The Effect of Ferrite Content on Stress Corrosion Cracking in Duplex Stainless Steel Weld Metals at Room Temperature

Constant extension rate tests have been conducted on Type 304 stainless steel base metal specimens and on stainless steel weld metal specimens with ferrite contents of Ferrite Number 1, 3, 6, 11, 16, and 24, at room temperature in deaerated, 1 N HCl. Stress corrosion cracking in wholly austenitic Type 304 base metal occurs transgranularly, while cracking in duplex weld metal occurs either by the combined action of stress assisted ferrite dissolution and stress corrosion cracking (SCO in the austenite or entirely by stress assisted dissolution of the ferrite. Ferrite content and distribution are important in determining both the stress corrosion susceptibility and crack morphology of duplex weld metals. The most susceptible duplex weld metals are those which exhibit a continuous or nearly continuous vermicular ferrite structure.