Influence of Welding Energy on Intergranular and Pitting Corrosion Susceptibility of UNS S32205 Duplex Stainless-steel Joints

Abstract

This study analysed the integrity of welded joints of a UNS S32205 duplex stainless steel, using different welding energies: 0.5 kJ.mm^-1, 1.0 kJ.mm^-1, and 3.5 kJ.mm^-1. Microstructural characterisation, tensile testing, intergranular attack susceptibility testing (ASTM A262 practice A) and pitting/crevice corrosion resistance tests (critical pitting temperature test, ASTM G48 practice C) were performed in these welded joints. The results showed that the tensile properties of the welded joints did not vary significantly with the welding energy. The microstructure's ferrite content in the molten zone (MZ) was proportional to the welding energy: the ferrite concentration in the 0.5 kJ.mm^-1 weldings was approximately 75%. When the welding energy increased to 3.5 kJ.mm^-1, the amount of ferrite dropped to 54%. The 3.5 kJ.mm^-1 welded joint featured a comparatively higher proportion of coarser austenite grains. The HAZ of the 3.5 kJ.mm^-1 welded joint was comparatively more susceptible to the intergranular attack along the α/γ interfaces, while in the base metal and the other two welded joints, the intergranular attack along the α/γ interfaces was not prominent. Additionally, the pitting corrosion took place preferentially in the ferrite phase of the HAZ for all welding conditions.

Keywords:
duplex stainless-steel; UNS S32205; welding energy; intergranular corrosion; pitting corrosion