Abstract
Full Text
CHEMISTRY
R. B. Golubtsova and L. A. Nudz
STUDY OF THE CONDITIONS FOR ISOLATING THE METALLIC COMPOUND Ni₃Al FORMED IN MULTICOMPONENT NICKEL ALLOYS
(Presented by Academician I. I. Chernyaev on 16 IX 1961)
This paper presents the results of a study of metallic compounds formed in alloys* of the system Ni—Cr—W—Mo—Al—Nb—Ti, isolated by the method of electrolytic dissolution. The chemical composition and heat-treatment conditions of the alloys are given in Table 1.
Table 1
| Alloy No. | Heat-treatment conditions | Al | Nb | Ti | Cr | W | Mo | Ni |
|---|---|---|---|---|---|---|---|---|
| 1 | 1200°—100 h | 4.33 | — | — | 9.60 | 6.09 | 3.02 | balance |
| 2 | 1200°—100 h | 3.86 | 3.00 | — | 9.50 | 6.00 | 3.00 | balance |
| 3 | 1200°—200 h | 6.87 | 1.59 | — | 9.56 | 6.10 | 2.90 | balance |
| 4 | 1200°—200 h | 8.47 | — | — | 3.43 | 2.41 | 1.12 | balance |
| 5 | 1100°—200 h | 3.46 | — | 3.85 | 9.65 | 5.50 | 2.72 | balance |
The cast alloys were heated to 1100 or 1200°, held for 100 or 200 h, and cooled in air.
To select conditions for the electrolytic dissolution of the indicated alloys, electrolytes widely used by various authors for isolating the γ′ phase from nickel-base alloys were tested (¹–³). The comparative data obtained are presented in Table 2 and in Fig. 1.
Table 2
Results of chemical and X-ray structural analysis of anodic powders isolated from alloy No. 1
| Electrolyte No.* | Current density, A/cm² | Dissolution duration, min | Weight of dissolved anode, g | Ni | Cr | Al | Mo | W | Total | Ni | Cr | Al | Mo | W | Ni/Al | X-ray structural analysis data |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 0.075 | 30 | 0.4090 | 8.60 | 0.55 | 1.30 | 0.27 | 1.25 | 11.97 | 68.26 | 4.89 | 22.42 | 1.31 | 3.12 | 3.05 | Ni₃Al |
| 2 | 0.075 | 30 | 0.4012 | 8.42 | 0.55 | 1.27 | 0.27 | 1.21 | 11.72 | 68.22 | 5.00 | 22.36 | 1.33 | 3.09 | 3.05 | Ni₃Al |
| 3 | 0.25 | 9 | 0.4028 | 8.51 | 0.54 | 1.29 | 0.27 | 1.21 | 11.82 | 68.20 | 4.85 | 22.57 | 1.32 | 3.06 | 3.02 | Ni₃Al |
| 4 | 0.05 | 45 | 0.3926 | 8.47 | 0.54 | 1.28 | 0.27 | 1.23 | 11.79 | 68.26 | 4.88 | 22.42 | 1.32 | 3.12 | 3.04 | Ni₃Al |
| 5 | 0.05 | 45 | 0.3602 | 8.44 | 0.55 | 1.27 | 0.26 | 1.22 | 11.74 | 68.31 | 4.98 | 22.30 | 1.28 | 3.13 | 3.06 | Ni₃Al |
* For the composition of the electrolytes, see the caption to Fig. 1.
As is evident from the data obtained (Table 2), from alloy No. 1 in all electrolytes an anodic powder is isolated, which is a solid solution based on the chemical compound Ni₃Al (in an amount of 11.8%), with a composition close to the stoichiometric one. The potential arising in
* The indicated alloys are being studied by L. I. Pryakhina for the purpose of constructing a phase diagram.
in the process of anodic dissolution of the alloy under study No. 1 at various electrolytic regimes, ranges from \(+1.25\) V to \(+1.39\) V (Fig. 1).
All the electrolytes used ensure preservation of the \(\mathrm{Ni}_3\mathrm{Al}\) phase during its electrolytic isolation. However, as the best one we selected the electrolyte with methanol (1), which completely prevents the hydrolytic precipitation of niobic and tungstic acids. Anodic dissolution of the alloys under study in this electrolyte takes place at an anodic-potential value from \(+1.35\) V to \(+1.5\) V (Fig. 2). Under these conditions the quantitative isolation of the \(\mathrm{Ni}_3\mathrm{Al}\) phase is also ensured.
According to the data obtained, the phase isolated from various alloys is a solid solution based on the chemical compound \(\mathrm{Ni}_3\mathrm{Al}\), in which other elements are dissolved (see Table 3). To check for the possible presence, in addition to \(\mathrm{Ni}_3\mathrm{Al}\), of other phases (for example, \(\mathrm{Ni}_3\mathrm{Nb}\)), we subjected alloys containing niobium to anodic dissolution in another electrolyte intended for isolating \(\mathrm{Ni}_3\mathrm{Nb}\) (4, 5). In this case dissolution of the alloys occurs at a low value of the anodic potential (Fig. 3), and no anodic powder is isolated. This indicates that in the alloys investigated only one intermetallic compound, \(\mathrm{Ni}_3\mathrm{Al}\), is formed, which is not isolated in the electrolyte tested.
