A post-treatment to reduce stress concentration sensitivity under intermediate-temperature fatigue in GH4169: High-energy impact composite modification

The study focuses on a novel post-treatment method, high-energy impact composite modification, combining mechanical shot peening and laser shock processing to improve the fatigue performance of the nickel-based superalloy GH4169 at intermediate temperatures. The synergistic interaction between mechanical impact (SP-induced plastic deformation) and laser-induced shock waves enabled a 2.5-fold increase in effective treatment depth (up to 1500 μm) compared to SP alone (400 μm), while achieving a surface hardness of 520 HV and compressive residual stress of -1465 MPa, exceeding single-process results by 4.5% and 54.2%, respectively. The dual-impact approach significantly enhanced surface hardness and compressive residual stress, addressing the high sensitivity to stress concentration. Experimental results demonstrate that HEICM eliminated stress concentration sensitivity at 650 °C, elevating the fatigue limit of notched specimens (Kt=3) to 638 MPa – equivalent to the fatigue strength of smooth specimens (Kt=1) in conventional grinding states (636 MPa). This represents a 116% improvement over untreated notched specimens (295 MPa) and surpasses SP-treated counterparts (446 MPa) by 43%, thereby extending the fatigue life of GH4169 alloys in aerospace applications.