Due to its long range ordered structure, Ni.sub.3 Al is a very strong alloy; however, its brittleness has rendered it useless for structural applications. Recently, the intermetallic and its alloys have been attracting much attention since it was found that addition of a small amount of boron significantly increases the ductility of an otherwise very brittle alloy. A problem that now must be addressed is the difficulty encountered when attempts are made to weld the alloy.
Nickel aluminide has a face centered cubic (FCC) crystalline structure, and, like many FCC alloys, impurities have a way of being transported to the grain boundaries rendering the material brittle and subject to hot cracking upon welding.
Studies done at Oak Ridge National Laboratory have established that boron content has an effect on weldability. Results indicate that hot cracking response to boron content increases at low boron levels below 50 ppm and at higher levels above 300 ppm. Fortunately, a minimum is obtained at about 200 ppm which is about an optimum boron content for ductilizing Ni.sub.3 Al. Thus the presence of boron in a concentration range of 100 to 300 ppm actually improves the weldability of Ni.sub.3 Al.
Other work involving mechanical and electropolishing a surface prior to welding helped reduce cracking but did not provide sufficient improvement to be considered a solution to the problem. Therefore there is a need to provide a method for welding aluminides that does not result in hot cracking of the metal.