Diffusion in the Ni3Al phase was investigated at various temperatures using NiAlX (X = Ti, V, Nb, Mo, Ta) pseudo-binary diffusion couples (table 21). The magnitude of the interdiffusion coefficients was in the descending order of V, Mo, Ti, Nb and Ta at all experimental temperatures ranging from 1423 to 1573K. Diffusion data obtained in this study were compared with those of Re and Ru available in the literature as Re and Ru were now being added to modern Ni-based superalloys. Diffusion retardation occurred for Ti, V, Nb, Mo and Ta as compared to Ru, and this could be explained by an anti-site diffusion mechanism. The high activation energy for anti-site formation was required for β-site (Al-site) elements, such as Ti, V, Nb, Mo and Ta. However, as Ru could diffuse either via α- (Ni-site) or β-site preferences without creating local disorder, Ru diffusion was not retarded by the anti-site diffusion mechanism.
Diffusion of Al and Al-Substituting Elements in Ni3Al at Elevated Temperatures. Moniruzzaman, M., Fukaya, H., Murata, Y., Tanaka, K., Inui, H.: Materials Transactions, 2012, 53[12], 2111-8
Table 20
Average ternary interdiffusion coefficients in Ni3Al
Treatment | Coefficient | Value (m2/s) |
1523K, 100h | DMoMoAl | 3.64 x 10-15 |
1523K, 100h | DMoMoNi | 2.10 x 10-15 |
1523K, 100h | DAlAlNi | 1.60 x 10-13 |
1523K, 100h | DNiNiAl | 7.50 x 10-13 |
1523K, 100h | DMoAlNi | 2.42 x 10-15 |
1523K, 100h | DAlMoNi | 2.51 x 10-14 |
1523K, 100h | DMoNiAl | 4.50 x 10-16 |
1523K, 100h | DNiMoAl | 1.71 x 10-14 |
1473K, 120h | DMoMoAl | 6.70 x 10-16 |
1473K, 120h | DMoMoNi | 4.60 x 10-16 |
1473K, 120h | DAlAlNi | 4.10 x 10-14 |
1473K, 120h | DNiNiAl | 1.43 x 10-13 |
1473K, 120h | DMoAlNi | 1.82 x 10-15 |
1473K, 120h | DAlMoNi | 1.47 x 10-14 |
1473K, 120h | DMoNiAl | 3.91 x 10-16 |
1473K, 120h | DNiMoAl | 1.01 x 10-14 |
1423K, 120h | DMoMoAl | 2.10 x 10-16 |
1423K, 120h | DMoMoNi | 1.40 x 10-16 |
1423K, 120h | DAlAlNi | 1.32 x 10-14 |
1423K, 120h | DNiNiAl | 3.17 x 10-14 |
1423K, 120h | DMoAlNi | 7.80 x 10-16 |
1423K, 120h | DAlMoNi | 8.28 x 10-15 |
1423K, 120h | DMoNiAl | 1.06 x 10-16 |
1423K, 120h | DNiMoAl | 4.36 x 10-15 |
Figure 23
Tracer diffusion coefficient of Mo in Ni3Al