Influence of Heat Input and Cold Wire Feeding Rate on Pitting Corrosion Resistance of Submerged Arc Welding Duplex Stainless Steel Welds

Abstract

Welding thermal cycles may severely impair duplex stainless steel (DSS) performance, especially local pitting resistance and toughness. The restricted welding energy between 0.5 and 2.5\xa0kJ\xa0mm−1 represents a limiting factor for productivity increase in DSS welding, and the addition of cold wire is an interesting alternative to increase the welding deposition rate without adding extra heat. The aim of this work is to evaluate the influence of the cold wire feeding rate (CW) and heat input (HI) on pitting corrosion behavior of DSS UNS S32304 bead-on-plate welds obtained by submerged arc welding (SAW). Cyclic potentiodynamic polarization was carried out in transverse weld sections using 1\xa0mol\xa0L−1 NaCl solution at room temperature. Most pitting corrosion spots were located on the heat-affected zone (HAZ), and the pitting potentials were lower than the base metal due to higher ferrite fractions and the presence of chromium nitrides. Considering the same CW, the HI increasing reduced Epit for 1.6, 1.9, 2.2\xa0kJ\xa0mm−1, but increased Epit for 2.7\xa0kJ\xa0mm−1, due to a balance between the HAZ width and the austenite fraction.