Influence of Welding Parameters on Austenitic Stainless Steel Pipe Weldments Produced by Friction Stir Welding

This study investigates how welding travel speed and spindle speed influence the quality of welds in 270 mm diameter AISI 316L stainless steel pipes joined through friction stir welding (FSW). The FSW process was performed with spindle speeds of 250 rpm and 300 rpm, and travel speeds of 50 mm/min and 100 mm/min, utilizing a PCBN-coated W-Re tool in position control mode. Axial force, spindle torque and penetration depth were evaluated. The microstructure was analyzed using an optical microscope to understand the effects of spindle and travel speeds. High-resolution microscopy was employed to identify variable grain sizes across different weld zones. Vickers micro-hardness tests showed higher hardness in the stir zone and adjacent thermo-mechanically affected regions. The joint welded at 300 rpm and 100 mm/min displayed the highest hardness in the stir zone at 254 HV, indicating grain refinement confirmed by microstructural evaluation.