Comparative study of GTAW and GMAW for WAAM: Microstructural and mechanical insights in ER70S-6 and 316L stainless steel depositions

This study compares gas tungsten arc welding (GTAW) and gas tungsten arc welding (GMAW) for wire arc additive manufacturing (WAAM) using ER70S-6 steel and 316L stainless steel (SS) filler wires for single-wall deposition. Optimised parameters were determined through single-layer experiments, with GMAW, especially in synergy mode, showing better consistency and fewer defects than GTAW. GTAW walls had rough edges and height variations, while GMAW walls were smoother. Microstructural analysis revealed consistent ER70S-6 patterns, but significant variations in 316L SS, particularly in the heat-affected zone. Mechanical testing showed consistent hardness and tensile strength for ER70S-6, while 316L SS had higher hardness but greater variability, especially with GTAW. GMAW samples had higher tensile strength but lower elongation. The study suggests heat treatment to reduce mechanical property variations, especially for 316L SS.