Influence of Cs+ ions on codeposition of SiC particles with Ni–Co alloy

Abstract

Ni–Co/SiC composite coatings were produced by electrodeposition from a Watt's-type bath. The effect of current density and SiC concentration on the weight percentage of embedded particles was determined. Enhanced SiC incorporation was observed in the presence of small amount of cesium ions in the plating bath. It was attributed to increased adsorption of Co²⁺ and Ni²⁺ on the particles induced by Cs⁺ ions. Preferential adsorption of Cs⁺ was also observed. Validation of the Guglielmi model was confirmed for the codeposition process in the Ni–Co/SiC system. The incorporation of SiC within the alloy matrix resulted in the improvement of the microhardness of the deposits. Morphology and particle distribution in the deposits was studied by optical and electron (SEM, TEM) microscopy.     

Effect of α-Al2O3 coatings on the interface of Ni/SiC composites prepared by electrodeposition

This paper describes an investigation on the effect of α-Al₂O₃ coating on the interface between nickel and SiC particle. Uniform, dense and well-adhered α-Al₂O₃ coatings were obtained on the surface of SiC particles by sol–gel technology. The nickel-based composites reinforced with α-Al₂O₃-coated SiC particles (CS_p) or uncoated SiC particles (UCS_p) prepared by composite electrodeposition were heated at 600 °C to study the reactivity and the resulting interfaces. The results showed that the Ni/CS_p composites presented excellent thermal stability without interfacial reaction, while nickel silicide formed in the Ni/UCS_p composites. It indicated that high-temperature interfacial reaction between SiC particles and nickel matrix was efficiently inhibited by the α-Al₂O₃ coatings. Moreover, great differences of the local mechanical properties of interfaces were observed by the nanoindentation characterization.     

Chromium electroplating from sulfate-oxalate solutions containing nanoparticles of alumina and silicon carbide

The effect of the introduction of Al₂O₃ and SiC particles into the base chrome-plating sulfate-oxalate Cr (III) bath on the electrochemical characteristics of chromium deposition, as well as the structure and mechanical properties of deposits, is studied. It is shown that Al₂O₃ particles are incorporated only into the surface film and are not detected in the bulk of the coating. Particles SiC are incorporated into both the surface film and the deposit. Introducing the particles into the bath makes the cathode polarization at a fixed current density, as well as the current efficiency and the bath throwing power, increase. Original Russian Text ? E.N. Lubnin, N.A. Polyakov, Yu.M. Polukarov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 2, pp. 199–206.     

Reactive oxide-dispersed Ni3Al intermetallic coatings by sediment co-deposition

Ni–Al-reactive oxide (REO) ternary composite coatings were successfully deposited from a Watt's nickel bath containing Al particles and REO particles via the sediment co-deposition (SCD) technique. Three different composite systems, Ni–Al-nano CeO₂, Ni–Al-5 μm CeO₂, and Ni–Al–Y₂O₃ (<1 μm), were studied. The volume fraction of the Al particles in the composite coatings was significantly decreased with an increase of the REO bath loading, while the REO particle content positively increased. The REO particles in the plating bath evidently interfered with the deposition of Al particles. The development of intermetallic phases in the annealed Ni–Al-REO composite coatings mainly depended on the Al content in the coatings. REO-dispersed Ni₃Al intermetallic coatings could be formed as long as the REO particle loading in the bath was controlled below a critical level. Transformation of CeO₂ phase to CeAlO₃ was found in the Ni–Al-nano CeO₂ composite coatings during the annealing treatment at 800 °C.     

Characterization of interface between the particles in NiNbZrTiPt metallic glassy matrix composite containing SiC fabricated by spark plasma sintering

We investigated the microstructure, in particular, the interface structure between powder particles in the Ni_52.5Nb₁₀Zr₁₅Ti₁₅Pt_7.5 bulk glassy alloy composites containing 10 vol.%SiC particulates prepared by a spark plasma sintering (SPS) process by means of scanning and transmission electron microscopies. The SiC particulates were dispersed homogeneously in the Ni_52.5Nb₁₀Zr₁₅Ti₁₅Pt_7.5 glassy matrix. No crystallization of the Ni_52.5Nb₁₀Zr₁₅Ti₁₅Pt_7.5 glassy alloy took place during the SPS process. The good bonding states between SiC particulates and glassy matrix, as well as between glassy particles were recognized. No intermediate layer in the bonded interfaces was observed.     

