Nickel-tungsten Alloys Research Articles

Determination of five-parameter grain boundary characteristics in nanocrystalline Ni-W by scanning precession electron diffraction tomography

Determining the full five-parameter grain boundary characteristics from experiments is essential for understanding grain boundaries impact on material properties, improving related models, and designing advanced alloys. However, achieving this is generally challenging, in particular at nanoscale, due to their 3D nature. In our study, we successfully determined the grain boundary characteristics of an annealed nickel-tungsten alloy (NiW) nanocrystalline needle-shaped specimen (tip) containing twins using Scanning Precession Electron Diffraction (SPED) Tomography. The presence of annealing twins in this face-centered cubic (fcc) material gives rise to common reflections in the SPED diffraction patterns, which challenges the reconstruction of orientation-specific virtual dark field (VDF) images required for tomographic reconstruction of the 3D grain shapes. To address this, an automated post-processing step identifies and deselects these shared reflections prior to the reconstruction of the VDF images. Combined with appropriate intensity normalization and projection alignment procedures, this approach enables high-fidelity 3D reconstruction of the individual grains contained in the needle-shaped sample volume. To probe the accuracy of the resulting boundary characteristics, the twin boundary surface normal directions were extracted from the 3D voxelated grain boundary map using a 3D Hough transform. For the sub-set of coherent Σ3 boundaries, the expected {111} grain boundary plane normals were obtained with an angular error of <3° for boundary sizes down to 400 nm². This work advances our ability to precisely characterize and understand the complex grain boundaries that govern material properties.

High-Hardness Cemented Carbide With Nickel-Tungsten Alloy Binder

High-Hardness Cemented Carbide With Nickel-Tungsten Alloy Binder

Unraveling Stoichiometry Effect in Nickel-Tungsten Alloys for Efficient Hydrogen Oxidation Catalysis in Alkaline Electrolytes.

Anion-exchange membrane fuel cells provide the possibility to use platinum group metal-free catalysts, but the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics and its source is still debated. Here, over nickel-tungsten (Ni-W) alloy catalysts, we show that the Ni : W ratio greatly governs the HOR performance in alkaline electrolyte. Experimental and theoretical studies unravel that alloying with W can tune the unpaired electrons in Ni, tailoring the potential of zero charge and the catalytic surface to favor hydroxyl adsorption (OHad). The OHad species coordinately interact with potassium (K+) ions, which break the K+ solvation sheath to leave free water molecules, yielding an improved connectivity of hydrogen-bond networks. Consequently, the optimal Ni17W3 alloy exhibits alkaline HOR activity superior to the state-of-the-art platinum on carbon (Pt/C) catalyst and operates steadily with negligible decay after 10,000 cycles. Our findings offer new understandings of alloyed HOR catalysts and will guide rational design of next-generation catalysts for fuel cells.

Electrodeposition of Nickel-Tungsten Alloy with Functional Concentration Periodically Graded Material Structure for Low Stress and High Hardness

A nickel-tungsten alloy film was deposited using an electrodeposition process. The tungsten concentration in the nickel-tungsten alloy was controlled by the applied current density. The surface morphology, micro-structure, internal stress, and hardness were characterized as a single-layer structure. Hardness increased as the tungsten content increased, but micro-cracks occurred on the surface. A multi-layered structure was selected to increase the hardness without micro-cracks. The multi-layered nickel-tungsten alloy film was deposited to form two types: functional periodic materials and functional graded materials. These multi-layered structures were deposited by changing the applied current density periodically and gradually, respectively, during the deposition process. The mechanical properties, such as internal stress and hardness of the nickel-tungsten alloy, were characterized as a function of the tungsten concentration of the nickel-tungsten alloy film. As the number of periods increased, the internal stress decreased, and micro-cracks were removed from the surface. However, the gradually varied nickel-tungsten alloy had higher internal stress than the periodically varied alloy. Similar hardness was observed because the concentration of nickel-tungsten film at the top of the multi-layered structure was the same. Overall, we demonstrated enhanced mechanical properties, including low internal stress and high hardness, of concentration periodically graded nickel-tungsten alloy.

