Hydrogen in Steel Visualized by Energy-resolved Neutron Imaging

Visualizing hydrogen distributions via neutron imaging allows for quantification and a better interpretation of the processes involved in hydrogen embrittlement (HE)-assisted fatigue crack growth in austenitic and martensitic steels. Hydrogen is identified from the transmission intensities in both charged and uncharged samples. A gradient of hydrogen within the samples depending on outward diffusion of hydrogen with time is going to be considered. Once the detection limits on IMAT have been established, local hydrogen detection ahead of crack tips will be examined and correlated to fatigue crack growth rates (FCGRs). Samples strained and unstrained are considered for this purpose to understand the effect of straining, thus facilitating an understanding of the relationship between H concentration and FCGRs in steel. A major aspect of this methodical study is to utilize energy-resolved neutron imaging for detection of hydrogen in steel. Correlation of Bragg edge transmission at shorter neutron wavelengths with imaging beyond the Bragg edge cutoff of steel will allow optimizing hydrogen contrast. The outcome of this experiment will advance our mechanistic understanding of hydrogen transport, storage and embrittlement in structural materials