Measurements of H evolution rates were used to study the lattice, and overall, diffusion rates in various alloys. Classical reaction kinetics were used to describe the movement of H in ferritic steels at 100 to 350C. The processes of H lattice diffusion and H release from traps in the metal were treated as being consecutive reactions, with the former being the rate-controlling one at high temperatures and the latter controlling at low temperatures. In the intermediate region, where neither process was predominant, there was a gradual transition from one mode of reaction to another. The true lattice and overall diffusivity coefficients were calculated in the intermediate-temperature region (table 51).

F.R.Coe, J.Moreton: Metal Science Journal, 1969, 3, 209-15

 

 

 

Table 51

Diffusivity of H in Fe Alloys

 

C (%)

Mn (%)

Cr (%)

Temperature (C)

Dlattice (cm2/s)

Doverall (cm2/s)

0.055

1.5

-

640

-

1.0 x 10-4

0.055

1.5

-

410

-

7.6 x 10-5

0.055

1.5

-

330

-

6.4 x 10-5

0.055

1.5

-

270

1.0 x 10-4

6.6 x 10-5

0.055

1.5

-

105

3.9 x 10-5

2.7 x 10-5

0.055

1.5

-

55

-

3.1 x 10-6

0.055

1.5

-

20

-

2.0 x 10-6

0.003

-

5.58

640

-

1.8 x 10-4

0.003

-

5.58

545

 

1.4 x 10-4

0.003

-

5.58

450

1.8 x 10-4

1.1 x 10-4

0.003

-

5.58

350

1.7 x 10-4

9.9 x 10-5

0.003

-

5.58

250

1.0 x 10-4

5.8 x 10-5

0.003

-

5.58

200

7.8 x 10-5

3.5 x 10-5

0.003

-

5.58

120

5.2 x 10-5

3.0 x 10-5

0.003

-

5.58

103

3.9 x 10-5

2.3 x 10-6

0.003

-

5.58

80

-

7.0 x 10-6

0.003

-

5.58

50

-

2.3 x 10-6

0.003

-

5.58

30

-

1.8 x 10-6

0.73

-

-

650

-

9.9 x 10-5

0.73

-

-

395

-

7.5 x 10-5

0.73

-

-

350

1.0 x 10-4

5.1 x 10-5

0.73

-

-

310

1.0 x 10-4

5.1 x 10-5

0.73

 

-

250

8.9 x 10-5

6.2 x 10-5

0.73

-

-

210

8.9 x 10-5

6.2 x 10-5

0.73

-

-

155

7.8 x 10-5

4.9 x 10-5

0.73

-

-

60

-

2.0 x 10-7

0.73

-

-

44

-

5.2 x 10-8