To determine the amount of the \(\mathrm{Ni}_3\mathrm{Al}\) phase in the alloys, and also to establish the distribution of alloying elements between the basic \(\gamma\)-solid solution and the \(\mathrm{Ni}_3\mathrm{Al}\) phase, anodic dissolution of the alloys was carried out in the selected electrolyte (1), followed by chemical analysis of the anodic powder. From the data obtained, the distribution of alloying elements between the phases was calculated (see Table 4).
The \(\gamma\)-solid solution + \(\mathrm{Ni}_3\mathrm{Al}\) phase given in Table 4 corresponds to the composition of the alloy. The \(\mathrm{Ni}_3\mathrm{Al}\) phase represents the composition of the anodic powder, referred to the weight of the alloy-anode dissolved during the experiment. The composition of the \(\gamma\)-solid solution was calculated from the difference between the contents of the elements in the alloy and in the anodic powder.
Table 3
Chemical and X-ray structural analysis of anodic powders isolated in the electrolyte: 35 g citric acid, 5 g \((\mathrm{NH}_4)_2\mathrm{SO}_4\), 15 ml \(\mathrm{HNO}_3\) (1:4); 1000 ml \(\mathrm{CH}_3\mathrm{OH}\), \(i = 0.075\ \mathrm{A/cm^2}\)
| Alloy No. | Chemical composition of anodic powders, wt. %: Ni | Chemical composition of anodic powders, wt. %: Al | Chemical composition of anodic powders, wt. %: Nb | Chemical composition of anodic powders, wt. %: Ti | Chemical composition of anodic powders, wt. %: Cr | Chemical composition of anodic powders, wt. %: W | Chemical composition of anodic powders, wt. %: Mo | Chemical composition of anodic powders, wt. %: sum | Chemical composition of anodic powders, at. %: Ni | Chemical composition of anodic powders, at. %: Al | Chemical composition of anodic powders, at. %: Nb | Chemical composition of anodic powders, at. %: Ti | Chemical composition of anodic powders, at. %: Cr | Chemical composition of anodic powders, at. %: W | Chemical composition of anodic powders, at. %: Mo | Chemical composition of anodic powders, at. %: ratio Ni : Al | X-ray structural analysis data** |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 71.92 | 10.84 | — | — | 4.60 | 10.33 | 2.25 | 99.94 | 68.33 | 22.36 | — | — | 4.91 | 3.12 | 1.28 | 3.05 | \(\mathrm{Ni}_3\mathrm{Al},\ a = 3.56\ \mathrm{kX}\) |
| 2 | 73.60 | 10.89 | 5.66 | — | 3.27 | 5.44 | 0.86 | 99.72 | 69.05 | 22.19 | 3.30 | — | 3.42 | 1.60 | 0.44 | 3.11 | \(\mathrm{Ni}_3\mathrm{Al},\ a = 3.5769\ \mathrm{kX}\) |
| 3 | 74.46 | 11.29 | 3.12 | — | 5.05 | 3.27 | 2.17 | 99.83 | 68.55 | 22.38 | 1.77 | — | 5.21 | 0.91 | 1.18 | 3.06 | \(\mathrm{Ni}_3\mathrm{Al},\ a = 3.5674\ \mathrm{kX}\) |
| 4 | 80.17 | 12.25 | — | — | 2.87 | 2.95 | 1.48 | 99.72 | 71.65 | 23.83 | — | — | 2.89 | 0.84 | 0.79 | 3.00 | \(\mathrm{Ni}_3\mathrm{Al},\ a = 3.5580\ \mathrm{kX}\) |
| 5 | 78.34 | 8.86 | — | 6.66 | 2.61 | 2.09 | 0.98 | 99.54 | 71.26 | 17.52 | — | 7.43 | 2.67 | 0.59 | 0.53 | 2.85* | \(\mathrm{Ni}_3\mathrm{Al},\ a = 3.5744\ \mathrm{kX}\) |
* Here the ratio \(\mathrm{Ni}/\mathrm{Al}, \mathrm{Ti}\) is given.
** X-ray structural analysis was performed in the X-ray laboratory of TsNIITMASH by R. I. Rogovoi, Yu. G. Sorokina, and V. A. Smirnova under the direction of S. A. Yuganova.
