جستجوی مقالات مرتبط با کلیدواژه « electroplating » در نشریات گروه « مواد و متالورژی »

In this article, the microstructural characteristics of silicon-aluminide coatings with and without chromium applied on the Rene-80 nickel base superalloy substrate are presented and analyzed. To add chromium to the aluminide coating, enriching the surface layer of the alloy with chromium was carried out in two ways: (1) chrome plating and (2) pack cementation chromizing. Besides, the diffusion annealing of the plated chromium layer was also carried out with the aim of increasing the depth of the chromium-rich layer. SEM, EDS and XRD methods were used to characterize the coatings, including the quantity and quality of the coating layers, microstructural characteristics and elemental and phase composition. Investigations showed that the addition of chromium to the silicon-aluminide coating causes the presence of chromium in the upper part in the form of chromium silicide precipitates. The silicon precipitates in the upper part of the aluminide coatings is in the form of deposits of refractory elements, and the silicide chrome precipitates is formed more than other precipitates. In order to provide resistance to hot corrosion, at least 8% by weight of chromium and 10-13% by weight of silicon are required in the upper layer of the coating. The amount of chromium and silicon elements in the upper part of both CrSiAl-P and CrSiAl-E coatings was relatively similar and in the range of 12-14 and 13-14% by weight, respectively. Of course, the observations indicated that added chromium in both types of coating contributes to the formation of chromium-rich deposits, but more in the lower areas of the coating.

this research focused on investigating the optimization and corrosion studies of rhodium plating coatings. Firstly, a rhodium coating was applied to the Inconel 600 super alloy substrate for 2, 5, 10, 20 and 50 minutes, using the electroplating process of sulfate solution. Using scanning electron microscope (SEM) and X-ray energy spectroscopy (EDS) images, the thickness, morphology and elemental analysis of the surface coatings were investigated and effect of rhodium plating time on the thickness and surface roughness of the coating was investigated. Finally, the corrosion resistance of rhodium coatings in 3.5%wt NaCl solution was evaluated using electrochemical tests: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and tafel polarization, respectively. The results of SEM and roughness measurement studies in comparison results of rhodium coating showed that the electroplated rhodium coating had the highest resistance to electrochemical corrosion in 10 minutes, the thickness of the coating was 1.27μm and the corrosion current was 6.25nA/cm2 and the corrosion potential was determined to be 193mV vs SCE. the changes in the surface roughness were similar to the results of fitting the simulated electrical equivalent circuit for the double layer capacitance of the electrochemical impedance test.

Among the applications of austenitic stainless steels, it can be mentioned the application in solid oxide fuel cells and boiler tubes. It is necessary to protect these steels at high temperatures. One of the best effective methods to increase the life of these steels at high temperature is to apply surface coatings. In this research, Ni-Co-CeO2-ZrO2 composite coating was fabricated by electroplating method on the surface of AISI 304 austenitic stainless steel. In order to investigate the high temperature corrosion resistance, isothermal oxidation tests at 800°C for 300 hours and cyclic oxidation at 800°C for 50 cycles were performed on uncoated and coated samples. Scanning electron microscope (SEM) was used to observe the morphology and X-ray diffraction (XRD) was used to determine the formed phases. The results showed that the formed coating at the current density of 15 mA/cm2, pH of 3, and a concentration of 25 g.l-1 of ZrO2 particles and a concentration of 10 g.l-1 of CeO2 particles was without holes and cracks. In isothermal and cyclic oxidation tests, the coated samples showed a lower weight gain than the uncoated samples due to the formation of NiFe2O4 and CoFe2O4 spinels. These spinels prevented the outward diffusion of chromium cations from and improved the oxidation resistance of the 304 steel substrate.

