Characterization and wear behavior of WC-0.8Co coating on cast steel rolls by electro-spark deposition

To prepare high wear resistance and high hardness coatings, electro-spark deposition was adopted for depositing an electrode of a mixture of 92wt%WC＋8wt%Co on a cast steel roll substrate. The coating was characterized by classical X-ray diffractometer （XRD） and scanning electron microscopy （SEM） with energy dispersive X-ray analysis （EDX）. The results indicate that the coating shows nanosized particulate structure and dendritic structure including columnar structure and equiaxed structure. The primary phases of the coating contain Fe3W3C, Co3W3C, Fe2C and Si2W. The coating has a low friction coefficient of 0.13, its average wear-resistance is 3.3 times that of the cast steel roll substrate and the main mechanism is abrasive wear. The maximum microhardness value of the coating is about 1573.9 Hv0.3. The study reveals that the electro-spark deposition process has the characteristic of better coating quality and the coating has higher wear resistance and hardness.

Interface behavior and microstructure transformation of welded joint of 35CrMo steel by electro-spark deposition

Electro-spark deposition has been carried out on the 35CrMo steel by filling and restoring the simulated slot specimens, and continuous surface coating with extra low porosity was obtained with proper parameters. The microstructure transformation and interface behavior of deposited joint were observed and analyzed. It shows that a transition region with 15μm in depth was obtained between base metal and deposited metal, and metallurgical bonding was achieved between restored base metal and deposition coating.

Tribological properties of cobalt-based alloy coating with different cobalt contents by electro-spark deposition

The cobalt-based alloy coating with different Co contents was deposited on 45 steel by electro-spark deposition with the self-made electrode. The coating has a compact and uniform microstructure with low porosity and no visible microcracks. When Co content increases grad- ually, oxygen content of coating samples 1-5 decreases first and then increases in the range of 2.52 wt%-3.05 wt%; sample 3 has the lowest oxygen content of 2.52 %. Mi- crohardness of the coating is improved remarkably com- pared with the substrate （HV 230.18）. With Co content increasing, microhardness of the coating samples 1-5 first rises slightly and then declines rapidly in the range of HV 580.61-1052.33. Sample 3 gets the maximum of HV 1052.33, which is about 4.6 times that of the substrate. The coating presents excellent wear resistance, which first increases and then decreases when Co content increases. Sample 3 shows the best wear resistance of about 6.4 times that of the substrate. Main wear mechanism of the coating is abrasive wear and fatigue wear, along with oxidation wear under high speed or heavy load conditions.

Preparation of Diamond-like Carbon Films on the Surface of Ti Alloy by Electro-deposition

In this paper, diamond-like carbon (DLC) films were deposited on Ti alloy by electro-deposition. DLC films were brown andcomposed of the compact grains whose diameter was about 400 nm. Examined by XPS, the main composition of the filmswas carbon. In the Raman spectrum, there were a broad peak at 1350 cm^(-1) and a broad peak at 1600 cm^(-1), which indicatedthat the films were DLC films.

Wear characteristics of spheroidal graphite roll WC-8Co coating produced by electro-spark deposition

Electro-spark deposition（ESD） was adopted for preparing high property coatings by depositing WC-8Co cemented carbide on an spheroidal graphite roll substrate.The microstructure and properties of the coating were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） with energy dispersive X-ray（EDX） and ball-disc configuration wear tester.The results show that nanosized particles and amorphous structures prevail in the coating which is metallurgically bonded to the substrate.The microstructures of the transition zone include columnar structure and equiaxed structure.The primary phases of the coating contain W2C, W6C2.54, Fe3W3C, and Co3W3C.The results of abrasive test show that the coating has low friction coefficients（μaverage = 0.18） and the wear mechanisms are mainly abrasive wear, fatigue wear, and oxidation wear.The maximum microhardness value of the coating is about 17410 N/mm2.The study reveals that the electro-spark deposition process has better coating quality and the coating has high wear resistance and hardness.

