Effect of cyclic recovery heat treatment on surface recrystallization of a directionally solidified superalloy

Microstructural evolution and micro-hardness of a directionally solidified Ni-base superalloy subjected to shot-peening during cyclic recovery heat treatment was studied. It was found that γ' dissolved and dislocation annihilation occurred during heating, while γ' re-precipitated when temperature dropped. Due to the formation of a stable dislocation network at γ/γ' interface, full recovery and therefore complete elimination of the surface recrystallization are difficult by the present cyclic recovery heat treatment.