In situ formed nickel tungsten oxide amorphous layer on metal–organic framework derived ZnxNi1−xWO4 surface by self-reconstruction for acid hydrogen evolution reaction

Noble metal free electrocatalysts for hydrogen evolution reaction (HER) in acid play an important role in proton exchange membrane-based electrolysis. Here, we develop an in situ surface self-reconstruction strategy to construct excellent acidic HER catalysts. Firstly, free-standing zinc nickel tungstate nanosheets inlaid with nickel tungsten alloy nanoparticles were synthesized on carbon cloth as pre-catalyst via metal–organic framework derived method. Amorphous nickel tungsten oxide (Ni-W-O) layer is in situ formed on surface of nanosheet as actual HER active site with the dissolution of NiW alloy nanoparticles and the leaching of cations. While the morphology of the free-standing structure remains the same, keeping the maximized exposure of active sites and serving as the electron transportation framework. As a result, benefiting from disordered arrangement of atoms and the synergistic effect between Ni and W atoms, the amorphous Ni-W-O layer exhibits an excellent acidic HER activity with only an overpotential of 46 mV to drive a current density of 10 mA cm−2 and a quite good Tafel slope of 36.4 mV dec−1 as well as an excellent durability. This work enlightens the exploration of surface evolution of catalysts during HER in acidic solution and employs it as a strategy for designing acidic HER catalysts.

Production of Single-Crystal Seeds [001] from Nickel–Tungsten Alloys by Directional Crystallization

Production of Single-Crystal Seeds [001] from Nickel–Tungsten Alloys by Directional Crystallization

Highly Regular Hexagonally-Arranged Nanostructures on Ni-W Alloy Tapes upon Irradiation with Ultrashort UV Laser Pulses.

Nickel tungsten alloy tapes (Ni—5 at% W, 10 mm wide, 80 µm thick, biaxially textured) used in second-generation high temperature superconductor (2G-HTS) technology were laser-processed in air with ultraviolet ps-laser pulses (355 nm wavelength, 300 ps pulse duration, 250–800 kHz pulse repetition frequency). By employing optimized surface scan-processing strategies, various laser-generated periodic surface structures were generated on the tapes. Particularly, distinct surface microstructures and nanostructures were formed. These included sub-wavelength-sized highly-regular hexagonally-arranged nano-protrusions, wavelength-sized line-grating-like laser-induced periodic surface structures (LIPSS, ripples), and larger irregular pyramidal microstructures. The induced surface morphology was characterized in depth by electron-based techniques, including scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), cross-sectional transmission electron microscopy (STEM/TEM) and energy dispersive X-ray spectrometry (EDS). The in-depth EBSD crystallographic analyses indicated a significant impact of the material initial grain orientation on the type of surface nanostructure and microstructure formed upon laser irradiation. Special emphasis was laid on high-resolution material analysis of the hexagonally-arranged nano-protrusions. Their formation mechanism is discussed on the basis of the interplay between electromagnetic scattering effects followed by hydrodynamic matter re-organization after the laser exposure. The temperature stability of the hexagonally-arranged nano-protrusion was explored in post-irradiation thermal annealing experiments, in order to qualify their suitability in 2G-HTS fabrication technology with initial steps deposition temperatures in the range of 773–873 K.

Effect of pulse reverse current waveform on tribological and mechanical properties of electrodeposited nickel–tungsten alloys on brass substrate

ABSTRACT The precise control of tungsten content of electrodeposited nickel–tungsten (NiW) on brass substrate was achieved by applying a well-designed pulse reverse current waveform. A crack-free, uniform and, mirror-like finish surface was obtained by using a novel derivative of propargyl compound, propargyl-oxo-propane-2,3-dihydroxy, as a brightener and grain refiner into the electrodeposition bath. This study indicates that the electrodeposited nickel–tungsten alloys with an optimum tungsten content (32 wt%) possesses outstanding mechanical and, wear performance, also with very low friction of coefficient of 0.2.

