An investigation was made of the permeability of a series of steels (containing up to 1.0%C and having a granular cementite structure) at 140 to 650C. It was found that ln[P] decreased linearly with increasing C-content, and increased with increasing temperature. There was a break in the Arrhenius plot at 400C. The effective activation energy at high temperatures was 18kcal/mol while, at low temperatures, it was 22.5kcal/mol. After deformation and annealing at 270C, the permeability was higher than in the initial (non-deformed) state. Increasing the annealing temperature to 375C reduced the permeability, but a further increase to 420C again increased the permeability.

V.A.Goltsov, V.P.Levchenko, P.V.Geld: Fiziko-Khimicheskaya Mekhanika Materialov, 1969, 5[5], 588-91