scholarly journals Influence of Pulse Current Forward-Reverse Duty Cycle on Structure and Performance of Electroplated W–Cu Composite Coatings

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1233
Author(s):  
Yuchao Zhao ◽  
Nan Ye ◽  
Haiou Zhuo ◽  
Chaolong Wei ◽  
Weiwei Zhou ◽  
...  
Keyword(s):  
Composite Coating ◽  
Duty Cycle ◽  
Electrode Materials ◽  
Pulse Current ◽  
Electrical Discharge Machining ◽  
Composite Coatings ◽  
Electrical Contact ◽  
Pulse Plating ◽  
Fusion Welding ◽  
Raw Material

Tungsten-copper (W–Cu) composites are widely used as electrical contact materials, resistance welding, electrical discharge machining (EDM), and plasma electrode materials due to their excellent arc erosion resistance, fusion welding resistance, high strength, and superior hardness. However, the traditional preparation methods pay little attention to the compactness and microstructural uniformity of W–Cu composites. Herein, W–Cu composite coatings are prepared by pulse electroplating using nano-W powder as raw material and the influence of forward-reverse duty cycle of pulse current on the structure and mechanical properties is systematically investigated. Moreover, the densification mechanism of the W–Cu composite coating is analyzed from the viewpoints of forward-pulse plating and reverse-pulse plating. At the current density (J) of 2 A/dm2, frequency (f) of 1500 Hz, forward duty cycle (df) of 40% and reverse duty cycle (dr) of 10%, the W–Cu composite coating rendered a uniform microstructure and compact structure, resulting in a hardness of 127 HV and electrical conductivity of 53.7 MS/m.

Preparation and Numerical Simulation of Ni-SiC Composite Coatings Deposited by Electrodeposition

2014 ◽  
Vol 543-547 ◽  
pp. 3707-3710
Author(s):  
Yong Wang ◽  
Lei Zhang
Keyword(s):  
Composite Coating ◽  
Current Density ◽  
Pulse Current ◽  
Composite Coatings ◽  
Maximum Error ◽  
Duty Ratio ◽  
Sic Particles ◽  
Ultrasonic Parameters ◽  
Steel Substrates ◽  
Sic Coatings

In order to investigate and predict effects of preparation parameters on wear mass loss of Ni-SiC composite coatings, Ni coatings and Ni-SiC composite coatings were prepared on steel substrates by electrodeposition process. The results showed that the contents of SiC particles increased with density of pulse current and on-duty ratio of pulse current increasing. The predictive curves of wear mass losses predicted by ANN had the similar shapes with the measured curve, and the maximum error was 9.7%. When the current density was between 30 A/dm2 and 50 A/dm2, the wear losses of Ni coatings and Ni-SiC coatings decreased with the increase of current density. SiC particles in a composite coating electrodeposited by ultrasonic parameters were much greater in number and were dispersed homogeneously in the deposit, and the Ni-SiC composite coating exhibited a dense structure.

Corrosion Resistance of Ni-ZrO2 Nanocomposite Coating Prepared by Pulse Electrodeposition with Rotating Cathode in an Ultrasonic Field

2013 ◽  
Vol 278-280 ◽  
pp. 422-425 ◽  
Author(s):  
Ya Fang Tian ◽  
Xian Hui Li ◽  
Zheng Hong Ao ◽  
Yu Jun Xue
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Composite Coating ◽  
Pulse Current ◽  
Composite Coatings ◽  
Ultrasonic Field ◽  
Nanocomposite Coating ◽  
Pulse Electrodeposition ◽  
Lower Corrosion Rate ◽  
Surface Morphologies

The Ni- ZrO2 nanocomposite coatings were prepared by pulse electrodeposition with rotating cathode in an ultrasonic field, and the corrosion resistance of the coatings were studied in 5% H2SO4. The surface morphologies of composite coatings after corrosion were analyzed by scanning electron microscope (SEM). And corrosion rate was tested using an electronic balance. The results shows that, compared with pure Ni coating, pulse current composite coating and pulse current composite coating with ultrasound, the Ni-ZrO2 nanocomposite coating prepared by pulse electrodeposition with rotating cathode in an ultrasonic field has more uniform micro-structure, more compacted grain and lower corrosion rate. Peculiarly, it exhibits excellent corrosion resistance.

scholarly journals Effect of Transition Metals Oxides on the Physical and Mechanical Properties of Sintered Tungsten Heavy Alloys

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 825
Author(s):  
Ayman H. Elsayed ◽  
Mohamed A. Sayed ◽  
Osama M. Dawood ◽  
Walid M. Daoush
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Electrode Materials ◽  
Electrical Discharge Machining ◽  
Electrical Contact ◽  
Transition Element ◽  
Physical And Mechanical Properties ◽  
Tungsten Heavy Alloy ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys

