Investigation of the localized corrosion associated with phase transformation of tube-to-tube sheet welds of hyper duplex stainless steel in acidified chloride environments

The localized corrosion associated with phase transformation of tube-to-tube sheet welds of hyper duplex stainless steel (HDSS) was investigated in acidified chloride environments. The localized corrosion resistance of the HDSS tube-to-tube sheet welded with an Ar shielding gas supplemented with N2 increased greatly due to a decrease in the α-phase fraction and Cr2N, and a decrease in the pitting resistance equivalent number (PREN) difference between the α-phase and γ-phase in the weld metal and heat-affected zone. It was found that the HDSS tube-to-tube sheet welds showed significantly better localized corrosion resistance than a costly super austenitic grade (S32050) welds.

► N2 added Ar shielding gas enhanced the corrosion resistance of the HDSS welds.
► N2 added Ar shielding gas decreased the α-phase fraction in the WM and HAZ.
► N2 added Ar shielding gas decreased PREN of the α-phase phase in the WM and HAZ.
► The corrosion resistance of the HDSS welds was superior to that of the S32050 welds.
► We elucidated the corrosion mechanism based on Cr2N and PREN of the two phases.