Nickel Solid Solution Research Articles

Alloying-Element Loss During High-Temperature Processing of a Nickel-Base Superalloy

The effect of exposure at temperatures commonly used for wrought processing/heat treatment of nickel-base superalloys on the loss of alloying elements at the free surface has been determined. For this purpose, LSHR superalloy samples were exposed at 1408 K (1135 °C) for 0.25 to 4 hours in a vacuum or air furnace. Samples heat treated in the air furnace were either bare or enclosed in quartz capsules that had been evacuated or backfilled with argon. Following heat treatment, the alloy composition as a function of depth below the surface was determined by wavelength dispersive spectroscopy. Samples that had been heat treated in the vacuum furnace exhibited significant depletion of only chromium, a behavior explained on the basis of its high activity in nickel solid solution and corresponding rapid rate of evaporation. By contrast, samples heat treated in air exhibited an irregular scale at the surface and an underlying grain-coarsened, gamma-prime-depleted metal layer lean in aluminum, titanium, and chromium. A yet different behavior characterized primarily by aluminum loss at the surface was noted for samples that had been heat treated in evacuated or argon-backfilled capsules. These observations were interpreted in the context of a reaction between the quartz capsule and the aluminum evaporant.

Effect of cobalt content on microstructure and property of electroplated nickel‐cobalt alloy coatings

AbstractNickel‐cobalt alloys were electrodeposited on copper sheets in sulfate bath containing 288.5 g/l NiSO4·6H2O, 30 g/l CoSO4·7H2O, 40 g/l HBO3, 15 g/l NaCl and 0.08 g/l lauryl sodium sulfate. The effects of cobalt content on microstructure, microhardness, and wear resistance of electroplating nickel‐cobalt alloys were studied by using SEM and XRD techniques, and microhardness tester and wear tester. The relationship between the microhardness of nickel‐cobalt alloy coatings and heat treatment procedures was also investigated. The experimental results show that cobalt content (Wt) in coating increases with Co2+/(Co2+ + Ni2+)% (X) in plating solution. Fitted regression equation is as following: Wt = –0.7399 + 2.2847X – 0.0133X2. The increase of cobalt content leads to that the longitudinal section morphology of coating transforms from the cone into sphericity and at last into the shape of willow leaf, and its structure transforms from face centered cubic (fcc) nickel solid solution into fcc cobalt solid solution and at last into hcp cobalt solid solution. The increase of cobalt content results in the increase of microhardness of nickel‐cobalt alloy coatings, and the hardness reaches a maximum value (363 HV) when cobalt content is 54.9%. After heat treatment at 400°C and 600°C, the microhardness of coatings begins to decrease except the coating containing 79.2% Co. Moreover, the wear resistance of electroplated coatings increases with the increase of cobalt content.

Effect of Heat Treatment to Ni-20wt.%Al Coating Diffusion

Ni-20wt.%Al coating was fabricated on the 6061-T6 aluminum alloy substrate in twin wire arc spraying technology. Heat treatment temperature was 400°C，480°C and 550°C, and each heat treatment time was 4h, 24h and 48h. Reaction mechanism and diffusion behavior of elements of coating/substrate interface were discussed. The XRD results showed that NiAl and Ni3Al phases were diminished and the nickel solid solution was gradually improved in volume. And some oxide phases existed, such as two types of alumina and nickel oxides. The SEM and EDS analysis showed, there was no obvious diffusion. At the low temperature condition, the diffusion phenomenon was existed in the interface.

Intergranular pitting tendency of yttrium implanted Inconel 600 in acidic chloride media

Yttrium ions of energy 0.5MeV were implanted to modify the surface of Inconel 600 by using a Pelletron Accelerator. Microstructural and XRD studies reveal austenitic nickel solid solution (γ) and intergranular carbides. The surfaces were electrochemically investigated by potentiodynamic polarization, Electrochemical impedance spectroscopy and Mott–Schottky techniques in acidic saline solution. The results indicate that the yttrium ions implantation significantly reduces the intragranular pitting as compared to the intergranular pitting tendency of the alloy. The low passive current density, minor pseudo-capacitive behavior and high flat band potential with p-type nature of passive film limit the electrochemical dissolution of the yttrium implanted Inconel.

