Influence of laser beam welding parameters on local mechanical properties of duplex stainless steel joints

Duplex stainless steels (DSS) are dual-phase alloys consisting of austenitic and ferritic phases in the microstructure. DSS provide an ideal compromise between mechanical properties and corrosion resistance. Welding of DSS leads to a change in the ferrite/austenite ratio in the microstructure and to degradation of the properties of the weld joints. Therefore, it is very important to control the microstructure of the weld joint directly during the welding process. An innovative method of laser welding applying a dual beam was used. By spreading the energy of the laser beam over two spots, additional heat is introduced into the weld, which ensures a slowdown in the cooling rate of the DSS and possibly ensures the desired ratio of ferrite and austenite in the microstructure. The influence of laser welding parameters and energy distribution of the dual beam on the fusion zone (FZ) geometry, resulting microstructure and mechanical properties of the weld joints was monitored. The tensile and shear strength was measured. The coefficient of proportionality between shear and tensile strength was calibrated to be as 1.38 ± 0.01.