Microstructure and creep behavior of DMS4-type nickel based superalloy single crystals with orientations near 〈0 0 1〉 and 〈0 1 1〉

The influence of microstructure and orientation on creep and rupture behavior of DMS4-type nickel-based superalloy single crystal rods has been studied. While microstructures have been examined by optical, scanning and transmission electron microscopy, compositions and orientations have been studied by electron microprobe analyzer and electron backscattered diffraction, respectively. Creep experiments carried out on near-〈0 0 1〉 oriented specimens at stress and temperature ranges of 90–450 MPa and 870–1110 °C, respectively have shown similar strains for specific fraction of rupture life irrespective of stress, rupture strengths superior to or comparable with that of commercial single crystal alloys, and rafting of γ′ precipitates perpendicular to loading direction with average raft thickness decreasing with stress. Rupture-life and creep-ductility for near-〈0 1 1〉 oriented specimens are found to be lower than that for near-〈0 0 1〉 orientations, due to formation of inclined rafts in the former specimens, which are less effective as obstacles for dislocation motion than those perpendicular to load-axis.