Influence of primary and secondary crystal orientations on strengths of Ni-based superalloy single crystals

In this study, by using the single crystals of the experimental superalloy which shows distinct active slip systems, the influence of primary and secondary crystal orientation on creep and fatigue strengths of Ni-based superalloy single crystals was investigated, It was revealed that the strengths of the notched specimens were affected by the crystallographic orientation not only in the tensile direction but also in the thickness direction. The influence of crystallographic orientations and plastic anisotropy on the creep and fatigue strengths of single crystals of the Ni-base superalloy was discussed on the assumption that {111} <101> and {111} <112> slip systems were activated. In the case of creep strength, the results were in agreement with the assumption of the operation of the {111} <112> slip in the primary creep and {111} <101> slip in the secondary creep. The notched creep behavior was found to be influenced by the additional aging at 850degreesC for 20 h, which prohibited activity of {111} <112> slip systems. The fatigue lifetime and crack growth behavior depended on both plastic anisotropy caused by arrangement of {111} <101> slip systems and the stress state.