Origin of localized rafting in Ni-based single crystal turbine blades before service and its influence on the mechanical properties

The origin of localized rafting has been investigated in a single-crystal second-generation-superalloy Ni-based turbine blade. Localized rafting is observed at the center of the airfoil close to the platform. To explore the role of plastic deformation during the manufacturing process, the microstructure of a fir-tree-root replica is also investigated. Chemical selective characterization methods and neutron diffraction measurements suggest that plastic strains are at the origin of the rafting and not chemical segregations, as is often reported. The formation of rafted microstructures leads to a reduction of ∼12% of the yield strength of the Ni-based superalloy measured at 20 °C.