GB882317A - Improvements relating to the joining of metals - Google Patents

Abstract

882,317. Making turbines; welding by pressure. WIGGIN & CO. Ltd., HENRY. April 28, 1958 [April 26, 1957], No. 13471/57. Classes 83 (2) and 83 (4). In joining preformed parts of chromium containing alloy a very thin layer or layers of nickel is interposed between the parts, the parts are forced together and the assembly is heated in a non-oxidizing atmosphere to 1000- 1100‹ C. to diffuse the nickel substantially completely into the parts. The parts may have spigot and socket connection when one is forced into the other in a press and heated without maintenance of the applied pressure. If the parts have other shapes they may be held under an external pressure during the initial heating e.g. to 700‹ C. to promote initial diffusion and the pressure may then be released. The pressure may be obtained by interfitting after shrinking in dry ice. The nickel may be in foil, powder, sprayed or plated form. In embodiments the trapezoidal section root 2 of a gas turbine blade 1, Fig. 1, of nickel-chromium or nickel-chromium-cobalt alloy is covered with nickel foil 5 or is coated with nickel and is joined to the slot 3 machined in the rim of a rotor 4 of the same nickel-chromium or nickel-chromium-cobalt alloy. The sides of the slot which may be cut by spark erosion and the root sides may be parallel. A frusto-conical root 2, Fig. 2, of a turbine blade of 20% chomium, 20% cobalt, 2.4% titanium, 1.5% aluminium, 0.07% carbon, balance nickel is forced into a socket 3 in a rotor 4 of the same alloy with an intermediate layer of nickel 5 and the assembly heated in hydrogen to 1100‹ C. for 8 hours. The nickel foil covered or plated ends of a section of turbine blade 6, Fig. 4, with holes 7 formed by extruding a billet having inserts of filler metal, subsequently removed, are secured in sockets cut by spark erosion in root and shroud 8, 9. These parts may be assembled by shrinkage fitting. A number of sleeves are shrink fitted on turbine blade stock coated with nickel and joined thereto and the assembly is cut into blades with roots. Stainless-steel cutlery blades may be joined to stainless-steel shanks. According to the Provisional Specification if the surfaces to be joined are of superlative quality the interposed layer may be dispensed with-preliminary heating at 600‹ C. is then effected before pressing the parts together.