RESUMO
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.
RESUMO
In this study, the effects of pseudo-ternary oxides on mechanical properties and microstructure of 316L stainless steel tungsten inert gas (TIG) and activating tungsten inert gas (ATIG) welded joints were investigated. The novelty in this work is introducing a metaheuristic technique called the particle swarm optimization (PSO) method to develop a mathematical model of the ultimate tensile strength (UTS) in terms of proportions of oxides flux. A constrained optimization algorithm available in Matlab 2020 optimization toolbox is used to find the optimal percentages of the selected powders that provide the maximum UTS. The study indicates that the optimal composition of flux was: 32% Cr2O3, 43% ZrO2, 8% Si2O, and 17% CaF2. The UTS was 571 MPa for conventional TIG weld and rose to 600 MPa for the optimal ATIG flux. The obtained result of hardness for the optimal ATIG was 176 HV against 175 HV for conventional TIG weld. The energy absorbed in the weld zone during the impact test was 267 J/cm2 for the optimal ATIG weld and slightly higher than that of conventional TIG weld 256 J/cm2. Fracture surface examined by scanning electron microscope (SEM) shows ductile fracture for ATIG weld with small and multiple dimples in comparison for TIG weld. Moreover, the depth of optimized flux is greater than that of TIG weld by two times. The ratio D/W was improved by 3.13 times. Energy dispersive spectroscopy (EDS) analysis shows traces of the sulfur element in the TIG weld zone.
