Ni-W Alloy Research Articles

Deposition of highly oriented (K,Na)NbO3 films on flexible metal substrates

In view of developing flexible, highly textured Pb-free piezoelectric thin films, (K,Na)NbO3 was deposited by chemical solution deposition on cube-textured Ni-W alloy substrates. After heat treatment, a strong (001)pc out-of-plane preferential orientation is created in the (K,Na)NbO3 layer, which also exhibits a sharp in-plane texture with 45°-rotated epitaxial relation to the substrate. The microstructure of the film is strongly dependent on the heat treatment temperature; sub-micrometer grains versus up to 2 μm long particles forming at 600 °C and 900 °C respectively. K4Nb6O17 and (K1−xNax)2Nb4O11 impurity phases were identified depending on the processing temperature.

Effect of tungsten on microstructures of annealed electrodeposited Ni-W alloy and its corrosion resistance

The ultrafine grained pure Ni and Ni-W alloy were obtained by electrodeposition technique and subsequent annealing treatment. The effects of annealing on the microstructures, the mechanical properties and the corrosion resistance of pure nickel and Ni-W alloy were investigated. The EBSD analyses showed that annealed pure Ni displayed preferred grain orientation, while annealed Ni-W alloy showed relatively more random grain orientation. Moreover, abnormal grain growth was observed in annealed pure Ni, while annealed Ni-W alloy displayed a more uniform grain size distribution. It could be predicted that solid solution of tungsten significantly suppressed grain growth and induced uniform grain size distribution during low temperature annealing process. Moreover, comparing with annealed pure Ni, the tungsten in annealed Ni-W alloy changed the semiconducting characteristic of surface passive films. Annealed Ni-W alloy showed higher corrosion resistance than annealed pure Ni in 3.5 wt% NaCl solution and in borate buffer solution.

Electrolytic Synthesis of Ni-W-MWCNT Composite Coating for Alkaline Hydrogen Evolution Reaction

Nickel–tungsten multi-walled carbon nanotube (Ni-W-MWCNT) composite films were fabricated by an electrodeposition technique, and their electrocatalytic activity toward hydrogen evolution reaction (HER) was studied. Ni-W-MWCNT composite films with a homogeneous dispersion of MWCNTs were deposited from an optimal Ni-W plating bath containing functionalized MWCNTs, under galvanostatic condition. The presence of functionalized MWCNT was found to enhance the induced codeposition of the reluctant metal W and resulted in a W-rich composite coating with improved properties. The electrocatalytic behaviors of Ni-W-MWCNT composite coating toward HER were studied by cyclic voltammetry (CV) and chronopotentiometry techniques in 1.0 M KOH medium. Further, Tafel polarization and electrochemical impedance spectroscopy (EIS) studies were carried out to establish the kinetics of HER on the alloy and composite electrodes. The experimental results revealed that the addition of MWCNTs (having a diameter of around 10-15 nm) into the alloy plating bath has a significant effect on the electrocatalytic behavior of Ni-W alloy deposit. The Ni-W-MWCNT composite coating was found to show better HER activity than the conventional Ni-W alloy coating. The enhanced electrocatalytic activity of Ni-W-MWCNT composite coating is attributed to the MWCNT intersticed in the deposit matrix, evidenced by surface morphology, composition and phase structure of the coating through SEM, EDS and XRD analyses, respectively.

A comparative study on the electrocatalytic activity of electrodeposited Ni-W and Ni-P alloy coatings

Bright Ni-W and Ni-P alloy coatings were synthesized through direct electrolysis from an aqueous alkaline citrate bath. The effect of alloying elements, W and P, on the electrocatalytic activity of Ni was studied, based on their induced codeposition behavior and related to the composition, structure and surface morphology of the developed coatings. The electrocatalytic activity of the alloy coatings towards hydrogen evolution reaction (HER) was studied using electrochemical techniques such as cyclic voltammetry (CV) and chronopotentiometry (CP), in 1.0 M KOH medium. A comparison of the electrocatalytic efficiencies of these Ni-based alloys was made in consideration with its physical and electrochemical characteristics. The obtained results showed that the alloying of Ni with W gives superior properties towards HER, attributed by its better hydrogen adsorption energy than in Ni-P alloy. The surface appearance, chemical composition and phase structure of the coatings were studied using SEM, EDS and XRD analyses, respectively.

