Friction stir welding of maraging steel (Grade-250)

The feasibility of friction stir (FS) welding of maraging steel is demonstrated using W–Mo base tool. The FS weldements were evaluated by performing hardness, impact toughness and metallographic evaluations. The base metal has a microstructure consisting of martensite and austenite islands. Refined grains of the martensite phase in friction stir zone was observed, and attributed to dynamic recrystalization. A significant improvement in toughness was observed in friction stir welds compared to base metal in both as-welded (27%) and aged (114%) condition. Although more development work is needed, particularly to improve tool materials, the present results indicate that FS welding does indeed have potential for joining maraging steels in aerospace applications.