Nanoscale γ′ precipitates dominated high-temperature creep of additive manufacturing repaired single crystal superalloy

In this study, the high-temperature creep behavior of nickel-based single-crystal (SX) superalloy repaired by direct energy deposition (DED) was investigated by comparison with the substrate. We found that the cladding layer is composed of fine cellular dendrites and contains abundant nanoscale γ′ (Ni 3 Al) strengthening phases and high-density dislocations. At 980 °C, the cladding layer exhibits superior creep performance, which is mainly attributed to the fact that the size of γ′ phases in the cladding layer is always significantly smaller than that in the substrate throughout creep, effectively increasing the critical resolved shear stress required for dislocation climb and shearing through the γ′ phases. Furthermore, only long and straight dislocations with non-compact cores along the <110> crystallographic direction were observed in the cladding samples; however, in the substrate samples, in addition to superdislocations of both straight and curved morphologies, a special type of dislocation arrangement configuration was also identified, and these dislocation features have rarely been reported in previous studies.