| Abstract Scope |
Wire arc additive manufacturing (WAAM) and laser powder bed fusion (LPBF) are promising additive techniques for the energy industry, spanning sub-millimeter features to structures meters wide. For 17-4PH steel, both processes generate spatially heterogeneous, metastable mixtures of martensite, δ-ferrite, and retained austenite departing from wrought material. WAAM's higher heat input favors coarse, vermicular δ-ferrite, while LPBF's faster cooling produces columnar grains with a range of retained-austenite fractions, depending on processing parameters. How these microstructures affect hydrogen embrittlement is poorly understood.
This work investigates the hydrogen susceptibility of WAAM and LPBF 17-4PH using slow strain-rate tensile testing under in-situ electrochemical charging, alongside SEM, EBSD, KPFM, and electrochemical permeation testing to characterize fracture pathways, susceptible microstructural features, hydrogen segregation, and trap populations.
We establish a direct link between hydrogen trapping and mechanical degradation, informing build strategies and post-processing techniques to mitigate embrittlement-susceptible features enabling safer, more reliable additively manufactured structures. |