Hydrogen-Embrittlement-Aware Crack Evolution Modeling for Additively Manufactured Pressure-Bearing Components: A Systematic Review

Abstract

The unique microstructures, defect populations, and residual stresses created by Additively Manufactured (AM) metallic components make prediction of hydrogen-assisted cracking highly complex and require more research. This systematic review collates 22 sources from the AM process science, hydrogen embrittlement (HE) mechanisms, experimental data on AM alloys and phase field fracture theory in a coherent framework to develop crack evolution modelling of AM pressure-bearing components accounting for HE. Stress-assisted multi-trap hydrogen transport is combined with Taylor-based crack-tip hardening models, first-principles-informed fracture energy degradation models, regularised phase field fracture models and hydrogen-accelerated fatigue models and tested against reported benchmarks. The synthesis indicates that hydrogen charging at −50 °C did not significantly affect the ductility of the conventionally manufactured 316L but did cause the hot isostatically pressed AM 316L to have almost double the ductility, the elongation based embrittlement index of laser powder bed fused 316L lattices increased from approximately 4.0% to 17.6% as the thickness of the struts increased from 0.6 to 1.4 mm, and hydrogen caused the rate of fatigue crack propagation in heat-treated laser powder bed fused Inconel 718 to increase by a factor of 2.8. Damage coefficients of 0.89, 0.67, and 0.41 are used for the degradation laws of the iron, aluminium, and nickel anchor, while explicit consideration of the evolution of hydride and Ti3Al has to be made for electron beam melted Ti-6Al-4V between 0.29 and 0.90 wt.% hydrogen. The major barriers are: (1) unmeasured trap energetics in printed microstructures, (2) limited gaseous-hydrogen fatigue data, and (3) lack of qualifying criteria based on simulations.