Structure of the continuously cast Ni-based superalloy GMR 235

In this work we characterized the structure of continuously cast small cross-section rods (Ø10 mm) of the Ni-based superalloy GMR 235. In the microstructure prevailed dendritic columnar γ-grains with γ′-precipitates. In the interdendritic regions MC-carbide and M3B2-boride were identified. The inverse macrosegregation was very faint, except at the secondary witness marks and natural corrugations. It was found that the alternating drawing mode had much greater influence on microstructure than other casting parameters. Special attention was given to explanation of processes leading to formation of surface marks (primary and secondary witness marks and natural corrugations). Formation of hot tears and appearance of inverse segregation is also discussed.