Ni-W Alloy Research Articles

Formation of amorphous electrodeposited Ni-W alloys and their nanocrystallization

Ni-W alloys containing about 5 to 30 at. % W were prepared by electrodeposition. The plating bath for the electrodeposition contained nickel sulfate, citric acid, sodium tungstate and ammonium chloride, and was operated at various bath concentrations and conditions of electrolysis. X-ray diffraction peaks of the deposited alloys broadened with increasing tungsten content and an amorphous pattern appeared at a tungsten content of about 20 at. %. Nanocrystallization behavior of the amorphous Ni-25.0 at. % W alloy has been studied by X-ray diffraction, high resolution transmission electron microscopy and small angle X-ray scattering. The Hall-Petch strengthening mechanism was observed for the hardness extending to a finest grain size of about 10 nm. When the grain size was less than about 10 nm, decrease of the hardness was observed. This decrease may be due to the significant increase of the intercrystalline volume fraction, especially the fraction associated with the triple junction.

Processing, structure and properties of Ni-W alloys fabricated by mechanical alloying and hot-isostatic pressing

The structure and properties of Ni-W alloys fabricated through MA and subsequent consolidation of the alloyed powders have been investigated. In comparatively W rich alloys, extensive solid solution of W in Ni accompanies MA and there is also evidence of partial or complete amorphization taking place during milling. During consolidation of these powders, W and an intermetallic (based on NiW) precipitate from the glassy matrix, which itself crystallizes. As-consolidated hardnesses of such materials are higher, by quite a bit, than the hardnesses of WHA formed via LPS. Structures obtained following consolidation remain nonequilibrium in that the W content of the matrix exceeds the equilibrium low temperature solubility and NiW is not stable at the post-consolidation heat-treatment temperature employed. This heat-treatment results in a gradual approach to the equilibrium structure and an increase in material microstructural scale. It is also accompanied by significant decreases in material hardnesses.

Nanocrystallization and Mechanical Properties of an Amorphous Electrodeposited Ni<sub>75</sub>W<sub>25</sub> Alloy

An amorphous Ni-W alloy containing about 25 at. % W has been prepared by electrodeposition. Nanocrystallization behavior of this alloy has been studied by X-ray diffraction, high resolution transmission electron microscopy (HR-TEM) and small angle X-ray scattering. The Hall-Petch strengthening mechanism was observed for the hardness extending to a finest grain size of about 10 nm. When the grain size is less than about 10 nm, decrease of the hardness was observed. This decrease may be due to the significant increase of the intercrystalline volume fraction, especially the fraction associated with the triple junction.

Characterization of sputter-deposited Ni-Mo and Ni-W alloy electrocatalysts for hydrogen evolution in alkaline solution

Binary Ni-Mo and Ni-W alloy coatings with good adhesion to nickel substrate are successfully prepared by d.c. magnetron sputter deposition method. These alloy electrodes are found to be active hydrogen evolution electrocatalysts in 1 M NaOH solution at 30 °C. Ni-Mo alloy electrodes exhibit the highest activity, which is higher than that of smooth platinum electrode. Leaching treatment in hot concentrated caustic solution for Ni-Mo alloys significantly enhances the activity.

A New Amorphous Alloy Deposit with High Corrosion Resistance

Abstract The corrosion behavior of electrodeposited Ni-P, Ni-W, Ni-W-P, and Fe-W alloys was tested, and the effects of the additive elements W and P on the corrosion resistance of amorphous deposit...

Electrodeposition of Ni-W-B amorphous alloys

Partial polarization curves at the glassy carbon rotating disc electrode have been used to study the electrodeposition of Ni and Ni-W alloy from citrate-containing solution. For deposition of Ni-W alloys, the partial polarization curves indicate diffusion control for nickel reduction and stoichiometric limitation for tungsten deposition by the composition of the alloy. Plating experiments show that current efficiency of the electrodeposition and composition of the resulting alloy depend on the parameters of the electrolysis. The best conditions for electrodeposition of the alloy Ni-W-B are current density of 45–50 mA cm−2, temperature of 60–70 °C, Ni(II) concentration of 20–25 mm, and pH 8.5. Pulsed galvanostatic plating at 1 Hz increased slightly the current efficiency. The concentration of Ni(II) in the solution can be self-regulated by using a nickel bipolar electrode in the cathode compartment.