Effectiveness of tungsten addition on the performance of electroplated nickel diffusion barriers for copper metallization on textured silicon

In this work, the nickel-tungsten alloy is used as the diffusion barrier for copper metallization on textured silicon. Nickel silicides formed as the seed layer for the nickel-tungsten alloy. Then, copper metallization was performed by an electroplating method to create the Cu/NiW/NiSiy/Si structure. The Cu/NiW/NiSiy/Si samples were annealed at various temperatures for 10 minutes in an annealing furnace under Ar/H2 atmospheres. The annealed Cu/NiW/NiSiy/Si samples were characterized by X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy. For the Cu/NiW/NiSiy/Si samples with NiW thicknesses of 300 nm and 350 nm, the Cu3Si phase developed at annealing temperatures of 500 °C and 600 °C, respectively. The NiW layer is a better diffusion barrier against copper than the Ni layer.

Production of single-crystal seeds [001] from nickeltungsten alloys by directional crystallization

The problem of obtaining priming materials from Ni-W alloys arose in connection with the development of technology for casting single-crystal turbine blades of gas turbine engines (GTE) from hightemperature alloys. This technology uses a seed method for producing single-crystal castings with a crystallographic orientation [001] using seedings from alloys of the Ni-W system with a melting point 120–140°C higher than the casting alloy. The use of such primers greatly simplifies the casting process of turbine blades with a single-crystal structure, increases its reliability both in pass-through furnaces of the PMP-2 type and in high-gradient furnaces of the UVNK-9A type. The article presents the results of the study of the influence of temperature-velocity parameters of directional crystallization, namely, the temperature gradient GZ on the structure of the obtained single-crystal seed blanks, as well as the study of effects of tungsten and carbon on the structure of single-crystal seed blanks, and makes recommendations for optimizing the technological process of single-crystal casting of Ni–W seed blanks adjusting the alloy composition for the seed blanks.

Nanocrystalline nickel-tungsten alloys assisted by thermosonication: Effect of temperature on the anticorrosive properties

Ni-W coatings were evaluated considering the effect of ultrasound-assisted deposition and the electrolytic bath's temperature on the faradaic efficiency. Electrodeposition occurred with and without thermosonication (TS) at 40, 50, and 60 °C. Both process variables were significant (p-value<0.05). The temperature profile indicated that the nominal power of the system was 10.8 ± 0.3 W. The W content increased with the increase of the temperature and the use of ultrasound. Microcracks decreased due to an increase in the diffusion process generated by acoustic cavitation. The alloys presented nanocrystalline structures of Ni17W3 composition, with preferential orientation in the plane (220). The peaks slightly decreased with the increase of the temperature and under TS, indicating a tendency to amorphization. The coating produced at 50 °C without TS exhibited the highest polarization resistance value of 20.50 kΩ cm2. The electrochemical impedance spectra confirmed the Ni-W alloy's anticorrosion property with an equivalent circuit mainly composed of a non-ideal capacitor and a Warburg element.

