The mechanism of the effect of dual-sided waterjet peening on the surface integrity and fatigue performance of 12 mm thick Inconel 718

Abstract

This study aims to explore the mechanisms of residual stress formation and the effects on fatigue performance of 12 mm thick Inconel 718 under single-sided one-pass, two-pass, and dual-sided two-pass waterjet peening. Finite element models for waterjet peening and fatigue analysis were established using ABAQUS and Fe-safe, respectively. The study focused on analyzing the residual stresses, surface roughness, and fatigue cycle numbers of Inconel 718 after waterjet peening. The results were validated by conducting waterjet peening experiments and post-peening fatigue tests to ensure their reliability. The research findings indicated that the induced residual compressive stress was most effective with dual-sided two-pass waterjet peening, followed by single-sided two-pass and single-sided one-pass waterjet peening. Among them, after WJP-290 mm/s peening, the maximum residual compressive stresses for dual-sided two-pass, single-sided two-pass, and single-sided one-pass were 718.6, 906.4, and 1042.7 MPa, respectively. The maximum residual compressive stress depth after WJP-230 ∼ 290 mm/s peening was positively correlated with the jet velocity. Surface deterioration occurred after WJP-350 mm/s peening, leading to a significant reduction in the induced residual stress effect. After WJP-230 mm/s peening, the specimen exhibited an overall residual compressive stress of about 507.7 MPa at a depth of approximately 13.1 μm, with a total residual compressive stress depth of about 34.8 μm. Increasing the jet velocity to 290 mm/s shifted the maximum residual compressive stress depth to about 27.2 μm, with a maximum residual compressive stress increase of about 535 MPa, reaching 1042.7 MPa. At the same time, the overall residual compressive stress depth also increased to 39.9 μm. After increasing the jet velocity to 350 mm/s, a maximum residual compressive stress of about 708.7 MPa was induced at a depth of approximately 11.9 μm. The surface roughness, average roughness, and maximum roughness of the specimens were positively correlated with the jet velocity, with the most significant morphological changes occurring at the edges of the waterjet peened area, which coincided with the region prone to fatigue fracture in the cyclic fatigue tests. Increasing the number of jet impacts had a “peak-to-valley” effect on the surface of the peened specimens, making the surface flatter. The specimens peened with dual-sided waterjet showed significantly higher fatigue cycle numbers than those peened with single-sided waterjet. After WJP-230 mm/s peening, the fatigue life at stress levels of 93, 132, and 150 MPa was approximately 2,182,922, 258,000, and 56,575 cycles, respectively, which increased by about 399 %, 274 %, and 218 % compared to single-sided one-pass peening and by about 165 %, 139 %, and 125 % compared to single-sided two-pass peening.