In this research, Ni-Co/Gr nanocomposite coating was applied on a low carbon steel substrate based on electrodeposition method under pulse-reverse current using watt plating solution in the presence of saccharin with 0.05 g/L graphene. For better graphene distribution, the plating solution was sonicated. The microstructure of the coating was examined by scanning electron microscopy, atomic force microscopy, and X-ray diffraction, and its corrosion resistance was assessed by polarization and Electrochemical Impedance Spectroscopy (EIS) analysis. The results showed that the coating included Ni-Co/Gr alloy with a smooth surface morphology and contained about 26 % by weight of cobalt. Graphene reinforcing particles were co-deposited on the surface. The average grain size of the Ni-Co/graphene composite coating was obtained as about 7 nm, indicating the formation of a very fine-grained structure. The hardness value of the sample increased from 220 HV (microhardness of the substrate) up to 496 HV followed by nanocomposite coating application. The results of the corrosion tests showed that the corrosion resistance of the coated sample was much higher than that of the uncoated steel. As a result of applying this coating, the corrosion rate decreased from 0.611 mm/y to 0.0029 mm/y.

The results of various research activities show that coating is one of the effective ways to increase the corrosion resistance and wear of metallic substrates. Synthesizing composite coatings using nanoparticles can also further protect the substrate. In this study, using electroplating process and PTFE particles (with concentrations of 10, 20 or 30 g / l), Ni-P-PTFE coatings were prepared and their corrosion and abrasion properties were investigated and compared with Ni-P coating. Using scanning electron microscopy (SEM ) and X-ray diffraction (EDS) methods, the surface morphology and elemental composition of the coatings were studied and finally, using open circuit potential (OCP) techniques, electrochemical impedance spectroscopy (EIS) and polarization techniques, the corrosion resistance of the resulting coatings were evaluated in NaCl solution. M icrohardness and pin on disk tests were also utilized to investigate the effect of PTFE concentration on the tribological properties of the coatings. The results of SEM and EDS studies confirmed the formation of nanocomposites. Electrochemical studies also showed that Ni-P-PTFE coatings, at a concentration of 20 g/L PTFE, had the highest electrochemical corrosion resistance. M icrohardness decreased with increasing PTFE particles in the coating and reached its lowest value in 20 g/l PTFE . Using the wear test, the lowest coefficient of friction obtained in composite coatings obtained at a concentration of 20 g/l, which shows the applicability of PTFE particles as a solid lubricant in Ni-P coatings.

Ferritic stainless steels are widely used in equipment, including parts in turbines, electrical industries, aerospace, automotive and decorating industries. One of the problems with this type of steels is their low wear resistance. One of the ways to overcome this problem is to apply a wear-resistant coating on the surface of steel. In this research, nickel phosphorus-titanium oxide coating was deposited onto the AISI 430 steel using electrical plating technique and the effect of TiO2 particles concentration on microstructure and wear behavior was studied. To test the abrasion resistance of the coated and uncoated samples, a pin on the disk test was used. Also the michardness was measured by Vickers microhardness device. X-ray analysis (XRD) was used to determine the available phases and calculate grain size. Characterization of the coating was performed using SEM (Scanning Electron Microscopy). The results of the tests showed that the addition of titanium oxide particles causes the decrease of grain size and the increase of microhardness and abrasion resistance

One of the best ways to improve the abrasion resistance and toughness of stainless steels is to apply surface coatings. Among these coatings are nickel base alloy and composite coatings. In this research, nickel-phosphorus-titanium oxide coatings were developed using electrical plating technique and the effect of pH (3, 3.5 and 4) on microstructure and their wear and tear behavior were studied. In this research, nickel phosphorus-titanium oxide coating was deposited onto the AISI 430 steel using electrical plating technique and the effect of TiO2 particles concentration on microstructure and wear behavior was studied. X-ray analysis (XRD) was used to determine the available phases and calculate grain size. Characterization of the coating was performed using SEM (Scanning Electron Microscopy). The michardness was measured by Vickers microhardness device. To test the abrasion resistance of the phosphorus-titanium oxide coated and uncoated samples, a pin on the disk test was used. The results of X-ray analysis showed that the increase of pH causes the increase of grain size. Also the results of microhardness and pin on disk tests showed the increase of pH causes decrease of microhardness and abrasion resistance. The highest hardness (618.18 Vickers) was related to the coating created at pH =3 and TiO2 =40 gr / L. The highest wear resistance and lowest weight loss (0.15 mg) were also observed in the same coating.

