Comparative study of microstructure and mechanical properties of laser-arc hybrid welded joints using solid and flux-cored wires

A 25 mm-thick A710 steel was subjected to laser-arc hybrid welding using solid and flux-cored wires. Surface weld formation, internal defects, crystallographic and mechanical properties were examined. Compared to solid wire welds, the flux-cored wire welds produced more uniform weld formation but both welds without defects. Oxide inclusions in flux-cored wire welds promoted acicular ferrite and suppressed polygonal ferrite. The fine, widely distributed acicular ferrite in flux-cored wire welds reduced grain size by 45.5% and increased the fraction of high-angle grain boundaries by 13.3%. Flux-cored wire welds exhibit weaker texture features than solid wire welds. Tensile and yield strengths of flux-cored wire joints exceeded those of solid wire joints, while elongation was lower. Tensile fracture surfaces of solid wire welded joints showed larger, more uniform dimples than those of the flux-cored wire welded joints. Microhardness in the upper layer of flux-cored wire welds (241 HV) was 5% higher than in solid wire welds (229 HV), with minimal differences in the lower layer. The average low-temperature impact energy of flux-cored wire welds decreased by approximately 42% relative to solid wire welds. Overall, flux-cored wire welded joints exhibited higher strength and hardness, whereas solid wire welded joints showed better low-temperature impact toughness.