Mechanical Properties and Microstructure of Rotary Friction Welded Super Duplex Stainless Steel Pipe.

Super duplex stainless steel has strong mechanical properties and performance. The demand for this material in various industries in the world of engineering has increased due to its reliability. This material has been considered as an alternative to high alloy steel and other grades of stainless steel for their good technical and economic benefits. The performance comes from the structure of the material that consists of approximately equal rates of ferrite and austenite. However, this ratio and the material's structure can be influenced by production activities, such as the welding process. The level of degradation of properties can be reduced or prevented by utilizing the solid-state welding process due to its reduced heat input, thermal cycle, and absence of melting and recrystallization. Rotary friction welding is a solid-state welding process that can serve as an alternative to fusion welding, reducing and preventing the formation of undesired phases. In this study, the effect of rotary friction welding process parameters on microstructure and mechanical properties has been investigated. Different friction forces and forging forces are used to weld super duplex stainless-steel pipes. An acceptable result has been achieved, as the efficiency of the welded joint for the best case exceeds 100%. The ultimate tensile strength in this case is 928 MPa, surpassing the strength of the base material. The microstructure of the welded samples shows a good result for this welding process, so it can be considered for joining super duplex stainless steel to improve joint efficiency.