Abstract
The present work describes the influence of the parameters employed in the gas tungsten arc welding process (GTAW) when nickel powder is used as a filler metal in 2304/2507 duplex stainless-steel dissimilar joints. Multi-objective optimization was applied in order to maintain the austenite/ferrite percentage in the welded zone. A microstructural and phase quantification analysis was performed in each sample through optical and scanning electron microscopes. It was found that a nickel powder addition combined with low heat input increased the biphasic ratio across the different zones of the dissimilar welded samples. Although the austenite volume fraction increased in the 2304 heat-affected zone (HAZ) near to 25%, it was not sufficient according to international standards. The obtained results led to the maintenance of the 50/50 phase percentage in the 2507 HAZ welded joint side, as well as to the increment of the austenite percentage in the 2304 HAZ.
Highlights
Duplex stainless steel (DSS) derives its name from the stable microstructure at room temperature, which consists of approximately 50% austenite phase (γ) and 50% ferrite phase (δ)
The highest content value of austenite in the fusion zone (FZ) and heat-affected zone (HAZ) in both steels was obtained by employing a welding current of 136A and an advancing speed of 2.89 mm s−1
This article shows the research work carried out to analyze the influence of the gas tungsten arc welding process (GTAW) process parameters on dissimilar joints of lean duplex stainless steel UNS S32404 and super duplex stainless steel UNS S32507
Summary
Duplex stainless steel (DSS) derives its name from the stable microstructure at room temperature, which consists of approximately 50% austenite phase (γ) and 50% ferrite phase (δ). The welding processes used to join this type of material promote variations to the dual percentage of ferrite-austenite, because the microstructural heterogeneity generated by the thermal gradients can locally generate microstructural changes, influencing the mechanical behavior of the joint [3,4,5,6]. Controlling this dual percentage is of great importance to the maintenance of the mechanical properties, especially of the corrosion resistance. In 2019, studied this topic, focusing on the difference among various methods to measure the A/F ratio on the welds correctly [7,8]
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