Grinding media wear during mechanical alloying of Ni-W alloys in a SPEX mill

Mechanical alloying (MA) is utilized for producing powdered materials having intriguing properties and structures. Some of these materials manifest extended solid solubility. Mechanical alloying has also been used to synthesize equilibrium and nonequilibrium intermediate (or intermetallic) phases, amorphous materials and inorganic nonmetallics. In their laboratory the authors have been studying the amorphization of Ni-W alloys, accomplished by extended grinding in a SPEX mill. It was brought to The authors' attention (by the reviewer of a manuscript ) that perhaps the authors ought to be paying some attention to the effect of wear debris on the tendency for, and extent of, the amorphization the authors observed. This paper reports on the contamination that accompanies SPEX milling of No-W alloys. The authors will show that wear debris, while only a small fraction of the total grinding media charge, is sufficient to alter appreciably the composition of the milled powder.

Laser Surface Treatment of Thick Ni-W Alloy Electroplated on Cu Substrate

Laser Surface Treatment of Thick Ni-W Alloy Electroplated on Cu Substrate

Photoemission and electronic structure of tungsten-based metallic glasses and alloys.

The structure and electronic density of states of intertransition-metal glasses of the form ${\mathit{T}}_{\mathit{x}}$${\mathrm{W}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ have been investigated, where T=Cu, Ni, and Co. The film samples were prepared by cosputtering in a chamber with a rapidly rotating, water-cooled substrate. Experiments included x-ray diffraction and ultraviolet photoemission at photon energies of 21.2 and 40.8 eV, and electronic-structure calculations were performed with a self-consistent linear combination of muffin-tin-orbitals method. For the calculations the structures were simulated by either disordered crystalline or amorphous clusters of 60--64 atoms in a periodically extended supercell. The range of amorphous alloy formation was determined approximately for each alloy series, and it was found that this range was larger when the atomic-radii difference of the two elements is larger. In both the photoemission and theoretical results for the crystalline and amorphous Cu-W alloys the Cu 3d band is a distinct feature whose position is well reproduced by the calculations. In the Ni-W and Co-W alloys the 3d and 5d bands overlap significantly. In the case of crystalline Ni-W alloys, the theory gives a good representation of the observed occupied density of states.

溶融Ni-Cr,Ni-MoおよびNi-W合金の珪素による脱酸平衡

In order to understand the effects of the various alloying elements on the equilibrium constant of deoxidation of liquid nickel, the deoxidation of nickel based alloys with silicon has been studied at temperature range between 1550°C and 1650°C by the use of silica crucible.In nickel-chrominium alloy, the deoxidation product, logK'Si(Ni-Cr), which drastically increased by the addition of chromium up to 20 pct chromium, was empirically represented to be.logK'Si(Ni-Cr)=log K'Si(Ni) + 0.347[%Cr]-0.010[%Cd]2Cr<15%, 0.65 % Si, 1550°C1650°Cwhile the deoxidation product in nickel-molybdenum alloy, logK'Si(Ni-Mo), which also lineally increased with increasing molybdenum content, was given by the expression :log K'Si(Ni-Mo) = log KSi(Ni)+0.047[%Mo]Mo<16%, 0.65% Si, 1550°C1650°CIn nickel-tungsten alloy, the value of log K'Si(Ni-W) was found to be as follows :log K'Si(Ni-W) = log KSi(Ni)+ 0.007[%W]Mo<11%, 0.4% Si, 1550°C1650°CFor the effect of the alloying elements on the activity coefficient of oxygen in nickel, the following parameters were obtained :logfCrO(Ni) = -0.171 [%Cr] Cr<5%log fMoO(Ni)=-0.025[%Cr] Mo<16%logfWO(Ni)=-0.004[ %Cr] W<11%

Secondary neutral mass spectrometric investigations on the formation of sputter-generated molecules by atomic combination

The direct bombardment mode of secondary neutral mass spectrometry (SNMS) has been employed for the investigation of the neutral particle flux from a series of NiW and NiMo alloys under normal bombardment with Ar + ions at energies of up to 1200 eV. Making use of the direct proportionality between the intensities of the SNMS signals and the individual formation probabilities of the detected species, a critical examination of the atomic combination model for the formation of sputter-generated molecules is performed. It is shown that this model applies to the generation of the detected dimers and trimers formed by the atomic constituents of the alloy samples.