Effect of Graphene Oxide on the Electrocatalytic Activity of Ni-W Alloy Coating

Nickel-Tungsten-reduced Graphene Oxide (Ni-W-rGO) composite coating was developed through composite electrodeposition method, and its electrocatalytic activity for alkaline hydrogen evolution reaction (HER) was studied. The development of composite coating with a homogeneous dispersion of rGO nanosheets was achieved from an optimal Ni-W plating bath loaded with nanosheets was achieved from an optimal Ni-W plating bath loaded with graphene oxide (GO), synthesized through the chemical oxidation of graphite. The electrocatalytic efficacy of the composite coating for HER was tested using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques in 1.0 M KOH medium. A remarkable increase in the HER activity was observed for the Ni-WrGO composite coating compared with the Ni-W alloy coating. The variation in composition, surface morphology and crystal structure of the composite coating effected by the incorporation of rGO into the alloy matrix favor the enhanced HER activity, as evidenced by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Tungsten content and grain boundary misorientation angle effect on crack blunting in nanocrystalline Ni-W alloy

The effect of tungsten (W) content and grain boundary misorientation angle (GBMOA) on crack blunting of nanocrystalline Ni-W alloy (20–100 nm) is researched theoretically, considering the coupled effects of dislocations and grain boundaries (GBs). In our proposed model, W atoms are clustered in the dislocation free region (DFZ), impeding dislocation slip, and W additions lead to GB segregation so that the boundary energy is reduced. The dislocations emitted from the crack tip are stopped at or/and penetrated through GBs, which depends on the total force acting on the dislocations as well as the critical penetration stress. The critical penetration stress is bound up with GB energy and residual Burgers vector. The number of dislocations emitted from the crack tip and penetrated through GB is calculated by using W content and GBMOA. The results show that an increase in W content decreases the critical penetration stress and increases the number of dislocations emitted from the crack tip. The critical stress intensity factors by considering the interactions between dislocations and GBs are larger than those of dislocations stayed at GBs. It is demonstrated that crack blunting depends significantly on both W content and GBMOA.

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-Parisi-Zhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.

Electrodeposition of dilute Ni-W alloy with enhanced thermal stability: Accessing nanotwinned to nanocrystalline microstructures

We report on the effects of W content on the microstructure, mechanical properties and thermal stability of dilute NiW electrodeposits − up to 5at% W. The microstructure of NiW is significantly affected by W content. Pure Ni films were nanocrystalline (nc), whereas NiW films with 0.5at% W showed a bimodal microstructure consisting of nanotwinned (nt) fiber-like micrometer-grains and nc-grains. Further microstructural change was observed at 4at% W and more; the growth of nt-grains was largely suppressed and nc-grains were uniformly distributed in the film. This microstructural transition with W content can be explained by two distinct and competing effects of W: the reduction of stacking fault energy and the grain growth restriction. Nc-NiW shows an enhanced hardness compared with those of nc-Ni and nt-NiW, due to the grain refinement effect of W. Moreover, it shows a grain-boundary stability significantly superior to nc-Ni, suggesting potential improvement in the time-dependent deformation properties. Because a dilute Ni-W alloy can be electrodeposited with a relatively low stress, which is essential for thick-film applications, such an alloy will be a promising alternative of nc-Ni for applications to micromechanical components where thick films with better thermal stability and creep resistance are required.

Mechanical and tribological properties of Ni-W-TiB2 composite coatings

Pure Ni, Ni-W alloy, and Ni–W–TiB2 composite coatings were prepared on the copper substrate by electrodeposition technique. Surface morphology and elemental composition of as prepared samples were observed and analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) technique was used to analyze the crystallinity and phase composition of the samples. XRD patterns show a typical FCC Ni-W alloy phase of the Ni-W-TiB2 composite coating. Vickers microhardness of Ni-W-TiB2 composite coating is significantly improved as compared to pure Ni and Ni-W alloy coatings. Wear and coefficient of friction of the Ni-W-TiB2 composite coating are found to be improved. Adhesive wear is found to be predominant in pure Ni, and Ni-W coating whereas abrasive nature of wear is obtained in Ni-W-TiB2 composite coating. The Ni-W-TiB2 composite coating exhibited improved scratch resistance over pure nickel and Ni-W coatings. The scratch resistance of the composite coating is influenced by W alloying and TiB2 incorporation to the nickel matrix.

