Mechanical, Microstructure and Corrosion Properties of Friction Stir Welded Dissimilar Austenitic Stainless Steel Joints

In many industries, challenges arise when welding dissimilar materials using traditional methods, such as fusion welding. These challenges often lead to problems like cracking, phase segregation, and intermetallic formation. To solve these issues, a low-operating-temperature friction stir welding (FSW) technique was employed to fabricate dissimilar stainless steel joints. In this study, AISI 304 and AISI 316 dissimilar butt joints were welded by friction stir welding at different tool rotational speeds of 600 to 900 rpm with a constant welding speed of 40 mm/min and an axial load of 15 kN. AISI 304 was on the retreating side, and AISI 316 was on the advancing side during the welding operation. At a tool rotation speed of 800 rpm, defect-free, dissimilar FSW joints with good mechanical characteristics were achieved. The tensile result indicates that the yield strength of the welded metal is higher than that of both base metals. Similarly, the hardness of the weld metal was higher than those of the base metal. It is due to the microstructural refinement of the weld metal attained by dynamic recrystallization caused by the stirring action of the tool at elevated temperatures. The microstructural results indicate ductile fracture properties. The pitting potential of dissimilar steel joints is less than that of similar AISI 304 and AISI 316 joints. However, it can stand in severe, corrosive environments.