Ｎｉ−Ｗ合金めっきの性状に及ぼす浴中クエン酸濃度の影響

This study was carried out to improve the properties and as-plated conditions of 44wt%W Ni-W alloy, since that composition is considered optimum for the electroplated alloy. The experiments were conducted using citric acid-ammonia baths of pH 6, 70°C, containing 40g/L of NiSO4·6H2O, 70g/L of Na2WO4·2H2O plus citric acid and NH4OH, taking the citric acid concentration in the bath as the parameter. When citric acid monohydrate concentration was varied from 80g/L to 140g/L and the current density was kept constant at 10A/dm2, the composition of the plated alloys retained the value of 43±0.6wt%W, which closely corresponds to Ni4W stoichiometry. The alloys assumed the highest ductility at a citric acid concentration of 100g/L, and at citric acid concentrations exceeding 120g/L, the whole surface of the plates was mirror bright. As-plated alloy from 100g/L citric acid bath had a hardness of Hv 620, but showed a room temperature hardness of Hv 1310 after heating at 700°C for 1h, and a hot hardness of Hv 950∼980 at temperatures of 550∼670°C. It was also found that the quantity of the codeposited trace elements, carbon, oxygen, nitrogen and sulfur, was less for alloy plated from 100g/L citric acid bath than for all other alloys. From the results of measurements of electrode surface pH, crystallite size, physical density and trace elements in the alloys, it was inferred that the main species adsorbing on the electrode surface will change from hydroxide to citric acid, when citric acid concentration in the bath exceeds 100g/L.

Ｎｉ‐Ｗ合金めっきの高温特性と加熱相変態

Hot hardness and dilation curves were measured and the associated X-ray studies were conducted on electroplated Ni-W alloys of 40, 44 and 51wt%W during heating at a rate of 1°C/min. The increase in hot hardness started at around 200°C, and softening began at about 600°C. The 44wt%W alloy showed the highest hot hardness-Hv900-between 450°C and 550°C. Along with such well known Ni-W crystals as face centered cubic solid solution, Ni4W and nearly pure tungsten, a new phase was found to be precipitated. For example in 40wt%W alloy, the new phase had a body centered tetragonal structure with a=9.136A and c=10.268A±0.038A, having 74 or more atoms of anomalously small atomic volume in a giant unit cell. Although the new phase appeared first on heating, it was fairly thermally stable and was the predominant precipitate at the peak hardness of the alloys. The origin of the formation of the new phase is discussed, and the precipitation of pure tungsten which was found on heating the 40 and 44wt%W alloys, was experimentally analyzed.

有機錯体浴からのＮｉ‐Ｗ合金めっき用アノードについて

This study was conducted on the insoluble anode materials that are required to prevent the degradation of a citric acid-ammonia Ni-W alloy plating bath of pH 6, 70°C. Bath degradation occurs by anodic oxidation of citric acid. It accompanies the evolution of CO2 gas from the anode and leads to the formation of highly stressed brittle deposits. Anode materials such as Pt, Pb, graphite, Ni and SUS 304 stainless steel exhibited a problem in terms of vigorous CO2 gas evolution. A specially baked RuO2/TiO2 mixed oxide electrode on a Ti substrate exhibited a problem in terms of service life. Finally, a low polarization, amorphous, insoluble electrode, which completely prevents CO2 gas evolution and possesses a reasonably long service life (∼4000h, at ia=20A/dm2) was found in Ir/Ta mixed oxide system. Pretreatment of the substrate, oxide composition, solvent selection and the baking temperature for the electrode were described. It is expected that the development of such a high performance electrode will render bath maintainance practicable.

ｐＨ６のクエン酸浴によるＮｉ‐Ｗ合金めっきの組成と電流効率および皮膜特性

A high temperature bath of pH8 to 9, continuously supplied with ammonia water, has long been believed optimum for tungsten alloy plating. However, since ammonia is volatile and harmful to both working personnel and peripheral devices, we have formulated a citric acid-ammonia Ni-W alloy plating bath of pH6, which is free of ammonia smell even on boiling. On the basis of the data on alloy composition and current efficiency, we selected a bath temperature of 70°C as optimum. Baths of high nickel concentrations of pH6, 70°C yielded alloys of high tungsten content with relatively high current efficiencies, eg.44wt%W alloy at 49%CCE. The highest tungsten content obtained was 61wt%, which corresponds to Ni2W stoichiometry. The tungsten content of the deposits did not show any abrupt change on variation of nickel concentration in the bath, and remained almost constant at current densities exceeding 8A/dm2. The room temperature hardness of 44 and 51wt%W alloys was about Hv 1350 after heating at 650°C for 1h. Dilation measurements showed that the alloys were more densely deposited than those plated at high temperature/pH conditions. On the basis of these encouraging findings, studies on metal ion replenishment were also conducted. The methods recommended are the addition of ammonium para-tungstate solution for tungsten, and the use of a soluble nickel anode for nickel.

