Surface morphology and experimental investigation on joint characteristics of solid-state welded duplex stainless steel tubes

The aim of this work was to systematically find the optimum parameter combination using the response surface methodology (RSM) technique for welding of UNS S31803 tubes and to find the effect of parameters on mechanical and metallurgical properties. In the present work, the experimental investigations of friction-welded UNS S31803 tube joints are discussed in detail with characterization, radiography, and corrosion studies. The most important parameter that has the greatest impact on the tensile strength of the joints is the upset pressure, which is followed by heating time, heating pressure, and upset time. As the upset pressure and time increased, the joint strength also increased. The radiographic evaluation of the weldments revealed no significant flaws at the weld contact. In comparison to the parent metal zone, the microstructure indicated coarse grain structure in the weld metal zone, with grain orientation changing with upset time. For the optimal parameter combination, the austenite phase is primarily spread in the weld metal zone. In comparison to the partially deformed zone and the parent metal zone, the weld zone had lower hardness values. In the high strength and optimum parameter joints, fractography investigation revealed ductile failure.