Pulse and DC Electrodeposition of Ni-W-TiO2 Thin Film Composites

Tungsten alloys with nickel are well known for their superior properties in the following areas: corrosion resistance, hardness, wear resistance, and catalytic activity towards hydrogen evolution, as comprehensively reviewed.1 In aqueous electrolytes, tungsten cannot be electrodeposited alone, but requires iron-group ions, such as Ni(II), in the electrolyte to induce its reduction.2 Composite electrodeposition of Ni-W alloys allows for further tailoring of properties. For example, Kumar et al. 3 showed that the hardness was further increased with the addition of titania in the deposit, and when pulse deposited there was an enhancement in corrosion resistance. Similarly, Goldasteh and Rastegari4 reported an increase in hardness due to refining of the crystallite size in the deposit with titania. Corrosion resistance was found to be better in pulse deposited Ni-W-TiO2 composites, compared to their DC counterparts. Both of these studies target low tungsten deposit composition and use ammonium-containing electrolytes. In the presented work, composites with high tungsten content are examined from an ammonium-free electrolyte. The influence of the TiO2particle on the metal ion reduction rate and on the deposit morphology is investigated under DC and pulsed current density (PC) deposition. A boric acid, sodium citrate, ammonium-free electrolyte with micro- or nano-scaled titania particles, at a pH of 8, and 25 °C, is used to electrodeposit the alloys onto a rotating cylinder Hull (RCH) cell. The RCH was employed to evaluate the deposit composition over a range of current densities, and an assessment of primary or secondary current distribution was made. Frequency was varied, from 0.2 Hz to 200 Hz, to examine the effect of PC deposition on the deposit composition. The composition and thickness of the deposits were measured by X-ray fluorescence (XRF). The partial current densities of Ni and W were calculated by Faraday’s law. Scanning electron microscopy (SEM) was used to examine the morphology of the deposits at both low and high magnifications. Under DC deposition, the trend in particle incorporation with the amount of particles in the deposit followed a limit of the Guglielmi model,5where a Langmuir adsorption behavior dominates. The amount of particle incorporation for nano-particles compared to micro-particles was lower. Under PC deposition, the composition was slightly altered compared to DC. For example, with micro-particles, the tungsten deposit content decreased with PC compared to DC more at low current densities (PC 45 wt % W vs. DC 55 wt % W) and had little effect once the side reaction was high. SEM images show that there was a significant change in the surface morphology with the inclusion of particles; adding particles produced a rougher surface. PC deposition with different frequencies did not significantly alter the roughness at the micro-scale, but it did effect the presence of small nano-pits observed at low current densities; the higher the frequency the smaller the pit diameter and density found on the deposit surface. A discussion on the influence of frequency with both nano- and micro-sized particles will be presented. The authors acknowledge support from NASF and NSF. N. Tsyntsaru, H. Cesiulis, M. Donten, J. Sorte, E. Pellicer, and E. J. Podlaha-Murphy , Surface Engineering and Applied Electrochemistry, 48 491 (2012).A. Brenner, Electrodeposition of Alloys: Principles and Practice, p. 347, Academic Press Inc., New York (1963).K.A. Kumar G. P. Kalaignan, and V.S. Muralidharan, Ceramics International, 39 2827 (2013).H. Goldasteh and S. Rastegari, Surface and Coatings Technology, 259 393 (2014).N. Guglielmi, Journal of the Electrochemical Society, 119 1009 (1972).

Effect of magnetic field on corrosion protection efficacy of Ni-W alloy coatings

High corrosion resistant Ni-W alloy coatings were developed using magnetoelectrodeposition (MED) approach for the protection of mild steel substrates. The conditions for the development of more corrosion resistant MED Ni-W alloy coatings were optimized by inducing a magnetic field (B) during deposition, in terms of intensity and direction. The applied magnetic field was used as a tool to alter the crystallinity, composition and thereby the corrosion resistance of the coatings. It was demonstrated that the corrosion resistance of Ni-W alloy coatings can be improved to many folds of its magnitude by MED approach. Significant increase in corrosion resistance exhibited by MED coatings (under both parallel and perpendicular magnetic field, B) is attributed to the increased W content of the alloy affected by an increase in limiting current density (iL). The high corrosion resistance of the MED Ni-W alloy coatings was explained in the light of magnetohydrodynamic (MHD) effect, responsible for the increased W content, brought about by the enhanced mass transport. The inherent limitations of the bath like low iL and induced type of codeposition which impedes the development of W rich alloy coatings has been successfully resolved by MED method. Drastic improvement in corrosion resistance is ascribed to the basic difference in the process of electrocrystallization and phases formed during MED, confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. The results are discussed with greater insight into binary alloy deposition and mass transfer process at cathode/electrolyte interface.

