Influence of Shot Peening on Surface State and Low-cycle Fatigue Performance of DD6 Single Crystal Superalloy

The effect of shot peening on the surface state of DD6 single crystal superalloy was investigated, including surface roughness, residual stress gradient and microstructure. And low-cycle fatigue test was used to evaluate the effect of shot peening parameters. Combined with surface state and fracture analysis, the strengthening mechanism of shot peening was analyzed. The results show that the modified χ method is suitable for testing the surface residual stress of DD6 single crystal superalloy after shot peening, while the pole figure method is suitable for testing the residual stress gradient. After shot peening, the low-cycle notch fatigue life of DD6 is significantly improved. Among them, the fatigue life of the specimens under ceramic shot and shot peening strength of 0.20 mm A is the highest, and its average life is 6.5 times longer than that of the original specimens. With the rise of shot peening intensity, the surface roughness increases, but the depth of compressive residual stress and surface dislocation density of DD6 also increase, so its fatigue life is prolonged.