Fabrication of Fe–30Al alloy using plasma arc welding powered twin-wire directed energy deposition-arc process: Droplet transfer, microstructure, and mechanical property investigation

Abstract

Intrinsic brittleness and cold cracking sensitivity of Fe–Al intermetallic compounds make their fabrication and processing difficult. In recent years, an innovative additive manufacturing (AM) technology, twin-wire directed energy deposition-arc (TW-DED-arc), has been developed to prepare defect-free Fe–Al alloys via in-situ alloying of Fe and Al elements in a gas tungsten arc welding (GTAW) generated molten pool. However, unconstrained plasma of regular tungsten arc leads to excessive heating area and residual stress during AM buildup. And relatively weak arc pressure of GTAW makes composition inhomogeneity a concern in the in-situ alloying molten pool. To solve the two potential drawbacks, plasma arc welding (PAW) possessing higher energy density and arc pressure is used to power the TW-DED-arc process and fabricate Fe–30Al alloy. In the present research, a special wire-feeding strategy for stable twin-wire feeding of Fe and Al wires is successfully developed to overcome the droplet transfer difficulty induced by constrained arc of PAW and large thermophysical properties difference of heterogeneous filler wires. And according to microscopy characterization results, the innovative PAW powered TW-DED-arc process is capable of fabricating defect-free Fe–30Al bulk sample with homogeneous Al content and epitaxial columnar grain structures. The successful application of PAW-powered TW-DED-arc technique in fabrication of iron aluminide provides stabler and more efficient route for iron aluminide component.