The use of commercially available filler metals for wire and arc additive manufacturing (WAAM) of duplex stainless steel components results in a microstructure with a very low ferrite content. The ferrite–austenite ratio in the duplex stainless steel weld metal depends on both the cooling rate and particularly on the chemical composition. However, the research and testing of special filler metals for additive deposition welding using wire and arc processes is time-consuming and expensive. This paper describes a method that uses an additional cold wire feed in the gas metal arc welding (GMAW) process to selectively vary the alloy composition and thus the microstructure of duplex stainless steel weld metal. By mixing different filler metals, a reduction of the nickel equivalent and hence an increase in the ferrite content in additively manufactured duplex stainless steel specimens was achieved. The homogeneous mixing of electrode and cold wire was verified by energy dispersive spectroscopy (EDS). Furthermore, the addition of cold wire resulted in a significant increase in sample height while the sample width remained approximately the same.

Direct energy deposition with arc and wire (DED-AW) is a versatile, low-cost, and energy-efficient technology for additive manufacturing of medium- and large-sized metallic components. In this study, the effects of arc energy and shielding gas in cold metal transfer (CMT) welding of walls and blocks on cooling time, mechanical properties, and macro- and microstructure have been studied using precipitation-hardenable Ni-based superalloy Haynes^® 282^®. The arc energy and consequently the cooling rate were varied by changing the wire feed rate and the travel speed. As expected, increasing the arc energy leads to higher cooling times for the walls. Due to the 2D thermal conduction, the thin walls cool down much slower than multi-layer welded blocks, but this reduces the strength values only very slightly. While the walls have no sensitivity to the occurrence of unacceptable seam irregularities, the multi-layer blocks show isolated seam defects, such as hot cracks or lack of fusion. Despite shielding gas variation, the as-welded blocks show acceptable strength properties at room temperatures (RT) and impact values at RT and −196 °C. However, the use of an N-containing shielding gas results in lower elongation and notched bar impact energy. Precipitation-hardened specimens tested at 871 °C exhibit a similar strength level to transverse tensile specimens of gas metal arc welding (GMAW) welded joints on 12.7 mm thick plates with fracture in the weld metal.

Due to their mechanical and corrosive properties, nickel-based alloys are very important in several industrial sectors like power stations, chemical apparatus, and the oil industry. While flux-cored arc welding (FCAW) of carbon steels often uses flux-cored wires (FCW), the use of Ni-based flux-cored wires is industrially less common. The reasons for this include the lower degree of recognition and the higher material costs compared to solid wires. In comparison to solid wires, flux-cored wires have some technological benefits such as the possibility of welding without pulsed arc technology using low-cost standard mixed gases, which has a much lower tendency to weld defects due to high penetration depth. Depending on the slag, the flux-cored wires have a good weldability and excellent mechanical properties. Based on the self-stressed and externally stressed hot crack tests, the basic FCW showed a higher hot cracking susceptibility, contrary to the original assumption. Even if the causes have not yet been finally clarified, a negative influence of the comparatively high sulfur and oxygen contents in the basic FCW is suspected. The weld metal of the solid wires showed the highest hot crack resistance.