The superalloys were heat-treated so as to obtain various microstructures. The H permeability (tables 35 and 36) and diffusivity (tables 37 and 38) 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 35
Permeability of H in IN718
Heat Treatment |
0(mol/msMPa½) |
Q(kJ/mol)
|
cold-rolled 75% |
0.000198 |
59.03 |
980C, 2h; ac | 0.000236 | 60.19 |
980C, 2h; ac; 720C, 8h; fc(50C/h); 620C 8h; ac | 0.000212 | 59.53 |
980C, 2h; ac; 720C, 100h; ac | 0.000259 | 62.69 |
ac: air-cooled, fc: furnace-cooled
Table 36
Permeability of H in GH761
Heat Treatment |
0(mol/msMPa½) |
Q(kJ/mol)
|
1090C, 2h; wc |
0.000352 |
63.45 |
1090C, 2h; wc; 850, 4h; ac | 0.000177 | 62.39 |
1090C, 2h; wc; 850, 4h; ac; 750C, 24h; ac | 0.0000890 | 58.23 |
1090C, 2h; wc; 770, 4h; ac | 0.000777 | 70.57 |
ac: air-cooled, fc: furnace-cooled
Table 37
Diffusivity of H in IN718
Heat Treatment |
D0(m2/s) |
Q(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
Table 38
Diffusivity of H in GH761
Heat Treatment |
D0(m2/s) |
Q(kJ/mol)
|
1090C, 2h; wc |
4.61 x 10-7 |
49.80 |
1090C, 2h; wc; 850, 4h; ac | 1.91 x 10-7 | 60.93 |
1090C, 2h; wc; 850, 4h; ac; 750C, 24h; ac | 1.23 x 10-7 | 60.39 |
1090C, 2h; wc; 770, 4h; ac | 6.37 x 10-7 | 57.01 |
ac: air-cooled, fc: furnace-cooled