Corrosion behaviour of alloy 31 - UNS N08031 - under conditions of oil & gas production

High‐temperature high‐pressure SCC testing of corrosion‐resistant alloys

“…It was proposed that the higher molybdenum content of alloy 31 has compensated for his lower content of nickel when compared with alloy N08825. [28] Some other austenitic alloys 926, 28, and 266 were tensile-stressed and immersed in the solution containing 0.27 bar pH 2 S at 200°C. Results indicated full SCC resistance of the materials during 1000 h. [119]…”

“…Besides 36Mo, alloy 31 and all four heats of 27-7MO have demonstrated high SCC resistance at 7 bar pH 2 S and 150-177°C. [28,30] Generally a higher PREN was all the time associated with a better resistance in sour service, but the effect of nickel was emphasized as well. [29] According to Klöwer, [28] a higher concentration of chromium does not necessarily result in high resistance to SCC.…”

“…[28,30] Generally a higher PREN was all the time associated with a better resistance in sour service, but the effect of nickel was emphasized as well. [29] According to Klöwer, [28] a higher concentration of chromium does not necessarily result in high resistance to SCC. Other findings indicate that the combined effect of high chromium and nickel content is more important than a high Mo content when it comes to SCC resistance in a deaerated H 2 S/Cl environment.…”

“…Ferritic-austenitic duplex stainless steel (2205) and super duplex stainless steel (2507) are promising alloys that exhibit good corrosion resistance in deep gas wells with high partial pressure of CO 2 , high concentration of chloride, but show limited resistance to SCC in the presence of H 2 S. [28,[92][93][94][95][96][97][98][99] There appear to be risks of SCC of 22Cr duplex stainless steel (21.4Cr-5.3Ni-2.78Mo) in saline sour gas environments. As shown in Figure 3, the critical H 2 S partial pressure was approximately 0.3 bar at 150-250°C, the elongation ratio was decreased remarkably beyond this value.…”

“…This is due to the higher contents of chromium, molybdenum, and nitrogen to these grades (PREN > 40). [1,6,23,[25][26][27][28][29][30][31][32] Duplex stainless steels have a composition of Cr-Ni-Mo-N, their relatively high chromium level may vary between 21% and 25%, while the level of nickel varies between 1% and 7%. [3,6,9,33,34] The combination of high corrosion resistance and excellent mechanical properties of duplex stainless steels can be explained by their chemical composition and balanced "duplex" microstructure of ferrite and austenite.…”