Investment casting of NiAl single-crystal alloys

Significant progress has been made in the understanding of solidification conditions, microstructure evolution, and defect formation during investment casting of NiAlsingle crystals. The high liquidus temperatures of NiAl alloys result in a larger dendrite arm spacing than is found in superalloy Rene N5. Because of their higher thermal conductivities, NiAl alloys have higher cooling rates and lower temperature gradients during solidification than Rene N5. These differences give NiAl alloys a lower tendency to form freckles and a higher tendency to form equiaxed grains. However, with the aid of process modeling, single crystals of various shapes of NiAl alloys have been produced.