Plasma Spray Coatings of Ni-Al-SiC Composite

Ni-Al-SiC powder mixture containing 12 wt.% SiC was prepared by conventional ball milling. Morphological and microstructural investigations showed that powder particles after 15 h of milling time had the optimum characteristics with respect to their size and microstructure. X-ray diffraction patterns of powder particles included only the elemental Ni, Al, and SiC peaks without any traces of oxides or intermetallic phases. The powder mixture was then deposited onto a steel substrate by atmospheric plasma spray (APS) process under different conditions. The results showed that under APS conditions used here, the coatings were composed of various intermetallics including Ni-Al and Ni₂Al₃. The mean hardness of coating was found to be about 567 HV. It was also found that by increasing current density of APS, the coating/substrate adhesive strength was increased.     

粉煤灰作惰性粒子的镍复合镀层

用粉煤灰(FA)作为惰性粒子,电沉积得到复合镀层Ni/FA。粉煤灰的尺寸为3?7μm,主要成分是72%SiO2和25%Al2O3。进行电沉积的工艺条件是瓦兹镀镍液含粉煤灰的浓度为5、20、50 g/L,电流密度为2、4 A/dm2,温度为50°C,磁搅拌速度为250 r/min。采用扫描电子显微镜(SEM+EDX)、电化学测试和硬度测量来研究复合镀层Ni/FA 的形态、成分和性能。镀层中粉煤灰的含量与镀液中粉煤灰的浓度以及相关工艺参数有关。由于镀层中加入了粉煤灰从而使镀层的力学与电化学性能得到改善。复合镀层Ni/FA的硬度达HV430,而纯Ni镀层的硬度只有HV198。电化学测试表明,复合镀层Ni/FA的耐腐蚀比纯镍镀层的高。     

Thermal conductivity of plasma-sprayed W/SiC composite for high-temperature energy applications

W/SiC metal matrix composites were produced by gas tunnel type plasma spraying (GTPS) using a mixture of 12 wt.% SiC-88 wt.% W feedstock powder. This work aimed at the optimization of the plasma gun current for deposition of a W/SiC composite with fine microstructure on AISI 304 substrate. Characterization of deposits was performed in order to assess microstructure, micro-hardness, thermal diffusivity and thermal conductivity. WO₃ was detected in the composite deposits, which indicated that the tungsten partially oxidized during plasma spraying. Also, the deposit composite was dense and nearly free of pores due to the little mismatch between the coefficient of thermal expansion (CTE) for W and SiC. Microhardness values gradually decreased as a function of input current due to the formation of WO₃ and the decomposition of SiC particles in high temperature flame region. The thermal conductivity as high as ∼ 59 W/mK was obtained at gun current 80 A. It was found that both tungsten oxide and structure imperfections have a significant influence on the thermal conductivity and mechanical properties.     

Erosion-corrosion behavior of nano-particle-reinforced Ni matrix composite alloying layer by duplex surface treatment in aqueous slurry environment

The present study concerns a duplex surface treatment of AISI 316L stainless steel to enhance the erosion-corrosion resistance. The duplex surface treatment consisted of Ni/nano-SiC and Ni/nano-SiO₂ predeposited by brush plating and a subsequent surface alloying with Ni-Cr-Mo-Cu by double glow process of the substrate. Results showed that under alloying temperature (1000 °C) condition, the amorphous nano-SiO₂ particles still kept the amorphous structure, whereas the nano-SiC particles had been completely decomposed and Ni, Cr reacted with SiC to form Cr_6.5Ni_2.5Si and Cr₂₃C₆. The electrochemical corrosion behaviors of composite alloying layers compared with the single alloying layer and 316L stainless steel were measured under a range of hydrodynamic conditions by recording the current response, open circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results showed that the increase of the impact velocity had significant influence on the current density of composite alloying layer with brush plating Ni/nano-SiC particles interlayer obtained under flowing condition at a potential of 200 mV, whereas there were only small fluctuations occurred at current response of composite alloying layer with brush plating Ni/nano-SiO₂ particles interlayer. The results of potentiodynamic polarization indicated that, with increasing impact velocity under slurry flow conditions, the corrosion potentials of test materials decreased and the corrosion current densities of test materials increased. The corrosion resistance of composite alloying layer with brush plating Ni/nano-SiO₂ particles interlayer was prominently superior to that of single alloying layer under slurry flow conditions; the corrosion resistance of composite alloying layer with brush plating Ni/nano-SiC particles interlayer was evidently lower than that of single alloying layer, but higher than that of 316L stainless steel under slurry flow conditions. The results of EIS indicated that, with respect to the R_tot obtained in sand-free flow, the impacts of sand particles dramatically decreased the R_tot values of composite alloying layer with brush plating Ni/nano-SiC particles interlayer, single alloying layer and 316L stainless steel, whereas the impact action slightly decreased that of composite alloying layer with brush plating Ni/nano-SiO₂ particles interlayer. The weight loss rate studies suggested that the highly dispersive nano-SiO₂ particles were helpful to improve the erosion-corrosion resistance of composite alloying layer, whereas the carbides and silicide phase were deleterious to that of composite alloying layer due to the fact that preferential removal of matrix around the precipitated phase takes place by the chemical attack of aggressive medium.     

