Characterization of distribution of residual stress in shot-peened layer of nickel-based single crystal superalloy DD6 by nanoindentation technique

Hardness, elastic modulus, yield strength, work hardening exponent, and residual stress within shot-peened layer of nickel-based single crystal superalloy DD6 were experimentally obtained by nanoindentation under a maximum load of 100 mN. The residual stresses calculated by different models have similar variation with the depth, but the values differ significantly with Wang's model most suitable for shot-peened DD6. It is found: the maximum residual compressive stress is 1.23 GPa at the depth of 40 mu m; and the total depth of residual compressive stress layer is 140 mu m. Mechanical properties such as indentation hardness and yield strength are affected by residual stress, which has little effect on elastic modulus. The effects of residual stress on various indentation parameters such as indentation work/displacement and contact depth/stiffness were quantified by linear expressions. The microstructural change in the shot-peened layer was found to be associated with the distribution of residual stress.