Handbook-Hardsurfacing, Building

Hard-Facing with Tungsten Carbide. To apply the composite hard- facing materials which are made up of

crushed tungsten carbide and a binding alloy is relatively easy. Use an excess acetylene flame. Try to avoid melting the base metal any more than necessary, but do not hesitate to move the rod about a little to secure even distribution of the tungsten carbide particles. Surfaces hard-faced with tungsten carbide materials are almost always used ”as is”, with no attempt at finishing. Rebuilding As noted at the start of this chapter, many bronze-surfacing operations and some hard-facing operations can be considered ”rebuilding”. There are also other occasions when it may be necessary to rebuild a part using a metal substantially equivalent to that from which the part was made originally. If it takes several years for a steel part to wear to the point where something must be done to restore it to its original dimensions, it may not make sense to go to the extra trouble and expense of hard-facing the worn section. The same may also be true of a cast iron part. Opportunities for that kind of rebuilding are many. The skill required is usually no more than that needed to lay down a uniform bead on a flat surface. In the case of steel, it may be possible to obtain an increase in future service life by flame-hardening the rebuilt surface after it has been ground or machined to the proper contours and dimensions. We shall discuss flame-hardening in some detail in Chapter 20. Right here we would like to make the point that a small area can sometimes be flame-hardened with the same torch used for rebuilding, and an elementary water quench. Sometimes hardness and wear resistance can be doubled by a few minutes of work. In closing, let us make this point again: That the use of the oxy-acetylene welding torch to increase the life of wearing parts is a major use of the torch. While many hard-facing applications call for the application of engineering skills, there are hundreds of bronze-surfacing and other rebuilding jobs that call for no more than a bit of ingenuity and imagination on the part of the man with the torch.