Phase transformation behavior of nanocrystalline Ni-W-P alloys containing various W and P contents

In the present investigation, electroless (EL) ternary Ni-W-P coatings were prepared using hypophosphite based alkaline bath by varying sodium tungstate as tungsten source (5-80 g/L). Maximum amount of W incorporation (8.2 ± 1 wt.%) was obtained when the bath contained about 20 g/L of tungsten source. At very high concentrations of W source in the bath the deposit contained about 4 wt.% W and 2 wt.% P. All the as-deposited ternary coatings exhibited nodular surface morphology. X-ray diffractograms (XRD) obtained for as-deposited EL NiWP alloys indicated that crystallinity of the coatings increased with decrease in phosphorus content. Calculated grain size for the deposits varied from 1.2 to 12.7 nm when the tungsten source varied from 5 to 80 g/L in the bath. Higher crystallization temperatures were obtained due to W codeposition in NiP matrix. Presence of metastable phases such as Ni₅P₂ and NiP apart from stable Ni and Ni₃P was identified for the heat treated deposits (400 °C/1 h) containing lower amount of W and higher amount of P. Whereas other ternary deposits after the heat treatment predominantly revealed face centered cubic (f.c.c.) Ni (111) peak. Activation energy for the crystallization of all the alloys has been carried out by modified Kissinger method. Microhardness measurements were carried out on all the deposits isothermally heat treated at 600 °C for 1 h.     

Effect of electrodeposition conditions on the composition, microstructure, and corrosion resistance of Zn-Ni alloy coatings

The formation, composition, and structure of electrodeposited zinc-nickel alloys were investigated. It has been shown that both anomalous and normal codeposition of zinc and nickel can be realized by changing the bath composition and deposition conditions, with the nickel content in the resultant deposit being varied in a wide range (from 2 to 90 at.%). It has been also shown that the ammonical diphosphate electrolyte allows deposition of Zn-Ni coatings with a homogeneous phase structure (Ni₅Zn₂₁ and Ni₃Zn₂₂ intermetallides, a solid solution of Zn in Ni, or a solid solution of Ni in Ni₅Zn₂₁), whereas the weak acid chloride electrolyte produces two-phase coatings consisting of Ni₅Zn₂₁ with the admixture of polycrystalline Zn or Ni. The Zn-Ni coating with a nickel content of 19 at.% consisting of Ni₅Zn₂₁ intermetallic phase exhibits the highest corrosion resistance.     

Ti-coated SiC particle reinforced sintered Fe-Cu-Sn alloy

Ti-coated SiC particles were developed to improve the wear resistance of Fe-Cu-Sn alloy metal matrices designed for diamond tools. The phase structure of the Ti-coated SiC particles was investigated by X-ray diffraction. Ti coating on SiC was composed of Ti₅Si₃, TiC, and Ti. Excellent interfacial bonding between SiC and the matrix was realized. The SiC/iron alloy composites, prepared by hot pressing at 820 °C, were studied by wear and bending strength tests, and scanning electron microscope. For the composites reinforced by uncoated SiC particles, the wear resistance was improved, but the bending strength decreased. The composites with Ti-coated SiC particles outperformed the composites with uncoated SiC particles in both wear resistance and bending strength tests.     

Degradation of strength properties and its fracture behaviour of TiB2-TiC-based composite ceramic cutting tool materials at the high temperature

Strength retention is important for tool materials at high temperature because cutting temperature in machining is ranged from room temperature to 1000 °C. A study examining the strength properties and fracture behaviour of TiB₂-TiC-based composite ceramic cutting tool materials is presented at different temperatures. MoSi₂ and SiC additives are considered to investigate their effects on the density, microstructure, strength and failure mechanism of composites. It is found that the addition of SiC contributed more to the high-temperature strength of composites than MoSi₂, but it did not improve the room-temperature strength, despite grain refinement. The TBAVS8 composite has a flexural strength of 800 MPa at room temperature and can retain 75% at 900 °C. At room temperature, the fracture behaviour of composites was dominated by the strong bonding of the Ni binder phase. At high temperatures, the softer Ni binder phase was pinned, and its sliding was inhibited by SiC particles, which decelerated the strength degradation.     