The addition of transition element oxides to tungsten heavy alloys (WHAs) fabricated by powder metallurgy technique provides new materials with higher density and electrical conductivity, which may be adequate in some applications such as kinetic energy penetrators. Additionally, materials with higher electrical conductivity are required for electrical contact applications such as electrical discharge machining (EDM) electrode materials. WHAs were fabricated by compacting its mixed constituents followed by sintering. Ni, Co and Fe are used as binding phases of the tungsten particles and oxides of Zr, Ti and Y are used as oxide dispersing strengthening (ODS) agents of the sintered materials. The results show that all of the chosen factors (i.e., pressure of compaction process, temperature of sintering, type of binding material and type of oxide) have clear effects on all properties of ODS tungsten heavy alloy specimens. The density and electrical conductivity increase with the increase in sintering temperature. Hardness and compression strength were also measured to evaluate the mechanical properties of sintered samples.

Studies on the Properties and Structure of Pulse Electrodeposited Ni-W-P Series Multi-Composite Coatings

2008 ◽  
Vol 41-42 ◽  
pp. 329-333
Author(s):  
Zhong Cheng Guo ◽  
Xiao Yun Zhu ◽  
Rui Dong Xu
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Rare Earth ◽  
Composite Coating ◽  
Pulse Current ◽  
Composite Coatings ◽  
Pulse Frequency ◽  
Treatment Temperature ◽  
Wear Rates ◽  
Ptfe Composite

The hardness, wear rates, phase structure and morphologies of DC(direct current) and PC(pulse current )electrodeposited Ni-W-P-SiC, RE-Ni-W-P-SiC, RE-Ni-W-P-SiC-MoS2 and RENi- W-P-SiC-PTFE composite coatings are studied. The results indicate that the hardness of pulse composite coatings is higher than that of DC composite coatings, but the hardness of RE-Ni-W-PSiC- PTFE composite coating is lower. The hardness of the four kinds of composite coatings increases with the rise of heat treatment temperature and reaches the highest value at 400°C, thereafter, the hardness begins to decrease. The hardness of RE-Ni-W-P-SiC composite coating is the highest when duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz and the hardness of RE-Ni-W-P-SiC composite coatings at 0.8 is higher than that at 0.6; the wear rates of Ni-W-P-SiC, RE-Ni-W-P-SiC, and RE-Ni-W-P-SiC-PTFE pulse composite coatings are lower than that of DC composite coatings and the wear rates of RE-Ni-W-P-SiC-MoS2 and RE-Ni-W-P-SiC-PTFE composite coatings are the lowest. Ni-W-P-SiC and RE-Ni-W-P-SiC pulse composite coatings are amorphous, and RE-Ni-W-P-SiC-MoS2 pulse composite coating is mixture, but the RE-Ni-W-PSiC- PTFE composite coating is crystal as–deposited. The crystalline grain size of PC composite coatings is smaller than that of DC composite coatings, and the addition of rare earth into the coatings can make crystalline grains become fine, all kinds of grains in the coatings distribute equably and there are not cracks on the surface and in the sections.

Investigations on the properties of composite coatings electro co-deposited on AZ80 Mg alloy using triangular waveform pulse current

2021 ◽  
Author(s):  
Peter Pushpanathan ◽  
Alagumurthi Natarajan ◽  
Pradeep Devaneyan
Keyword(s):  
Magnesium Alloy ◽  
Wear Rate ◽  
Surface Properties ◽  
Current Density ◽  
Duty Cycle ◽  
Pulse Current ◽  
Composite Coatings ◽  
Specific Wear Rate ◽  
Triangular Waveform ◽  
Az80 Magnesium Alloy

Abstract In this research, boron carbide (B4C) and titanium carbide (TiC) nanoparticles were deposited along with Nickel on AZ80 magnesium alloy substrates. Triangular waveform pulse current was used for depositing the coatings on the substrate. The objective of this research is to investigate the microstructural evolution of the coatings in response to the current density, duty cycle and the concentration of reinforcements in the bath. The influence of process parameters were also assessed in terms of the microhardness and specific wear rate. To enhance the surface properties of AZ80 magnesium alloy, a three component layer was successfully applied via electro co-deposition technique for the first time. The magnesium alloy substrates were cleaned and pretreated as per ASTM B480−88. The pretreated samples were coated at three levels of current density viz. 1.5 A/dm2, 2 A/dm2 and 2.5 A/dm2, and the duty cycle was varied between 30%, 40% and 50%. The concentrations of reinforcements in the bath were kept at 0 g/L, 0.5 g/L and 1 g/L. The samples were coated according to Taguchi L9 orthogonal array with two replications. The microstructural studies conducted using scanning electron microscope (SEM) revealed the defects, grain refinement and homogeneous distribution of reinforcements in the Ni matrix. The deposition and orientation of reinforcements in preferred planes were investigated with XRD. Vickers microhardness tests conducted as per ASTM E384-17 revealed that the sample coated with 2.5 A/dm2current density, 30 % duty cycle, 1 g/L B4C and 0.5 g/L TiC produced the coatings with the highest hardness of 412.56 Hv. The results of the pin on disc wear tests conducted according to ASTM G99 were in agreement with the hardness results and the corresponding microstructure. The sample with the maximum microhardness exhibited the minimum specific wear rate of 2.1 E-08 mm3/Nm. The ability of triangular pulse current waveform to deposit hybrid composite coatings on AZ80 magnesium alloy and enhance its surface properties has been confirmed by the results of this research.