Table 4
Distribution of elements between the $\gamma$-solid solution and the $\mathrm{Ni}_3\mathrm{Al}$ phase
| Alloy No. | Constituent phases of the alloys studied | Ni* | Cr | W | Mo | Nb | Ti | Al | Total |
|---|---|---|---|---|---|---|---|---|---|
| 1 | $\gamma$-solid solution + $\mathrm{Ni}_3\mathrm{Al}$ phase | 76.96 | 9.60 | 6.09 | 3.02 | — | — | 4.33 | 100.00 |
| 1 | $\mathrm{Ni}_3\mathrm{Al}$ phase | 8.60 | 0.55 | 1.25 | 0.27 | — | — | 1.30 | 11.97 |
| 1 | $\gamma$-solid solution | 68.36 | 9.05 | 4.84 | 2.75 | — | — | 3.03 | 88.03 |
| 2 | $\gamma$-solid solution + $\mathrm{Ni}_3\mathrm{Al}$ phase | 74.64 | 9.50 | 6.00 | 3.00 | 3.00 | — | 3.86 | 100.00 |
| 2 | $\mathrm{Ni}_3\mathrm{Al}$ phase | 19.62 | 0.87 | 1.44 | 0.23 | 1.52 | — | 2.91 | 26.59 |
| 2 | $\gamma$-solid solution | 55.02 | 8.63 | 4.56 | 2.77 | 1.48 | — | 0.95 | 73.41 |
| 3 | $\gamma$-solid solution + $\mathrm{Ni}_3\mathrm{Al}$ phase | 72.98 | 9.56 | 6.10 | 2.90 | 1.59 | — | 6.87 | 100.00 |
| 3 | $\mathrm{Ni}_3\mathrm{Al}$ phase | 37.30 | 2.50 | 1.60 | 1.04 | 1.56 | — | 5.57 | 49.57 |
| 3 | $\gamma$-solid solution | 35.68 | 7.06 | 4.50 | 1.86 | 0.03 | — | 1.30 | 50.43 |
| 4 | $\gamma$-solid solution + $\mathrm{Ni}_3\mathrm{Al}$ phase | 84.57 | 3.43 | 2.41 | 1.12 | — | — | 8.47 | 100.00 |
| 4 | $\mathrm{Ni}_3\mathrm{Al}$ phase | 13.87 | 0.50 | 0.51 | 0.25 | — | — | 2.12 | 17.25 |
| 4 | $\gamma$-solid solution | 70.70 | 2.93 | 1.90 | 0.87 | — | — | 6.35 | 82.75 |
| 5 | $\gamma$-solid solution + $\mathrm{Ni}_3\mathrm{Al}$ phase | 74.82 | 9.65 | 5.50 | 2.72 | — | 3.85 | 3.46 | 100.00 |
| 5 | $\mathrm{Ni}_3\mathrm{Al}$ phase | 30.60 | 1.02 | 0.83 | 0.39 | — | 2.60 | 3.46 | 38.90 |
| 5 | $\gamma$-solid solution | 44.22 | 8.63 | 4.67 | 2.33 | — | 1.25 | 0.0 | 61.10 |
* The nickel content in the alloy was calculated by difference.
Fig. 1. Change in anodic potential as a function of the amount of electricity passed through the electrolyte during dissolution of alloy No. 1. Electrolytes: 1—1000 ml $\mathrm{CH_3OH}$, 35 g citric acid, 5 g $(\mathrm{NH_4})_2\mathrm{SO_4}$, 15 ml $\mathrm{HNO_3}$ (1.4); 2—1000 ml $\mathrm{H_2O}$, 35 g citric acid, 5 g $(\mathrm{NH_4})_2\mathrm{SO_4}$, 15 ml $\mathrm{HNO_3}$ (1.4); 3—1000 ml $\mathrm{H_2O}$, 10 g ammonium citrate, 100 g $\mathrm{CuSO_4}$, 10 ml $\mathrm{H_2SO_4}$ (1.84)(2); 4—1000 ml $\mathrm{H_2O}$, 10 g ammonium citrate, 20 g $\mathrm{CuSO_4}$, 5 ml $\mathrm{H_2SO_4}$ (1.84)(2); 5—1000 ml $\mathrm{H_2O}$, 9 g citric acid, 9 g $(\mathrm{NH_4})_2\mathrm{SO_4}$.
Fig. 2. Change in anodic potential with time during electrolytic dissolution of the alloys (electrolyte: 1000 ml $\mathrm{CH_3OH}$, 35 g citric acid, 5 g $(\mathrm{NH_4})_2\mathrm{SO_4}$, 15 ml $\mathrm{HNO_3}$ (1.4)). The curve numbers correspond to the alloy numbers.
Fig. 3. Change in anodic potential with time during electrolytic dissolution of the alloys (electrolyte: 1000 ml $\mathrm{CH_3OH}$, 35 g citric acid, 50 ml $\mathrm{HCl}$ (1.19)). 1—alloy No. 3; 2—alloy No. 2.
The investigation carried out showed the reliability of the selected optimum regime for isolating the compound $\mathrm{Ni}_3\mathrm{Al}$ from multicomponent nickel-base alloys containing Cr, W, Mo, Al, Nb, Ti. It has been shown,
that in the multicomponent alloys studied, one of the constituent phases is the metallic compound $\mathrm{Ni}_3\mathrm{Al}$.
Institute of Metallurgy named after A. A. Baikov
Academy of Sciences of the USSR
Central Scientific Research Institute
of Technology and Machine Building
Received
5 IX 1961
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