Effect of Sulfur and Dissolved Oxygen Content on Corrosion Fatigue Property in High Temperature and High Pressure Water

Low cycle fatigue tests of reactor pressure vessel steel A533B were performed in simulated high temperature and high pressure water environment.Effects of sulfur and dissolved oxygen content on fatigue life and crack initiation were discussed.It was found that fatigue life decreased with increasing sulfur content in the steel when sulfur content was less than 0.015 (wt) %,and fatigue life was saturated when sulfur content was more than 0.015 (wt)%.Under high sulfur content condition,fatigue cracks were multiple initiation,and mainly nucleated at sulfur-bearing inclusions on or near the surface of specimens.Fatigue life decreased with increasing dissolved oxygen content in the water when dissolved oxygen content was between 0.05 mg/L and 0.5 mg/L.Furthermore,fatigue life was saturated when dissolved oxygen content was more than 0.5 mg/L or less than 0.05 mg/L.When dissolved oxygen content was high,cracks were mainly formed at pits on the surface.Fracture surface was mainly covered with Fe3O4 under low dissolved oxygen content condition,but with Fe2O3 under high dissolved oxygen content condition.