SYNTHESIS AND CHARACTERIZATION OF Zr-BASED AMORPHOUS AND CRYSTALLINE COMPOSITE COATING ON Ti SUBSTRATE BY LASER CLADDING

2014 ◽  
Vol 21 (01) ◽  
pp. 1450007 ◽  
Author(s):  
D. M. TANG ◽  
D. C. ZHANG ◽  
W. PENG ◽  
Z. C. LUO ◽  
X. Q. WU ◽  
...  
Keyword(s):  
Composite Coating ◽  
Amorphous Phase ◽  
Laser Cladding ◽  
Laser Scanning ◽  
Composite Coatings ◽  
Scanning Speed ◽  
Raw Material ◽  
Thin Strip ◽  
Beam Diameter ◽  
Laser Scanning Speed

A thin strip of a Zr -based alloy with a composition of Zr 60 Cu 25 Fe 5 Al 10 (in atom percent) was used as a raw material, and the composite coatings containing Zr -based amorphous phase and crystallites on Ti substrate were fabricated by a one-step laser cladding method without protection. The microstructure, phase constitution, microhardness and wear properties of the coatings were investigated. The results indicate that the microstructure of the coatings is strongly dependent on the laser scanning speed under the conditions of the laser power of 1300 W and laser beam diameter of 6 mm, and the composite coating mainly containing amorphous phase with a small amount of the crystallites can be obtained at the laser scanning speed of 10 mm/s. The composite coating exhibits much higher microhardness than the pure Ti substrate, and thus it behaves superior wear resistance in comparison with the substrate.

SYNTHESIS OF HYDROGEN IN ACOUSTOPLASMA DISCHARGE IN A LIQUID-PHASE STREAM

2019 ◽  
pp. 42-48 ◽  
Author(s):  
N. A. Bulychev
Keyword(s):  
Liquid Phase ◽  
Organic Compounds ◽  
Electrode Materials ◽  
Solid Phase ◽  
Plasma Discharge ◽  
Raw Material ◽  
Two Phase ◽  
Reduced Pressure ◽  
External Power Source ◽  
Phase Medium

In this paper, the plasma discharge in a high-pressure fluid stream in order to produce gaseous hydrogen was studied. Methods and equipment have been developed for the excitation of a plasma discharge in a stream of liquid medium. The fluid flow under excessive pressure is directed to a hydrodynamic emitter located at the reactor inlet where a supersonic two-phase vapor-liquid flow under reduced pressure is formed in the liquid due to the pressure drop and decrease in the flow enthalpy. Electrodes are located in the reactor where an electric field is created using an external power source (the strength of the field exceeds the breakdown threshold of this two-phase medium) leading to theinitiation of a low-temperature glow quasi-stationary plasma discharge.A theoretical estimation of the parameters of this type of discharge has been carried out. It is shown that the lowtemperature plasma initiated under the flow conditions of a liquid-phase medium in the discharge gap between the electrodes can effectively decompose the hydrogen-containing molecules of organic compounds in a liquid with the formation of gaseous products where the content of hydrogen is more than 90%. In the process simulation, theoretical calculations of the voltage and discharge current were also made which are in good agreement with the experimental data. The reaction unit used in the experiments was of a volume of 50 ml and reaction capacity appeared to be about 1.5 liters of hydrogen per minute when using a mixture of oxygen-containing organic compounds as a raw material. During their decomposition in plasma, solid-phase products are also formed in insignificant amounts: carbon nanoparticles and oxide nanoparticles of discharge electrode materials.

scholarly journals Preparation and Degradation Characteristics of MAO/APS Composite Bio-Coating in Simulated Body Fluid

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 667
Author(s):  
Zexin Wang ◽  
Fei Ye ◽  
Liangyu Chen ◽  
Weigang Lv ◽  
Zhengyi Zhang ◽  
...  
Keyword(s):  
Simulated Body Fluid ◽  
Composite Coating ◽  
Body Fluid ◽  
Composite Coatings ◽  
Degradation Process ◽  
Ceramic Coatings ◽  
Immersion Test ◽  
Substrate Material ◽  
Atmospheric Plasma

