Abstract
Additively manufactured (AM) Inconel 718 holds great potential in aerospace, power generation and oil & gas applications due to its excellent mechanical properties and corrosion resistance. However, Inconel 718 is susceptible to the hydrogen embrittlement (HE) in environments which might promote hydrogen adsorption. In this study, the HE of the alloy was studied in a wrought and additively manufactured condition that was processed by laser powder bed fusion. Comprehensive examination of microstructure and mechanical properties were carried out by scanning electron microscope (SEM), electron backscatter detector (EBSD) and Slow Strain Rate Tensile (SSRT) test for the non-charged and cathodically pre-charged samples in 3wt% NaCl electrolyte for 1 to 14 days. While the wrought condition was characterized by equiaxed grains, the AM one has columnar grain containing dense dislocation cells. SSRT shows the transition from ductile (for non-charged) to brittle (for H-charged) for both conditions with the AM exhibiting larger degrees of embrittlement. Post-mortem fractography analysis brings insight into the HE mechanisms driving the failure process; mainly, microvoids formation (MVC), localized plasticity (HELP) and decohesion of lattice (HEDE) that leads into intergranular cracking along the equiaxed grains in wrought or along cellular dendritic boundaries in AM specimens.