Abstract
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.
Highlights
Duplex stainless steels (DSS) are steels with a dual-phase microstructure consisting of ferrite and austenite
Recent investigations show that the application of the welding recommendations results in a microstructure with disproportionately high austenite content in additive multilayer welds if these were produced with a cold metal transfer (CMT)
The melting of cold wire during gas metal arc welding is basically possible in combination with the energy reduced CMT process
Summary
Duplex stainless steels (DSS) are steels with a dual-phase microstructure consisting of ferrite and austenite. For successful welding of highly alloyed, corrosion-resistant DSS, several welding recommendations have been developed over the past decades that guarantee the required material-specific properties of the welds. These include, for example, the adherence to specific energy input per unit length and interpass temperatures, as well as the use of similar filler metals with an increased nickel content compared to the base metal. Recent investigations show that the application of the welding recommendations results in a microstructure with disproportionately high austenite content in additive multilayer welds if these were produced with a cold metal transfer (CMT). The high austenite content, as well as the formation of secondary austenite, significantly reduces strength and corrosion resistance [3]
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