Influence of heat treatment on microstructure and mechanical properties of pulse electrodeposited Ni-W alloy coatings

The present study deals with the electrodeposition and structural characterization of as-deposited and heat treated nickel-tungsten (Ni-W) alloy coatings. The coatings were deposited using pulse reverse electrodeposition (PRED) and pulse electrodeposition (PED) from a Ni-W plating bath. Wide range of alloy compositions have been obtained with tungsten (W) percentage in the alloy ranging from 0% to 25at% by altering pulse parameters. The coatings were subsequently heat treated at a temperature of 700°C for 1h and were characterized in terms of phases present, grain size, hardness and elastic modulus. It was observed that the coatings were crystalline up to 12at% W and beyond which the coatings were found to be a mixture of amorphous and crystalline phases. Heat treatment resulted in crystallization of amorphous phase and precipitation of secondary phases. Substantial grain growth had occurred after heat treatment and as a result, the hardness of heat treated coatings was found to be less than that of their as-deposited counterparts up to 17at% W. Beyond 17at% W hardness of heat treated Ni-W was found to be higher due to dispersion hardening.

β-relaxation related bright bands in thin film metallic glasses: Localized percolation of flow units captured via transmission electron microscope

We report that β-relaxation of amorphous NiW alloy film was effectively enhanced by adding two thin crystalline layers into the amorphous layer. Correspondingly, more bright bands, i.e., nano shear bands, were captured in the amorphous layer, which experienced more pronounced β-relaxations. Based on the potential energy landscape theory, the bright band was proposed to be the localized percolation of flow units corresponding to β-relaxation. Our findings may help connecting experimentally β-relaxation with flow units and shed light on the microstructure origin of β-relaxation.

Surface defects on the Gd2Zr2O7 oxide films grown on textured NiW technical substrates by chemical solution method

Epitaxial growth of oxide thin films has attracted much interest because of their broad applications in various fields. In this study, we investigated the microstructure of textured Gd2Zr2O7 films grown on (001)〈100〉 orientated NiW alloy substrates by a chemical solution deposition (CSD) method. The aging effect of precursor solution on defect formation was thoroughly investigated. A slight difference was observed between the as-obtained and aged precursor solutions with respect to the phase purity and global texture of films prepared using these solutions. However, the surface morphologies are different, i.e., some regular-shaped regions (mainly hexagonal or dodecagonal) were observed on the film prepared using the as-obtained precursor, whereas the film prepared using the aged precursor exhibits a homogeneous structure. Electron backscatter diffraction and scanning electron microscopy analyses showed that the Gd2Zr2O7 grains present within the regular-shaped regions are polycrystalline, whereas those present in the surrounding are epitaxial. Some polycrystalline regions ranging from several micrometers to several tens of micrometers grew across the NiW grain boundaries underneath. To understand this phenomenon, the properties of the precursors and corresponding xerogel were studied by Fourier transform infrared spectroscopy and coupled thermogravimetry/differential thermal analysis. The results showed that both the solutions mainly contain small GdZrO clusters obtained by the reaction of zirconium acetylacetonate with propionic acid during the precursor synthesis. The regular-shaped regions were probably formed by large GdZrO frameworks with a metastable structure in the solution with limited aging time. This study demonstrates the importance of the precise control of chemical reaction path to enhance the stability and homogeneity of the precursors of the CSD route.

Properties of CrC+(Ni-W) Duplex Layers Produced in Vacuum Chromizing Process Combined With Galvanic Treatment

Abstract Diffusion chromizing was applied to increase the durability of tools, which operate under wear conditions. Vacuum chromizing, as opposed to other known methods, i.e., powder pack, gas, and molten salt baths, is ecological on account of non-toxic substrates, as well as absence of harmful wastes. Vacuum chromizing of tool steel results in hard and wear resistant chromium carbide coatings. However, the obtained carbide layers exhibited rather poor corrosion resistance in chloride media. To improve their corrosion resistance, Ni-W alloy was deposited electrolytically on the steel surface before the chromizing process. This resulted in the formation of CrC+(Ni-W) type duplex layers with modified characteristics. The objective of this paper was to determine the structure of these duplex layers on tool steel surface, their tribological properties and corrosion resistance in chloride solutions. Investigations of layers’ thickness, their morphology, phase composition, hardness, and depth profiles of elements in the layer diffusion zone have been carried out. The chemical composition and distribution of the phases formed in the surface region of the samples were examined by a SEM microscope, equipped with a BSE detector and an EDS spectrometer. Wear resistance tests were carried out by the three-cylinder-cone method. Electrochemical corrosion measurements of obtained layers were performed in a 0.5 M NaCl solution. The tests proved that the wear resistance of duplex layers of the CrC+(Ni-W) type, produced by vacuum chromizing of electrolytically coated steel, is as good as that of carbide layers of the CrC type, produced on bare steel surface, but their corrosion resistance is higher.

