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 Na2SO4 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.