Ni Metal Matrix Research Articles

Exploiting magnetic sediment co-electrodeposition mechanism in Ni-Al2O3 nanocomposite coatings

• Magnetic sediment co-electrodeposition (MSCD) mechanism of Ni-Al 2 O 3 nanocomposites. • Coating morphology, crystal structucture, e, microhardness, nanoparticles loading and zeta potential were the main criteria. • Two phenomena control MSCD: (i) magnetohydrodynamic (MHD) and (ii) gravitational force. • MHD predominates for nano-sized particles (<100 nm) by reducing the thickness of the diffusion layer. • Gravitational force is dominant for agglomerated particles (>300 nm). Our focus in this work is to exploit a mechanistic view of magnetic sediment co-electrodeposition (MSCD). Ni-Al 2 O 3 nanocomposite coatings were electrodeposited in the presence and absence of an external magnetic field using sediment co-deposition (SCD) cell design. The dispersion, zeta potential, and size of Al 2 O 3 particles in solution were measured and interpreted for the MSCD mechanism. The effects‌ of magnetic field on morphology, crystallographic texture, microhardness, dispersion of Al 2 O 3 nanoparticles in Ni metal matrix were studied and a co-deposition kinetic model was accordingly postulated. Magnetic sediment co-electrodeposition not only changes the surface morphology of Ni-A 2 O 3 from pyramidal-shaped to spherical grains, but it also increases the microhardness (from 365 to 500 HV) by decreasing the crystallite size (from 130 to 110 nm). Calculations of relative texture coefficient (RTC) values and Rietveld analysis showed that the growth of texture (2 0 0) of Ni-Al 2 O 3 composite coatings is reinforced in the presence of a magnetic field. Based on our assumed model, two determining phenomena control the magnetic sediment co-deposition process: (i) magnetohydrodynamic (MHD) and (ii) gravitational force. MHD predominates for nano-sized particles (<100 nm) by reducing the thickness of the diffusion layer, whereas, the gravitational force is dominant for agglomerated particles (greater than300 nm).

Sintered Ni metal as a matrix of robust self-supporting electrode for ultra-stable hydrogen evolution

For the self-supporting catalysts of Hydrogen evolution reaction (HER), the rational design and fabrication of substrate with porous structure and sufficient mechanical strength are critical to promoting the industrial HER application. In this work, a novel porous sintered Ni metal as the matrix for supporting catalysts was successfully prepared by powder metallurgy, and a self-supporting electrode for HER was fabricated via a simple sulfurization process on this sintered Ni metal matrix. For instance, MoS2/Ni3S2 nanorods (NRs) were vertically grown on the as-sintered porous Ni matrix, and the morphology of the sintered Ni matrix significantly affected the growth of MoS2/Ni3S2 NRs. The [email protected] Ni electrode shows a low overpotential of η10 = 56 mV and Tafel slope of 82 mV dec−1. Compared with [email protected] foam, the [email protected] Ni exhibits superior stability, where no exfoliation and cracks are observed on the surface of the electrode after 5000 CV cycles. Ultra-high stability and long-term durability are obtained over 100 h even at high potentials of 200 and 300 mV. Moreover, the tensile strength of the as-obtained electrode based on the sintered Ni manifests nearly 260 times higher than that of [email protected] foam, evidencing an excellent mechanical property. This work provides an idea for the preparation of self-supporting metal-based catalytic electrodes in large-scale hydrogen production.

On the microstructure-dependency of mechanical properties and failure of low-pressure cold-sprayed tungsten carbide-nickel metal matrix composite coatings

This study improves upon understanding of the effects of reinforcing particle content and microstructure on the mechanical properties and failure of low-pressure cold spray fabricated tungsten carbide-nickel (WC-Ni) metal matrix composite (MMC) coatings. Image analyses were performed on scanning electron microscope (SEM) micrographs of the coatings to characterize the microstructure and measure the total interfacial area between the reinforcing WC particles and the Ni metal matrix, the mean free path between the particles, the average particle size, and the porosity of the coating. Uni-axial quasi-static tensile testing was conducted on the as-sprayed coatings. The tensile stresses that were measured were coupled with the evolving strains that were calculated by using the digital image correlation (DIC) technique. The results showed that mechanical properties, namely tensile strength and Young's modulus, of the composite coatings increased with increasing WC content in the coatings. The increases were due to the refined microstructural features that occurred with the decrease in the porosity of the coating that was caused by significant consolidation of the Ni metal matrix. Furthermore, this increase in strength and Young's modulus was also related to the increase in the interfacial area between the reinforcing carbide particles and the metal matrix that was caused by the increase in carbide content in the coating, a decrease in the average size of the carbides in the coating, and a reduction of the mean free path between the carbide particles. A framework was presented to elicit the micro-macro relationships between the microstructure and the tensile strength of the cold-sprayed composite coatings. Based on the developed framework, two distinct coating mechanical strength regimes were observed, indicating a significant increase in the tensile strength of the coatings that were comprised of more than 30 wt% WC due to the refined microstructure of the coatings. The higher value tensile strength regime was also confirmed by the larger average mechanical energy absorbed to failure under tensile loading and lower damage accumulation. This collection of data of mechanical properties and the microstructures presented in this study are important to validate numerical-based failure models for cold-sprayed composite coatings. Altogether, the results of this study will enhance understanding of the sensitivity of mechanical response of a composite coating to microstructural changes.

