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Abstract
Grain refinement of superalloys K3 and K4169 is achieved by adding refiners A, B, or mixed refine (A + B) into the melt of alloy K3, and refiner C into the melt of alloy K4169 under different casting parameters. Results indicate that the mixed refiner (A + B) produces the best refiningeffect for alloy K3. In this case, the average equiaxed grain size is reduced from 4.9 to 1.5 mm, i.e. to ASTM M9, and the proportion of equiaxed grains at traverse cross-section has been improved from 40 to 84%. Moreover, the average main axis length of dendrites reduces, and the morphologies of MC carbides change from rod-like and Chinese-script type to discrete block type after grain refinement. For alloy K4169, adding C into the melt can refine the grains to the order of ASTM M9.5. Meanwhile, the proportion of equiaxed grains increases 31% and the average main axis length of dendrites reduces 2.85 mm. In addition, the amount and size of both Laves phase of eutectic morphology and MC carbides reduce. Interdendritic segregation level of elements of both alloys is reduced.