Abstract
Objectives: The aim of the present work was to investigate the influence of welding process variation as well as post weld thermal aging treatment on the metallurgical properties of Duplex Stainless Steel (DSS) 2205 welds. Method: Butt welded joints were fabricated using 10 mm thick plates of DSS 2205 by two different welding processes namely, Gas Tungsten Arc Welding (GTAW) process and Flux Cored Arc Welding (FCAW) process. These welded specimens were further subjected to thermal aging treatment at 800°C for 40 minutes to study the precipitation tendencies in the welds. Findings: Ferrite content was found to increase more in case of thermally aged FCAW joints as compared to the thermally aged GTAW joints. Also, GTAW weld metal showed a softening effect while FCAW weld metal underwent hardening after thermal aging treatment. Aging resulted into variation of ferrite content indicating that the process change can affect the important metallurgical ratio of austenite to ferrite in these welds. Ferrite phase was the predominating phase that showed dissolution which led to different inter-metallic phase formations like carbides, oxides as well as sigma phase formation. Application/Improvements: The present study is beneficial from the industrial view point, as the data generated through this piece of research can be directly used for DSS fabrications. Keywords: DSS, FCAW Process, GTAW Process, Metallurgical Properties, Welded Point
Highlights
Duplex Stainless Steel (DSS) possesses balanced double phase structure of ferrite and austenite in fixed ratio of approximately 1:1, due to which these steels have excellent combination of corrosion resistance and mechanical properties[1]
Ferrite evaluations carried for Gas Tungsten Arc Welding (GTAW) and Flux Cored Arc Welding (FCAW) joints reveal that ferrite percentage did not vary much for the joints in the as welded condition
The Root Pass (RP) weld zone showed a higher value of ferrite than the Cover Pass (CP) zone which could be attributed to the fact that the welding heat input that was used for giving the root pass was lower as compared to the one used for CP, which resulted into higher cooling rate and the time required for the transformation of ferrite into austenite was less
Summary
Duplex Stainless Steel (DSS) possesses balanced double phase structure of ferrite and austenite in fixed ratio of approximately 1:1, due to which these steels have excellent combination of corrosion resistance and mechanical properties[1]. At high temperature operating conditions (5000C to 8000C) these steels degrade in terms of mechanical properties and corrosion resistance due to thermal aging embrittlement[2,3]. The unique behavior of duplex stainless steels towards the corrosion and mechanical properties is due to its ferrite/ austenite phase balance. Ferrite/austenite balance in case of welding of DSS cannot be maintained as in base metal. The desired 30-55% (typically about 45%) ferrite necessary for imparting combination of excellent corrosion resistance and mechanical properties can only be achieved by the selection of proper welding process, judicially designing the welding procedures and selecting the proper filler metal[6]. This research area has received little attention and needs to be explored for better understanding of the metallurgical aspects of DSS joints welded using conventional processes like GTAW and FCAW process
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