Surfacing and hardfacing of metals
Surfacing is a process of depositing metal on items that have been worn down, or are subject to wear corrosion or other damage to help extend the life of the tool. This kind of welding is done not for creating joints or for joining metal, but for building up, and laying a protective layer or bead on top of vulnerable parts and pieces that are subject to wear such as backhoe buckets, or farm equipment plow points. More often than not, the surfacing is done to restore the metal back to the rough original dimensions, or to protect areas receiving uneven wear. There are two basic types of surfacing. The first is called hardfacing.
Hard facing generally involves the Stick or MIG process and uses special (and usually expensive) filler metal to build up the overall surface of the metal. These beads are often not laid solid across the entire face of the metal, but in random or organized patterns that intersect or overlap to provide a raid, bumpy like surface that takes the brunt of the wear or impact. Hardfacing is done to improve either abrasive wear or impact resistance of the metal.
The second method is known as “metallizing”. This is a special welding process in which nearly or all of the entire affected area is coated with molten spray of metal. This spray is used to build up the overall surface so that in many cases the original dimensions can be restored to the metal, such as in a crankshaft in an engine is deeply scored or overly worn on the journals. A special machine sprays tiny pieces of molten metal onto the crankshaft, building up the surface. Once it is sufficiently built up the area is turned back down in a lathe and polished so that it can be reused.