Corrosion-induced failure mechanism and life model of low-cycle fatigue in Nickel-based single crystal superalloys

This study investigates the corrosion-induced failure mechanism and life prediction of low-cycle fatigue (LCF) in a Nickel-based single crystal superalloy subjected to pre-corrosion in a marine environment. Pre-oxidation corrosion was conducted at 850 °C for 25 h and 50 h using NaCl–Na₂SO₄ eutectic salts, followed by stress-controlled LCF testing at 850 MPa, 875 MPa, and 900 MPa. Results demonstrate that Type I hot corrosion catastrophically reduces LCF life by over one order of magnitude. Pre-corroded specimens exhibit accelerated three-stage ratcheting behavior with severely truncated stabilization, driven by surface corrosion pits acting as strain localization sites. Fractographic analysis reveals a transition from internal defect-initiated cracking in air to surface-dominated multi-site crack nucleation in corroded material, with subsequent crystallographic propagation along {111} slip planes. A modified Basquin model incorporating a normalized corrosion-layer thickness damage factor successfully predicts LCF life across all conditions. These findings provide a mechanistic foundation for life assessment and corrosion-resistant design of turbine blades in carrier-based aero-engines.