Abstract: Cast structures of grain size, dendrite morphologies and the shape of MC type carbides of a nickel-base superalloy IN738LC are investigated with the melt addition of carbides, nitrides, boron and intermetallic compounds, It is found that the grain size of ingots can be refined extensively to the order of ASTM M11～12 by combination of an intermetallic compound addition together with lowering the melt homogeneous treatment temperature during the melting process. The addition of the intermetallic compound has the advantages of little influence on the freezing characters, alloy composition as well as on phase constitutions. Therefore, this process is considered as an effective and practical method of grain refinement for superalloys.

Key words: heat resistant alloys, crystallites, additives, intermetallics