The evolution of microstructure and intergranular corrosion resistance of duplex stainless steel joint in multi-pass welding

This work focused on the microstructure and intergranular corrosion resistance of duplex stainless steel at different periods of multi-pass welding. Roots protected with pure Ar and Ar-N-2 mixing gas were investigated. The austenite content of the root shielded by pure Ar raised with the increasing of welding layers, but its intergranular corrosion resistance was significantly deteriorated. The microstructure showed that much secondary austenite (gamma(2)) formed after the root was reheated by the subsequent welding layer and in the final joint. Meanwhile, the results of the root shielded with Ar-3% N-2 showed that its austenite content in the root of final joint was similar to the pure Ar shielded root, but its intergranular corrosion resistance was not obviously deteriorated in multi-pass welding process. It is suggested that a suitable austenite-ferrite phase ratio in the final DSS multi-pass joint cannot guarantee a good intergranular corrosion performance, the microstructural evolution process, e.g., the precipitation of chromium nitride and the formation of gamma(2), also affect the corrosion resistance.