Stress Corrosion Cracking of 3Cr17Ni7Mo2SiN Stainless Steel in Sulfide Hydrogen Solutions

Abstract

Sulfide stress corrosion cracking(SCC) behavior of 3Cr17Ni7Mo2SiN stainless steel(SS) is investigated by using slow strain rate test(SSRT),U-bent specimen immersing test and fractography observation by scanning electronic microscopy(SEM).3Cr17Ni7Mo2SiN SS is subject to SCC in test solutions containing NaCl(5% in mass) and H2S(no less than 0.1%) within pH range of 2.7 to 4.5.The time to SCC occurrence of 3Cr17Ni7Mo2SiN SS increases with the rising of pH or with the lowering of mass fraction of H2S.SCC under a low pH(pH=2.7) condition grows faster than that under a high pH condition,which initiates in an intergranular mode and then propagates transgranularly,however,in a high pH(pH=4.5) solution,SCC growth is slow with a blunt cracktip due to anodic dissolution mechanism.Inclusions,effects of hydrogen induced cracking(HIC) and corrosion pits will promote the occurrence of SCC.