Cathodic micro-arc electro-deposition of ZrO_2 coatings in an aqueous solution containing colloidal particles

By a novel technique-cathodic micro-arc electro-deposition (CMED), ZrO_2coatings were deposited on an FeCrAl alloy. Experimental results show that the necessary conditionsfor obtaining ZrO_2 coatings are to apply a pulse peak voltage over a critical value and addmoderate amounts of ZrO_2 colloidal particles and Zr(NO_3)_4 in the aqueous solution. Theas-deposited coatings are porous because hydrogen, water, and other vapors are generated andreleased from the coatings to the solution during the spark reaction. The coatings containmonoclinic and tetragonal crystalline ZrO_2 with certain degree of amorphous structure. Theprocessing parameters and mechanism of CMED were discussed.

Mechanical Characterization of Close Cell Aluminum Foams Reinforced by High Voltages Electro-deposition

The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.

Unweldable superalloy component repair using electro-spark deposition with high strength filler material

Nickel-base superalloy components with high Al+Ti content are difficult to weld repair using high strength filler materials with conventional welding methods like TIG welding. A feasibility study of electro-spark deposition (ESD) for unweldable superalloy component repair with a high strength filler material was carried out. SEM analysis reveals that a fully dense, crack-free, metallurgical bonded deposition layer can be obtained on the K24 substrate. The as-deposited microstructure characterizes fine cellular structure and the post weld heat treatment precipitates fine γ′particles. The room temperature tensile testing and 975℃, 196MPa stress rupture life testing indicate that ESD makes positively contribution to mechanical performance of repaired specimens. Based on these results, ESD has the potential as an effective alternative to repair of damage and defects in superalloy components, but more efforts should be made before it can be applied in engineering repair.

Electro-Deposition of Ni-La Film in Urea-NaBr Melt and Its Hydrogen Evolution Properties

The Ni-La alloy was electro-deposited in urea-NaBr melt. The codeposition behavior and effect of the cathodic current density on the coating composition were examined. As a result, lanthanum codeposited with nickel to form Ni-La alloy under the inducement effect of nickel. With the increase of the cathodic current density, the content of lanthanum of the deposit rose at first, then decreased, and reached the maximal value (10.3%(atom fraction)) at the current density 15 mA·cm-2. The crystallization behavior of Ni89.7La10.3 coating was investigated by means of differential scanning calorimetry and X-ray diffraction. The structure of Ni89.7La10.3 as-plated coating was amorphous phase. The amorphous phase was converted into center cubic close packed Ni-La (Fm3m) solid solution at 469.8 ℃. The electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was studied using electrochemical experiments, the results showed that the electro-catalytic activity of hydrogen evolution of Ni89.7La10.3 coating was better than that of nickel.

Mechanism of Building-Up Deposited Layer during Electro-Spark Deposition

This paper studies the mechanism of formation of the deposit layer by (ESD) electro-spark deposition process. Inconel 738 substrates are coated with a deposited layer of NI6625 (Inconel 625). Selections of these two alloys have been done because they had wide applications and importance in the industry especially in gas turban blades in inland stations and in aircraft engines. ESD is suggested because it has a low input heat process which eliminates the effect of HAZ in these Ni-superfluous due to their sustainability to micro-cracks. The coating contains many deposited sub-layers coming from evaporated and melted micro-regions as a result of locally high heat generated by discharging a series of capacitors charged and discharged in a controlled manner between electrode and substrate material. The maximum deposition rates at the beginning of the process and decreases until been in a steady state condition due to the nature of the resultant morphology of the created surface.

Preparation of uranium targets by electro-deposition method

In this paper,uranium targets are prepared by electro-deposition.Hydrated uranium dioxide films are electrodeposited into stainless steel plates using uranyl nitrate in ammonium oxalate solution.The results show that the deposition efficiency of the uranium depends on many parameters,such as pH value,supporting electrolyte, current density,and cell design.The uranium films were characterized by infrared spectrum,scanning electron microscope,and X-ray spectrum.The uranium films,with a yield of 98%,are in the thickness of about 6 mg·cm^(-2).