Phase transformations at high pressures and temperatures and the structure of a hypoeutectic 1Ni-99Al alloy

The phase transformations in a hypoeutectic 1Ni-99Al alloy are studied by differential barothermal analysis in the temperature range up to 750°C at a compressed argon pressure up to ∼100 MPa. The Al matrix of the initial alloy is found to be saturated by micropores at a concentration of 3.7 × 1010 cm−3. After melting and solidification in a compressed argon atmosphere, the micropore concentration increases to 3.2 × 1011 cm−3. As a result of melting and solidification at a high pressure, the initial fine-grained structure of the alloy with an average grain size of 16 μm transforms into a coarse-grained structure during dendritic solidification. The processing of electron-microscopic images is used to determine the volume content of intermetallic compound Al3Ni in the Al matrix. The liquidus temperature of the alloy at 100 MPa increases by 10°C, and the solidus temperature is 5°C higher than the eutectic transformation temperature in aluminum-rich Al-Ni alloys. The solid-phase decomposition of the supersaturated solid solution of nickel in aluminum occurs at 630°C. At 100 MPa, the field of solid solutions of nickel in aluminum extends to 1.2 at % Ni as compared to the Al-Ni system at atmospheric pressure. The lattice parameters of Al and Al3Ni are found to increase in the alloy solidified at 100 MPa. The microhardness of the Al matrix in the alloy is measured after a barothermography cycle. A portion of the Al-Ni phase diagram is proposed for a pressure of 100MPa in the nickel content range 0–4.3 at %.

The effect of Ti on the microstructure, hydrogen absorption and diffusivity of V–Ni alloy membranes

Vanadium is highly permeable to hydrogen which makes it one of the leading alternatives to Pd alloys for hydrogen-selective alloy membrane applications. The tendency of vanadium to embrittle can be reduced through alloying, thereby enabling V-based membranes to be developed for specific operating regimes. Foremost amongst these alloying additives are Ni and Ti. Ni is known to form V–Ni solid solutions with decreased hydrogen absorption and diffusivity compared to V. The influence of Ti is more complex due to phase segregation, and this work focuses the influence of Ti on the microstructural and chemical properties of hydrogenated vanadium–nickel solid solution alloys. Alloy membranes of the compositions V90−xTixNi10 (where 2≤x≤10) were prepared by the sectioning arc-melted ingots and the deposition of a Pd dissociation/recombination catalyst at each surface. Hydrogen permeation measurements were undertaken using the constant pressure method, with feed pressures ranging from 1 to 10 bar, permeate pressures <0.05 bar via use of a sweep gas, and temperatures of 350 and 400 °C. Hydrogen absorption of these same alloys was measured under corresponding conditions using the Sieverts' method. The microstructures featured a dendritic (branched) body-centred cubic vanadium solid solution matrix with interdendritic Ni–Ti compounds. The Ti content in the matrix increased, while the Ni content decreased, with increasing bulk Ti content. Hydrogen diffusivity increased with increasing bulk Ti content and increasing dissolved hydrogen concentration. The Ni–Ti compounds, known for being weakly hydrogen absorbing, also scavenge oxygen from the vanadium matrix, both of which are important in enhancing the embrittlement resistance of these alloys. This work has shown that Ti is a favourable additive for vanadium–nickel alloy membranes when added in the amount of ∼10 at%, with a hydrogen diffusivity (DH) equal to 4.2×10−8 m2 s−1 and hydrogen permeability of 1.2×10−7 mol−1 s−1 Pa−0.5 corresponding to a feed pressure of 10 bar and temperature of 400 °C.

Barothermal analysis and structure of the eutectic Al-Ni (2.7 at % Ni) alloy

Phase transformations of the 2.7Ni + 97.3Al eutectic alloy have been characterized by differential barothermal analysis (DBA) at temperatures of up to 750°C and pressures of up to ∼100 MPa. The results demonstrate that the Al matrix of the as-prepared alloy was saturated with micropores. After melting and crystallization in compressed argon, the micropore density increased. As a result of melting and solidification, the fine-grained structure of the as-prepared alloy transformed to a macrocrystalline, dendritic structure. Electron microscopy was used to determine the volume fraction of the intermetallic phase NiAl3 in the Al matrix. Supersaturated solid solutions of nickel in aluminum decompose at 626°C to give a mixture of Al〈Ni〉 and NiAl3. At 100 MPa, the nickel-aluminum solid-solution range extends to 2.7–2.8 at % Ni, and the nickel content at the eutectic point may reach 3.1–3.3 at %. The Al and NiAl3 in the alloy solidified at 100 MPa had reduced lattice parameters. We determined the microhardness of the Al matrix after DBA.

