt by a gaseous pressure medium.

Method of manufacturing an object of metallic or ceramic material

Disclosed is an improved method for manufacturing an object of silicon nitride. In the method, a body preformed from silicon nitride powder and enclosed in a casing of glass is isostatically pressed with a gaseous pressure medium in a pressure vessel at a temperature required for sintering of silicon nitride. After pressing and sintering are completed, the pressure and the temperature in the pressure vessel are adjusted such that the temperature maintains the glass in a plastic state and the pressure in the pressure vessel is below the partial pressure of nitrogen gas for silicon nitride at that temperature so that the glass casing is blown up around the body and the body is freed from or can easily be freed from the glass casing.

A method for manufacturing an object of silicon nitride by isostatic pressing of a preformed body of silicon nitride powder utilizing a pressure medium at a temperature sufficiently high to sinter the silicon nitride. The preformed body is subjected to a degassing operation before isostatic pressing. An inner porous layer of a first material and then an outer porous layer of a second material are applied on the preformed powder body. The inner porous layer is transformable, at a temperature below the sintering temperature for silicon nitride, into a pressure medium impermeable layer. The outer porous layer is also transformable into a pressure medium impermeable layer, but at a temperature which is lower than the temperature when the inner porous layer is converted into its pressure medium impermeable form. Thus, the preformed body is first subjected to a degassing and to a heating to the temperature for transforming the outer porous layer into a pressure medium impermeable layer while the inner porous layer is maintained in a porous form. Thereafter the preformed body and the surrounding layers are heated further to the temperature for converting the inner porous layer into its pressure medium impermeable form while a pressure greater than the gas pressure inside the layers is maintained on the outside of the layers. The isostatic pressing of the preformed object is then carried out.

Method of manufacturing an object of silicon nitride

In manufacturing objects by isostatic pressing of a preformed powder body enclosed in a deformable casing at elevated temperatures and pressures, the body of powder is preformed and is then arranged in a glass capsule of a first material which is embedded in a glass powder having a higher softening temperature than the first material. The capsule with the embedded body is evacuated and sealed, and the capsule with its contents is heated and subjected to isostatic pressure.

Method for hot isostatic pressing powder bodies

For hydrostatically hot pressing bodies of borides, carbides or nitrides of titanium, zirconium or chromium from a powder having an excess of boron, carbon or nitrogen, the power is enclosed in a sealed container of a material which forms compounds with boron, carbon or nitrogen which have a melting point at least equal to that of the material of the container. Container materials may be for example metals from Group IVb of the Periodic System, particularly titanium and zirconium or their alloys in the case of titanium or chromium compounds and zirconium or zirconium base alloys in the case of zirconium compounds. This allows pressing at temperatures of up to 1700.degree.-1800.degree. C, which is high enough to cause bonding between the powder grains.

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Robertsfors, Sweden

Jan Adlerborn