Fabrication and mechanical properties of SiCw/MoSi2–SiC composites by liquid Si infiltration of pyrolyzed rice husk preforms with Mo additions

Dense SiC ceramic matrix composites containing SiC whiskers (SiC_w) and MoSi₂ phase (SiC_w/MoSi₂–SiC) are fabricated by a liquid Si infiltration (LSI) method. Pyrolyzed rice husks (RHs) containing SiC whiskers, particles and amorphous carbon are mixed with different amounts of Mo powder to form preforms for the infiltration. Microstructure and mechanical properties of the composites are studied. Fracture mode of the composites is discussed. Results show that the SiC whiskers and fine particles in the pyrolyzed RHs were preserved in the composites after the LSI process. The amorphous carbon and Mo powder in the preforms reacted with molten Si, forming SiC and MoSi₂ in the composites. The presence of MoSi₂ in the composite increases the elastic modulus but lowers the flexure strength. Content of MoSi₂ of ca. 20 wt.% provides an enhanced fracture toughness of 4.1 MPa m^1/2 for the composite. But too large amount of MoSi₂ caused crack formation in the composite. The compressive residual stress introduced by the formation of MoSi₂ and SiC, and the de-bonding of the fine SiC particles and SiC whiskers from the residual Si phase are considered to favor the fracture toughness of the composites.     

Effect of Cerium Oxide on Morphologies and Electrochemical Properties of Ni-W-P Coating on AZ91D Magnesium

AZ91D magnesium alloy substrate was first pretreated in a phosphoric acid to obtain a phosphate coating, and then, the electroless ternary Ni-W-P coating was deposited using a sulfate nickel bath. The morphologies of the Ni-W-P coating were observed by using scanning electron microscope, the deposition rate of the coating was examined with the method of gravimetric analysis, and the phase analysis was identified by x-ray diffractometer. Electrochemical property was tested by means of an electrochemical analyzer. The results indicated that the addition of an optimum concentration of CeO₂ (cerium oxide) particles could evidently improve the deposition rate and the stability of the plating bath. However, it acted as an inhibiting effect as the concentration of CeO₂ particles exceeded to 8 mg/L in the sulfate nickel bath. The results also revealed that the morphology of Ni-W-P coating became more smooth, compact and uniform with the increase in the concentrations of CeO₂ particles in the bath, but the corrosion resistance decreased due to the precipitation of crystal phases (Ni₃P, Ni₄W, etc.) after heat treatment.     

The influence of SiC and Al2O3 micrometric particles on the electrodeposition of ZnNi films and the obtainment of ZnNi-SiC and ZnNi-Al2O3 electrocomposite coatings from slightly acidic solutions

In this work it was studied the influence of micrometric SiC and Al₂O₃ ceramic particles on the electrodeposition of ZnNi films from a moderately acid solution. At the same time, the possibilities of obtainment of ZnNi-SiC and ZnNi-Al₂O₃ electrocomposites were demonstrated. In the first part, it will be analyzed the effects of SiC and Al₂O₃ on the individual electrodeposition curves for Zn, Ni and on ZnNi films and on the hydrogen evolution reaction (HER). Both, SiC and Al₂O₃, causes the current densities in the electrodeposition curves of Zn, Ni and ZnNi to be increased. This was attributed to an additional mass-transport component to the electrode surface given by the flux of impinging particles to it. This makes the deposited quantities to be increased during the potentiodynamic sweeps. Regarding HER, in the blank solution, on a pure Zn substrate, SiC causes an increase on HER and Al₂O₃ has negligible effects on it. In the second part, it will be shown that it was possible to obtain ZnNi-SiC and ZnNi-Al₂O₃ electrocomposites. The compositional analysis of the films showed that the ZnNi electrodeposition is anomalous for the whole analyzed range and for all the systems. However, it was verified that, while, Al₂O₃ has practically no effects on the [Ni/Zn] ratio of the metal matrix, compared to pure ZnNi films, SiC promotes a decrease in this relation, directly related to its concentration in the solution. SiC augmented the anomalous behavior. Considering the high Zn content in electrodeposited ZnNi there would be the favoring of HER by SiC in these cases. There would be more favorable conditions for the formation of insoluble Zn(OH)₂ at the electrode surface. The hindering in the Ni²⁺ reduction will be more effective and could explain the decrease in [Ni/Zn].     

