ESSC & DUPLEX 2019

**Abstract** For the successful welding of high-alloy and corrosion-resistant duplex stainless steels, a number of welding recommendations have been established over the past decades which guarantee the required material-specific properties of the welds. These include, inter alia, compliance with defined heat input and interpass temperatures as well as the use of filler metals over-alloyed with nickel compared to the base material. Despite of the rapid cooling, the higher nickel content guarantees a sufficient austenite content in the weld metal of welded joints or weld claddings. Investigations by Posch et al. [1] for the production of additive manufactured turbine blades with the filler metal 22 9 3 N L have shown an excessively austenitic structure with ferrite contents of less than 30 %. Studies by Hoefer et al. [2] have shown that the excessive formation of austenite and the precipitation of secondary austenite are caused by repeated heat input and passing through the temperature range of 1200 to 800 °C when welding the following layers. Stützer et al. [3] have shown that the cooling time also increases with the number of layers. This additionally promotes the formation of austenite and leads to a significant reduction in strength. The slow cooling rates during wire and arc additive manufacturing therefore require an adjustment of the alloy composition with regard to the nickel-over-alloying of the filler metal. This presentation informs about the possibility of influencing the microstructure by varying the alloy composition of the filler metal. For this purpose test specimens with modified filler metals (nickel concentration of 5.5 up to 8.8 % & silicon concentration of 0.5 up to 0.8 %) were manufactured and inspected by material testing (metallography, ferrite measurement, hardness measurement, X-ray examination). In order to determine the influence of the chemical composition, spectral analyses (OES) and melt extractions were carried out on the filler material as well as on the weld metal. In addition, the microstructure was specifically adjusted by mixing alloys using cold wire feed - gas metal arc welding process. The reduction of the nickel equivalent proved to be an effective way of reducing the austenite content in the weld metal. Especially the reduction of the nickel concentration but also the increase of the silicon concentration resulted in an increase of the ferritic microstructure. With cold wire additions, test specimens with ferrite contents of 46 up to 72 FN (32 - 50 %) could be produced. The homogeneous mixing of electrode wire and cold wire could be verified by EDX-Line-Scans. Furthermore, the addition of cold wire resulted in an increase of the average specimen height by approximately 30 %. **Literatur** [1] G. Posch, K. Chladil, H. Chladil (2017): Material properties of CMT–metal additive manufactured duplex stainless steel blade-like geometries, Welding in the World, Vol. 61, Issue 5, pp 873-882, https://doi.org/10.1007/s40194-017-0474-5 [2] K. Hoefer, A. Haelsig, P. Mayr (2018): Arc-based additive manufacturing of steel components – comparison of wire- and powder-based variants, Welding in the world, Vol. 62, Issue 2, pp 243-247, https://doi.org/10.1007/s40194-017-0527-9 [3] J. Stützer, M. Zinke, S. Jüttner, P. Findeklee (2018): Additive Fertigung von Bauteilen aus Duplexstahl durch Schutzgasschweißen, Fachtagung Werkstoffe und Additive Fertigung: 25. 26.04.2018, Potsdam: Tagungsband - Sankt Augustin: Deutsche Gesellschaft für Materialkunde e. V., S. 103-108; [Konferenz: DGM-Tagung, 25.-26. April 2018, Potsdam]