Stress corrosion cracking behaviour of two stainless steels in hydrogen sulfide environment

Stress corrosion cracking (SCC) of 3Cr17Ni7Mo2SiN and 00Cr22Ni5Mo3N (2205) stainless steels in acidic hydrogen sulfide solutions was investigated by slow strain rate tensile test and U-bent specimen immersing test. The time to SCC failure of 2205 stainless steel was much longer than that of 3Cr17Ni7Mo2SiN stainless steel. 2205 stainless steel was highly susceptible to SCC at a lower pH level in saturated H₂S solution, and its SCC susceptibility sharply decreased with increasing pH value or decreasing H₂S concentration in solution. 3Cr17Ni7Mo2SiN stainless steel showed a high susceptibility to SCC in solution with a HES concentration higher than 10³ mg·L^-1 and pH≤4.5. However, the susceptibility varied slightly with the change of pH value and H₂S concentration. SCC of 3Cr17Ni7Mo2SiN stainless steel initiated in an intergranular mode, which transformed into transgranular cracking as the SCC propagated further. For 2205 stainless steel, SCC originated at the place where hydrogen-induced cracking (HIC) occurred along the ferrite/austenite matrix boundaries firstly, and then propagated transgranularly.