The present work investigates γ-channel dislocation reactions, which govern low-temperature (T = 750 °C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered γ’-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems $[01\overline{1}](111)$ and $[11\overline{2}](111)$ . These two shear systems share the same glide plane but differ in loading direction. The $[11\overline{2}](111)$ shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the $[01\overline{1}](111)$ shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.

This study proposes that creep-induced segregation to planar faults reflects the dynamic establishment of a new compositional steady state within the two-phase $$\gamma $$ γ / $$\gamma ^{\prime }$$ γ ′ single-crystal Ni-base superalloy during creep. The temperature difference between the alloy’s aging condition and the creep-experiment temperature drives a creep-induced partitioning flux, causing elements to redistribute within the $$\gamma ^{\prime }$$ γ ′ phase and accumulate at planar faults. In this work, the single-crystal Ni-base superalloy ERBO-1 (SX) was creep-deformed using double-shear creep testing at 250 MPa and 750 °C, which is 120 °C below the preceding aging treatment temperature. At 1 and 2 pct strain, the interrupted creep states show planar faults with solute segregation as commonly observed in this low-temperature, high-stress regime. Solute segregation at superlattice extrinsic stacking faults (SESF), anti-phase boundaries (APB), and microtwins in the $$\gamma ^{\prime }$$ γ ′ phase reveals systematic depletion of Ni and Al, accompanied by enrichment of Re, Co, Cr, Mo, and Ti. Thermodynamic calculations predict the temperature-dependent $$\gamma $$ γ / $$\gamma ^{\prime }$$ γ ′ compositions. Under the present experimental conditions, this results in increased uptake of Ni and Al and rejection of Re, Co, and Cr by the $$\gamma ^{\prime }$$ γ ′ phase. Consequently, depletion of Ni and Al and enrichment of Re, Co, and Cr are detected at planar defect sites. In contrast, Ti, Mo, Ta, and W segregation at microtwins and SESFs cannot be explained by bulk $$\gamma ^{\prime }$$ γ ′ partitioning and is instead attributed to localized phase transformations in the vicinity of the defects.