Influence of W content on microstructure and surface morphology of hard Ni-W films fabricated by magnetron co-sputtering

Due to their unique mechanical, tribological, thermal, and anticorrosion properties, nickel-tungsten (Ni-W) alloy films have become indispensable for many industrial applications. The present study investigates the impact of W content on the microstructure and mechanical properties of Ni-W thin films. By co-sputtering of Ni and W on silicon wafers coated with a thin buffer layer (∼20 nm) of titanium (Ti), six Ni-W coatings were fabricated, ranging from pure Ni to pure W. The samples were characterized using energy dispersive spectroscopy, x-ray diffraction, scanning electron microscopy, atomic force microscopy, and microindentation. The results show that hardness of the Ni-W films is primarily a function of the W content, which changes the microstructure and surface morphology of the samples. When W concentration is smaller than 40 at. %, the Ni-rich samples have a face-centered cubic structure and the hardness increases with the W content. For the samples having 40 &amp;lt; W &amp;lt; 55 at. %, the sensitivity of the hardness to the W content becomes markedly low, which could be due to the presence of an amorphous phase. Finally, the impact of W addition on the hardness of the samples containing 55–80 at. % W is two times greater than that of W &amp;lt; 40 at. %. The extra hardening effect could be attributed to the dominancy of a solid solution hardened body-centered cubic W phase and electronic interaction between two transition metals. This sharp increase in the hardness leads to obtaining a high hardness of 21.9 ± 2.0 GPa for the Ni-79 at. % W film. The findings of this study show that solid solution strengthening could be considered the main hardening mechanism of these films.

Еfficiency of hot gasostating of bars made from NV5-VP alloy for manufacturing of details for microwave devices

The possibilities of healing of defects in the NV5-VP bars made from vacuum-melted nickel-tungsten alloy by the method of hot gasostating are being studied.

Assessment of Abrasion Resistance in Plated Nickel–Tungsten Alloy Specimens by Employing Two Types of Direct and Pulse Flow

Nickel–Tungsten alloy electroplating done in a bath containing NiSo4 0.1 mL, Na2Wo4 0.5 mL and Na3Cit 0.4 mL at pH 8 under the 70°C with a rotating magnetic particle at 200 rpm and 0.25 A/cm2 direct flow density. The Tungsten with the coverage of 80%, on time 62.8 and 45.49% by weight for the plated sample with direct flow. The percent of Tungsten in coating is affected by flow rate, pH and time percentage. The anomalous sequestration system in direct flow coating became the induction sequestration system in the pulsed plating process. The morphology of the probe was filamentous in a pulsed flow and in a straight flow. The wear resistance behavior of the specimens in the weight loss test differed in relation to the amount of shot length under load on the specimen for the specimen, tested in the two flow types.

Development of Ni-W alloy coatings and their electrocatalytic activity for water splitting reaction

This study reports the electrodeposition of Nickel-Tungsten (Ni-W) alloy coatings and their efficiency as electrode material for water splitting applications. Ni-W alloy coatings were electrodeposited and their electrocatalytic activity towards alkaline water splitting for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH were studied. Cyclic voltammetry (CV) and chronopotentiometry (CP)techniques were used to quantify their electrocatalytic behaviors. It demonstrated the inverse dependency of electrocatalytic behaviors of coatings towards HER and OER at low and high c.d.'s, respectively. This is attributed to the change in the composition, in terms of Ni and W content of the alloy. The surface features, structural and compositional change of coatings, responsible for improved electrocatalytic activity were examined using Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDS) techniques. Experiment results revealed that alloy deposit can be used as a potential material for water splitting applications.

Creep of a thermally stable nanocrystalline nickel tungsten alloy as measured by high temperature nanoindentation

The creep behavior of pure nanocrystalline (nc) fcc metals has not been studied above 200 °C because the nanoscale grains tend to grow at temperatures moderately above ambient. In this work, we study the creep of nanocrystalline Ni–W (nc Ni–W) up to 450 °C, near its thermal stability limit. A nanoindenter with the capability to heat both the specimen and the indenter tip addresses the issue of heat flow and provides more accurate test temperatures when compared to heating only the specimen. Creep experiments are performed on a nc Ni–W film (grain size ~15 nm) at 300, 350, 400 and 450 °C using the constant load and hold (CLH) method combined with the constant stiffness measurement (CSM) technique in which the peak load is maintained at a constant level. No grain growth occurs even at the highest temperature and highest stress. We conduct an analysis that accounts for the effect of the oscillating loads used in this combined CLH-CSM technique on creep. We find that nc Ni–W exhibits negligible creep at 300 °C, and that at 350 °C, creep in nc Ni–W is three orders of magnitude smaller than creep in pure nc Ni at 100 °C. The creep response of nc Ni–W differs significantly from that predicted by the standard Coble creep model and is attributed to the dislocation–grain boundary interaction.

