Surface characterization and fatigue evaluation in GH4169 superalloy: Comparing results after finish turning; shot peening and surface polishing treatments

In this study, shot peening was applied to the GH4169 superalloy, and the effect of surface polishing treatment on fatigue life of shot-peened specimens was investigated. The surface layer properties after five kinds of integrated processes were carefully characterized using a contact profilometer, 3 dimensional optical devices, vickers hardness tester, X-ray stress analyzer and scanning electron microscopy. The rotating bending fatigue tests were performed at room temperature to evaluate the effects of different integrated processes on the fatigue properties of GH4169 superalloy. The results showed that the longest fatigue life of 4.93 × 10⁵ cycles and sub-surface fatigue crack nucleation are obtained after TS3P process. Compared with FT, TS1, TS2, TS3 process, the TS3P process improves approximately the 699%, 62.7%, 71.8%, and 48.9% fatigue life of GH4169 superalloy, respectively. This is because the TS3P process has the lowest surface roughness (R_a = 0.041 µm), the thicker compressive residual stress layer (h_r = 100–330 µm) and hardening layer (h_H = 95 µm).