Super Duplex stainless steels (SDSS) are alloys based on the Fe-Cr-Ni-N system. The chemical composition is tailored to achieve a balanced microstructure of 50% ferrite and 50% austenite. Hyper Duplex Stainless Steels (HDSS) are also duplex materials distinguished by their remarkable yield strength (≥700 MPa) and corrosion resistance (PREN>48). They have been developed as an alternative to the well-established SDSS when superior mechanical and corrosion performance is required. This enhanced performance is attributed to alloying additions, primarily Cr, Mo, and N. In this study, a comparison is conducted between filler metals of SDSS and HDSS for the root welding of SDSS plates. The gas tungsten arc welding (GTAW) process was used to carry out root welding passes and Gas Metal Arc Welding (GMAW) for filling passes on SDSS substrates arranged in a V groove to simulate a repair scenario. The heat input was controlled in both processes, keeping it below 2.0 kJ/mm in the GTAW and 1.2 kJ/mm in the GMAW. GTAW with constant current was used and the parameters achieved producing full penetration welds with SDSS and HDSS. In this case, Nitrogen was used as backing gas to avoid oxidation of the root. Thus, a special GMAW-Pulsed version was applied to achieve good wettability and defect-free joints. ASTM G48 tests were performed to evaluate the corrosion resistance through Critical Pitting Testing (CPT) analysis on the root pass, microstructural analysis via optical microscopy, and impact toughness. Consequently, a comprehensive examination of the welded joints outlines manufacturing conditions, limitations, and the applications of SDSS and HDSS filler metals.

Solidification cracking (SC) is a defect that occurs in the weld metal at the end of the solidification. It is associated with the presence of mechanical and thermal stresses, besides a susceptible chemical composition. Materials with a high solidification temperature range (STR) are more prone to the occurrence of these defects due to the formation of eutectic liquids wetting along the grain boundaries. The liquid film collapses once the structure shrinks and stresses act during the solidification. Thus, predicting the occurrence of SC before the welding process is important to address the problem and avoid the failure of welded components. The nuclear power industry has several applications with dissimilar welding and SC-susceptible materials, such as austenitic stainless steels, and Ni-based alloys. Compositional optimization stands out as a viable approach to effectively mitigate SC in austenitic alloys. The integration of computational modeling into welding has significantly revolutionized the field of materials science, enabling the rapid and cost-effective development of innovative alloys. In this work, a SC resistance evaluation is used to sort welding materials based on a computational fluid dynamic (CFC) model and the alloy's chemical composition. An index named Flow Resistance Index (FRI) is used to compare different base materials and filler metals as a function of dilution. This calculation provides insights into the susceptibility to SC in dissimilar welding, particularly within a defined dilution range for various alloys. To assess the effectiveness of this approach, the relative susceptibility of the materials was compared to well-established experimental data carried out using weldability tests (Transvarestraint and cast pin tear test). The FRI calculation was programmed in Python language and was able to rank different materials and indicate the most susceptible alloy combination based on the dilution and chemical composition.