The Role of Hydrogen-Metal Interactions in Increased Hydrogen Environmentally Assisted Cracking Susceptibility in Additively Manufactured 17-4 PH Stainless Steel

RIP2025-00062: The role of hydrogen (H)-metal interactions in enhanced H environment-assisted cracking (HEAC) susceptibility of additively manufactured (AM) 17-4 PH stainless steel via laser powder bed fusion (LPBF) is examined. The motivation was the finding of high stage II crack growth rates and mixed intergranular as well as transgranular cracking of the AM alloy when compared to the wrought condition under cathodic polarization in seawater. Study of hydrogen metal interactions was facilitated by investigation of key microstructural features, hydrogen trapping characteristics, effective hydrogen diffusivity (Deff), and diffusible H content (CH,diff) between wrought 17-4 PH and AM 17-4 PH in the peak-aged and over-aged tempers. The increase in CH,diff as a function of hydrogen overpotential was assessed via the barnacle cell electrode technique, and Deff was determined using electrochemical permeation. Results demonstrate that the AM alloys consistently exhibit a lower CH,diff but increased Deff relative to wrought materials with the same strength, ductility, heat treatment, and composition. Potential contributions of microstructural features to the observed differences in H-metal interactions behavior are also examined, and the role of these features as well as hydrogen interactions in altering HEAC resistance are phenomenologically explored in the context with a well-known decohesion based H-affected Stage II crack growth rate model.