Deciphering Hydrogen Uptake Behavior and Its Effect on Hydrogen Embrittlement of Additive Manufactured Alloy 718

Abstract Additive manufactured (AMed) Alloy 718 has attracted growing interest in high-performance applications due to its ability to produce complex geometries and improve material utilization. However, its susceptibility to hydrogen embrittlement (HE) is still a concern for structural integrity and operational safety, especially in harsh environments. In this study, we investigated the hydrogen uptake behavior and its impact on HE in AMed Alloy 718 via hydrogen charging and in-situ tensile test. Hydrogen was charged cathodically on both AMed and conventionally manufactured (CMed) Alloy 718 samples to achieve comparable hydrogen concentrations, which were measured by Thermal Desorption Spectroscopy (TDS). To better understand hydrogen uptake, trapping and distribution mechanisms, a combination of advanced surface characterization techniques was employed, including Glow Discharge Optical Emission Spectroscopy (GDOES), Time of Flight, Second Ion Mass Spectroscopy (ToF-SIMS) and Atomic Force Microscopy (AFM). ToF-SIMS revealed the spatial distribution of hydrogen and its dynamic desorption behavior in hydrogen charged samples. AFM was utilized to compare the surface morphology and potential differences of samples before and after the hydrogen charging. Regions identified as hydrogen trapping sites exhibited a higher Volta potential than hydrogen-free areas. The results demonstrate that AM-induced microstructural heterogeneities significantly influence hydrogen uptake and embrittlement behavior. AMed samples exhibited a more pronounced loss in ductility and a higher tendency for embrittlement after hydrogen charging.