Effect of Warm Laser Shock Peening on the Low-Cycle Fatigue Behavior of DD6 Nickel-Based Single-Crystal Superalloy

By conducting tension–tension low-cycle fatigue tests on three groups of specimens, this paper determined the mechanism and effect of warm laser shock peening (WLSP) on the fatigue performance of DD6 nickel-based single-crystal superalloy. The WLSP treatment induced ripples at the specimen surface, residual stress fields, and dislocation structures in the near-surface layers. The induced ripples increased the surface roughness of the specimens, and the residual stress fields and dislocation structures improved their surface microhardness. Moreover, both the surface roughness and surface microhardness exhibited a tendency to increase with the increase in the WLSP treatment number. During the low-cycle fatigue tests, the specimens underwent plastic deformation, and the a/2⟨110⟩{111} slip system was activated. In addition, the WLSP-induced dislocation structures developed during the low-cycle fatigue tests produced dislocation networks and superlattice intrinsic stacking faults, both of which had a positive effect on prolonging the fatigue life of the material. Furthermore, the fatigue life of the material tended to increase with the increasing number of WLSP impacts.