Diffusion welding

In 1953, a new method of joining metals by welding was developed - this is diffusion welding. It is a type of pressure welding in which highly heated parts undergo mutual diffusion of atoms in contact over time. This method allows for very strong joining of different metals and their alloys, ferrous and non-ferrous, of varying thicknesses.  Diffusion welding It can be automatic or semiautomatic, with parts welded in various positions. Welding occurs through heat and pressure in a protective environment.

Diffusion welding of metals

Feature diffusion welding of metal The difference from other pressure welding methods is the high heating temperature of the metal 0.5 - 0.7T_pl, as well as relatively low specific compressive pressures of 0.5-0 MPa when maintaining isothermia for a few minutes to several hours. Diffusion bonding of atoms is determined by physical and chemical processes during welding, namely: the interaction of the heated metal and gases in the surrounding environment, cleaning of the weld surface from oxides, and the development of recrystallization and creep.

For successful completion diffusion welding of metal, It is necessary to reduce the oxidation rate of the workpieces. This is achieved by using reducing gases, fluxes, molten salts, and coatings, but inert gases and vacuum are the most common. In this type of welding, homogeneous metals achieve a strong bond when the structure of the joining zone is the same as that of the base material. This is facilitated by grains that are common to the materials being joined. Diffusion welding Creates high-quality joints between dissimilar materials. Workpieces can vary in shape and have compact contact surfaces.

Diffusion welding technology:

• To begin with, the metal surface is thoroughly cleaned, and a sufficient distance is established between the workpieces to establish a metal connection;
• then strong heating occurs, which helps protect the surface from contamination, clean it, and desorb oxides deep into the metals;
• Subsequent pressure smooths out the unevenness, plastic deformation occurs, a metallic bond is established across the entire contact surface, and diffusion accelerates, enhancing the reliability and strength of the joint. In some cases, after the pressure is released, the welded parts remain at the welding temperature to stabilize the crystallization processes.

Diffusion welding technology When welding homogeneous metals, no dividing line is left, and when welding dissimilar metals, the joining zones are determined by the differences in their structures. The surface is thoroughly cleaned to ensure a good bond, according to grades 4–6. Sometimes, an intermediate layer, such as nickel powder, is used to promote a strong weld.

Different heating methods are used:

• radiation;
• induction
• passing current;
• electron beam;
• glow discharge.

Diffusion welding technology occurs in two stages:

•  compression of metal surfaces;
•  the process of forming the structure of a welded joint.

Advantages of this type of welding:

• does not require solders;
• no need for additional mechanical processing;
• low energy consumption.