Formation of Lateral Sliver Defects in the Platform Region of Single-Crystal Superalloy Turbine Blades

Sliver defects are known to extend along the casting axial direction. In this study, the lateral sliver defects on the platform base of single-crystal (SX) superalloy turbine blades were detected by macrocorrosion and electron backscattering diffraction. It was identified that misorientation between adjacent sliver textures was limited within medium-angle misorientation defects (10.5 deg). Moreover, the lateral sliver defects were more prone to occurring at a lower withdrawal rate. Based on the evolution of thermal profile and stress contours, the high stresses around the boundary between the blade body and the platform region were supposed to be the formation mechanism of lateral sliver defects.