Parts made via additive manufacturing (AM) are being adopted broadly among many industries and used
in an array of applications. AM parts are attractive to these industries for several reasons. Complex
geometries that otherwise cannot be manufactured using traditional methods can be printed. Also, the
ability to use AM to produce parts mitigates the need to maintain an inventory of replacement parts and
avoids lengthy delivery times. Alloy 718 is widely used in demanding applications due to its high strength
at high temperatures and excellent creep and corrosion resistance. Parts and components of this alloy
can be created using AM techniques. However, in hydrogen and hydrogen-producing environments, alloy
718 is susceptible to hydrogen embrittlement (HE). The overall objective of this research program was to
understand the underlying mechanisms governing the susceptibility of AM alloy 718 to HE by
investigating the mechanical performance in high-pressure gaseous hydrogen and examining the
microstructure to compare the wrought and AM materials. The fatigue crack growth rate tests showed
that the wrought and all additively manufactured specimens had very similar mechanical response.
Testing in gaseous hydrogen demonstrated that the AM and wrought materials had accelerated crack
growth rates in the hydrogen gas environment; however, the effects of hydrogen were more pronounced
in some materials than others. Metallurgical characterizations revealed differences in precipitates and
metallurgy, and the post-test fracture surface examinations showed similar fracture morphology for all
materials. No metallurgical feature or fracture morphology could be correlated with the more dramatic effects of hydrogen on the fatigue crack growth rates when comparing AM configurations and the wrought
material.