Development of compositionally modulated multilayer Zn-Ni deposits as replacement for cadmium

Compositionally modulated multilayer (CMM) Zn-Ni deposits were electrodeposited from single acidic bath (pH = 4.7) by using a potentiostatic sequence. The Zn and Ni composition in the alloy was tailored as a function of distance from the steel substrate. X-ray diffraction studies of the deposit showed the presence of γ-phase with a composition of Ni₅Zn₂₁. The corrosion properties of modulated multilayer coatings were studied in 5% NaCl solution using electrochemical corrosion techniques. The polarization resistance of the deposits varied as a function of Ni content between 1700 and 3440 Ω. CMM Zn-Ni with 20 wt% Ni exposed in ASTM B117 salt spray test did not show any red rust formation after 400 h.     

Investigation of corrosion resistance of electrodeposited Ni–W/SiC composite coatings

In this research, Ni–W/SiC composite coatings were electrodeposited from a plating bath containing suspension of SiC particles. The influences of SiC particle concentration in the plating bath on the composition of composite coatings were investigated. The surface morphology and composition of the composite coatings were characterised by scanning electron microscopy, energy dispersive X-ray measurements and X-ray diffraction analysis. The corrosion characteristics of Ni–W/SiC composite coatings were investigated by mass loss and electrochemical measurements, including open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarisation in a 3·5 wt-%NaCl solution. The results showed that the addition of SiC particle to the deposition bath of Ni–W significantly increased the corrosion resistance. The significant improvement in corrosion resistance observed for Ni–W/SiC composite coatings (17100 Ω cm²) compared to Ni–W (5619 Ω cm²) could have resulted from the microstructural differences.     

Characterization of hot pressed SiC whisker reinforced TiB2 based composites

TiB₂–SiC ceramic composites, with different contents of SiC whiskers (SiC_w), as a ceramic sinter-additive, were prepared by the hot pressing process at 1850 °C for 2 h under a pressure of 20 MPa. For comparison, a monolithic TiB₂ ceramic was also fabricated under the identical temperature, pressure, atmosphere, and holding time by the hot pressing process. The effects of fabrication process and SiC whiskers on microstructural features, phase evolution and mechanical properties were investigated. Hardness measurements revealed an initial increase in hardness for TiB₂–SiC compared to TiB₂. Also the improvement of the fracture toughness was attributed to the toughening and strengthening effects of SiC whiskers such as crack deflection. The results showed that promoted densification of TiB₂–SiC ceramic composites is due to addition of SiC whiskers and reduction of oxide impurities by reacting with SiC whiskers and removing them from the surface layer of TiB₂ particles. The reaction between TiB₂ particles and SiC whiskers led to in-situ formation of TiC phase in the matrix as well. In general, it is concluded that the sinterability of TiB₂-based composites was remarkably improved by introducing SiC whiskers compared to the single phase TiB₂ ceramic.     

Microstructure and mechanical properties of TiB2–SiC ceramic composites by Reactive Hot Pressing

TiB₂–SiC ceramic composites with different contents of Ni as additive were prepared by the Reactive Hot Pressing (RHP) process at 1700 °C under a pressure of 32 MPa for 30 min. For comparison, a monolithic TiB₂ ceramic and TiB₂–SiC ceramic composite were also fabricated under the identical temperature, pressure and holding time by the Hot Pressing (HP) process. The effects of the fabrication process and Ni on the microstructure and mechanical properties of the composites were investigated. About 8 vol.% of elongated TiB₂ grains with an aspect ratio of 3–6 and a diameter of 0.5–1 μm were produced in the composite prepared by the RHP process. The improvement of the fracture toughness was attributed to the toughening and strengthening effects of SiC particles and the elongated TiB₂ grains such as crack deflection. The TiB₂–SiC–5 wt.% Ni ceramic composite had the optimum mechanical properties with a flexural strength of 858 ± 87 MPa, fracture toughness of 8.6 ± 0.54 MPa·m^1/2 and hardness of 20.2 ± 0.94GPa. The good mechanical properties were ascribed to the relatively fine and homogeneous microstructure and the strengthening effect of Ni. Ni inhibited the anisotropic growth of TiB₂.