Stress Corrosion and Hydrogen Cracking off 17-7 Stainless Steel

Abstract

Abstract Whether a stainless steel fails by stress corrosion cracking or by hydrogen cracking depends on its structure. A pure ferritic 18–8, body-centered cubic as quenched, fails by hydrogen cracking when cathodically polarized in dilute sulfuric acid containing arsenic trioxide. However, it is resistant to stress corrosion cracking in MgCl2 solution boiling at 154 C (310 F). A similar composition austenitic 18–8, face-centered cubic as quenched and tested similarly is resistant to hydrogen cracking but fails by stress corrosion cracking. Type 301 austenitic 17–7 stainless steel, which transforms in part to ferrite on cold rolling, is resistant, therefore, to hydrogen cracking as annealed-quenched or slightly cold reduced. It fails within 10–30 minutes when cold reduced more than 20 percent even though it transforms only partially to ferrite. In MgCl2 solution, both the annealed-quenched and the cold-reduced alloy fail, cracking times being prolonged by cathodic polarization, characterizing the failures as stress corrosion cracking. Contrary to reactions observed in pure phase alloys, stainless steels containing mixtures of austenite and ferrite may fail either by hydrogen cracking or by stress corrosion cracking, depending on the environment.