Activity of carbon in nickel-rich Ni-Mo and Ni-W alloys

Effects of molybdenum and tungsten on carbon activity in nickel have been experimentally determined at 1000, 1100, and 1200 °C. Seventeen nickel-molybdenum and thirteen nickel-tungsten binary alloys were carburized in a flow of purified methane and hydrogen mixed gas. A sealed capsule technique was also employed for carburization of a few series of nickel-molybdenum alloys. The carbon concentration was determined either by hot extraction techniques (LECO and Coulomatic) or by weight gains of these specimens. The carbon concentration at a constant carbon activity decreases with increasing either molybdenum or tungsten concentration in nickel. The effect of tungsten on the carbon solubility in nickel is slightly larger than that of molybdenum. The experimental data were analyzed in terms of the regular solution model with two sublattices due to Hillert and Staffansson. Temperature dependence of the interaction coefficients between carbon and molybdenum or tungsten was expressed as DGMo/RT = −4.45 + 11650/T andDG W /R = 1.21 + 9010/.

Measurement of the Energy Distributions of Secondary Ions from Pure Metals and Alloys

Precise measurement of the energy distribution of secondary ions was attempted in order to study the correlation with surface properties. The experiments revealed that the peak of the energy distribution shifts towards the lower energy as the partial pressure of oxygen becomes higher for both Al and Mg under Ar+ ion bombardment. The measurement was then extended to Ni-W and Cu-Ni alloy samples to see whether any difference between the peaks of secondary ions of constituent atoms could be found, the same as those of sputtered Ni- and W-atoms from Ni-W alloy reported by Oechsner et al. The results suggest that no substantial difference exists in the energy distribution of secondary ions of constituent atoms for both the Ni-W and Cu-Ni alloys even though the peak positions of the secondary ions of constituent atoms with higher sublimation energy are always slightly higher.

Short range order and the development of long range order in Ni 4Mo

The short-range ordered structure present in quenched Ni 4Mo and the initial development of the long-range-ordered structure have been studied using single crystal X-ray diffuse scattering techniques. Measurements of the diffuse X-ray intensities were made in a volume in reciprocal space for the f.c.c. alloy resulting in a quantitative determination of the three dimensional local-order parameters. The local-order parameters were used for a computer simulation of the atomic configuration. The local atomic arrangements for the quenched alloy consist of a strong preference for no molybdenum atom pairs as first neighbors. The atoms tend to satisfy the long-range-ordered structure of Ni 4Mo in which there are no Mo-Mo pairs as first neighbors, only one Mo atom as second neighbors and six or more as third neighbors. A rodlike morphology consisting of a strong preference for 200 and 400 Mo-Mo pairs exists on ordering for 5 min at 650°C. This result is similar to the rodlike morphology present in dilute Ni-W alloys and explains the [100] streaking of the short-range order peaks observed in the diffraction studies.

Mössbauer Study of 182W on Ni-W Alloys

Mössbauer Study of ¹⁸²W on Ni-W Alloys

クエン酸浴によるニッケル-タングステン合金メッキの浴組成と表面状態について

The compositions of citric acid-ammonia baths for Ni-W alloy plating were studied for practical purposes as well as conditions of electrolysis, amount and component ratio of the alloy deposited.The results obtained were as follows:(1) The composition and amount of the alloy deposited were kept constant in a relatively wide range of variation in composition of the baths containing nickel sulfate, sodium tungstate, and citric acid, and a deposit of good quality, containing 35-40% of W, was obtained.(2) A deposit of good quality was also obtained by the addition of ammonium citrate as a complexing agent. However, pH of the bath had to be adjusted to about 9.0 with sodium hydroxide.(3) The addition of a small amount of hydrazine sulfate as a reducing agent was effective in the improvement of deposition efficiency.(4) The hardness of Ni-W alloy deposit as plated was 500-600Hv. It was elevated to 900-1000Hv by the heat treatment at 500-600°C in a vacuum furnace.(5) Ni-W alloy plating was converted into Ni-W solid solution when it was heat- treated at 500-600°C.