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.

Hydrogen Permeation Behavior in IN718 and GH761 Superalloys. J.Xu, X.K.Sun, Q.Q.Liu, W.X.Chen: Metallurgical Transactions A, 1994, 25[3], 539-44

 

Table 116

Diffusivity of H in GH761

 

Heat Treatment

Do (m2/s)

E (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