The migration of H was measured by using a gas permeation technique. Plastic deformation of the ferritic stainless steel was found to decrease markedly the diffusion (table 57) and permeation (table 58) of H and to increase slightly the solubility. The differences in behavior of this, and other, stainless steels were explained in terms of trapping and phase transformations. The uniformly deformed material was studied with the aim of eventually simulating the state of the material at the tip of a H-embrittlement crack. The observed differences in the crack propagation behaviors of the alloys could be rationalized in terms of H transport and solubility in the deformed state.

T.P.Perng, M.Johnson, C.J.Altstetter: Acta Metallurgica, 1989, 37[12], 3393-7

 

 

 

Table 57

Effect of Deformation upon H Diffusion Parameters

for Fe-Cr-Mo-Ni (AL 29-4-2)

 

Deformation (%)

Do (cm2/s)

E (kJ/mol)

0

6.40 x 10-5

7.0a

0

8.45 x 10-2

33.7b

25

1.71 x 10-2

36.7

50

2.34 x 10-2

37.2

75

9.03 x 10-2

45.5

a: temperatures greater than 170C

b: temperatures less than 170C

 

 

 

Table 58

Effect of Deformation upon H Permeation Parameters

for Fe-Cr-Mo-Ni (AL 29-4-2)

 

Deformation (%)

Po (cm2/sPa½)

E (kJ/mol)

0

2.20 x 10-6

38.4a

25

6.60 x 10-7

40.3b

50

2.75 x 10-6

45.4b

75

2.96 x 10-6

47.3b

a: 80 to 320C, b: 110 to 260C