Evaluation of friction hydro-pillar processing welding in duplex stainless steels (UNS S31803)

Abstract

This research investigates the effect of the process on the material mechanical and metallurgical properties. Fracture toughness tests were conducted employing C(T) specimens extracted from the welding mixing zone of the joint. A metallographic examination was performed to determine the morphology of the ferrite and austenite after the welding. Phase quantification indicated that the FHPP weld maintains the ferrite content below 70% in accordance with specifications required for equipment used in oil and gas production. The optical microscope analyses did not indicate a significant precipitation of intermetallic phases. X-ray diffraction indicates the presence of the sigma phase in the thermomechanically affected zone (TMAZ). The impact of the weld on the corrosion resistance of the UNS S31803 joint was evaluated by small-scale electrochemical polarizations. The toughness tests conducted on the welding mixing zone indicated a value (0.58 mm) similar to that observed in the original material (in the longitudinal direction). Those results indicates that the FHPP welding technique is adequate for maintaining the microstructural, corrosion and toughness properties according to the specifications required for equipment used in oil and gas exploration.