Versions of many wrought nickel-base alloys
are available in cast form. The specifications
for the castings are given in the ASTM A494
standard. Table 3 gives the composition of the
most popular cast nickel-base alloys and the
approximate equivalent to the wrought versions.
The main difference in the chemical composition
between the cast alloys (Table 3) and their
wrought versions (Table 2) is in the higher
amount of impurities, such as carbon and silicon,
allowed in the cast alloys. Carbon is naturally
present in the melt and cannot be removed without
special treatment, such as argon oxygen
decarburization (AOD). Silicon is necessary in
the melt, because it contributes to fluidity during
pouring and filling of the molds.