Nickel base hardfacing alloys serve to mitigate corrosion losses at elevated temperatures. Efficacy of Nickel base hardfacing alloys can be compromised when applied onto Fe base substrates due to ...iron dilution in hardfacing. The degree of Fe dilution can be reduced by using advanced deposition methods and optimized deposition parameters. Gas Tungsten Arc Welding (GTAW) method is commonly employed for its cost-effectiveness and versatility, but it tends to induce higher Fe dilution due to increased heat input. This study aims to reduce the degree of Fe dilution and enhance corrosion resistance by introducing a nickel base buffer layer (alloy 625) between the nickel base hardfacing alloy and AISI 316L stainless steel substrate. For comparative purposes, Ni base hardfacing alloy was deposited on the substrate without any buffer layer. Hardfacing depositions were prepared using manual GTAW process. Process parameters namely, deposition current, voltage, travelling speed, pre-heating temperature, and cooling method were kept constant. Samples underwent aging at 1123 K for 4 h, followed by microstructural examination via optical and scanning electron microscopes. Iron (Fe) dilution quantification was performed using energy dispersive spectroscopy (EDS). The EDS analysis showed that the use of buffer layer between the hardfaced deposit and the substrate decreased the degree of Fe dilution in the hardfaced deposit. X-Ray diffraction (XRD) analysis was performed to identify various phases formed in the hardfaced deposit. Potentiodynamic polarization test was performed to assess the corrosion resistance of hardfaced deposit in 3.5 wt% NaCl solution. Results show significant improvement in corrosion resistance of hardfacings deposited sample with buffer layer as compared to those without buffer layer. Aging treatment further enhanced corrosion resistance. The corrosion resistance data is correlated with the microstructure and phases formed in various samples.
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•The impact of buffer layer on hardness, microstructure, Fe dilution, and corrosion resistance in Ni-based hardfacing using the GTAW method.•Higher Ni concentration in the hardfacing deposition reduces Fe dilution, improving the Ni/Fe ratio in Ni-based hardfacing.•Presence of Mo and Nb in the hardfacing refine microstructure and improve corrosion resistance.•Solidification analysis performed to assess the impact of Mo and Nb addition using phase and Scheil diagrams.
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.
HER activity of MxNi1-x (M = Cr, Mo and W; x ≈ 0.2) alloy behaves differently in acid and alkaline media. The DFT calculation suggesting the adsorbed OH holds the key and will alter the adsorption energy (ΔGH∗) of neighboring H atom on the surface. It well accounts for their HER activity in acid and alkaline media, which can possibly be applied in other system in the future. Display omitted
•High purity of targeted alloys were synthesized by using rapid arc-melting method.•MoxNi1-x (x ≈ 0.2) alloy delivers high HER activity (η10 = 64 mV) in acid media.•Adsorption energy of H and OH on sample surface were explored by using DFT.•The role of adsorbed OH on sample surface toward HER activity is discussed.
The present work investigated the microbial-induced pitting behavior of the 70/30 copper-nickel (Cu-Ni) alloy. Unlike the MIC of Cu by Desulfovibrio vulgaris, the alloy exhibited considerable pitting ...sensitivity and pit nucleation frequency under the 10%, 50%, and 100% carbon source (CS) levels. The metastable pit was more likely to evolve into stable growth in the full-strength medium. Meanwhile, a model was established to explain the alloy pitting mechanism induced by D. vulgaris. New evidence further verified that Cu-Ni alloy MIC was not only ascribed to the biogenic H2S but the electroactive D. vulgaris biofilms via extracellular electron transfer (EET) for energy harvest.
●The pitting corrosion of 70/30 Cu-Ni alloy by D. vulgaris is studied using Hilbert spectroscopy analysis.●The alloy exhibits high pitting sensitivity for the 10%, 50%, and 100% CS levels.●A model is established to explain the pitting mechanism induced by D. vulgaris.●Metastable pitting is more likely to transform into stable in the full-strength medium.●New evidence further proves that two types of MIC mechanisms coexist in the Cu-Ni alloys MIC.
