Investigation of the sensitization and intergranular corrosion of tube-to-tubesheet welds of hyper duplex stainless steel using an electrochemical reactivation method

•Cr2N was precipitated at the high temperature during welding process.•Degree of sensitization generated due to Cr2N was evaluated through modified DL-EPR test.•The addition of N2 to the Ar shielding gas decreased the susceptibility to sensitization.•The intergranular corrosion was initiated at Cr-depleted regions adjacent to Cr2N.

The sensitization and intergranular corrosion associated with a phase transformation of tube-to-tubesheet welds of hyper duplex stainless steel were investigated using modified double loop electrochemical potentiokinetic reactivation. The susceptibility to sensitization of the hyper duplex stainless steel tube-to-tubesheet welded with an Ar shielding gas supplemented with nitrogen gas decreased owing to a decrease of the ferrite phase fraction and precipitation of chromium nitrides, thereby increasing the intergranular corrosion resistance. The intergranular corrosion in the hyper duplex stainless steel welds was selectively initiated at the Cr-depleted regions adjacent to the chromium nitride precipitates in the ferrite phases.