Effect of CO₂ Laser Beam Welding on Microstructure and Tensile Strength of C250 Maraging Steel

Maraging steels are preferred in critical components over carbon steels owing to superior strength coupled with fracture toughness. Laser beam welding (LBW) is an excellent choice for joining maraging steel to limit HAZ growth and reverted austenite formation. Maraging steel C250 plates of 3 mm thickness were joined using CO₂ based LBW by varying the scanning speed from 0.5 m/min to 3.0 m/min. Successful joints were obtained without pores and cracking. The highest scanning speed produced a lack of fusion. The fusion zone presented a typical solidified dendritic microstructure which consisted of both columnar as well as cellular grain structure. The grain structure experienced refinement as the scanning speed was increased. Barring 0.5 m/min scanning speed, there was no softening recorded inside the fusion zone. The joint strength of the weldment matched the strength of the base metal except using the lowest and the highest scanning speeds. The weldments manifested sufficient ductility before failure by tensile loading.