A Feasibility study on quantifying hydrogen uptake in steels by neutron imaging

Hydrogen (H2) ingress can dramatically alter mechanical performance, leading to phenomena such as embrittlement, delayed cracking, and premature failure. However, the extent and nature of these effects are strongly dependent on the microstructure and crystallographic structure of the material. Different crystal structures exhibit markedly different behaviours in the presence of H2. Ferritic steels such as X70 pipeline steel, typically show higher diffusivity but lower solubility, making them more susceptible to hydrogen embrittlement (HE) under certain conditions. On the other hand, FCC materials, such as austenitic stainless steels, generally have higher H2 solubility and better resistance to HE, though localised effects such as stress-assisted diffusion and trapping can still cause concern.
Conventional ex-situ methods for measuring H2 content, such as infrared absorption and thermal conductivity, are often destructive and suffer from inaccuracies. Others, such as thermal desorption spectroscopy (TDS), are limited by H2 degassing, restricted spatial resolution, and constraints on sample size. In contrast, in-situ techniques like neutron imaging offer a powerful, non-destructive means to monitor internal strains and correlate lattice changes with H2 uptake in real time. Establishing this correlation is a crucial first step toward understanding how H2 is absorbed, trapped, and retained across different material systems and weld regions.