Indentation behavior of creep-feed grinding induced gradient microstructures in single crystal nickel-based superalloy

• Gradient microstructures including nanograins, submicron grains, and dislocation structures were induced in SX alloy by creep-feed grinding. • Indentation hardness and elastic modulus of gradient structures were higher by 8–10% than bulk material. • The topmost layer containing nanograins is unfavorable to enhance creep performance. • Dislocation activities in ground layer dominate the indentation creep deformation. The gradient microstructures of surface layer in single crystal nickel-based superalloy were produced by creep-feed grinding. The mechanical properties (i.e., hardness, elastic modulus) and room-temperature (RT) creep behavior of such structures were evaluated using a nano-indentation technique. Results show that the gradient structures along depth from ground surface consisted of nanograins, submicron grains and lamellar-shape structures, and dislocation structures. Furthermore, it was found that the hardness and elastic modulus of gradient structures were higher by 8–10% than that of bulk material on average. However, the regions containing nanograins showed a remarkable increase in creep depth compared to bulk material, implying that the creep behavior of ground layer was changed unfavorably. The obtained stress exponents of gradient structures suggested that dislocation activities were the main mechanism for indentation creep deformation.