Environmentally friendly hybrid coating prepared by electro-deposition method at various seawater conditions

The formation mechanism of calcareous deposit films in seawater involves an increase in pH at the metal/solution interface due to cathodic reactions, a raised carbonate ion concentration at the interface and precipitation of inorganic deposits such as CaCO3, Mg(OH)2. Environmentally friendly hybrid calcareous deposit films were formed by an electrochemical technique on steel substrates in various solution environments. And the influence of dissolved gas on formation of calcareous deposit films was investigated by scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray diffractometry(XRD). Consequently, these results showed that formation of good overall calcareous deposited films by dissolved gas in seawater environments can be achieved by controlling the material composition and structure through effective use of electrochemical method.

Electro-deposition tangsten coating on low activation steel substrates from Na_2WO_4-ZnO-WO_3 melt salt

Tungsten coating is considered as a promising alternative material for plasma facing materials(PFC) in future fusion devices.The electro-deposition of tungsten in Na_2WO_4-ZnO-WO_3 melt at 1173 K on low activation steel substrates was studied in this work.Adherent and smooth tungsten films were deposited under various pulsed current conditions.The crystal structure and microstructure of tungsten deposits were characterized by XRD,SEM and EDX techniques.The results show that pulsed current density and duty cycle have a significant influence on tungsten nucleation and electro-crystallization phenomena.Uniform and smooth tungsten coating with high purity and high adherence is obtained on low active steel substrates as cathodic current density ranges from 35 to 25 mA·cm_(-2).

Microstructure and Deposition Mechanism of C/SiCN Composites Prepared by Rapid Electro-thermal Pyrolysis CVD

Carbon fiber-reinforced silicon carbonitride ceramic matrix composites （C/SiCN） were prepared by rapid electro-thermal pyrolysis CVD using liquid polymer hexamethyldisilazane （HMDS, （CH3）3SiNHSi（CH3）3） as precursor. Microstructure morphology and production technique of C/SiCN composites were investigated. Scanning electron microscopy and transmission electron microscopy were respectively employed to characterize microstructures of the as-received C/SiCN composites samples. The high temperature pyrolysis of HMDS results in destruction of molecular chain, fracture of bonds, as well as liquid-gas-solid conversion from polymer to ceramic. Microstructures observation indicates that there is a high degree of coalescence between SiCN matrix and C fiber. The deposition model of liquid precursor electro-thermal pyrolysis CVD is different from that of gas precursor isothermal chemical vapor infiltration. Rapid liquid flow and slow gas diffusion are key factors for the difference of two methods. Preparation of rapid electro-thermal pyrolysis CVD consists of four steps including liquid polymer infiltration, polymer pyrolysis, rapid deposition of pyrolyzed substances and rapid densification, respectively.

Effect of Pulse Parameters on Deposition in Concrete Crack using Pulse Current Electro-deposition

To evaluate the effect of pulse parameters on the formation of electrodeposits in concrete cracks, five different types of pulse current were set up, and ZnSO_4 and MgSO_4 solutions were used as the electrolytes. The rate of weight gain, rate of surface coating, rate of crack closure and crack filling depth were measured. Scanning electron microscopy was used to assess the morphology of the electrodeposits, and energy dispersive spectroscopy was used to analyze the mineral composition of the electrodeposits in the cracks. The experimental results demonstrate that, among five different pulse parameters, when T_（on）/T_（off）=0.8 ms/0.8 ms, the healing effect of electro-deposition is the best. The pulse mode hardly affects the mineral composition of the electrodeposits but changes the micromorphology. In addition, for both ZnSO_4 and MgSO_4 solutions, when T_（on）/T_（off）=0.8 ms/0.8 ms, the crystal structure of the electrodeposits is the most uniform and the densest.

