EXO-MELT(TM) PROCESS FOR MELTING AND CASTING INTERMETALLICS

Melting of Ni3Al-based intermetallic alloys was successfully accomplis hed by the Exo-Melt(TM) process by modifying the furnace-loading seque nce to initiate the highly exothermic NiAl reaction to form superheate d NiAl liquid initially. Recorded images of the melting process showed the occurrence of exothermic diffusional reactions between liquid alu minum and solid nickel melt stock. Combustion synthesis of NiAl and Ni 3Al is also described and compared with the Exo-Melt(TM) process. In c ontrast to the Exo-Melt(TM) process, the conventional melting practice of adding aluminum to molten nickel increased the temperature of the bath from 1600 to 2300 degrees C, and a vapor cloud formed due to the oxidation of alloying elements. The Exo-Melt(TM) process results in po wer savings of 47% over conventional melting practices, and the proces s has been used to melt and cast a total of 8000 kg of Ni3Al-based all oy. Reaction mechanisms involved in the Exo-Melt(TM) process and conve ntional melting processes are described and compared with the reaction mechanisms operating in combustion synthesis.