Cycled hydrogen permeation through Armco iron – a joint experimental and modeling approach

Understanding hydrogen embrittlement in steels requires research in hydrogen diffusion and trapping at microstructural defects. The present paper deals with hydrogen permeation and trapping at defects in the base material, Armco iron, eliminating effects coupled with alloying and precipitation. Cycled permeation curves are recorded and evaluated by using sound diffusion models to identify hydrogen trap sites as dislocations, grain boundaries and vacancies and assign their trapping energies. Furthermore, trap densities are evaluated and used together with the trapping energies as parameters in an adapted diffusion equation for hydrogen, interpreting the experiments significantly better than simple use of classical Fick's laws.