This study investigates single-layer and double-layer thermally sprayed nickel alloy coatings (bond and top coatings). Ni-5 wt% Al and Ni-20 wt% Cr were used as bond coatings, whereas highly alloyed ...Ni-based coatings, Hastelloy C276 or Inconel 625 were used as top coatings. Arc spraying (A) and high-velocity oxy-fuel (HVOF) techniques were used to create the coatings on a 304 stainless steel substrate. The samples were studied by performing potentiodynamic polarization tests in a 20 vol% H2SO4 solution at room temperature. The scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) techniques were used to investigate the microstructure and chemical composition of the coatings. The arc sprayed coatings are composed of a lamellar microstructure with low porosities, unmelted particles, and high oxides at the intersplats. A uniform and compact coating with minimal oxides and porosity was achieved for all coatings via HVOF technique. In single-layer coatings, arc spray coating surpasses HVOF coating owing to its oxide layers, which impede sulfuric solution penetration and bolster resistance against electrolyte infiltration. Double-layer coatings, comprising a bonding layer and a top coating, using the same thermal spray method have shown to enhance corrosion resistance.
•In comparison to Hastelloy C276 coatings, Inconel 625 coatings exhibited consistent passive film stability.•Ni-20wt.% Cr bond coatings demonstrated remarkable corrosion resistance attributed to protective Cr oxide films.•Cracks along intersplats are observed in arc sprayed coatings while HVOF coating seems to have less corrosion damage.•For HVOF coatings, localized corrosion occurred along boundaries of semimolten particles and inside molten splats, intersplats, and in open porosity.
The microbiologically influenced corrosion (MIC) behavior of the copper-nickel (Cu-Ni) alloy welded joint induced by Desulfovibrio vulgaris was investigated. Distinct gradient changes in MIC behavior ...were observed in different regions, with the heat-affected zone (HAZ) consistently exhibiting higher localized corrosion sensitivity. Specifically, the asymmetric corrosion of HAZ was attributed to the galvanic effect between HAZ and welding zone (WZ). On a submicroscopic scale, the WZ acted as a cathode, mitigating corrosion in the later stages of Desulfovibrio vulgaris incubation. Additionally, the deep corrosion propagation at the HAZ/WZ interface was caused by the combined action of galvanic effect and Desulfovibrio vulgaris.
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•The MIC behavior in different regions of Cu-Ni alloy welded joint is investigated.•The microstructure evolution and its correlation with microhardness is analyzed.•The corrosion behavior in HAZ is quite different from those of in BM and WZ.•The HAZ is an active region that can be preferentially and more quickly corroded.•D. vulgaris intensifies the galvanic and asymmetric corrosion in the welded joint.
The paper explains the mechanical lead and wears the properties of composites made from the cross-section of Nickel composite metal using the common shape. Nickel and nickel-containing base ...composites are used as critical and important materials in a broad variety of current applications due to their wonderful properties, such as exceptional mechanical strength, advanced mix safety, and complex process control. As a result, these materials had a steadily increasing enthusiasm for exhibiting predominance in different applications in their mechanical and tribological properties. Improving these more exceptional materials with improved workmanship for mechanical and tribological applications has led experts to develop new and innovative materials from the hypothetical processes to be developed. Product lattices composites have an advantage over the end, because they are particularly suitable for applications requiring outstanding stability at high temperatures, unrivaled basics, dimensional protection and light weight. This composite material, in the same way, offers a mix of impenetrable disintegration, heat exhaustion, heat staggering, quality, robustness, metallurgical quality, workability, weldability and, in addition to its ability to withstand a wide range of conditions of Extraordinary work, including high temperatures, is of similar concern to creeping material. Several professionals have shown that strengths such as silicone oxides, graphene, aluminum particles; silicon carbide, tungsten, graphite, etc. particles, without a very noticeable stretch, are joined together in a nickel mixture organized for the progression of the compounds. Nickel and nickel blends of world class use are widely used in steel, marine, avionics, watches, cars, improvements, PCs, etc.
