GB760265A - Improvements relating to the joining of refractory metals - Google Patents

Abstract

760,265. Jointing. BRITISH THOMSONHOUSTON CO., Ltd. April Z, 1955 [April 2, 1954], No. 9802/54. Class 83 (4). A method of joining together the refractory metals, molybdenum, molybdenum tungsten alloys, tungsten and tantalum consists in causing the surfaces to be joined to contact directly at a multiplicity of small areas by a labyrinthine mass through which a reducing gas is passed while the contacting parts are heated in order to cause intergrowth at the contacting surfaces with, and of, the mass, whereby to form electrical contact and mechanical connections between the surfaces and simultaneously and/or subsequently siliciding the joint to protect it from oxidation. The labyrinthine mass may be formed of powdered metal and/or metal oxide the powder being mixed with a liquid containing a binder, e.g. a solution of high viscosity nitrocellulose in amylacetate, to form a paste. The pasted joint is heated to approximately 900‹ C. in a reducing atmosphere containing hydrogen. In an embodiment the ends of the molybdenum wires of an electrical heating element for igniting highly oxidizing fuel are crinkled, pasted with oxidized powdered molybdenum and then forced into a recess in a molybdenum terminal block said recess being preferably filled with the paste. The assembly is then heated as hitherto to reduce the oxide and cause the intergrowth between the particles and the surfaces of the wires and the block. The reduction may be effected simultaneously with the siliciding process by heating the joint with the attached paste in hydrogen mixed with silicon tetrachloride. Specification 730,855, [Group II], is referred to.