Microstructure, mechanical properties, and pitting corrosion resistance of SAF 2205 duplex stainless steel after friction hydro-pillar processing

Duplex stainless steels (DSSs) are widely used in the oil and gas industry. Unfortunately, fusion welds of these alloys might exhibit inappropriate microstructures, face cracks, and even failures during service. In this context, friction hydro-pillar processing (FHPP) is a suitable friction-based welding technique for repairing cracks in offshore engineering with promising outcomes. Accordingly, the present work evaluates the effects of FHPP on one of the most widely used DSS known as SAF 2205. The welded joint features were evaluated by optical microscopy and X-ray diffraction (XRD). Furthermore, mechanical properties were evaluated by microflat tensile tests and microhardness, and pitting corrosion resistance was analyzed by the ASTM G48 Method A. Intense grain refinement in the dual-phase microstructure induced by the FHPP led to the formation of a microduplex microstructure, which resulted in enhanced microhardness and mechanical properties. The pitting corrosion mainly occurred near the weld interface, for which the formation of Cr2N nitrides and the consequent decrease in pitting resistance equivalent number (PREN) was found to be a significant factor.