Platinum-based catalysts are the best HER catalysts, but their high price affects their mass application, so how to reduce the amount of platinum in catalysts has become a hot research topic. Herein, ...we synthesized low platinum dosage and highly dispersed nano-alloy catalyst PtNi/CB using a one-step solvothermal approach. Characterization shows that in the PtNi/CB catalyst, nickel element mainly exists in the form of oxidation state and promotes the dissociation of water molecules, resulting in the formation of a hydrogen-rich chemical microenvironment on the catalyst surface, while platinum element mainly exists in the form of metal state, electron flow from nickel to platinum forms an electron-rich platinum structure with high proton affinity, which can well regulate the adsorption/desorption energies of intermediate H*. The combined effect of platinum and nickel enhances catalyst performance and stability. Based on this, the PtNi/CB catalyst requires only 29 mV overpotential to achieve a current density of 10 mA cm−2 in 1 M KOH, which is much better than that of commercial Pt/C catalyst (49 mV), and can be operated stably for a long time.
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•One-step solvothermal synthesis of Pt–Ni alloy with only 3.1% Pt loading.•Nickel in the oxidized state promotes the dissociation of water molecules.•Platinum in the metallic state can modulate the adsorption/desorption of H*.•PtNi/CB exhibits HER performance and stability beyond commercial 20% Pt/C.
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•FeNi-NCNT was prepared by carbonizing Ni2+/Zn2+-PAT-Fe(CN)63− complex precursor.•FeNi-NCNT offered high ORR/OER activities with E1/2 = 0.835 V and Ej = 10 = 1.560 V.•FeNi-NCNT-based ...aqueous RZAB showed ultralong cycle life (400 h at 25 mA cm−2).•FeNi-NCNT-based solid RZAB exhibited excellent stability and flexibility.
In this work, we present an efficient bifunctional electrocatalyst comprising iron-nickel (FeNi) alloy nanoparticles confined in nitrogen-doped carbon nanotubes (denoted FeNi-NCNT) for zinc-air batteries. The FeNi-NCNT electrocatalyst is fabricated by anion-exchange of nickel(II) ion/zinc(II) ion-2,4,6-tris-(di(pyridin-2-yl)amino)-1,3,5-triazine complex with ferricyanide anion followed by mixing with melamine and then carbonization. The resultant FeNi-NCNT electrocatalyst displays excellent bifunctional activity with a low reversible oxygen electrode index of 0.725 V. The rechargeable aqueous zinc-air battery fabricated with FeNi-NCNT air cathode manifests both high specific capacity (819 mAh g−1Zn at 5.0 mA cm−2) and long cycle life (1500 cycles/1000 h at 10 mA cm−2, 600 cycles/400 h at 25 mA cm−2, and 165 cycles/110 h at 50 mA cm−2). Moreover, flexible solid-state zinc-air battery assembled with FeNi-NCNT air cathode can deliver a specific capacity of 765 mAh g−1Zn at 5.0 mA cm−2, a power density of 84.8 mW cm−2, and a cycle life of 110 h (330 cycles) at 2.0 mA cm−2.
Metal matrix composites (MMCs) are which are incorporated with various reinforcing phases to achieve higher mechanical properties over metals. MMCs have variety of applications which can be found in ...structural parts used in aviation, marine and automotive industries. Of those most prominent are Nickel based MMCs which have outstanding properties such as high strength, corrosion resistance and enhanced tribological properties. Therefore, there has been an increasing interest for developing Nickel based MMCs for different applications. In the present work, a sand molding process was used to develop Ni-alloy/Al2O3/TiO2 hybrid composites to study their density and mechanical properties. With the help of an induction furnace, Ni-alloy hybrid composites were prepared with variable weight fractions (3–12%) of aluminium oxide (Al2O3) and a fixed weight fraction of titanium dioxide (TiO2) particles. Micrographic images showed equal distribution of the reinforced elements Al2O3 and TiO2 in the Ni-alloy matrix. EDS and XRD analyses revealed the presence of reinforced particulate matter in the Ni-alloy. The results indicated that mechanical properties such as tensile strength, yield strength, and hardness increased to 9% by weight Al2O3/TiO2 and then decreased slightly. The density of the hybrid composites decreased with an increase in the volume portion of the reinforcement.