Austenitic stainless steels are high performance steels that have various applications in solid oxide fuel cells and boiler tubes under high temperature operating conditions. The Cr2O3 oxide layer formed on the steel surface becomes unstable at high temperatures and reduces the oxidation resistance of the steel. Therefore, protection of these steels at high temperatures is essential. Therefore, one of the best effective ways to extend the life of these components against oxidation is by applying protective coatings. In this research, Ni-Co-CeO2-ZrO2 composite coating was created by direct electrodeposition on the surface of AISI 304 austenitic stainless steel. In order to obtain proper coating, the effect of current density, pH and concentration of ZrO2 in the bath was investigated. To create the optimum deposition, the bath parameters were investigated. Influence of ZrO2 content (5, 10 and 25 g/L), current density (15, 20, 25 and 30 mA/cm-2) and pH (3, 3.5, 4 and 4.5) on the deposition amount of ceramic particles and microstructure of the coating has been investigated. Scanning electron microscopy (SEM) and EDX analysis were used to determine the morphology. The results showed that with increasing ZrO2, the amount of ZrO2 deposition increased and the amount of CeO2 deposition decreased. Also, with increasing current density and pH, the amount of ZrO2 and CeO2 particles decreased.

Polymer electrolyte membrane fuel cells have received more attention than other fuel cells because of their advantages such as low operating temperature, high power density and short startup time. One of the most important components of a polymer electrolyte membrane fuel cell is bipolar plate which has various types. Metallic bipolar plates have advantages such as higher strength, lower thickness and lower weight than graphite-based composite bipolar plates. Corrosion resistance and interfacial contact resistance of metallic bipolar plates are some of the challenges of using metallic bipolar plates. For this reason, metallic bipolar plates are coated to increase corrosion resistance and reduce contact resistance. In this study, the properties and morphologies of gold coating on copper and stainless steel substrates were studied by using electroplating and sputtering methods. The surface morphologies of the specimens were investigated by scanning electron microscopy. In addition, interfacial contact resistance tests were used to evaluate contact resistance of coated and uncoated specimens. Finally, corrosion resistances of the specimens were studied using galvanostatic and potentiostatic tests. The results showed that the use of electroplating method produces many holes and pores in the specimen surface. It was also found that using sputtering method significantly resulted in an increase in corrosion resistance and decrease in contact resistance of coated specimens.

In this research hybrid nanocomposite coating of Ni-P/Al2O3-SiC and Ni-P coating were codeposited and deposited by electrodeposition on copper substrate. Electrodepositions for both cases was done by DC current. Sic nanoparticles sizes and Al2O3 nanoparticles sizes which were used for preparing nanocomposite bath, were respectively 55nm and 50nm. Charactrizaton and surface morphology of coating were done by scanning electron microscopy and energy dispersive spectroscopy.The tribological behavior of the coatings were evaluated by pin-on-disc test, and microhardness of coating were also evaluated by Vickers microhardness test. Morphology of surface coating was evaluated by optical electron microscopy. Results show that adhesion of hybrid nanocomposite coating on copper substrate is perfect. Participation of nano Al2O3 particles and nano SiC particles, causes improvement in the microhardness and wear resistance of hybrid nanocomposite coating. High strength of nano Al2O3 particles and nano SiC particles, improved the microhardness and wear resistance of hybrid nanocomposite coating. Also, increases in current density for electrodeposition improve microhardness of Ni-P coating and Ni-P/Al2O3-SiC coating.