Structure and Magnetic Properties of Ni Nanowires Array Fabricated by Direct Current Electro-deposition in Anodic Alumina Membrane

Ordered nanostructure arrays of Ni-Al 2O 3 were synthesized by direct current electro-deposition in anodic alumina membranes (AAM). The investigation with a n electron microscope,an X-ray diffractmeter and a vibration sample magnetomete r indicates that the Ni nanowires, growing in the pores of AAM with about 45nm i n diameter, are monocrystalline and have a definite preferred crystallizing orie ntation. The magnetic behavior of the arrays and their mechanism were discussed.

Electro-Deposition of Cu on Open Cell Aluminum Foams

This manuscript deals with the electro-deposition of Cu on aluminum foams. Metallic foams are highly porous materials which present complex structure of three-dimensional open cells. This aspect causes strong limitations in mass transport due to electro-deposition technology. Experimental tests were performed to study the influence of the operational parameters on the overall performance of the coated aluminum foams. The experimental findings revealed that the manufactured metal foams were characterized by a high thermal conductivity and low process costs, making these materials very promising in many technological fields. On the basis of the experimental results, analytical models are proposed to predict the quantity and the quality characteristics of the coating.

Morphology and Size Control of Cu_2O Nanoparticles by Electro-deposition on Aluminum

The size and morphology of the Cu2O nanocrystals are crucial to improving the performance of photoelectric devices.In this paper,Cu2O nanocrystals have been deposited onto aluminum substrates.The effect of different applied potentials on the chemical composition,morphology and grain size has been investigated.Compared with previous work,it has been found that the potentials have strong effect on particle size,while the morphology changes only when the potentials over-0.5 V,but no other compositions such as CuO or Cu exist in the products,which could clarify the formation mechanism of the Cu2O nanocrystals.

Pd micro-nanoparticles electrodeposited on graphene/polyimide membrane for electrocatalytic oxidation of formic acid

A novel Pd electrocatalyst with flowerlike micro-nanostructures was synthesized by electrochemical deposition on a flexible graphene/polyimide（Gr/PI） composite membrane and characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）.The Pd micro-nanoparticles were prepared on a COOH-CNTs/PI membrane as a comparative sample.The XRD and SEM investigations for Pd electrodeposition demonstrate that the particle size of Gr/PI composite membrane is smaller than that of COOH-CNTs/PI membrane,while the uniform and dense distribution of Pd micro-nanoparticles on the Gr/PI composite membrane is greater than that on the COOH-CNTs/PI membrane.The electrocatalytic properties of Pd/Gr/PI and Pd/COOH-CNTs/PI catalysts for the oxidation of formic acid were investigated by cyclic voltammetry（CV） and chronoamperometry（CA）.It is found that the electrocatalytic activity and stability of Pd/Gr/PI are superior to those of Pd/COOH-CNTs/PI catalyst.This is because smaller metal particles and higher dense distribution desirably provide abundant catalytic sites and mean higher catalytic activity.Therefore,the Pd/Gr/PI catalyst has better catalytic performance for formic acid oxidation than the Pd/COOH-CNTs/PI catalyst.

Corrosion resistance of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in phosphoric and ferric chloride

Corrosion rate and anode polarization curves of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in various concentrations of phosphoric and ferric chloride were researched. The results show that corrosion rate of the composite coatings increases with the increasing concentrations of phosphoric and ferric chloride, and reaches the maximum value when phosphoric concentration is 40% and ferric chloride concentration is 20% (mass fraction, the same below if not mentioned). Anode polarization curves of the composite coatings show that anode polarization current density of the composite coatings heat-treated at 200 ℃ or 500 ℃ is lower than that of other coatings heat-treated at 300 ℃ or 400 ℃, which displays that the composite coatings heat-treated at 200 ℃ or 500 ℃ have better corrosion resistance. Besides, corrosion resistance of the composite coating heat-treated at 500 ℃ is better than that as deposited and RE-Ni-W-P-SiC composite coating heat-treated at 400 ℃, and is also better than that of 316L stainless steel.