Effect of weld metal ferrite content on mechanical properties and stress corrosion cracking resistance in 22 Cr 5 Ni duplex stainless steel

Welded 22 Cr 5 Ni duplex stainless steel is often used for chloride-containing environments and sour service applications. Chloride stress corrosion cracking (CSCC) during service poses a threat to the service life of the weldment. Yield strength and resistance to CSCC are considered to depend on the weld metal ferrite content, which is variously required to be 30 to 60%, 30 to 70 ferrite number, 35 to 75%, etc. Accordingly, the present work has been carried out in collaboration with a filler metal manufacturer to investigate the research gap pertaining to minimum ferrite content to obtain the required minimum weld metal yield strength and resistance to CSCC. In this study, 22 Cr 5 Ni weldments with weld metal ferrite content in the range of 14% to 30%, or 20 to 40 ferrite number, obtained by increasing the filler metal nickel content above the normal 9%, have been prepared and investigated. It was found that yield strength and tensile strength requirements of base metal and filler metal classifications were exceeded at all ferrite levels investigated and that no CSCC was observed after 1000-h exposure in the ASTM G 123 boiling 25% sodium chloride test.