Synthesis of Boron-Doped Silicon Film Using Hot Wire Chemical Vapor Deposition Technique

Boron-doped polycrystalline silicon film was synthesized using hot wire chemical vapor deposition technique for possible application in photonics devices. To investigate the effect of substrate, we considered Si/SiO2, glass/ITO/TiO2, Al2O3, and nickel tungsten alloy strip for the growth of polycrystalline silicon films. Scanning electron microscopy, optical reflectance, optical transmittance, X-ray diffraction, and I-V measurements were used to characterize the silicon films. The resistivity of the film was 1.3 × 10−2 Ω-cm for the polycrystalline silicon film, which was suitable for using as a window layer in a solar cell. These films have potential uses in making photodiode and photosensing devices.

Improving the Corrosion Resistance of the Nickel–Tungsten Alloy by Optimization of the Electroplating Conditions

Nickel–tungsten (Ni–W) alloy coating was electrodeposited on the copper substrate by direct current voltammetry. The optimization of a free-ammonium bath for electrodeposition of Ni–W alloy coating was investigated. Experiments were focused on elucidating the effect of W concentration and operating conditions on the corrosion performance of the obtained Ni–W alloy coating. The corrosion behavior of the coatings was investigated by potentiodynamic polarization (Tafel) test. Experimental data such as corrosion current density, corrosion rate and polarization resistance indicated that the operating conditions used during the electroplating had significant effects on the corrosion parameters of the Ni–W alloy coating. The results showed that the highest corrosion resistance was obtained for the coating with 56.7 wt% tungsten (Ni/W ratio of 1:2.5) which was prepared at the current density of 3.8 A dm−2. The increase in the corrosion resistance at the optimum current density was attributed to the lower interferences of the hydrogen evolution reaction. Energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) techniques were used to characterize the electrodeposited Ni–W alloy with the best anti-corrosion parameters.

Mechanical properties and load bearing capability of nanocrystalline nickel-tungsten multilayered coatings

Nanocrystalline nickel-tungsten alloys are of high industrial interest owing to their mechanical properties, wear and corrosion resistance, as well as their thermal stability. Since the patterning of their structures potentially enhances mechanical and tribological characteristics, layered nickel-tungsten alloys were developed by sequential electrodeposition of bi-layers (two different concentrations of tungsten) in the current study. The layer thickness was modulated in the range of 90 to 3000 nm. Using a modified pulse reverse current technique, all the layers were deposited from a fixed citrate-based electrolyte. Studying the material by microhardness and Palmqvist techniques revealed that the microhardness of the coatings was improved by reduction of layer thicknesses, in accordance with Hall-Petch relation. Wear test results indicated that layered coatings were more resistant in comparison with the monolithic counterparts. Furthermore, microscopy investigations showed that by reducing the layer's thickness, the plastically deformed region underneath the wear front narrows, thus increasing the load-bearing capabilities.

The effects of W content on solid-solution strengthening and the critical Hall-Petch grain size in Ni-W alloy

Nanocrystalline and amorphous nickel-tungsten alloy with relatively high tungsten contents of up to 34 at.% were produced by electrodeposition. The Hall-Petch relationship and breakdown was studied in this alloy, with grain sizes ranging from 25 nm to fully amorphous. In this higher tungsten content alloy, evidence of solid-solution strengthening was found, which was previously absent in alloys with <13 at.% tungsten. A Hall-Petch trend with a critical grain size of 5 nm was observed, in line with expectations.