WELD OVERLAY / CLADDING

CLADDING OR WELD OVERLAY

Definition:

Weld Overlay (WOL), also known as cladding, hard facing, weld cladding, or weld overlay cladding, is a process where one or more metals are joined together via welding to the surface of a base metal as a layer. This is normally done to improve the material by adding either a corrosion resistant or hard facing layer to it. Surfaces prepared in this way can even be highly customized by layering and alloying multiple different materials together. Cladding is the bonding together of dissimilar metals. It is different from fusion welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure.

Work Principle:

A metal coating bonded onto another metal under high pressure and temperature. The process of forming such a coating. A protective or insulating layer fixed to the outside of a building or another structure.

Types of Weld Overlay or Cladding:

• Shielded Metal Arc Welding
• CO2 Welding
• Metal Inert Gas (MIG) Welding
• Tungsten Inert Gas (TIG) Welding
• Submerged Arc Welding
• Plasma Transferred Arc (PTA) Welding

Shielded Metal Arc Welding:

The most common of these is shielded metal arc welding, which is most commonly used with ferrous materials and employs rods as weld material. For this method the core wire is covered with a coating that adds special elements to weld metal and the weld metal is protected by slag created during welding.

CO2 Welding:

With CO2 welding, which is sometimes known as Metal Active Gas (MAG) or semi-automatic welding, the CO2 shield gas atmosphere protects the material from oxidation. For this process weld materials can consist of solid wire, metal-cored wire, and flux-cored wire. Because welding wire is used for the weld material, continuous welding is possible.

Metal Inert Gas Welding (MIG):

Metal Inert Gas (MIG) welding, which is sometimes known as Tungsten Inert Gas (TIG) or simply insert gas welding, is largely the same as semi-automatic welding except that during this process the area to be welded is shielded by an inert gas. It is primarily used with non-ferrous materials.

Plasma Transferred Arc Welding (PTA):

Plasma Transferred Arc (PTA) welding. Like TIG welding, an arc is generated from a non-consumable tungsten electrode and welding is performed with flux supplied externally into the arc. This method is possibly the most complex but it is capable of overlaying of hard complex carbide alloys, something that is difficult to do with most of the other methods. Since with PTA welding the weld material is a powder, these material powders can be blended to create original flux for easy overlay welding as well.

Weld Overlay or Cladding Users:

Weld overlay is commonly used within the gas industry and can be used on components as diverse as pipes, fittings, valves, and vessels.

Advantages:

• Best technique for coating any shape which increase life-time of wearing parts.
• Surface protection while still allowing the internal component enough strength to meet appropriate codes and standards.
• Providing a long-life and high-reliability corrosion resistance to harsh environment applications.
• Very economical way to provide excellent corrosion resistance for steel structures without jeopardizing design thickness.
• Built part is free of crack and porosity.