Hybrid Laser-arc welding (HLAW) and laser beam welding (LBW) of HG785D steel were investigated by comparing microstructure, mechanical properties and heat source melting efficiency. Same microstructure of lath martensite (LM) was observed in fusion zone (FZ) of the two welded joints. However, coarser grain size and more random crystallographic orientations of FZ in HLAW joint were investigated via electron back-scatter diffraction (EBSD) analysis. M-A constituent and equiaxed ferrite (EF) were observed in finer-grain HAZ of HLAW joint, whereas fine martensite was obtained in LBW joint. More M-A constituent and granular bainite (GB) appeared in coarse-grain HAZ of HLAW joint. Higher heat input and lower cooling rate of HLAW compared to LBW resulted in presence of different microstructure. All the tensile specimen in both cases fractured at the base metal, while distinct difference in microhardness and low-temperature impact property was observed. Lower microhardness and higher impact energy of fusion zone were obtained in HLAW joint. Moreover, heat source melting efficiency of HLAW for 6-mm-thick HG785D steel plate could be improved by 26% compared to LBW.

通过比较组织，力学性能和热源熔化效率，对HG785D钢的混合激光电弧焊（HLAW）和激光束焊接（LBW）进行了研究。在两个焊接接头的熔合区（FZ）中观察到板条马氏体（LM）具有相同的显微组织。然而，通过电子背散射衍射（EBSD）分析研究了HLAW接头中FZ的粗大晶粒尺寸和更随机的晶体学取向。在HLAW接头的细晶粒热影响区中观察到MA成分和等轴铁素体（EF），而在LBW接头中观察到细马氏体。HLAW接头的粗晶粒HAZ中出现更多的MA成分和颗粒贝氏体（GB）。与LBW相比，HLAW的较高的热量输入和较低的冷却速率导致存在不同的微观结构。两种情况下所有的拉伸试样都在母材处断裂，同时观察到显微硬度和低温冲击性能的明显差异。HLAW接头具有较低的显微硬度和较高的熔合区冲击能。此外，与LBW相比，厚度为6毫米的HG785D钢板的HLAW的热源熔化效率可提高26％。