Effects of solution heat-treatment and nitrogen in shielding gas on the resistance to pitting corrosion of hyper duplex stainless steel welds

The effects of solution heat-treatment and shielding gas on the pitting corrosion of hyper duplex stainless steel (HDSS) welds were investigated in highly concentrated chloride environments. The pitting resistance of a solution heat-treated HDSS after welding with an Ar shielding gas supplemented with N2 was greatly increased due to the dissolution of Cr2N in α-phase, which followed the diffusion of N atoms from the α-phase to the γ-phase and an increase of the γ-phase in the weld metal and heat affected zone. It was also attributed to a decrease of the pitting resistance equivalent number difference between the two phases.

Research highlights
► The pitting resistance of HDSS increased with the solution heat-treatment and the incorporation of nitrogen in the shielding gas.
► The PREN difference between α-phase and γ-phase was proportional to α-content.
► The effect of Cr2N on the pitting corrosion was elucidated.