Microsegregation in directionally solidified Ni-based superalloy

Structure and microsegregation was studied in directionally solidified Ni-b ased superalloy of the chemical composition Ni-11.7W-8.46Co-5.04Cr-4.72Al-1 .05Nb-1.05Ti-0.96Mo-0.16C (wt. %). The microstructure of Ni-based superallo y consisted of gamma -matrix with coherent gamma'-precipitates and complex monocarbides of (Nb,Ti,W)C type. It was shown that during solidification W and Co segregated in the dendrite cores with partition ratios higher than 1 , and Ni, Cr and Al segregated in the interdendritic region with partition ratios lower than I. At a constant temperature gradient at the solid-liquid interface of 12 000 K.m(-1), the measured partition ratios for Ni, W, Co, Cr, and Al depended neither on growth rate chosen from the interval (2.18 x 10(-6); 4.17 x 10(-5)) m.s(-1) nor on morphology of the solid-liquid inter face.