Enhanced Mechanical Properties and Hydrogen Embrittlement Resistance of LPBF Alloy 718 by Optimizing Printing Parameters

Abstract In this study, we investigate the effect of printing parameters on mechanical properties of UNS N07718 alloy and the optimized printing parameters are used to print AM samples. We also investigated the effect of hydrogen on additively manufactured (AM) alloy 718 and compared it with conventionally manufactured (CM) 718 samples. Electrochemical hydrogen charging was performed on both AM and CM 718 samples to achieve comparable hydrogen content in the samples, which was further measured by thermal desorption spectroscopy (TDS). Identically charged samples were mechanically tested by tensile test and hardness test to quantitatively correlate the mechanical degradation by introducing different contents of hydrogen into the samples. A combination of surface characterization techniques: Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD), and Electron Backscatter diffraction (EBSD) are deployed to accurately characterize and gain an improved understanding of the hydrogen embrittlement mechanism in CM and AM alloy 718. The higher presence of hydrogen reduced ductility in the as-built / as-received AM samples but did not significantly influence the response in CM materials. Hydrogen-charged samples exhibited a large area of brittle fracture mode, while hydrogen-free samples showed ductile fracture morphology.