The superalloys were heat-treated so as to obtain various microstructures. The H permeability (tables 113 and 114) and diffusivity (tables 115 and 116) were then determined by using a gaseous H permeation technique to study the effect of the microstructure upon the permeation behavior at temperatures ranging from 210 to 430C. It was shown that the temperature dependences of H permeability and diffusivity obeyed an Arrhenius law, and that the precipitated strengthening phases hardly affected the H permeation and diffusion behavior in IN718, but the H permeability and diffusivity in the aged condition were all slightly lower than those in the solution-treated condition for GH761.

J.Xu, X.K.Sun, Q.Q.Liu, W.X.Chen: Metallurgical Transactions A, 1994, 25[3], 539-44

 

 

 

Table 113

Permeability of H in IN718

 

Heat Treatment

o (mol/msMPa½)

Q (kJ/mol)

cold-rolled 75%

0.000198

59.03

980C, 2h; a

0.000236

60.19

980C, 2h; a; 720C, 8h; f; 620C 8h; a

0.000212

59.53

980C, 2h; a; 720C, 100h; a

0.000259

62.69

a: air-cooled, f: furnace-cooled

 

 

 

Table 114

Permeability of H in GH761

 

Heat Treatment

o (mol/msMPa½)

Q (kJ/mol)

1090C, 2h; w

0.000352

63.45

1090C, 2h; w; 850, 4h; a

0.000177

62.39

1090C, 2h; w; 850, 4h; a; 750C, 24h; a

0.0000890

58.23

1090C, 2h; w; 770, 4h; a

0.000777

70.57

a: air-cooled, f: furnace-cooled, w: quenched

 

 

 

Table 115

Diffusivity of H in IN718

 

Heat Treatment

Do (m2/s)

Q (kJ/mol)

cold-rolled 75%

2.82 x 10-7

45.82

980C, 2h; a

1.82 x 10-7

45.30

980C, 2h; a; 720C, 8h; f(50C/h); 620C 8h; a

6.16 x 10-7

51.22

980C, 2h; a; 720C, 100h; a

8.33 x 10-7

52.05

a: air-cooled, f: furnace-cooled

 

 

 

Table 116

Diffusivity of H in GH761

 

Heat Treatment

Do (m2/s)

Q (kJ/mol)

1090C, 2h; w

4.61 x 10-7

49.80

1090C, 2h; w; 850, 4h; a

1.91 x 10-7

60.93

1090C, 2h; w; 850, 4h; a; 750C, 24h; a

1.23 x 10-7

60.39

1090C, 2h; w; 770, 4h; a

6.37 x 10-7

57.01

a: air-cooled, w: quenched