Effect of anions on stress corrosion cracking behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo

The effects of chloride, sulfate and carbonate anions on stress corrosion behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo were studied by stress corrosion cracking (SCC) test method using double cantilever beam (DCB) specimens. The SCC morphology was observed by using scanning electron microscopy (SEM) and the composition of corrosion products was analyzed by using energy dispersive spectrometer (EDS). The results show that the crack propagates to bifurcation in NaCl and Na₂SO₄ solution, while the crack in Na₂CO₃ solution propagates along the load direction. The SCC rate in NaCl solution is the highest, while lower in Na ₂SO₄ solution and little in Na₂CO₃ solution. From the SEM morphologies, quasi-cleavage fracture was observed in NaCl and Na₂SO₄ solutions, but intergranular features in Na₂CO₃ solution. The mechanism of anion effect on SCC of steel 23Co14Ni12Cr3Mo was studied by using full immersion test and electrochemical measurements.