Abstract
Thick welded joints of UNS S32304 lean duplex stainless steel (LDSS) has been studied in acidified glycerin, a byproduct of biodiesel plants, using cyclic polarization technique. LDSS S32304 thick plates were welded by different processes commonly employed in the fabrication process: shielded metal arc welding, gas metal arc welding and flux cored arc welding. The electrochemical behavior of different weldment zones was characterized. Transmission electron microscopy and scanning electron microscopy (SEM) were used for sample characterization. SEM images showed that the heat affected zone was the most critical zone for pitting corrosion for all samples. The results were associated to the microstructural features of the materials. Generally, the breakdown potential of the top regions of welds was higher in acidified glycerin than the weld root for welds fabricated with two different filler metals. Basically, all the welded samples exhibited similar or higher corrosion resistance, compared with the corresponding base metal.
Highlights
Duplex stainless steels (DSSs) are materials that exhibit a combination of high yield strength, toughness and localized corrosion resistance, and they are being widely used in chemical, petrochemical, marine, nuclear and paper industry[1]
This study aims to evaluate the corrosion resistance of UNS S32304 lean DSS (LDSS) thick plates welded by three different welding processes in acidified glycerin, a byproduct of biodiesel industry
To previous investigations[22], the fusion zone (FZ) structure consists of austenite grains in the form of Widmanstätten plate precipitates and secondary austenite (γ2) within a matrix of ferrite, and FZ region showed higher proportions of austenite than heat affected zone (HAZ)
Summary
Duplex stainless steels (DSSs) are materials that exhibit a combination of high yield strength, toughness and localized corrosion resistance, and they are being widely used in chemical, petrochemical, marine, nuclear and paper industry[1]. The best properties are obtained with approximately equal amount of austenite (γ) and ferrite (α) phases[2]. DSS undergoes microstructural changes that impact on their mechanical and corrosion properties, especially corrosion resistance and toughness[2,3,4,5,6,7,8,9,10,11,12,13,14]. Multipass welding is more common during fabrication, reports about multipass welding are scarce, especially for pipes of medium thickness or more
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