HER activity of MxNi1-x (M = Cr, Mo and W; x ≈ 0.2) alloy in acid and alkaline media

Reported are the synthesis and HER activity of MxNi1-x (M = Cr, Mo and W; x ≈ 0.2) alloy in acid and alkaline media. It was realized that doping group ⅥB element (Cr, Mo, W) in Ni metal matrix can greatly improve corresponding HER activity in both acid and alkaline electrolyte. MoxNi1-x exhibits the highest HER activity among all samples in 1.0 M H2SO4 electrolyte, which it requires only 64 mV to reach current density of 10 mA/cm2. Calculated free-energy of ΔGH∗ for MxNi1-x (M = Cr, Mo and W) well explained their HER activity trend in acid and it follows the order of MoxNi1-x > WxNi1-x > CrxNi1-x. In alkaline condition, their HER activities all deteriorate except CrxNi1-x. HER activity of CrxNi1-x in 1.0 M KOH (η10(base) = 106 mV) surpasses that in 1.0 M H2SO4 (η10(acid) = 160 mV) is quite unexpected. The DFT calculation suggesting the adsorbed OH holds the key and will alter the adsorption energy (ΔGH∗) of neighboring H atom on the surface in alkaline condition. This case study offers a good opportunity to investigate the factor to influence HER behavior of electrocatalyst in acid and alkaline media.

Room-temperature magnetoresistance of nanocrystalline Ni metal with various grain sizes

The room-temperature magnetoresistance (MR) characteristics of nanocrystalline (nc) Ni metal with various grain sizes (between 30 and 100 nm) are investigated in this work for the first time. The nc-Ni foils were produced by electrodeposition and the results are compared with data measured on coarse-grained (bulk) pure Ni metal samples prepared by cold-rolling and annealing. The MR(H) curves measured in magnetic fields up to H = 9 kOe are analyzed in detail to determine the anisotropic magnetoresistance (AMR) ratio. The magnitude of the AMR ratio was found to be around 2.5% for bulk Ni and in the range from about 2 to 2.5% for the nc-Ni samples, the latter data not exhibiting a systematic dependence on the grain size. On the other hand, the field-induced resistivity anisotropy splitting ∆ρAMR in the magnetically saturated state of the nc-Ni series was found to be proportional to the zero-field resistivity of the same samples with different grain sizes. The slope of this proportionality relation provided an AMR ratio of 2.4% for all nc-Ni samples, matching well the value for the bulk Ni samples. Thus, the AMR ratio for polycrystalline Ni metal seems to be fairly independent of the microstructural features. This also means that the AMR ratio is an inherent characteristic of the Ni metal matrix and it remains the same even if the matrix resistivity changes (e.g., by introducing grain boundaries) without noticeably modifying the electronic density of states at least in the vicinity of the Fermi level.

Recent Developments on Wear and Corrosion Behavior of Iron/Iron–Nickel Metal Matrix Composites Reinforced with Zirconia

This article reports a brief review on the effect of process parameters on mechanical and corrosion properties of Fe-/Fe–Ni-based composites. Particle-reinforced metal matrix composites (MMCs) have gained a special interest in the field of structural, mechanical, aeronautical, and aviation industries. Iron-based MMCs are the one which are in high demand for tribological applications due to the high strength and high abrasion resistance properties. Different techniques have been used by different researchers for enhancing different properties of these composites during the last several years. Optimization of processing parameters, e.g., milling time, milling speed, reinforcement content, sintering time, and temperature are important for the development of composites by powder metallurgy route. Alloying of Ni in Fe–ZrO2 MMCs is found to play an important role in matrix phase formation during sintering. During sintering, the formation of γ phase in the matrix retards reactive sintering between metal and ceramic particles. Effect of some of the processing parameters on phase formation and various properties such as density, hardness, dry sliding wear properties, and corrosion reported in our previous studies have been summarized for particulate reinforced Fe/Fe–Ni metal matrix composites.

