Joint Design Influence on Laser-MIG Hybrid Welding of Maraging Steel

Laser-MIG Hybrid welding (LHW) was performed in a single- pass on M250 maraging steel plates of 10 mm thickness with three modified joint designs. A Y-groove joint preparation with included angles (IA) of 16°, 24°, and 30° and root face of 2.5 mm was used. Welding was performed using M250 W2 filler wire. The heat input for welding increased as the IA increased. The composition of weld fusion zone affected the reverted austenite (RA) volume fraction formed on aging. With an increase in base metal melting, the fusion zone was enriched with solute elements such as Ni, Mo and Ti, ultimately increasing RA after aging. When the transverse tensile strength of all welds was comparable to that of the parent metal, a significant reduction in KIc fracture toughness of fusion zone (FZ) was observed as the RA increased. The space between neighboring RA pools (formed in intercellular regions) was smaller in the laser fusion zone (LFZ) owing to its fine grain size compared to the arc fusion zone (AFZ), and the welds failed by connecting series of cavities that only arise in the RA. LFZ appears to play an important role in determining weld toughness of LHW welds.