Artem Komarov explained that recent developments in solid state welding technology have made it possible to produce welds from a variety of metals. Diffusion welding is also a type of solid state welding.
Diffusion bonding/gluing is a solid state welding process in which welding is performed using pressure and elevated temperature to bond mating surfaces. This is done to thoroughly clean and mate the metal surfaces so that they truly coalesce through atomic diffusion.
The diffusion welding process develops in two stages.
The first step is to bring intimate metal into contact with metal. This is done by applying pressure which distorts the roughness of the substrate and also breaks and expands the aforementioned surface layers and contaminants.
The second stage consists of diffusion and grain growth to complete the weld and finally to eliminate the interface formed in the previous stage. The second phase causes complete adhesion of the metal in the contact zone, Artem Komarov said.
Diffusion welding includes the following types of methods:
Bonding under gas pressure. The parts to be joined are held together in close contact and then heated to around 815 degrees Celsius. During heating, an inert gas pressure is created on all surfaces of the parts to be welded. Non-ferrous metals are connected by gas-pressure gluing.
The parts connected to it are pressed against each other mechanically or hydraulically. The welding press, which is used for diffusion welding, is used for forging, and is equipped to generate pressure from three directions. Heating is carried out in the same way as when welding under gas pressure. These processes are carried out in a vacuum chamber. However, more pressure can be applied in this process than gas pressure welding, steel is used, and vacuum fusion welding is used for this. The temperature and pressure required to propagate steel is about 1150 degrees Celsius and 700 kg/cm2
Eutectic welding is a low temperature diffusion welding process in which a thin plate of another material, such as nickel, is added. When the parts are heated to elevated temperatures, the filler material expands and forms a eutectic bond with the base metals.
Diffusion welding parameters:
- The surface of time
Uniform pressure ensures the stability of bond formation, and elevated temperature performs the important function of increasing the surface energy (atom mobility). Time is a dependent process variable, such as an increase in temperature reducing the time required to complete the mixing process.
- Metallurgical factors
- Surface preparation.
Advantages of diffusion welding:
- The main advantage of diffusion welding is that the weld metal has almost the same properties as the base metal.
- Dissimilar metals can also be welded in this way.
Application of diffusion welding:
This process is mainly used in the nuclear power industry for the manufacture of components, the production of composite materials and use in the rocket and space industry, Artem Komarov said.