Pitting corrosion of intermetallic compound Ni3(Si,Ti) with 2 at% Mo in sodium chloride solutions

The pitting corrosion of Ni3(Si,Ti) with 2at% Mo consisting of a single intermetallic compound Ni3(Si,Ti) phase of L12 structure and a two phase mixture of L12 and fcc nickel solid solution was investigated as functions of test temperature and chloride concentration in sodium chloride solutions by using a potential step method and compared with that of intermetallic compound, Ni3(Si,Ti). The pitting potential obtained for the Ni3(Si,Ti) with 2at% Mo decreased with increasing chloride concentration and test temperature. A critical chloride concentration below which no pitting corrosion took place was found to exist and to decrease with increasing test temperature. The specific pitting potential at the critical chloride concentration also decreased with increasing test temperature. The pitting potential of Ni3(Si,Ti) with 2at% Mo was higher than pure nickel, but lower than that of Ni3(Si,Ti). A critical chloride concentration was found to be lower than that of Ni3(Si,Ti), whereas the specific pitting potentials at the critical chloride concentration was found to be higher than that of Ni3(Si,Ti). Pitting corrosion occurred in the two phase mixture region.

Electroless Ni-P-Zn Alloy Deposition on Surface of Low Carbon Steel

Electroless plating technique was used to deposit Ni-Zn-P alloy on low carbon steel surface. The optimal process conditions for the Ni-Zn-P deposition rate were determined and under which the bath remained stable and the maximum deposition rate reached 14.5×10-5mol/(cm2•h). The optimal technical conditions for the Ni-Zn-P alloy corrosion resistance performance were also determined and under which the ternary alloy obtained the longest corrosion time. The SEM image and XRD pattern showed that the deposited Ni-Zn-P coating exhibited good smoothness, high density, free of defects and was proven to be a mixture of inhomogeneous phase and nickel solid solution at plating state.

Formation of composite coatings based on titanium carbide via electrospark alloying

This work concerns studying the coatings prepared via electrospark alloying. To deposit the coatings, we used STIM-2/30 electrodes derived from a combination of self-propagating high-temperature synthesis (SHS) and extrusion. It was found that the composite coating is formed from titanium carbides and a solid solution of nickel in iron and contains both large (4–5 μm) and small carbides (less than 1 μm); in addition, large grains of titanium carbide are formed in the central portion of the coating, and the grain size decreases to 100 nm while approaching the transition zone. Large grains of titanium carbide in the coating consist of dispersed carbides with sizes less than 1 μm. It is determined that the composition of the substrate has an effect on the size of the transition and diffusion zones. It ranges from 17 μm for steel 9KhSA to 26 μm for steel 20; that is, the higher the degree of alloying, the less the depth of the modified layer.

Electrochemical synthesis, structure, and properties of nickel-tungsten-hydrogen ternary systems

The composition and structure of the electrochemically synthesized Ni-W-H alloys were studied. The co-deposition of nickel with tungsten mainly led to nickel solid solutions, and nanocrystalline alloys formed if the hydrogen content in them was at least 3 at %. The deposits included ∼2% of all evoluted hydrogen. The lattice constant of the solid solutions was 1.7–1.9% higher than the that of nickel. The tungsten solid solution phase found in a number of alloys was not nanocrystalline. The hardness of the alloys was several times higher than that of pure nickel.

Microstructure in a Ni 60Pd 20P 17B 3 bulk metallic glass compressively fractured at cryogenic temperature

In order to clarify relationship between plasticity and microstructure for a Ni 60Pd 20P 17B 3 bulk metallic glass (BMG) at cryogenic temperature, we investigated the microstructures of both the shear band and fracture surface for the BMG compressively fractured at room temperature (RT) and 77 K (liquid Nitrogen temperature) using transmission electron microscopy (TEM). HRTEM images from the BMG fractured at 77 K clearly reveal that there are nanocrystalline particles around both shear band and fracture surface, but not in undeformed region. The sizes of the particles fractured at 77 K are smaller than those fractured at RT. These particles ranged from 3 to 5 nm in size are thought to consist of an fcc palladium–nickel solid solution phase. The particles with smaller size and the ductile fcc phase may effectively restrain the propagation of shear bands, resulting in enhancement of plastic deformation at cryogenic temperature.

