Investigations of Tungsten Inert Gas and Metal Active Gas Joints of SUS301L Stainless Steel: Electron Backscatter Diffraction Characterization and Fatigue Performance

SUS301L stainless steel joints with thickness of 2 mm were manufactured via the tungsten inert gas (TIG) and metal active gas arc (MAG) techniques, respectively. Electron backscatter diffraction results indicated that delta-ferrites with volume fraction of approximately 1.8% were formed in the weld seam of TIG joints, which was unbeneficial for the mechanical strength. By contrast, the microstructures were relatively fine and no delta-ferrites were formed in the MAG joints, showing a better microstructural quality compared with that of TIG joints. Nevertheless, the fatigue test results indicated that fatigue strength of TIG joints was higher compared with that of MAG joints. This was because that the lower weld reinforcement of TIG joints decreased the stress concentration at weld toe than that of MAG joints, which resulted in the better fatigue performance, implying that the fatigue behavior of welded joints was more influenced by the welding quality instead of microstructures.