Microstructure and Tensile Behaviors of Laser-Arc Hybrid Welds Comparing to Submerged Arc Welds of High-Manganese Steel for Cryogenic Applications

The weldability and the relationship between microstructure and tensile properties at 298 and 110 K produced by laser-arc hybrid welding (LAHW) in high-Mn steel welds were thoroughly investigated. In the laser zone of LAHWs using filler wire, more Mn vaporization in the laser zone was observed than at the arc zone of LAHWs. The arc zone showed a decrease in Mn content of ~0.6 wt%, while the laser zone showed a decrease of ~0.9 wt%. The arc and laser zones of the LAHWs showed stacking fault energies (SFEs) of 17.8 and 17.3 mJ/m², respectively. The tensile deformation of LAHWs at 298 K was conducted with a deformation twins mode, while it was shifted to deformation twins + ε-martensite transformation at 110 K. The yield strength was slightly higher in the laser zone, which had a finer grain size compared to the arc zone. The formation of ε-martensite with deformation twins preceded necking during tensile testing, therefore increasing the yield strength at 110 K. In terms of performance, the LAHW process demonstrated a 25% increase in productivity compared to the conventional submerged arc welding (SAW) process, with a yield strength exceeding 400 MPa, comparable to that of SAW. These findings indicate that LAHW is a highly effective welding method for high-Mn steels, particularly in cryogenic applications.