The study of morphology and wear behavior of nanocomposite Cr-WC coating produced via electrodeposition with direct and pulse current

Nanocomposite Cr-WC coatings are widely used in different industries due to the favorite characteristics such as high wear and corrosion resistance. In this article, at the first time the nanocomposite Cr-WC coatings are produced via square pulsed and direct current in Watts’ deposition bath containing tungsten carbide particles of 70 nm in diameter. And then the effects of applied current to deposition on the size of tungsten carbide particles, distribution in the coating, homogeneity, hardness and the coatings wear ratio are investigated. The morphology of coating is studied by scanning electron microscope (SEM). The weight percentage of the tungsten carbide particles and the coatings hardness are determined by EDX composite analysis and Vickers micrometer ingressive hardness system, respectively. The results reveal that the amounts of nanoparticles and homogeneous distribution in the pulse current coating are more than direct current. The coating wear behavior and homogeneity of thickness in pulse current are better than direct current.     

Effect of current density on the microstructure and morphology of the electrodeposited nickel coatings

The aim of this research work was to study the effect of deposition current density on microstructure and surface morphology of electrodeposited nickel coatings. For this purpose, nickel deposits have been synthesized by direct current from Watts bath without additive, to limit the incorporation of pollutants resulting from surface adsorption or electro-activity of these compounds. Nickel deposits have been investigated by scanning electron microscopy and X-ray diffraction. Cyclic voltammetry was also used to gain information on the general behavior of the deposition. The optimum conditions of deposition were established and the influence of current density on the grain size, surface morphology, and crystal orientation was determined.     

Micromechanical and tribological properties of nanocrystalline coatings of iron-tungsten alloys electrodeposited from citrate-ammonia solutions

The correlation between the composition, morphology, and properties of Fe-W alloy coatings containing up to 29 at % tungsten was investigated by means of scanning electron microscopy, X-ray diffraction analysis, and the wear resistance and nanohardness measurements. The coatings were deposited from the citrate-ammonia bath at a direct current, the current densities were ranged from 10 to 100 mA/cm². It is shown that, in contrast to metallurgical iron, the Fe-W coatings are nanocrystalline (amorphous, the grain size is 3.0–4.0 nm). This structure of alloys allows us to produce the coatings with a nanohardness of ～13 GPa, which is comparable to the electrolytic chromium coatings. The study of wear resistance of thus obtained coatings reveals their oxidation in the course of dry friction; as a result, the oxygen content in the debris increases by 2–3 times, and the wear volume due to the tribooxidation exceeds that for similar hard Co-W and electrolytic chromium coatings.     

Ni-W alloy coatings deposited from a citrate electrolyte

Ni-W alloy coatings were deposited by applying current pulses with different pulse parameters at 60°C onto mild steel substrates from aqueous electrolytes with different tungstate concentration. Morphology and composition of the alloys were analyzed by SEM and EDX, respectively. XRD was used to determine metallic phases. Scanning electron micrographs revealed that deposition parameters had a strong effect on the morphology of the coatings. Increasing the duty cycle or decreasing the off time led to a compact morphology. Corrosion properties of the coatings were investigated by potentiodynamic polarization in a chloride medium. It was found that compact morphology of the deposits and high content of tungsten in the coating contribute to satisfactory corrosion results of Ni-W alloy coatings under the conditions studied.     

Ecofriendly new nanocomposites coating formulation of zinc reinforced with calcium oxide nanoparticles synthesis from oyster shell

The zinc coating of mild undergoes rapid corrosion for a short period of time in harsh environments. This affects the durable life and overall performance of the zinc coatings. The electrochemical, oxidation, and wear performance, as well as the surface morphological properties of new nanocomposites coating formulations of zinc reinforced with calcium oxide nanoparticles, were studied in order to improve the corrosion and wear performance of zinc coatings. A current density of 1.5–2.0 A/cm² was used for the electrodeposition. The wear, oxidation, hardness, corrosion rate, and morphological properties were evaluated. The characterization of these composite coatings showed low wear rates and higher corrosion and oxidation resistance. At 1.5A/cm² current density, a 65.53% enhancement in the hardness values and 57.14% oxidation protection were obtained. The smaller crystallite size of the deposited sample is the main reason for the lower corrosion and wear resistance and higher hardness values obtained. It was established that waste oyster can be used for the electrodeposition of mild steel to enhance corrosion resistance and hardness values. CaOnp made from oyster shells has been shown to make mild steel more resistant to corrosion, wear, and oxidation.     

