Hydrogen-assisted fatigue crack propagation behavior of selective laser-melted Inconel 718 alloy

Hydrogen-assisted fatigue crack propagation behavior of selective laser melted Inconel 718 alloy was investigated under in situ electrochemical hydrogen charging, and by multi-scale microstructural analysis. Results suggest that hydrogen significantly increases the fatigue crack growth rate (FCGR), and such an effect is intensified for the post-heat-treatment sample by an acceleration of 2.8 times. Rapid hydrogen diffusion along grain boundaries, and planar-dislocation-slip-induced local hydrogen concentration induced abundant of intergranular cracking, and a decrease of deformation expansion. The suppressed dislocation emission and mobility by hydrogen significantly confine the plastic deformation ahead of the crack tip, thus accelerated the FCGR in the presence of hydrogen.