Study on microstructure and comprehensive properties of SAF2205 duplex stainless steel multilayer and multipass welded joint

TIG/PAW composite welding was used to weld SAF2205 duplex stainless steel with three layers and three channels, and solution treatment was carried out. OM, SEM, EBSD and electrochemical corrosion, tensile, impact and other experiments were used to study the relationship between the microstructure evolution of the weld and mechanical properties, corrosion resistance. The results show that the ferrite content of TIG filler wire weld is 70.5%, and the austenite grain of TIG filler wire weld is the largest (177 μm²), which is larger than that of base metal (142 μm²) due to the addition of welding wire. The ferrite content of PAW weld is 65.4%. Due to the different welding sequence, subsequent welding has a heating effect on the weld, resulting in the least ferrite content. In TIG weld, the large heat input results in the coarsening of ferrite grain (8 147 μm²), which is larger than the base metal (264 μm²), resulting in the reduction of austenite core location and only 3.96% austenite. Due to the difference of deformation mechanism and stacking fault energy between austenite and ferrite, the number of ferrite sub-grains is larger than that of austenite, while the number of recrystallized grains and high-angle grain boundary is smaller than that of austenite. After solution treatment at 1 050 ℃ for 60 min, the two phases of the weld are close to 1∶1, and the austenite tends to homogenize, and the corrosion resistance increases with the extension of solution time. The tensile fractures were all in the base metal, and the tensile strength of the weld were greater than 846 MPa. The weld impact energy is 144 J, less than the base metal (156 J), and the weld shows composite fracture.