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diffusion welding[də′fyü·zhən ‚weld·iŋ]
a method of welding without fusion of the basic metal by means of heating and compression of the parts to be joined. The diffusion of one metal into the other takes place at the site of welding of the parts. The parts, with carefully cleaned and fitted surfaces, are placed in a closed welding chamber maintained under a vacuum of up to ~0.01-0.001 newtons per sq m, or as little as 10−5 mm of mercury. The parts are compressed by a small, constant force and heated to 600°-800° C to increase their plasticity and accelerate diffusion. Several minutes after completion of the welding, the parts are cooled and unloaded from the chamber. Heating in the vacuum chamber leads to an extensive purification of the surfaces from organic impurities and oxides. Diffusion welding makes possible the production of high-quality welding seams without internal stresses and without overheating of the metal in the region near the weld.
Diffusion welding may be used for joining parts made of identical hard and brittle materials or of different materials, such as steel, hard alloys, titanium, copper, nickel, and their alloys. The welding of parts consisting of some nonmetallic materials—for example, two ceramics or a ceramic with a metal—is possible.
Diffusion welding is used mainly in the electronics industry, in machine building, and in the manufacture of metal-cutting tools and dies. The use of diffusion welding is limited by the expensive and complex apparatus required. The productivity of diffusion welding is not very high because of the necessity of performing such operations as evacuation of the chamber, heating of the parts, and holding for the execution of the diffusion itself.
K. K. KHRENOV