The majority of vacuum investment castings like turbine blades and vanes for the aircraft and industrial gas turbine industries are made from Ni-base superalloys and are produced in a vacuum induction melting and precision casting furnace. In vacuum precision casting furnaces, a master alloy composition is inductively melted and then cast into an investment mold. The solidification structure of the casting can be adjusted to be equiaxed (E) (uncontrolled, from outside to inside) or, through the use of an additional mold heater, directionally solidified (DS) or single crystal (SC).