Pev. Demiranda et Fd. Fassini, NEW METHODOLOGY FOR THE DETERMINATION OF HYDROGEN PERMEATION PARAMETERS IN LAYERED MATERIALS, Journal of Materials Science, 28(19), 1993, pp. 5148-5154
A new methodology for interpreting hydrogen permeation test data has b
een proposed with the objective of determining hydrogen permeability,
solubility and diffusivity in materials containing surface-coating lay
ers. The mathematical development of equations has been undertaken for
steady-state hydrogen permeation conditions allowing the determinatio
n of all parameters of interest for the composite material and the coa
ting layer itself. For a single-layered material, a set of three stati
stically significant permeation tests is enough to determine all varia
bles for the substrate, the composite material and the coating layer.
This methodology has been applied to published results on the hydrogen
permeation in nitrogen ion-implanted extra-low carbon steel, showing
that the hydrogen diffusion coefficient in such a coating layer is sev
eral orders of magnitude lower than that in the substrate. The hydroge
n solubility in the layer is, by contrast, increased. The magnitudes o
f these effects depend on the nitrogen concentration in the surface la
yer.