Abstract Generated abstract
This paper examines the phase composition of nickel-boron alloys containing 0.01 to 2.5 percent boron, with particular attention to the nickel-rich boride reported as Ni3B. The authors used metallographic observation, chemical and electrolytic isolation of precipitated phases, chemical analysis, and powder X-ray diffraction to characterize the boride separated from cast alloys. The isolated phase consistently gave a nickel-to-boron atomic ratio close to 3:1 and the same diffraction pattern across separation methods, supporting its identification as Ni3B. The study concludes that Ni3B exists in the binary Ni-B system and forms a eutectic with the nickel-based solid solution.
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CHEMISTRY
N. I. BLOK, M. N. KOZLOVA, N. F. LASHKO, and K. Ya. SHPUNT
ON THE COMPOUND $\mathrm{Ni_3B}$ IN NICKEL—BORON ALLOYS
(Presented by Academician S. I. Volfkovich, 30 XI 1956)
The binary phase diagram of Ni—B (up to 20% B) was first constructed by Guertler in 1915 ($^1$). Guertler found that the nickel-richest compound in the Ni—B system is $\mathrm{Ni_2B}$. Binet de Chassonne ($^2$) isolated this compound in nickel alloys with 5% B. Börstrom ($^3$), in an X-ray structural study of a Ni—B alloy, established that the $\mathrm{Ni_2B}$ phase (8.44% B) is isomorphous with the phases $\mathrm{Fe_2B}$ and $\mathrm{Co_2B}$ and has a body-centered tetragonal crystal lattice with parameters: $a = 4.90$ kX, $c = 4.236$ kX. Kiessling ($^4$), as a result of an X-ray structural study, indicated the existence in nickel-rich alloys, in addition to the $\mathrm{Ni_2B}$ phase, also of the $\mathrm{Ni_3B}$ phase, but did not give any data characterizing it.
Table 1
Content of Ni and B in the insoluble residue after heating the alloy with $\mathrm{H_2SO_4}$ (1 : 2) until dissolution ceased
| B in alloy, % | Ni in insoluble residue, % | B in insoluble residue, % | Ratio of atomic indices Ni : B |
|---|---|---|---|
| 0.19 | 1.48 | 0.085 | 3.2 : 1 |
| 0.34 | 2.48 | 0.17 | 2.8 : 1 |
| 1.62 | 13.6 | 0.76 | 3.3 : 1 |
| 2.27 | 20.0 | 1.19 | 3.1 : 1 |
| 2.49 | 20.8 | 1.30 | 3.0 : 1 |
We investigated the structure and phase composition of Ni—B alloys containing from 0.01 to 2.5% B. The alloys were cast by introducing a Ni—B master alloy containing 5% B.
Metallographic examination of the cast alloys showed that in these alloys along the grain boundaries there separates out a uniformly etched phase, forming a eutectic with nickel. The alloy with 2.5% B is hypereutectic (Fig. 1). We succeeded in isolating this phase both chemically and electrolytically. To isolate the phase by the chemical method, a small quantity of alloy turnings was heated with sulfuric acid (1 : 2) until dissolution ceased.
Table 2
Content of Ni and B in anodic precipitates isolated electrolytically in aqueous electrolytes
| B in alloy, % | Electrolyte | Ni in anodic residues, % | B in anodic residues, % | Ratio of atomic indices Ni : B |
|---|---|---|---|---|
| 2.49 | 1 | 5.80 | 0.40 | 2.7 : 1 |
| 2.49 | 2 | 10.63 | 0.62 | 3.2 : 1 |
| 2.49 | 3 | 11.84 | 0.80 | 2.7 : 1 |
Note. Composition of electrolytes: 1 — 10 g $(\mathrm{NH_4})_2\mathrm{SO_4}$, 35 g citric acid, 15 g $\mathrm{NH_2OH}$; 2 — 10 g $(\mathrm{NH_4})_2\cdot \mathrm{SO_4}$, 35 g citric acid, 25 g $\mathrm{NH_2OH}$, 1200 ml water; 3 — 10 g $(\mathrm{NH_4})_2\cdot \mathrm{SO_4}$, 30 g $\mathrm{NH_2OH}$, 1200 ml water, with cooling.
In electrolytic separation of the phases, a cylindrical alloy specimen was subjected to anodic dissolution under ordinary conditions with aqueous and nonaqueous electrolytes of the following composition: 1) 10 g $(\mathrm{NH_4})_2\mathrm{SO_4}$, 30 g hydrochloric hydroxylamine per 1200 ml water, and 2) 50 ml HCl per 1150 ml methanol, with cooling.
