Quantitative investigation on deep hydrogen trapping in tempered martensitic steel

In this work, the correlation between different microstructural components and hydrogen trapping with high density in tempered niobium carbide (NbC)-precipitated martensitic steel was quantitatively investigated using a combination of electrochemical hydrogen permeation experiments and thermal desorption spectroscopy. The martensite lath and a high density of dislocations, which constitute the reversible hydrogen trapping sites, with a density of 2.24 × 10²⁰ cm⁻³ in Fe-0.05C-1.10Mn-4.50Ni-0.50Cr-0.50Mo-0.05Nb wt.% martensitic steel. The dislocation with high density could disperse the hydrogen distribution. Furthermore, the uniformly distributed NbC nanoprecipitates, the high-angle grain boundaries, and the grain-boundary precipitates were found to act as irreversible hydrogen traps, with a density of 1.00 × 10²⁰ cm⁻³. These deep hydrogen trapping sites could not only trap hydrogen irreversibly, but also can inhibit the accumulation of hydrogen. The interpretation of hydrogen trapping is significant to enhance the hydrogen embrittlement resistance of high-strength martensitic steels.