Dendrite Deformation in the Rejoined Platforms of Ni-Based Single-Crystal Superalloys

Dendrite deformation often occurs during the preparation of single-crystal superalloy blades by directional solidification and can cause solidification defects, such as low-angle boundaries (LABs), slivers, and orientation deviations. Continuous dendritic deformation is uncommon and its mechanisms and influencing factors are poorly understood. However, this can lead to significant orientation deviation and performance degradation. Herein, a model with rejoined platforms is designed to study the dendrite growth and orientation evolution in a rejoined platform of Ni-based single-crystal superalloys. It is indicated in the results that, under certain conditions, the developed secondary dendrites deform continuously near the mold wall of the rejoined platforms and the resulting disorientation has a cumulative effect. Finally, LABs and dendritic fragments appear on the rejoined platforms. Thus, the integrity of the single crystal is destroyed. This can be the result of the local shrinkage stress on the long secondary dendrites within a sufficient growth space.