Effect of pH Value on Structure and Corrosion Resistance of Electrodeposited Ni-W Alloy Coating

Effect of pH Value on Structure and Corrosion Resistance of Electrodeposited Ni-W Alloy Coating

Nickel removal from wastewater by induced co-deposition using tungsten to formation of metallic alloys

In this work, nickel was removed from industrial effluent by an electrodeposition process and the alloy obtained with this metal was characterized. The removal tests occurred in optimized conditions, under those occurred the formation of Ni-W alloy from synthetic baths prepared in laboratory. Thus, an experimental planning was performed in order to investigate the variation of nickel concentration in the bath, temperature and density of the current applied. The variable of response considered was the faradic efficiency. The metallic alloy obtained through the nickel removal of an electroplating wastewater was characterized by X-ray Diffraction, Infrared Spectroscopy and Scanning Electron Microscope with chemical analysis by Dispersive Energy of X-rays. The faradic efficiency was strongly influenced by the nickel concentration, achieving a value of 51.4%. In the test of nickel removal from a real wastewater, the faradic efficiency registered was approximately 90% and the nickel removal was 38.76%. The coating obtained from the real wastewater was characterized by a high level of crystallinity and pureness. The Scanning Electron Microscope images showed that the metallic alloy of Ni-W was cracked, which may be related to its crystallinity. Ni and W contents in the alloy were approximately of 73 and 27%, respectively.

Influence of vanillin on the corrosion behavior of Ni-W alloy electrodeposits and its properties

A simple and viable electrodeposition technique has been implemented to fabricate nanocrystalline Ni-W electrodeposits from an alkaline citrate bath with variations of vanillin (additive) concentration. The optimization of additive in the bath was substantiated in terms of its corrosion resistance property (evaluated using Tafel polarization and electrochemical impedance spectroscopy). For alloys deposited in presence of additive (100ppm) in the bath, resulted in low corrosion rate (C.R) and high charge transfer resistance (Rct). The enhanced corrosion resistance property (i.e. low C.R and high Rct) was deduced in terms of its homogenous surface morphology (using scanning electron microscope), reduction in crystalline size (using X-ray diffraction study), diminish in surface roughness value (using atomic force microscopy) as compared with that of electrodeposits obtained in the absence of additive. The inclusion of additive in the electrodeposits during electrodeposition, showed a major impact for its significant corrosion resistance property (C.R.−0.12mm/year and Rct-2177.83Ω·cm2). With an increase in the additive concentration in the bath, the corrosion resistance of the Ni-W coating becomes inferior, due to its porous nature and relative decrease in its capacitive behavior at electrode/electrolyte (corrosive) interface.

On the implication of solute contents and grain boundaries on the Hall-Petch relationship of nanocrystalline Ni-W alloys

Nano-crystalline nickel-tungsten alloys are investigated in order to provide evidence of the contribution of the solute content (light elements and tungsten) and grain-boundaries on hardness. For this purpose, Ni-W alloys were elaborated by electrodeposition in an additive free citrate ammonium bath. The variation of electrodeposition conditions leads to W contents up to 18at%, with a broad range of grain sizes (5–650nm). The incorporation of light elements (H, O, C, N) depends on the deposition applied conditions and a progressive modification of the texture is observed with the following sequence: {110}, NT (Non-Textured) and {111} textures. We show that the Hall-Petch relationship for these alloys is influenced by the presence of light elements, the nature of the crystallographic texture and the grain boundaries character. The dependence of grain size on flow stress is a direct consequence of the solute content (solute strengthening) and the evolution of the internal stresses with grain size. To explain the experimental data, two competing physical mechanisms are suggested: grain boundary shearing and dislocation emission at grain boundary, which are affected by the nature of the grain boundary and the solute content.

Ni-W electrodeposited coatings: Characterization, properties and applications

Nowadays, application of nanocrystalline nickel-tungsten (Ni-W) alloys is receiving a great interest because they are an efficient replacement for hard chromium coatings owing to their premium hardness, wear, and corrosion properties. Moreover, heat-treated nanocrystalline Ni-W alloys demonstrate proper mechanical properties as well as thermal stability at high temperatures. The current paper reviews different aspects of electrodeposition, microstructure, corrosion, oxidation, wear, and mechanical properties Ni-W alloys and nano/micro composites. Besides, heat treatment effects on properties and thermal stability of these alloys are also reviewed.