Commercial casting of nickel aluminide alloys

Commercial development of nickel aluminides has been limited in the past by a lack of technological know-how for melting and casting these alloys. However, the Exo-Melt method, a patented process previously described in AM and P (June 1995), has recently been used to successfully melt and pour commercial-sized heats of this new class of engineering materials. As of August 1995, more than 3,400 kg (7,500 lb) of nickel aluminide alloys have been successfully melted using the Exo-Melt process in an induction furnace under argon cover. This work has been performed by United Defense LP, which is the sole foundry licensed to melt and pour nickel aluminide-based alloys, in conjunction with Oak Ridge National Laboratory. This article provides a close look at the commercialization of the Exo-Melt process at United Defense LP, and at the nickel aluminide-based alloys--their physical and mechanical properties, commercial applications,and some comparisons with traditional heat-resistant alloys.