Application of pulsed laser ND: YAG in superduplex steel uns S 32750: Autogenous laser welding, laser welding with refusion process by laser and hybrid welding (laser/Gtaw)

Abstract

The families of duplex and superduplex steels were developed to serve sectors that demand steels with extreme mechanical capacity and good corrosion resistance. Such characteristics are due to their structure being composed of a binary matrix with 50% austenite and 50% ferrite. However, when welding processes are employed, an imbalance of these phases occurs, leading to a loss of mechanical and corrosion properties. So, we carried out studies on the behavior of superduplex steel UNS S 32750, when submitted to autogenous welding with Nd:YAG pulsed laser, autogenous welding with Nd:YAG pulsed laser with subsequent (2, 3 and 4 times) refusion processes with Nd:YAG pulsed laser, and hybrid welding combining Nd:YAG pulsed laser and GTAW (gas-shielded tungsten arc welding) in two situations (coating of the laser welding with GTAW and laser shooting in the GTAW molten pool). The analyses were carried out with geometric analysis and qualitative quality analysis of different cross-sections of welding, along the longitudinal direction of the weld bead, and the percentage balance of the volumetric fractions, of ferrite and austenite on the weld metal, in each process.