A sensitive gas-phase technique was used to measure the transport parameters at temperatures ranging from 600 to 700K. It was found that the permeability and diffusivity of H in the stainless steel increased as the degree of sensitization increased (tables 62 and 63). This behavior was attributed to the depletion of Cr at the grain boundaries. An electrical analogue confirmed the importance of sensitization. On the basis of this model, the diffusivity in the grain-boundary zone was estimated to be 7.6 x 10-6cm2/s at 673K. The apparent solubility increased with the sensitization time.

D.L.Johnson, D.A.Davis: Scripta Metallurgica, 1989, 23[3], 321-6

 

 

 

Table 62

Permeation Parameters for AISI 304 Stainless Steel

 

Treatment

Po (cm3N-½/s)

E (kJ/mol)

as-received

1.02 x 10-5

49.50

1.5h, 923K

7.80 x 10-2

91.53

3.0h, 923K

3.42 x 10-5

46.87

 

 

 

Table 63

Bulk Diffusion Parameters for AISI 304 Stainless Steel

 

Treatment

Do (cm2/s)

E (kJ/mol)

as-received

1.03 x 10-4

36.20

1.5h, 923K

3.47 x 10-5

29.52

3.0h, 923K

7.47 x 10-6

19.02