In this work, ZK60 magnesium alloy was employed as a substrate material to produce ceramic coatings, containing Ca and P, by micro-arc oxidation (MAO). Atmospheric plasma spraying (APS) was used to prepare the hydroxyapatite layer (HA) on the MAO coating to obtain a composite coating for better biological activity. The coatings were examined by various means including an X-ray diffractometer, a scanning electron microscope and an energy spectrometer. Meanwhile, an electrochemical examination, immersion test and tensile test were used to evaluate the in vitro performance of the composite coatings. The results showed that the composite coating has a better corrosion resistance. In addition, this work proposed a degradation model of the composite coating in the simulated body fluid immersion test. This model explains the degradation process of the MAO/APS coating in SBF.

CORROSION AND WEAR PROPERTIES OF ELECTRODEPOSITED TERTIARY NANOCOMPOSITE Zn–Ni (ALUMINA–YITTRIA–GERAPHENE) COATING

2016 ◽  
Vol 24 (05) ◽  
pp. 1750066 ◽  
Author(s):  
HAMED RAHMANI ◽  
MAHMOOD ALIOFKHAZRAEI ◽  
ABDOSSALAM KARIMZADEH
Keyword(s):  
Duty Cycle ◽  
Zinc Sulphate ◽  
Pulse Current ◽  
Corrosion And Wear ◽  
Pulsed Current ◽  
Passive Current Density ◽  
Wear Properties ◽  
Nickel Zinc ◽  
Pulsed Electrodeposition ◽  
Passive Current

Nanocomposite Ni–Zn coatings containing 80 wt.% Al2O3, 5 wt.% Y2O3 and 15 wt.% graphene were fabricated by pulsed electrodeposition method in nickel–zinc sulphate-based electrolyte and effects of pulse current parameters on nickel and other element contents, microstructure, resistance to corrosion and tribological properties of the coatings were investigated. The pulsed current with duty cycle from 10% to 50% was applied to different samples and frequency changed gradually from 500 to 4000[Formula: see text]Hz in five steps during coating process. Increasing the duty cycle led to decrease of absorbed nanoparticles in the surface of the coatings from 4.4 vol% to 3.58 vol% The sample coated with 10% duty cycle had utmost alumina content in the coating surface, 3.5 vol% in first layer up to 4.4 vol% in fifth layer. The sample coated with 30% duty cycle had higher corrosion resistance with passive current density of 2.5[Formula: see text]mA/cm2. Furthermore, the results showed that by increasing the duty cycle, wear rate had been increased up to 1.3[Formula: see text][Formula: see text][Formula: see text]10[Formula: see text][Formula: see text]mm2/N[Formula: see text]m.

scholarly journals Isothermal Oxidation Performance of Laser Cladding Assisted with Preheat (LCAP) Tribaloy T-800 Composite Coatings Deposited on EN8

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 843
Author(s):  
Sipiwe Trinity Nyadongo ◽  
Sisa Lesley Pityana ◽  
Eyitayo Olatunde Olakanmi
Keyword(s):  
Iron Oxide ◽  
Composite Coating ◽  
Laser Cladding ◽  
Composite Coatings ◽  
Parabolic Rate Constant ◽  
Mass Gain ◽  
Isothermal Oxidation ◽  
Operational Parameters ◽  
Temperature Oxidation ◽  
Service Environments

It is anticipated that laser cladding assisted with preheat (LCAP)-deposited Tribaloy (T-800) composite coatings enhances resistance to structural degradation upon exposure to elevated-temperature oxidation service environments. The oxidation kinetics of LCAP T-800 composite coatings deposited on EN8 substrate and its mechanisms have not been explored in severe conditions that are similar to operational parameters. The isothermal oxidation behaviour of the T-800 composite coating deposited on EN8 via LCAP was studied at 800 °C in air for up to 120 h (5 × 24 h cycles) and contrasted to that of uncoated samples. The mass gain per unit area of the coating was eight times less than that of the uncoated EN8 substrate. The parabolic rate constant (Kp) for EN8 was 6.72 × 10−12 g2·cm−4·s−1, whilst that for the T-800 composite coating was 8.1 × 10−13 g2·cm−4·s−1. This was attributed to a stable chromium oxide (Cr2O3) layer that formed on the coating surface, thereby preventing further oxidation, whilst the iron oxide film that formed on the EN8 substrate allowed the permeation of the oxygen ions into the oxide. The iron oxide (Fe2O3) film that developed on EN8 spalled, as evidenced by the cracking of oxide when the oxidation time was greater than 72 h, whilst the Cr2O3 film maintained its integrity up to 120 h. A parabolic law was observed by the T-800 composite coating, whilst a paralinear law was reported for EN8 at 800 °C up to 120 h. This coating can be used in turbine parts where temperatures are <800 °C.

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