Enhanced sintering and conductivity study of cobalt or nickel doped solid solution of barium cerate and zirconate

BaZr (0.9 − x) Ce x Y (0.1 − y) Co y O (3 − δ) (with x = 0 and 0.2; y = 0.01; 0.02; 0.05) and BaZr (0.9 − x) Ce x Y (0.1 − y) Ni y O (3 − δ) (with x = 0 and 0.2; y = 0.01; 0.02) compounds have been synthesized by solid state reaction at 1400 °C and obtained as dense pellets after sintering at 1450 °C. Cobalt or nickel doping reduces the sintering temperature by about 250 °C. The samples are stable in a CO 2 rich atmosphere at 600 °C but the 5% B site Co doped samples are aging in wet atmosphere. The conductivity has been measured for the 1 and 2% doped samples (both cobalt and nickel), in different wet atmospheres and compared to the undoped compounds. The ionic and p-type conductivities have been determined, as well as the activation energy in wet reducing atmospheres, in which protonic conduction is dominant. A decrease of the ionic conductivity is noticeable for the cobalt or nickel doped barium zirconate ( x = 0), while not for cobalt or nickel solid solution of barium cerate and zirconate ( x = 0.2).

Electrodeposition and mechanical properties of Ni-W-B composites from tartrate bath

Electrodeposition of Ni-W-B alloys from plating baths containing tartrate in the absence of ammonia is studied. Detailed studies on the effects of bath temperature, pH, cathode current density and plating time have led to optimum operational conditions for obtaining satisfactory alloy deposits. The operational conditions for deposition the alloy with high hardness are; current density 30 mA cm−2, pH 6.0 and bath temperature of 60°C. The results have shown that the adherence of Ni-W-B is better than the Ni and Chromium on Cu substrate. It adheres to Cu substrates better than electrodeposited Ni and chromium. The morphology of the deposits was studied by SEM and the analysis of composition performed by EDX and inductively coupled plasma (ICP). The as-deposited alloy contained 21.66 wt % W and the highest cathode current efficiency for deposition of the alloy was about 38%. The deposit obtained under these conditions had an amorphous character with a hardness of about 800 HV, which is comparable to the hardness of chromium, occurred at a heat treatment temperature of 400°C. When heat treated up to this temperature, the initial metastable structure decomposed into fine particles of Ni4W in a nickel solid solution.

Properties of spark-deposited Ni–Cr–NiAl coatings

The structure and phase composition of sintered Ni–Cr–NiAl alloys and the kinetics of their electrospark deposition onto 45 steel are examined. It is shown that the mass transfer coefficient for the deposition with the sintered alloys is 50 to 71% lower than that when hot-pressed and cast alloys of the same composition are used. The microhardness and structure of the Ni–Cr–NiAl coatings are studied. It is shown that the structure is characterized by fine conglomerates of the phases––nickel and chromium solid solutions and nickel-aluminum intermetallides.

The oxidative dehydrogenation of n-hexane over Ni–Mo–O catalysts

The effect of chemical composition on nickel–molybdenum catalysts in the oxidative dehydrogenation of n-hexane was studied. The catalysts consisted of the following phases: nickel oxide, molybdenum trioxide, nickel molybdate (α-NiMoO 4 and β-NiMoO 4) and a solid solution of nickel in a lattice of nickel molybdate. Characterization of the catalysts was carried out using ICP-OES, BET, XRD, FTIR, SEM, TPR and XPS techniques. The effect of phase composition of the catalysts on their catalytic activity and selectivity to the products obtained in the temperature range 300–500 °C was also studied. The most selective catalyst for the synthesis of hexenes was the pure β-NiMoO 4, which gave 25% selectivity to 1-hexene and 10% selectivity to 2-hexenes and 3-hexenes at 9% conversion. The pure phases NiO and MoO 3, although active in hexane ODH, showed poor selectivity to hexenes, particularly to 1-hexene at comparable conversions suggesting that they are not responsible for the catalytic activity of the NiO–MoO 3 system. The pure β-phase was more selective towards the hexenes than the α-phase with the difference in the molybdenum coordination believed to be the reason for the different activities and selectivities of the two modifications of NiMoO 4. The α-phase with MoO 3 was more active, suggesting that a synergetic effect plays an important role in modifying catalytic activity.

