Relationship between microstructure and melt superheating time for directionally solidified DZ125 superalloys

The solidification microstructure evolution of Ni-based superalloy DZ125 with melt superheating time was investigated. The results show that the dendrite arms are evidently refined and the segregation is reduced with the increase of melt superheating time when the melt superheating time is less than 30 min. However, further prolonging melt superheating time, the dendrite arms become coarser lightly. The morphology of carbide presents from script-like to blocky and nodule when the melt superheating time increases from 15 to 30 min. But when melt superheating treatment time is prolonged to 60 min, the morphology of carbide is still mainly blocky and nodule. The reason of solidification microstructure evolution is the change of melt structure with the prolonging of melt superheating time.