Microstructure and Wear Resistance of ZrC-ZrB2 /Ni Composite Coatings Prepared by Plasma Transferred Arc Cladding

The ZrC-ZrB2/Ni metal matrix composite coatings were in-situ synthesized from a mixture of Ni, Zr and B4C by plasma transferred arc (PTA) cladding process. Microstructures and phase constituents of the coatings were characterized by electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD). Microhardness and wear resistance of the coatings were systematically investigated by means of vickers hardness tester and wear tester. The results showed that the main phases of the composite coatings were ZrB2 and ZrC. The coatings had a sound metallurgical bonding to the SA-283C steel substrate. Microhardness and wear resistance of the substrate were greatly improved by the composite coatings, and both of them showed a tendency to increase first and then decrease with the increase of the Ni content. As the content of Ni was 30 wt.%, the hardness of the coating reached the maximum value, 1522 HV, and the wear resistance was about 15 times that of the substrate.

Effect of Ultra-fine WC Particles on Microstructural Evolution and Wear Behavior of Ni-Based Nano-CeO2 Coatings Produced by Laser

The wear behavior and microstructure of CO 2 laser cladded Ni-based alloy coatings with 1 wt% nano-CeO 2 and 20 wt% WC addition (CeO 2 /Ni) was compared with Ni-based coatings with 1 wt% nano-CeO 2 addition (WC-CeO 2 /Ni). Both coatings were cladded on 30CrMnSiNi2A steel with good metallurgical bounding to substrate. The influence of ultra-fine carbide WC on the microstructure of WC-CeO 2 /Ni alloy composite coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). WC addition increased M 23 C 6 content, but decreased the M 7 C 3 . The comparison of comprehensive mechanical properties between coatings with and without fine WC particles was conducted on Vickers hardness and wear-resistance test system. Results indicate that the performance of WC-CeO 2 /Ni is better than that of CeO 2 /Ni metal matrix composition (MMC). Few hot cracks appeared in Ni-based WC-CeO 2 MMC production, which were investigated by SEM and EDS. The crack mechanism can be claimed as Fe dilution and coefficient of thermal expansion for WC-CeO 2 /Ni MMC differed from that of base material 30CrMnSiNi2A steel.

Electrodeposition of Ni-La2O3 composite on AA6061 alloy and its enhanced hardness, corrosion resistance and thermal stability

In this work, the microstructure, microhardness, corrosion behavior and thermal stability of Ni-La2O3 composite on AA6061 aluminum alloy were studied. Corrosion behavior was studied with 3.5wt% NaCl solution at room temperature in a static electrolyte condition. Ni-La2O3 showed nobler corrosion potential than the pure nickel and aluminum alloy and a maximum microhardness of 750HV (Vicker's hardness) was observed at optimized conditions. It is evident that the incorporation of La2O3 in the Ni metal matrix leads to the corrosion resistance and the hardness improvement. Thermal stability was studied by using differential scanning calorimetry (DSC) as well as annealing at constant temperature of 500°C for 5h in a furnace and it shows better thermal stability of the composite. Electrodeposited Ni-La2O3 composites were characterized by SEM/FESEM, EDS, XRD and electrochemical techniques.

Effect of CTAB concentration in the electrolyte on the tribological properties of nanoparticle SiC reinforced Ni metal matrix composite (MMC) coatings produced by electrodeposition

In this study, a nickel sulfate bath containing SiC nanoparticles (between 100 and 1000nm) was used to obtain hard and wear-resistant nanoparticle reinforced NiSiC MMCs on steel surfaces for anti-wear applications, such as dies, tools and working parts. The influence of stirring speed and surfactant concentration on particle distribution, microhardness and wear resistance of nano-composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The depositions were controlled to obtain a specific thickness (between 50 and 200μm) and particle volume fraction in the matrix (between 0.02 and 0.12). The hardness of the resulting coatings was also measured and found to be 280–571Hv, depending on the particle volume in the Ni matrix. The effects of the surfactant on the zeta potential, co-deposition and distribution of SiC particles in the nickel matrix, as well as the tribological properties of composite coatings, were investigated. The tribological behaviors of the electrodeposited SiC nano composite coatings sliding against M50 steel ball (Ø 10mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55–65 %). The results showed that the wear resistance of the nano composites was approximately 2–2.2 times higher than unreinforced Ni deposited material.

