Effect of Environmental Factors on Corrosion Fatigue Performance of Duplex 2507

Corrosion fatigue performance of welded duplex 2507 riser material environments containing high partial pressures of carbon dioxide (100–200 bar) and limited quantity of hydrogen sulfide (0–0.12 bar) is presented in this paper. da/dN vs ΔK at different frequencies as a function of various environmental were studied. In the range of environments studies there was no significant environmental effect on the FCGR. da/dN measurements were performed starting at an initial ΔK of 150Nmm-3/2 and crack growth was readily established suggesting that ΔKth were lower than this value. Frequency scan tests were performed in various environments and the FCGR was found to be weakly dependent on frequency. The highest increase in FCGR was about 3–4x over the air values. The effect of duplex microstructure will also be discussed by comparing results from plate samples of 2507 with differing microstructure. The FCGR was higher with the plate samples which had precipitation of ferrite within the austenite grains which may have led to the higher FCGR. Frequency scan results for the plate samples will be compared with the results from the riser material.