Formation of Sliver Defect in Ni-Based Single Crystal Superalloy

The formation mechanism of sliver defect in Ni-based single crystal superalloy was investigated by X-ray computed tomography and electron backscattered diffraction. The origin of sliver due to the localized deformation of 1-2 dendrites near the mold wall was experimentally observed. The diverging boundary was the favorite position for sliver initiation. It was found that the deformation that induced sliver occurred in the mushy zone and was limited in the lower part of the dendrite. Thermal contraction forces played an important role in the formation of sliver. The dendrite deformation was attributed to the imbalanced force loaded on the dendrite.