Effect of particle concentration on the structure and tribological properties of submicron particle SiC reinforced Ni metal matrix composite (MMC) coatings produced by electrodeposition

In the present work, a nickel sulfate bath containing SiC submicron particles between 100 and 1000nm was used as the plating electrolyte. The aim of this work is to obtain Ni–SiC metal matrix composites (MMCs) reinforced with submicron particles on steel surfaces with high hardness and wear resistance for using in anti-wear applications such as dies, tools and working parts for automobiles and vehicles. The influence of the SiC content in the electrolyte on particle distribution, microhardness and wear resistance of nano-composite coatings was studied. During the electroplating process, the proper stirring speed was also determined for sub-micron SiC deposition with Ni matrix. The Ni films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The depositions were controlled to obtain a specific thickness (between 50 and 200μm) and volume fraction of the particles in the matrix (between 0.02 and 0.10). The hardness of the coatings was measured to be 280–571HV depending on the particle volume in the Ni matrix. The tribological behaviors of the electrodeposited SiC nanocomposite coatings sliding against an M50 steel ball (Ø 10mm) were examined on a tribometer. All the friction and wear tests were performed without lubrication at room temperature and in the ambient air (with a relative humidity of 55–65%). The results showed that the wear resistance of the nanocomposites was approximately 2–2.2 times more than those of unreinforced Ni.

Improved Performance in Aerospace Structures with Ti and Ni Metal Matrix Composites

The external structures of supersonic vehicles are exposed in several critical regions to temperatures that could reach 1000°C. This limit is higher than any safe operative service not only for titanium alloys but also for commercial nickel superalloys. The simplest way to improve titanium and nickel matrices temperature behavior (i.e: strength and fatigue resistance) is to introduce a strengthening phase in its matrix. These class of materials are known as: Metal Matrix Composites (MMC). It is possible reinforce both titanium and nickel superalloys by mean of high temperature resistant ceramic fibers.

Porous nano-Al 2O 3/Fe–Cr–Ni composites fabricated by pressureless reactive sintering

Porous in situ nano-Al 2O 3 reinforced Fe–Cr–Ni metal matrix composites (MMCs) were fabricated from a mixture of Al/nano-Fe 2O 3/Cr/Ni powders via pressureless reactive sintering at 700–800 °C for 1–2 h. X-ray diffraction (XRD) demonstrated that the porous composites produced at 800 °C for 2 h consisted of Al 2O 3, Cr 0.7Fe 0.36Ni 2.9 and Fe–Cr phases generally. Scanning electron microscopy (SEM) showed that the Al 2O 3 particles were ultrafine and uniformly distributed in the metal matrix. The pore sizes ranged from 1 μm to 20 μm for the sintered porous composites fabricated at 800 °C for 2 h. The resultant porous composite prepared under prepressing pressure of 200 MPa before sintering had more homogeneous and finer pore structure, lower porosity and higher bending strength and fracture toughness than those prepared under prepressing pressure of 5–100 MPa.

Study of tribological characteristics and wear mechanism of nano-particle strengthened nickel-based composite coatings under abrasive contaminant lubrication

In desert areas, abrasive particles entering the machines cause serious wear of the sliding components. To improve the wear resistance of the machine parts, the Al 2O 3, TiO 2, Si 3N 4, diamond nano-particle strengthened nickel-based brush plating composite coatings were prepared by co-deposition of nano-particles with Ni metal–matrix. The effects of different types of nano-particle and nano-particle contents, in the solution, on the tribological properties of the composite coatings under abrasive lubrication conditions were tested on a commercial ball-on-disk friction and wear test machine. The scanning electron microscopy (SEM) was used to reveal the wear mechanisms. The results show that all of the composite coatings have finer microstructures and higher micro-hardness compared with the pure nickel coating, but only n-diamond/Ni and n-Al 2O 3/Ni composite coatings show improved tribological properties. Among them, the n-Al 2O 3/Ni composite coating has the highest cost performance. And the optimum Al 2O 3 nano-particle content in the solution is 20 g/L. The main wear mechanisms of the composite coating are plastic deformation, micro-cutting, and scuffing.

Preparation, microstructure and tribological properties of nano-Al 2O 3/Ni brush plated composite coatings

Nano-Al 2O 3/Ni brush plated composite coatings were prepared by co-deposition of Al 2O 3 nanoparticles with Ni metal matrix during brush plating. In this process nanocrystalline ceramic powders with grain sizes below 40 nm were suspended in the plating solution and deposited with the metal to produce nanoparticle strengthened metal matrix composite coatings. The microstructure, composition, microhardness and wear properties of the coating in abrasive contaminant lubrication were examined. The results show that the nanoparticles are uniformly distributed in the composite coating, and the microstructure of the composite coating is much finer and denser compared with the pure nickel plating coating. Moreover, the microhardness and tribological properties of the composite coating are higher than that of the pure nickel coating.