| Abstract Scope |
Super Duplex stainless steels (SDSS) are alloys within the Fe-Cr-Ni-N system, engineered to maintain a balanced microstructure of 50% ferrite and 50% austenite. Hyper Duplex Stainless Steels (HDSS), also duplex alloys, exhibit notable yield strength (≥700 MPa) and corrosion resistance (PREN>48), positioning them as alternatives to SDSS when elevated mechanical and corrosion properties are demanded. These enhancements are attributed to alloying elements such as Cr, Mo, and N. This study compares filler metals of SDSS and HDSS for root welding of SDSS plates. Gas tungsten arc welding (GTAW) was employed for root passes and Gas Metal Arc Welding (GMAW) for filling passes on SDSS substrates arranged in a V groove to mimic repair conditions. Heat input was carefully regulated and maintained below 2.0 kJ/mm for GTAW and 1.2 kJ/mm for GMAW. GTAW, utilizing constant current, ensured full penetration welds with both SDSS and HDSS filler metals, with Nitrogen serving as a backing gas to prevent root oxidation. A specialized GMAW-Pulsed version was deployed to ensure proper wettability and defect-free joints. Corrosion resistance was evaluated through ASTM G48 tests, specifically Critical Pitting Testing (CPT) analysis on the root pass, alongside microstructural analysis via optical microscopy and assessment of impact toughness by Charpy V-Notch (CVN) Impact test. This comprehensive examination of welded joints encompasses manufacturing conditions, limitations, and potential applications for both SDSS and HDSS filler metals. |