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The present work analyzed the microstructure, mechanical, and corrosion properties of a dissimilar activated tungsten inert gas (ATIG) welded 2205 duplex stainless-steel (2205 DSS) plate and AISI 316L austenitic stainless steel (316L ASS) and compared them to conventional dissimilar welded tungsten inert gas (TIG). The mixing design method is a tool used to establish the optimal combined flux to achieve a full-penetrated weld bead in one single pass. A microstructure study was carried out by scanning electron microscopy (SEM). The ATIG and TIG fusion zones revealed a matrix ferrite structure with intragranular austenite, Widmanstätten needles, allotriomorphic austenite at the grain boundaries, and plate-like precipitates free of deleterious phases such as sigma and chi phases or second austinite owing to the moderate heat input provided of 0.8 kJ/mm. Ferrite volume proportion measurements were carried out utilizing the areas image processing software. The average ferrite volume proportion attained 54% in the ATIG weld zone; however, it decreased to 47% for the TIG weld zone. The results showed that the optimal flux composed by 91% Mn2O3 and 9% Cr2O3 allowed a full penetrated weld to be obtained in one single pass. However, a double side weld is required for conventional TIG processes. The values of the tensile (599 Mpa), hardness (235 HV), and impact test (267 J/cm2) measurements of ATIG welds were close to those of conventional TIG welds. The elaborated flux did not degrade the mechanical properties of the joint; on the contrary, it reinforced the strength property. The width of the ATIG heat-affected zone was narrower than that of TIG welding by 2.6 times, ensuring fewer joint distortions. The potentiodynamic polarization test results showed a better electrochemical behavior for ASS 316L than with the weldment and the parent metal of DSS 2205. [ABSTRACT FROM AUTHOR]

In this study, 6 mm thick duplex stainless-steel grade 2205 plate was welded by active tungsten inert gas (ATIG) using different oxide fluxes and the effect of optimal oxide fluxes on structure, mechanical and corrosion properties was systematically analyzed and discussed. Initially, fourteen oxides were tested (SiO2, TiO2, ZnO, MnO2, Cr2O3, Fe2O3, ZrO2, SrO, CaO, MoO3, V2O5, Mn2O3, Co2O3 and MgO). Among these, three candidate oxides, i.e., SiO2, Ti2O and ZnO were selected for further evaluation based on the depth ratio, depth-to-width (D/W), and ultimate tensile strength (UTS) results. By using Minitab 17 software, optimal combinations of these fluxes for maximum penetrations were estimated. The obtained results revealed that the optimal flux composition is 76 % SiO2-24 % ZnO. The results showed that the depth attained by the optimized flux is 2.9 times greater than tungsten inert gas (TIG) weld. The D/W ratio was also improved 3.7 times when contrasted with typical TIG welding. The energy absorbed in fusion zone in the case of ATIG weld is greater when contrasted with TIG weld. It was found that the weld bead obtained with optimal flux combination in ATIG weld can better withstand sudden loads. The obtained UTS value (810 MPa) for ATIG weld was close to parent metal (825 MPa) and greater than the weld produced by TIG welding (766 MPa). However, the corrosion resistant property was found to be slightly decreased for metal welded with ATIG as compared to metal welded by using TIG. These results give a comprehensive guideline for further investigations on TIG welding of 2205 duplex stainless-steel. [ABSTRACT FROM AUTHOR]

Duplex stainless steel (DSSs) is characterized by excellent corrosion resistance with high strength. Twelve single-component fluxes (TiO2, Fe2O3, Cr2O3, ZnO, ZrO2, CaO, Mn2O3, V2O5, MoO3, SrO, MgO, and LaO2) were tested in the initial experiment using activated Tungsten inert gas (ATIG) technic, and then three couples of oxides were selected as binary fluxes (Fe2O3-Cr2O3, ZnO-Mn2O3, and V2O5-Mn2O3) for the rest of the study. The results show that the depth weld of binary oxides (Fe2O3-Cr2O3, ZnO-Mn2O3) was increased by 3.7 times in comparison with tungsten inert gas (TIG) weld bead. The hardness and the tensile strength of welds carried out with Fe2O3-Cr2O3 and ZnO-Mn2O3 binary fluxes were close to those of the parent metal. Weld bead executed with ZnO-Mn2O3 oxides has more capability to withstand sudden loads. Potentiodynamic polarization tests were performed. The metal welded with flux composed of Fe2O3-Cr2O3 has been found the most resistant to corrosion. [ABSTRACT FROM AUTHOR]