The electrodeposition of silver composites using deep eutectic solvents

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.     

Influence of pulse parameters on nanocrystalline zinc coatings electrodeposited from acidic sulfate electrolyte

The influence of pulse electrodeposition parameters (i.e., current-on time, current-off time and peak current density) on the grain size and orientation of zinc deposits was investigated in acidic sulfate electrolyte. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses indicate that the pulse parameters play an important role in the grain refinement of nanocrystalline zinc coatings. As varying peak current density (1–2 A/cm²), current-on time (1–6 ms) and current-off time (4–18 ms), nanocrystalline zinc coatings are produced in the grain range 60 to 35 nm. The pulse parameters have a slight influence on the orientation of nanocrystalline zinc coatings. Published in Russian in Elektrokhimiya, 2009, vol. 45, No. 3, pp. 310–315. The article is published in the original.     

Influence of powder-characteristics on the microstructure of ceramic plasma spray coatings

Summary The relationship between the properties of plasma spray powders and the resultant coating has been investigated. ZrO₂ powders, differing in grain size, state of agglomeration and morphology, have been used and coating properties such as microstructure, porosity, roughness, hardness, and wear resistance are described. Agglomerated powders cause high porosity, while sphericalized particles yield very dense layers. The homogeneity of an agglomerate is also responsible for the homogeneity of the microstructure of the coating. By selecting powders with defined characteristics it is possible to produce plasma spray coatings with defined properties; the microstructure of the layers can be varied over a wide range.     

Effect of pulse current on the electrodeposition of copper from choline chloride-ethylene glycol

Deep eutectic solvents (DESs) have been considered as alternatives to classic aqueous deposition baths used at room temperature. This work describes a preliminary study about the copper deposition process from a bath based on choline chloride/ethylene glycol deep eutectic solvents. The physical properties, such as viscosity and conductivity of the bath, are compared before and after the addition of CuCl₂?·?2H₂O. The process kinetics during copper deposition was investigated. By optimizing the concentration of metallic salts and operating temperature, deposits with compact surfaces and small grain size were obtained. However, the process has a very limited current efficiency. Pulse plating was applied to improve the mass transport and refine grain size. In this case, an important improvement was achieved. Current efficiency (CE) increased significantly compared to the results obtained in direct current. This proves that pulse plating can be used as an effective method to reduce deposition time and costs. Surface morphology of deposits was observed by scanning electron microscopy (SEM), and compositional analysis was quantified by energy-dispersive X-ray spectroscopy (EDXS).     

Inclusion of W in electroless Ni–B coating developed from a stabilizer free bath and investigation of its tribological behaviour

In the present study, tribological and corrosion behaviour of electroless Ni–B–W (ENB-W) coatings prepared from stabilizer-free baths and deposited on AISI 1040 steel substrates were examined. Three distinct coating bath temperatures (85 °C, 90 °C, and 95 °C) were varied for coating deposition. The coatings showed nodular morphology. Thermogravimetric study of ENB-W coatings revealed improved thermal stability attained at 95 °C bath temperature. The microhardness of ENB-W coating was 645, 690, and 720 HV₁₀₀ at bath temperatures of 85 °C, 90 °C, and 95 °C respectively. The inclusion of W to Ni–B coating enhanced the hardness by ∼150 HV₁₀₀. On a pin-on-disc tribometer, wear test was conducted. The precipitation of Ni (111) and its borides occurred post sliding wear at high temperatures (300 °C). Ni (111) crystallite size decreased because of high temperature sliding wear at 300 °C with an increase in coating bath temperature. With a reduction in crystallite size at high temperatures, both wear rate and COF decreases. The scratch hardness and first critical load of failure of the coatings was determined using a scratch tester. Using potentiodynamic polarization, corrosion resistance of ENB-W coatings in 3.5% NaCl was investigated. ENB-W coatings could provide shielding to AISI 1040 steel from corrosion. Though the corrosion resistance is poor with respect to lead stabilized coatings.     

