Effect of Potential on the Corrosion Fatigue Crack Growth Rate in Type 304 Stainless Steel in Sodium Sulfate Solution at 250°C

Abstract The corrosion fatigue crack growth (FCG) behavior of sensitized Type 304 stainless steel was studied in 0.01m Na2SO4 solution at 250°C. Crack growth rates at different frequencies ranging from 1.0 Hz to 2x10-2 Hz, and at different electrochemical potentials, were measured using a sinusoidal loading waveform at a load ratio R(=Pmin Pmax) of 0. 5. The results show that both the FCG rate and the fracture morphology depends upon the frequency and the applied potential. At a frequency of 2x10-2 Hz, there exists a critical potential (between -450 mVH and -200 mVH) above which the FCG rates are significantly enhanced over those observed at lower potentials. Intergranular cracking was observed above the critical potential, whereas at lower potentials the fracture morphology was principally transgranular in nature. No critical potential was observed at a frequency of 1 Hz, and fracture morphology was entirely transgranular in nature.