Dendritic Growth Transition During Laser Rapid Solidification of Nickel-Based Superalloy

The dendritic growth transition of nickel-based superalloy in the top region of the laser additive manufactured layer has been studied. The results show that the dendritic growth direction in the top region of the layer is changed from the perpendicular to parallel direction to the laser scanning direction. From the finite element simulation, the dendritic growth transition is found to be attributed to the increased deviation angle between the epitaxial dendritic growth direction and local thermal gradient in the top region of the molten pool. The critical transition angle is revealed to be 70°–80°. The origin of the top transition grains is mostly the re-nucleation sites generated in the last remaining liquid in the top region of the molten pool.