Microstructure Evolution of Directionally Solidified Ni-based CM247LC Superalloy
Ni-based CM247LC superalloy specimen was directionally solidified using Bridgman method with pulling speed of 2.5 mm/min to investigate the microstructure evolution along solidification direction.The microstructure and performance of as-cast specimen were characterized by stereomicroscope(SM),metallurgical microscope(OM),scanning electron microscope(SEM),energy spectrometer(EDS),as well as thermodynamic calculation software JMatPro and casting simulation software ProCAST.The results indciate that the competitive growth of columnar grains mainly occurs in the range of height below 60 mm from the water-cooling plate.The variation of dendrite arm spacing mainly depends on the axial temperature gradient and variation of growth rate,which gradually slows down with the distance from water-cooling plate increasing.The as-cast microstructure is composed of γ/γ'eutectic and MC carbides in addtition to γ dendrites,of which the size variation law is similar to that of dendrite arm spacing.
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