Constructing biomimetic skeletal structures on the surface of Ti17 repaired blade joints to enhance their fatigue performance

The wire-arc directed energy deposition technique offers a rapid and efficient method for repairing turbine blades in aircraft engines. However, the coarse microstructure and uneven stress distribution at the remanufactured joints negatively impact the service life of blades. In this study, we proposed a strategy that the employed various surface strengthening techniques created a gradient structure (GS) near the surface of remanufactured joints. This GS included compressive residual stress (CRS), phase size, and dislocation density gradients. This approach not only overcame the inherent issue of low fatigue strength but also enhanced their service stability of the remanufactured blades. The gradient CRS mitigated crack initiation, the gradient phase size suppressed dislocation movement under fatigue loading, and the gradient dislocation density slowed the propagation rate of fatigue cracks. Under the combined effect of these strengthening mechanisms, the fatigue limit of remanufactured joints with the GS was improved by 25.96 MPa compared to the conventional remanufactured joints, and the microstructure demonstrated excellent fatigue resistance even under prolonged high-fatigue loading. The proposed method for creating a GS on the surface of remanufactured blades not only improves the service reliability of aircraft engines but also offers a practical and effective strategy for enhancing the fatigue resistance of alloys.