Effect of heat treatment after wire-arc additive manufacturing on themicrostructure of duplex stainless steel

In this study, the effect of heat treatment on the microstructure of the ۲۲۰۹ duplex stainlesssteel wall fabricated by the Wire arc additive manufacturing (WAAM) process was investigated. Forthis purpose, the Gas metal arc welding (GMAW) process was employed to fabricate the wall on a۲۲۰۵ duplex stainless steel base metal. The wall was divided into four sections to examine themicrostructural variations. The results revealed that grains near the base metal were equiaxed,transitioning to a columnar structure as the distance from the base metal increased. In the final layer,the grains became equiaxed again, with a smaller grain size. In all regions, austenite was observed inmorphologies such as intragranular austenite, Widmanstätten austenite, and grain boundary austenite.The austenite phase fraction was analyzed across various regions of the wall. Microstructuralobservations indicated that the optimal microstructure of the base metal, with approximately ۵۰%ferrite and ۵۰% austenite, was entirely disrupted. Additionally, a significant amount of secondaryaustenite was formed due to the welding thermal cycles. Moreover, the austenite phase fractiondecreased with increasing distance from the base metal and near the topmost layer.To improve the wall's microstructure, heat treatment was performed at ۱۰۵۰°C, followed by waterquenching. The results demonstrated that at ۱۰۵۰°C, the desired ferrite-austenite phase ratio wasachieved. After solution heat treatment, the detrimental phases dissolved into the ferritic phase, andthe distribution of austenite became more uniform. Compared to the pre-heat-treatment state, thestructure became finer-grained, more equiaxed, and exhibited greater uniformity and alignment.

کلیدواژه ها:

Duplex stainless steel ، wire arch Additive Manufacturing ، Microstructure ، Heat treatment