diffusion welding

[də′fyü·zhən ‚weld·iŋ]

(metallurgy)

A welding process which utilizes high temperatures and pressures to coalesce the faying surfaces by solid-state bonding; there is no physical movement, visible deformation of the parts involved, or melting.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Diffusion Welding

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

Mentioned in

References in periodicals archive

Since for the metallization by diffusion welding is used relatively thick metal foil, it makes it possible to realize the clamp mode of packaging..

In this paper we have presented the basic principles and practical realization of diffusion welding technology for manufacturing contacts to semiconductors.

Diffusion Welding Techniques for Power SiC Shottky Packaging // International Conference on Silicon Carbide and Related Materials (ICSCRM2005).

Diffusion welded contacts and related art applied to semiconductor materials/Difuzija sujungtu kontaktu taikymas puslaidininkiniuose dariniuose

The following theoretical considerations, based on welding experiments, speak in favour of the diffusion welding of glass.

From literature, different hypotheses for the joint creation in the diffusion welding process are known, such as the thin layer, energy, recrystallization, diffusion and gap hypotheses [5,6].

The diffusion welding of quartz glass can be considered as a joining of low-molecular [Si.sub.x][O.sub.y] tetrahedron structures to form higher-molecular [Si.sub.x][O.sub.y] clusters.

Movements of tetrahedron chains and tetrahedron rings in the interlayer are primary processes in the diffusion welding. Rising temperature leads to increased movability of the [Si.sub.x][O.sub.y] structures and also individual [H.sub.2] and OH molecules as well as to the desorption of [H.sub.2]O and OH.

At diffusion from the pore volumes at a temperature higher than 500[degrees]C, [H.sub.2]O is important for diffusion welding. Single silanol bridges are broken and the number of OH-groups is increased.

Despite the use of the diffusion welding for substrate-to-substrate joining of different materials [13-14], the joining process of technical and optical glasses without interlayers, in order to maintain optical characteristics of joints, has not been studied in detail.

Quartz glass, which is high-temperature stable and chemically resistant, was used in order to examine the joining mechanisms that lead to a substance-to-substance joint in the diffusion welding process.

For the welding process itself, the following conditions for the diffusion welding of the same glasses as well as of different glasses with each other are to be considered:

The diffusion welding of the glasses was carried out in a vacuum/inert gas--high temperature furnace with an integrated vertical press capacity device (Fig.

Substance-to-substance joining of quartz glass/Kvartsklaasi difusioonliitmine