Measurements were made of H migration, in cryoformed samples, by using a gas-phase permeation technique. The specimens contained about 90% of α' martensite. It was found that the H diffusivity, described by:

D (cm2/s) = 3.7 x 10-2 exp[-41.4(kJ/mol)/RT]

was between the values for α- and γ-type steels. The separation of the permeation values, as described by:

P (cm3/cm s Pa½) = 1.57 x 10-5 exp[-43.5(kJ/mol)/RT]

was less clear. The difference between the activation energies for diffusion and permeation was considered to be anomalously low.

Hydrogen Permeation and Diffusion in Cryoformed AISI 301 Stainless Steel. T.P.Perng, C.J.Altstetter: Scripta Metallurgica, 1984, 18[1], 67-70

Table 59

Diffusion Parameters for H in Stainless Steels at 200 to 430C