Interaction of hydrogen with the microstructure of low-carbon steel

The interaction of hydrogen (H) with the microstructure of SAE 1008 type low-carbon steel is studied in this work. The objective is to determine the binding energy, ΔE, of H with the cementite (Fe3C) for three different conditions of the carbide. Electrochemical permeation tests are combined with the numerical resolution of Fick's equations assuming that hydrogen is delayed during de transport by reversible trapping sites. Techniques of H vacuum desorption are also employed to describe irreversible trapping. From permeation tests, we obtain the density of reversible trapping sites and the probabilities of H capture and release from which ΔE is evaluated. From effusion test, weak and strong trapping sites with energies in the range of ΔE ≈ 10–50 kJ/mol H were observed.