Process map, microstructure, hardness and corrosion properties of gas metal arc additive manufacturing (GMA-AM) of Invar 36 alloy

Invar 36 is a specialised Fe–Ni alloy adopted for its dimensional stability and service at elevated temperatures. Its adoption in Gas Metal Arc Additive Manufacturing (GMA-AM) is accelerating because the process provides a cost-effective route to medium- and large-scale components. Yet processing Invar 36 remains challenging: the alloy is prone to solid-state cracking and porosity, lacks dedicated synergic lines, and its distinctive thermal behaviour complicates parameter selection, hindering the establishment of a stable, reliable printing window. This study addresses these issues by first mapping the printability of Invar 36 across a range of process conditions. We then evaluate microstructural evolution, phase constitution by X-ray diffraction, electrochemical behaviour via potentiodynamic polarisation and electrochemical impedance spectroscopy, and hardness of test components produced using optimised short-circuit GMA-AM parameters. Relative to the literature, the selected strategy reduces heat input by approximately 20%, mitigating porosity and cracking without compromising build integrity.