Deposition welding

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As a cladding or cladding according to DIN 8580 coating by welding , the welding designated when exclusively by the welding material (wire or powder), a volume structure, usually in the form of a cover layer takes place. It therefore counts for coating .

For example, a high-alloy steel is applied to highly stressed metallic components as surface protection. In addition to conventional arc welding processes, laser deposition welding and plasma powder deposition welding are used.

Cladding build-up welding on a boiler tube

Under build-up welding, a distinction must be made between armor (against abrasive wear), plating (against corrosive attack) and buffers (for welding on a foreign metal). Furthermore, repairs of press molds and tracks are carried out using build-up welding. The main area of ​​application for build-up welding is power plant construction . In particular, membrane walls and bulkhead heating surfaces, which are exposed to very aggressive exhaust gases in power plants , are subject to very strong material removal. Waste incineration plants and biomass power plants for highly contaminated waste wood, which have a high sulfur and halogen content in the flue gas, are particularly affected . The greatest erosion occurs here in the area with the highest flue gas temperatures, unprotected heating surfaces and in the superheater area .

In the process, a high-alloy protective layer is applied to a lower-alloy base material. Nickel-based alloys such as Alloy 625 and Alloy 686 or Alloy 59 are preferably applied. The thickness of the protective layer is 2–3 mm, with membrane walls typically having a thickness of 4 to 5 mm. The protective layer is applied in two layers or offset. The base material must be sandblasted before cladding and given a temporary protective coating immediately. The MAG welding process is used as the application method. For a long service life, the layer thickness of the coating material must be uniform and the Fe-mixing (diffusion of iron into the coating during melting) must be low. The cladding process is used both to strengthen components damaged by corrosion and abrasion and for new components. The typical removal rate in waste incineration plants is 0.1 mm / 10,000 hours.

Cladding build-up welding in a pipe section with Inconel 625
Cladding build-up welding in a pipe section with Inconel 625

See also

Deposition welding (notation with two s) is carried out like contract welding on behalf of another company.

Web links

Individual evidence

  1. ↑ Alloy 625 data sheet.Retrieved May 11, 2017 .
  2. ↑ Alloy 59 data sheet.Retrieved April 11, 2017 .