Abstract

The reliable joining of 316L austenitic stainless steel, a primary material for temporary biomedical implants and surgical instruments, remains critical for ensuring device safety and performance. While Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding are widely used in medical device manufacturing, a systematic comparative analysis of their impact on biomedical-critical properties is lacking. This study comprehensively investigates the effects of TIG and MIG welding on the microstructure, mechanical integrity, and bio-corrosion resistance of 316L stainless steel joints. Autogenous butt welds were prepared using optimized parameters for each process. Microstructural characterization revealed that TIG welding produced a refined heat-affected zone (HAZ) with minimal delta-ferrite content, while MIG welding resulted in a coarser HAZ and the presence of retained ferrite. Mechanical testing demonstrated comparable tensile strength for both processes (above 85% of base metal), but with significant differences in micro-hardness distribution; TIG joints exhibited uniform hardness across the weld zone, whereas MIG joints showed elevated hardness in the HAZ attributed to residual stresses and martensitic transformation. Corrosion assessment in simulated body fluid (SBF) at 37°C indicated that TIG-welded samples possessed superior pitting corrosion resistance (Epit = 315 mVSCE) compared to MIG (Epit = 268 mVSCE), attributed to the lower HAZ sensitization and minimized carbide/nitride precipitation. The findings elucidate the process-specific microstructural evolutions and their direct correlation with joint integrity, providing critical guidance for selecting appropriate welding techniques in medical device fabrication.