Study of chemical composition and heat treatment of electroless Ni–B–Tl alloy coating on AISI 316 stainless steel

Despite having some useful properties, stainless steels suffer from lack of suitable surface hardness. In this research electroless Ni–B–Tl coating was used with the aim to increase their surface hardness. The effects of nickel chloride, sodium borohydride, thallium nitrate and ethylenediamine on chemical composition of coating were studied. To achieve an increase in hardness, the effects of heat treatment on the hardness of the deposited layer at various temperatures were also studied. The results showed that the deposition rate and surface hardness of the deposited layer are affected by the variation in concentration of bath components. The microstructure of the electroless Ni–B–Tl coating consists of nickel and super saturated solid solutions. It was also found that the hardness of the coating was increased due to the formation of Ni2B and Ni3B phases during heat treatment.

Study on corrosion resistance of electroplating zinc–nickel alloy coatings

AbstractElectrodeposited zinc–nickel alloy coatings have been widely adopted for surface treatment of automobile body steel sheet for high corrosion resistance. The corrosion behavior of the coatings has been related with the components of nickel, and the zinc–nickel alloy passive coatings have much higher corrosion resistance than that of zinc–nickel alloy coatings. In the present paper, the corrosion resistance behavior of the zinc–nickel alloy coatings obtained by new process and formulation has been studied by means of the electrochemistry test and neutral salt spray test. And it is discovered that the properties of corrosion resistance of zinc–nickel alloy passive coatings were better than that of zinc passive coatings, Cadmium passive coatings and alloys of electrodeposited cadmium–titanium. The components of corrosion productions, in terms of X‐ray diffraction (XRD), are mainly ZnO, ZnCl2 · 4Zn(OH)2 and small quantity of 2ZnCO3· 3Zn(OH)2. The component of zinc–nickel alloy coatings has been investigated with Glow Discharge Optical Emission Spectrometry (GDA‐750). And it is found that as the thickness of zinc–nickel alloy coatings increases, the component of zinc increases from beginning to end, but the peak value of nickel appears and an enrichment of nickel in the coatings comes into being. Because the electrodeposited zinc–nickel alloy coatings exhibit different alloy phases as a function of their alloy composition, in this paper, the crystal structure changing with the different component of nickel has been studied in terms of XRD. The result shows that electrodeposited zinc–nickel alloy has different phases: α‐phase, a solid solution of zinc in nickel with an equilibrium solubility of about more than 79% nickel; γ‐phase, an intermediate phase with a composition Ni5Zn21; η‐phase, a solid solution of nickel in zinc with less than 5% nickel; and δ‐phase (Ni3Zn22) appeared from η‐phase to α‐phase with increasing content of nickel. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Effect of alloy components on the performance characteristics of antifriction graphite-bronze powder material

The paper examines the effect of nickel and phosphorus on the performance characteristics of antifriction graphite-bronze powder materials under high pressures (to 20 MPa), at substantial sliding velocities (1-2 m/sec), and with a liquid lubricant supplied from an oil-impregnated felt pad. It is established that Cu-Ni-P-C graphite bronze of the optimal composition has a friction coefficient of 0.028-0.045 and can perform till 150°C in the above conditions. The material is microheterogeneous: the bearing structural component is α solid solution of nickel in copper with the hardening phase being evenly distributed along its boundaries (Cu 3 P mesh with inclusions of phosphide eutectic (Cu-Ni) + Cu 3 P); the antifriction structural component represents graphite inclusions evenly distributed in the material matrix.

High-throughput thermal conductivity measurements of nickel solid solutions and the applicability of the Wiedemann–Franz law

Thermal conductivity mapping with a spatial resolution of 3 μm and an acquisition speed of 3 points per second has been applied to binary Ni(Cr), Ni(Pd), Ni(Pt), Ni(Rh) and Ni(Ru) solid solutions to test the applicability of the Smith–Palmer equation and the Wiedemann–Franz law to Ni alloys. The lattice thermal conductivity of pure Ni and Ni(Pd) alloys is calculated by molecular dynamics. After subtracting the lattice component from the total thermal conductivity, the electronic thermal conductivity of pure Ni is 25% smaller than that predicted from the Wiedemann–Franz law. With the addition of solutes of Pt and Rh, the deviation from the Wiedemann–Franz law decreases. However, the negative deviation of the electronic thermal conductivity of Ni(Pd) alloys from the Wiedemann–Franz law increases slightly to 29% when the Pd concentration is 40 at.%. The Smith–Palmer equation is not a generally reliable method for predicting the thermal conductivity of Ni solid solution alloys from measurements of the electrical conductivity.