Friction Stir Welding of AISI 316L Stainless Steel in a 3.5 NaCl Aqueous Solution: Metallurgical and Mechanical Characterization

Abstract

Abstract Submerged friction stir welding (SFSW) was employed for joining AISI 316L stainless steel sheets. The effect of submerged friction stir welding on the metallurgical and mechanical properties of the weld joints was studied by varying tool rotational speed from 600 to 1,400 r/min, in steps of 400 r/min with other constant process parameters (welding speed of 55 mm/min, axial force of 12 kN, and tool tilt of 1.5°) in an artificially prepared 3.5 sodium chloride aqueous solution chamber. Characterization studies, such as scanning electron microscopy and electron backscattered diffraction, were used for studying the microstructural studies of the weld zone. The results of the experimental analysis reveal that the SFSW joints exhibited overall better joint strength, and the weld made at 1,000 r/min was superior in terms of strength and microstructural features to that of the base steel. The pitting corrosion behavior of the base steel and the weld joints depicts a stable pitting potential with no active passive behavior, in which the pitting corrosion resistance of all weld joints was marginally higher, especially the weld joint made at 1,000 r/min, which was superior to that of the base steel. The existence of the secondary precipitates was ruled out in all the cases, owing to lower peak temperatures and continuous (fast) cooling of the weld zone.