Electroplated nickel composite coatings have good wear resistance. In this study, by adding Ag particles as reinforcement and optimization of electroplating conditions, wear behavior, hardness and roughness of Ni-Ag have been studied. Taguchi design of experiment (DOE) technique was carried out for optimizing four effective parameters (Ag content, current density, time and additives) and three levels. Therefore, nine specimens were prepared and morphology and structure of the samples were analyzed by SEM and X-ray diffraction. To find out the wear resistance of the samples, pin–on–disk test was performed and worn surfaces were analyzed by SEM and EDS. The optimized parameters of electroplating, based on signal to noise ratio (SNR) curves, were 50 mg/L Ag content, 4A/dm2, 2 hours electroplating and Triton X100 as additive in order to achieve the lowest wear. Analysis of variance (ANOVA) calculation showed current density and Ag content are the most effective parameters on wear behavior of coatings, respectively. The process was then modeled in Artificial Neural Network and the counters of parameters together with the outputs were determined. The results showed that wear resistance decreased with increasing both Ag content and current density.

AISI 430 ferritic stainless steel is used as interconnects in solid oxide fuel cells. In order to improve the oxidation resistance of steel in operating conditions of solid oxide fuel cells, protective coatings can be employed. In this study Ni-TiO2 coating was deposited on an AISI 430 stainless steel substrate by electrocodeposition in Watt’s plating bath containing TiO2 particles. Composition and properties of Ni-TiO2 coating were investigated as a function of current density. The volume percentage of embedded TiO2 was raised by increasing in current density until 4 A/dm2 and beyond that reduced. Also grain size of Ni-TiO2 composite coating decreased until 3 A/dm2 and above this current density, the again grain size raised. Maximum value of microhardness obtained in 4 A/dm2 current density. In order to investigate the oxidation resistance, coated and uncoated specimens were subjected to isothermal oxidation at 800 ºC for 300 h. Results showed that the coated specimens at the bath containing of SDS surfactant and without SDS surfactant had less mass gain compared to uncoated ones. The microstructure of composite coatings, before and after oxidation was investigated by scanning electron microscope (SEM) and X-ray systems.

The purpose of this study is to demonstrate the advantages of computer simulation and parametric studies in improving the copper electroforming process. For this purpose, the finite element model for a cone geometry was prepared using the Comsol software, and the effect of key parameters including applied current density, solution electrical conductivity, electrode spacing, and anode length, on the thickness uniformity. In order to validate the model, a conical shell was produced in the laboratory by electroforming method, and the thickness distribution was compared with the simulation results. The comparison of the results showed that using the tertiary current distribution method to simulate the electroforming process is a precise and efficient model and can be used for parametric studies. Finally, after parametric study, it was determined that all selected variables had a significant effect on the thickness uniformity. In addition, it was found that the most to least significant variables were applied current density, solution conductivity, anode-cathode spacing, and anode length, respectively.

The aim of this study is to provide a method of making ultralight open cell copper foam with high surface area using chemical procedures. Among the various methods of making open-cell metal foams, electrodeposition method is selected because it can be done in a clean way and is cheaper than other methods. In this method, an open cell polyurethane sponge was used as substrate. Then by choosing appropriate chemical solutions with specific technical knowledge, first polyurethane surface has activated and then by electroless-deposition method, polyurethane activated surface covered with a thin layer of copper. In the final stage, with the aid of electrodeposition the thickness of copper layer was increased to the desired thickness with a minimum required strength. The results show that electrodeposition can increase the thickness of copper layer from3-5 microns that is obtained in electroless-deposition method to above100 to 150 microns. SEM results show that the micro structure of the deposited layer is globular. By controlling the thickness of deposited copper in electroplating, the surface area of the copper foam can be increased. According to results optimum time for electroless-deposition is between 5 to 7 minutes and for electrodeposition is 1 hour. The open-cell copper foam that is produced in this research is ultralight and due to it high surface can transfer heat with high rates.