Pulse plating effect on microstructure and corrosion properties of Zn–Ni alloy coatings

The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn₂₁Ni₅ phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity of grain distribution were established to be the main factors determining corrosion behaviour of the coating. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005     

Deposition and characterization of TiAlSiN coatings prepared by hybrid PVD coating system

TiAlSiN coatings with different Si contents were deposited on silicon and high‐temperature alloy by using a hybrid physical vapor deposition coating system, where the cathodic arc ion plating was combined with a twin target mid‐frequency magnetron sputtering. The chemical composition, microstructure, cross‐sectional structure and morphology were carried out by X‐ray photoelectron spectroscope (XPS), X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM), respectively. NanoTest 600 nanomechanical system and ball‐on‐disc friction tester were used to investigate the mechanical and friction properties of TiAlSiN coatings. The worn surface of the TiAlSiN coatings and counterballs were investigated by means of surface profilometer and optical microscope. The wear rates were also measured by surface profilometer. The results showed that the Si addition did not change the coatings growth orientation, and the coating transfered into amorphous phase when the Si content reached about 13.9 at.%. The tribological properties and the hardness were improved by solid solution of Si atoms and grain boundary strengthening of SiN_x amorphous phase with moderate Si content addition. In addition, the SiNx amorphous phase improved oxidation resistance of TiAlN coating, but with a high Si content (more than 8.3 at.% in this work) the agglomeration of SiN_x amorphous phase would reduce the mechanical properties and oxidation resistance of the coating. Copyright © 2014 John Wiley & Sons, Ltd.     

Controlled, rapid deposition of structured coatings from micro- and nanoparticle suspensions

The objective of the study was to develop the operational basis for rapid and controlled deposition of crystal coatings from particles of a wide size range. We deposited such structured coatings by dragging with constant velocity a small volume of liquid confined in a meniscus between two plates. Two types of structured coatings were characterized: latex colloidal crystals and thin layers from metallic nanoparticles. The crystal deposition was sped up by use of preconcentrated suspensions. Crystal coatings larger than a few square centimeters were deposited in minutes from aqueous suspension volumes of approximately 10 microL. The governing mechanism of crystal deposition is convective assembly at high volume fractions. The two major process parameters that allow control over the coating thickness and structure were the deposition speed and particle volume fraction. The evaporation rate was not found to affect the process to a large extent. A volumetric flux balance was used to relate the deposition parameters to coating structure and properties. Operational "phase" diagrams were constructed, relating the crystal layer thickness and packing symmetry to the process parameters. These diagrams could be instrumental in transforming the convective colloidal deposition into a robust scaleable technology.     

电沉积方式对Ni-nanoAl2O3复合镀层组织结构和耐蚀性能的影响

双脉冲;Ni-nanoAl2O3复合镀层;耐蚀性     

Electrodeposition of Zn–Mn alloys at high current densities from chloride electrolyte

The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn²⁺ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transition from dendritic and spongy to smooth, bright, and amorphous structure of Zn–Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hydroxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to decrease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.     

Influence of pulse plating conditions on the structure and properties of pure and composite nickel nanocrystalline coatings

An additive-free Watts type bath containing micron- and nano-SiC particles (1 μm and 20 nm respectively), as well as ultrafine-WC particles (200 nm), was used for the production of pure Ni and nickel matrix composite electrocoatings under both direct and pulse current conditions. Moreover, nickel nanocrystalline deposits were obtained from a Watts type bath containing small amounts of 2-butyne-1,4-diol, in order to investigate the combined advantages of additives and pulse technique on the properties of the deposits. The influence of the variable electrolysis parameters, the particle size and the organic additive concentration on the surface morphology, the structure and properties of the deposits were discussed. It has been proved that the application of pulse electrodeposition affects drastically the structural characteristics and properties of the deposits and under well-defined conditions could lead to the preparation of nanostructured materials with improved mechanical properties. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 6, pp. 802–811. The text was submitted by the authors in English.     