The phase isolated by one method or another was subjected to X-ray structural study and chemical analysis.
Figure 2 shows a typical X-ray diffraction pattern obtained from isolated phases using CuKα radiation. Below are the results of an X-ray structural analysis of the \(\mathrm{Ni}_3\mathrm{B}\) phase, carried out by the powder method.
| No. | Intensity | \(d\) in Å | No. | Intensity | \(d\) in Å |
|---|---|---|---|---|---|
| 1 | medium | 2.43 | 21 | very weak | 1.226 |
| 2 | strong | 2.35 | 22 | medium–strong | 1.187 |
| 3 | medium | 2.25 | 23 | strong | 1.159 |
| 4 | strong–medium | 2.12 | 24 | medium | 1.139 |
| 5 | very strong | 2.035 | 25 | strong | 1.123 |
| 6 | strong | 1.96 | 26 | medium | 1.106 |
| 7 | strong | 1.94 | 27 | medium–weak | 1.076 |
| 8 | very strong | 1.85 | 28 | very weak | 1.032 |
| 9 | medium–strong | 1.74 | 29 | weak | 1.001 |
| 10 | medium | 1.68 | 30 | very strong | 0.9679 |
| 11 | very weak | 1.64 | 31 | very weak | 0.2509 |
| 12 | medium | 1.62 | 32 | weak | 0.9298 |
| 13 | weak–medium | 1.57 | 33 | medium | 0.9242 |
| 14 | weak–medium | 1.44 | 34 | weak | 0.8632 |
| 15 | weak | 1.40 | 35 | strong | 0.8551 |
| 16 | weak | 1.38 | 36 | weak | 0.8413 |
| 17 | weak | 1.335 | 37 | strong | 0.8274 |
| 18 | strong | 1.294 | 38 | strong–medium | 0.8240 |
| 19 | strong–medium | 1.250 | 39 | strong | 0.8163 |
| 20 | weak | 1.232 | 40 | strong–medium | 0.8041 |
The results of chemical analysis of the phases isolated from the alloy by various methods are given in Tables 1–3, in which the analysis results are calculated relative to the weight of the dissolved alloy.
From the data given in Tables 1–3 it is evident that, in electrolytic separation of the phases, a considerable portion of nickel boride dissolves; the greatest amount of it is retained when the alloy is treated with sulfuric acid (1 : 2). In all cases the precipitate, according to X-ray structural investigation, represented one and the same phase. According to the results of chemical analysis, the composition of the isolated phase may be represented as \(\mathrm{Ni}_3\mathrm{B}\).
Table 3
Content of Ni and B in anodic precipitates isolated in an anhydrous electrolyte
(50 ml HCl (1.19) per 1150 ml \(\mathrm{CH}_3\mathrm{OH}\)) under strong cooling
| B in the alloy, % | Ni in the anodic precipitate, % | B in the anodic precipitate, % | Ratio of atomic indices Ni : B |
|---|---|---|---|
| 0.19 | 0.077 | 0.005 | 2.7 : 1 |
| 0.34 | 0.230 | 0.016 | 2.6 : 1 |
| 2.49 | 0.96 | 0.066 | 2.7 : 1 |
This nickel boride is a hard black substance. It is insoluble in dilute sulfuric acid (1 : 2). In concentrated sulfuric acid (1.84) it dissolves upon prolonged heating. In concentrated hydrochloric acid (1.19), and also in dilute hydrochloric acid (1 : 1), it dissolves only slightly upon prolonged boiling. In dilute nitric acid and in aqua regia it dissolves in the cold. It also dissolves readily in dilute hydrochloric and sulfuric acids in the presence of oxidizing agents—hydrogen peroxide, persulfate, etc.
Thus, on the basis of the investigation carried out, it may be asserted that in the binary Ni—B system there exists the chemical compound \(\mathrm{Ni}_3\mathrm{B}\), forming a eutectic with the solid solution based on nickel.
All-Union Scientific-Research
Institute of Aviation Materials
Received
28 XI 1956
CITED LITERATURE
- H. Giebelhausen, Zs. anorg. allg. Chem., 91, 257 (1915).
- A. Binet du Jassonneix, C. R., 145, 240 (1907).
- T. Bjurström, Ark. f. Kemi, Mineral., Geol., 11, A., 5, 1 (1933).
- L. Andersson, R. Kiessling, Acta Chem. Scand., 4, 160 (1950).
Fig. 1
Fig. 2
DAN, vol. 113, no. 4, Blok, Kozlova, Lashko, Shpunt