Tailoring the microstructure and tensile properties of directed energy deposition-arc buildup 2209 duplex stainless steel by variable polarity energy arrangement

The use of directed energy deposition-arc (DED-arc) to manufacture duplex stainless steel (DSS) shows great potential for marine propeller applications. However, this process can result in excessive austenite and anisotropic tensile properties in DSS deposits due to significant heat input and accumulation. Variable polarity cold metal transfer (VP-CMT) has lower heat input and can regulate the heat distribution on the filler wire and deposition layer. This is an effective way to reduce heat accumulation. The impact of energy arrangement based on this method on DSS deposit is not yet fully understood. This study uses the DED-arc powered by VP-CMT process to deposit DSS components with various electrode positive (EP) and electrode negative (EN) ratios. Effects of EP/EN on the microstructure and tensile properties of DSS walls are investigated accordingly. Results reveal that the DSS buildup wall consists of ferrite and austenite, and a distinct structure is formed along the deposition direction, with an alternating arrangement of the as-deposited zone and reheated zone. A (001) preferred orientation is observed in the ferrite column grain, and more austenite is formed in the reheated zone. Decreasing EP/EN reduces heat input per unit length and thermal accumulation of DED-arc process, leading to lower austenite content and smaller reheated zone, and more pronounced epitaxial growth of ferrite grain. These microstructure differences lead to greater anisotropy in tensile properties.