Electrodeposition and characterization of chromium–tungsten carbide composite coatings from a trivalent chromium bath

The electrodeposition of chromium from a trivalent chromium bath has been described in this work. The electrocomposite coatings of chromium with hard abrasive particles were investigated. The chromium–tungsten carbide (Cr? WC) composite coatings were obtained by suspending different concentrations of WC particles in a trivalent chromium plating solution to improve the various properties of the chromium deposit layers. The effect of operating conditions on the deposit layers has been studied. On the other hand, the effect of non‐ionic polymeric surfactant [nonyl phenol ethoxylate with 12 units of ethylene oxide (NPE)] as an additive in enhancing the incorporation of the WC ceramic particles in the chromium metal matrix was investigated. It was found that the co‐deposition of the WC ceramic particles depends on the concentration of the additive and its efficiency in reducing the surface tension of the electroplating solution. The mechanism of incorporation of WC particles into a growing deposit was suggested and discussed in view of the zeta potential and degree of wetability of WC particles in the plating solution. Furthermore, the adsorption behaviour of the additive on WC particles was analysed according to the Frumkin isotherm. The surface morphology and the distribution of WC in the chromium metal matrix were investigated. The properties of the deposit layers, hardness, corrosion resistance and wear resistance were determined and compared with free chromium deposits. The test results reveal that the Cr? WC deposit layer shows better performance compared with the chromium‐free deposit. Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation and Characterization of Nanostructured Ni-TiN Composite Films

Ni-TiN nanocomposite films were produced from a Ni plating bath containing TiN nanopar-ticles by using dc electroplating method. The structure and surface morphology of Ni-TiN composite coatings were analyzed by atom force microscope, X-ray diffraction, and trans-mission electron microscopy. Meanwhile, the anti-corrosion properties, hardness and ther-mostability of Ni-TiN nanocomposite films were also investigated and compared with the traditional polycrystalline Ni coatings. The results show that, compared with the tradi-tional polycrystalline Ni film, Ni-TiN nanocomposite coatings display much better corrosion resistance, higher film hardness, and thermal stability. In addition, the hardness of Ni-TiN nanocomposite coatings decreases slightly with the increase of electroplating current density,which may be due to the synergism of hydrogen evolution and faster nucleation/growth rate of nickel crystallites.     

Electrodeposition of nanocrystalline zinc from acidic sulfate solutions containing thiourea and benzalacetone as additives

Nanocrystalline zinc coatings were produced by pulse electrodeposition in acid sulfate bath containing thiourea and benzalacetone additives and characterized by X-ray diffraction and scanning electron microscopy techniques. The influence of benzalacetone concentration and pulse peak current density on the grain size and crystallographic orientation of zinc deposits was investigated. Zinc electrodeposited from additive-free solutions or with one of the two additives is not composed of nanosized crystals. The mixture additives of thiourea and benzalacetone give rise to the formation of particle-like nanocrystalline zinc with a (10ī1) random orientation. A change in peak current density from 2 to 1 A/cm² only increases the grain size from 60 to 62 nm.     

Structure and tribological properties of Cu–PU–PTFE composite coatings prepared by low‐energy electron beam dispersion with glow discharge

Polytetrafluoroethylene (PTFE) composite coatings doped copper acetate and polyurethane (PU) were prepared on rubber substrate by low‐energy electron beam dispersion technique. The effects of dopant and glow discharge treatment on the surface morphology, structure and tribological properties of the coatings were investigated. The results showed that Cu–PTFE composite coatings form uniform surface and dense column structure with spherical aggregations under glow discharge treatment. PU coating shows the large size of protuberance structure but PU–PTFE coating presents spherical structure. Both of the coatings become relative dense and smooth after discharge treatment, and Cu–PU–PTFE composite coatings possess a smoother surface and lower polar component of surface energy. Cu doping weakens the crystallinity and ordering degree of composite coatings, but glow discharge increases the ordering degree and branched structure of C―H groups. Friction experiment indicated that Cu fails to improve the wear resistance of PTFE coatings but glow discharge treatment can do it. Cu–PU–PTFE coatings after discharge treatment have the higher wear resistance and lower coefficient of friction. Copyright © 2016 John Wiley & Sons, Ltd.