Fatigue failure analysis for marine propeller used titanium alloy under salty-water environment with the effect of corrosion durations

The experimental investigation on marine propeller used titanium alloy under varying corrosion durations represents a significant research issue in both engineering practice and theoretical exploration. This study focuses on fatigue behavior and evaluation for marine propeller used TC4 titanium alloy through designed fatigue testing that corrosion duration exerts a non-negligible adverse impact on the failure mechanisms and life evaluation. The modified Murakami model incorporating coefficient fr demonstrated suitability for estimating the fatigue strength of pre-corroded TC4 with the combined influence of corrosion durations and surface scratches. Comparative analysis of fatigue life prediction models indicated that the modified Paris model provides stable life estimations with minimal error margins for TC4 under different corrosion durations. Microstructural characterization through scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) revealed a progressive grain coarsening phenomenon correlated with extended corrosion durations, accompanied by distinct cleavage and ductile fracture characteristics. EBSD imaging reveals coarse grain structures with significant strain concentration at low-angle grain boundary are detected, and the grain size significantly increases with the increases of pre-corrosion duration. These findings elucidate the mechanistic relationship between corrosion and fatigue failure in TC4, while the proposed modified models offer novel and essential tools for advancing fatigue research in marine equipment.