Abstract: Compressive residual stresses can be developed by underwater plasma transferred arc welding. The development of these compressive stresses act to prevent hot cracking and He embrittlement that can develop during welding or stress corrosion cracking that can develop subsequent to the welding operation.

Abstract: An apparatus and method feeds weld material to an underwater plasma transferred arc welding torch. The weld material comprises a powder, which can be entrained in a fluidizing gas flow. The weld material is fed by the apparatus from a first supply through at least one conduit to a supply container. The apparatus comprises a first powder supply pressurized with a powder carrier gas positioned above the surface of the body of water; a second powder supply container positioned below the surface of the body of water and the second powder supply container comprising at least one powder outlet port and a gas vent open to the above surface atmosphere; at least one powder conduit connecting the first container with the second container; an underwater welding torch positioned near the second container and having at least one powder inlet; and at least one powder conduit connecting the second powder supply container to the at least one powder inlet of the torch.

Abstract: An extension is formed directly on an article by dipping a portion or end of the article having an attached integral mandrel into a molten bath of a compatible alloy, followed by withdrawal of the end under controlled conditions sufficient to cause an integral extension to solidify on the article. A ceramic mold is utilized over the dipped end of the article and the integral mandrel with a mold cavity that generally defines the shape of the extension to be formed. The mold may be formed in situ on the mandrel, or preformed and attached to the subject article over the mandrel. The integral mandrel is melted within the mold by dipping the mandrel into the molten alloy. The mandrel acts as a buffer between the molten material and the article while permitting melting of the article end and solidification of the integral extension. Extensions formed by the method of this invention have a microstructure that is continuous and compatible with that of the article.

Abstract: An extension is formed directly on an article by melting a portion or end of the article having an attached integral mandrel within a ceramic mold, followed by cooling of the end under controlled conditions sufficient to cause an integral extension to solidify on the article. A ceramic mold is attached on the end of the article over the integral mandrel with a mold cavity that generally defines the shape of the extension to be formed. The mold may be formed in situ on the mandrel, or preformed and attached to the subject article over the mandrel. Extensions formed by the method of this invention have a microstructure that is continuous and compatible with that of the article. Such microstructures may include epitaxial growth of the extension from the microstructure of the article. The method establishes a temperature gradient within the article during solidification that may be further controlled by auxiliary heating and/or cooling of the article and/or extension during the practice of the method.

Abstract: An extension is formed directly on an article by melting a compatible alloy preform within a ceramic mold, followed by cooling of the end under controlled conditions sufficient to cause an integral extension to solidify on the article. A ceramic mold is attached on the end of the article with a mold cavity that generally defines the shape of the extension to be formed. The mold may be formed in situ on a removable mandrel, or preformed and attached to the subject article. Extensions formed by the method of this invention have a microstructure that is continuous and compatible with that of the article. Such microstructures may include epitaxial growth of the extension from the microstructure of the article. The method establishes a temperature gradient within the article during solidification that may be further controlled by auxiliary heating and/or cooling of the article and/or extension during the practice of the method.

Abstract: Nb--Sn precursor articles are described that include a Nb alloy article that is at least partially coated with a layer of a Sn alloy, such as a Sn--Cu alloy. The precursor articles described herein have a controlled concentration of the impurity elements As and S in the Sn alloy layer. The concentration of these elements in the Sn alloy layer is less than or equal to 50 ppm by weight. This invention also describes a method for making Nb--Sn precursor articles having a controlled concentration of As and S impurities.

Abstract: A superconductive article is made from interwoven superconductive, metallic tapes. The interwoven tapes are electrically interconnected by a plurality of superconductive interconnections that extend between the interwoven tapes. Articles of the invention may be formed from tapes comprising superconductive Nb.sub.3 Sn having Nb.sub.3 Sn interconnections.

Abstract: An improved high performance x-ray system having a rotating anode therein which includes an improved target/stem assembly comprising a metallic target and a large bore, thin-walled tubular metal stem which, when connected to a rotor body assembly, provides a rotating x-ray tube anode assembly is disclosed. An insert of an alloy, for example, tantalum alloy, is placed between the target layer and the large bore, thin-walled tubular niobium or niobium alloy stem and then bonded thereto to produce a composite x-ray tube target/stem assembly. The target/stem assembly is then connected to a rotor body assembly by fasteners, preferably threaded, to produce a rotating anode assembly having high bond strength that provides acceptable balance during x-ray tube operations.