The superalloy was heat-treated so as to obtain various microstructures. The H permeability (table 197) and diffusivity (table 198) were then determined by using a gaseous H permeation technique to study the effect of the microstructure upon the permeation behavior at 210 to 430C. It was shown that the temperature dependences of H permeability and diffusivity obeyed an Arrhenius law, and that the permeability and diffusivity in the aged condition were all slightly lower than those in the solution-treated condition.

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

 

Table 186

Diffusivity of H in IN718

 

Heat Treatment

Do (m2/s)

E (kJ/mol)

cold-rolled 75%

2.82 x 10-7

45.82

980C, 2h; ac

1.82 x 10-7

45.30

980C, 2h; ac; 720C, 8h; fc(50C/h); 620C 8h; ac

6.16 x 10-7

51.22

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

8.33 x 10-7

52.05

ac: air-cooled, fc: furnace-cooled