Hard surfacing wire, also known as welding wire or filler metal, is a type of wire that is used in welding applications to provide a protective layer over a surface to increase its hardness, durability, and resistance to wear and tear.

Hard surfacing wire is made of various materials, such as carbon steel, stainless steel, nickel alloys, or cobalt alloys, depending on the specific application requirements. The wire is typically fed through a welding torch or gun, where it is melted and applied to the surface being welded.

The choice of hard surfacing wire depends on the specific application and the type of base material being welded. Some common types of hard surfacing wire include:

1. Flux-cored wire: This type of wire is used in welding applications where a flux coating is necessary to protect the weld from atmospheric contaminants.

2. Gas-shielded wire: This type of wire is used in applications where a protective gas is needed to prevent oxidation during the welding process.

3. Metal-cored wire: This type of wire is used in applications where a high deposition rate is required, and it provides a more stable arc and better penetration.

4. Submerged arc wire: This type of wire is used in applications where a high deposition rate and deep penetration are required, and it is ideal for welding thick materials.

Hard surfacing wire is commonly used in industries such as mining, construction, agriculture, and manufacturing, where equipment and machinery are subject to heavy wear and tear.