Influence of arc energy and filler metal composition on the microstructure in wire arc additive manufacturing of duplex
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RESEARCH PAPER
Influence of arc energy and filler metal composition on the microstructure in wire arc additive manufacturing of duplex stainless steels Benjamin Wittig 1
&
Manuela Zinke 1 & Sven Jüttner 1
Received: 22 July 2020 / Accepted: 14 September 2020 # The Author(s) 2020
Abstract The influence of arc energy and filler metal composition on the microstructure of additively welded thin-walled structures of duplex stainless steels was investigated using different commercially available standard and superduplex solid wire electrodes commonly used today. As welding process, the cold metal transfer (CMT) process was used. The arc energy and cooling rate were varied by adjusting the wire feed and welding speed. Optical emission spectroscopy (OES) and carrier gas melt extraction (CGME) were used to determine the chemical composition of the specimens. The ferrite content was determined both by magnetic induction and by image analysis as a function of the wall height. In addition, the microsections were examined for intermetallic phases and precipitations. Moreover, corrosion tests were carried out according to ASTM G 48, Method A. The results indicate that an increase in arc energy leads to longer t12/8 cooling times. Depending on the filler metal composition, this leads to ferrite contents that are partially outside the values required according to ISO 17781. Furthermore, precipitates of secondary austenite are often found, which is attributed to the multiple reheating by the subsequent layers. Keywords Duplex stainless steels . Additive manufacturing . Ferrite content . Secondary phases . Thermal cycles . CMT
1 Introduction Currently, wire arc additive manufacturing (WAAM) is gaining enormous importance. Especially in the processing of highalloyed, expensive materials, the production of near net shape objects by means of layer-by-layer deposition welding offers considerable advantages, e.g., the ability to produce complex geometric shape elements with a high degree of material utilization [1–3]. However, a challenge in additive arc welding is the relatively high heat input coupled with relatively low heat dissipation. This can lead to residual stresses and distortion as
Recommended for publication by Commission II - Arc Welding and Filler Metals * Benjamin Wittig [email protected] 1
Institute of Materials and Joining Technology, Otto von Guericke University, Magdeburg, Germany
well as to changes in the microstructure and crack formation [4, 5]. This becomes particularly critical in the processing of materials that already require demanding handling from a welding point of view. Especially, the welding of duplex stainless steels requires an adjusted heat control to achieve material-specific properties in the weld metal. Current recommendations for welding duplex stainless steels focus on achieving a precipitation-free weld metal microstructure with balanced proportions of ferrite and austenite during joint welding and cladding [6, 7]. However, the application of these recommendations regarding arc ener
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