GB919031A - Improvements relating to the bonding of metals - Google Patents

Abstract

919,031. Welding by pressure. INTERNATIONAL NICKEL CO. (MOND) Ltd. April 1, 1960 [April 13, 1959], No. 12456/59. Class 83 (4). In joining two pieces of metal 1, 2 with or without the interposition of a thin layer 3 of another metal or alloy, by heat and pressure to form a bond by metallic diffusion, the pieces are maintained slightly separated within a sheath 8 which is deformable under the welding pressure and with the metal pieces forms an airtight assembly enclosing the surfaces to be joined, the resultant assembly is heated and pressure is applied to close the gap and deform the sheath while the atmosphere in the interior of the sheath is reactive and capable of dispersing or destroying oxide films or is inert and protective or is exhausted. Each piece 1, 2 is cylindrical and of creep-resisting nickel-chromium-cobalt alloy containing aluminium and titanium and has an end flange 7 to which one end of a cylindrical mild steel sleeve 8 is welded. A nickel foil 3 is arranged between the pieces in the gap therebetween and openings 10, 11 in the sheath in contact with the annular space 9 about the pieces register respectively with an opening in a tube 12 containing granular chromium and aluminium fluoride and an opening in a tube 13 connected to a vacuum pump and vessels in which aluminium fluoride vapour is absorbed in water. The assembly is placed in a furnace 6, the space 9 is evacuated and the assembly is heated to 1100‹ C. when an atmosphere believed to consist of hydrogen fluoride, hydrogen, nitrogen and chromyl fluoride and reactive to oxide films enters the space 9. A pressure of 2 tons per square inch is applied through members 4, 5 which deforms the sleeve and closes the gap and with pressure and temperature maintained for 15 minutes a diffusion bond is obtained. The pressure may be applied by forging blows, by rollers or by extrusion or the pressure applying members may be vibrated. The sheath may be heated by electric current and the inert atmosphere may be of dry argon or hydrogen. Composite billets, turbine blades with roots joined to blade sections and turbine discs joined to blades may be provided by the method. Specification 815,620 is referred to.