Primary α phase and its effect on the impact ductility of a high Cr content cast Ni-base superalloy

► Primary α-(Cr,Ni) forms at 1190 °C from liquid in as-cast high Cr Ni-base K4648 alloy. ► Primary α is hard and brittle and deteriorates the impact ductility of superalloy. ► Primary α solutionized or transformed to M23C6 carbides in the 1180-1220 °C range. ► Faster cooling during solidification is recommended to avoid the primary α formation.