Ni-SiC Coatings Research Articles

Process Parameter Optimization and Corrosion Performance Evaluation of Electrodeposited Ni-SiC Coatings Modified by Laser Remelting

Process Parameter Optimization and Corrosion Performance Evaluation of Electrodeposited Ni-SiC Coatings Modified by Laser Remelting

Microstructures and performances of Ni-SiC coatings manufactured by laser cladding deposition

45# steel substrates were coated with Ni-SiC by using the laser cladding deposition (LCD) method in this article. X-ray diffractometer (XRD), scanning electron microscope (SEM), micro-hardness meter, wear/friction tester and electrochemical workstation were used to examine the surface morphology, microhardness, wear and corrosion performances, and phase structure of the Ni-SiC coatings. The results indicated that the structures of Ni-10SiC and Ni-30SiC coatings were columnar dendrites and equiaxed crystals (finer in Ni-30SiC coating). The Ni-10SiC and Ni-30SiC coatings were passed through initial and stable wear stages. The average micro-hardness values of Ni-30SiC and Ni-10SiC coatings were separately about 851.3 HV and 748.4 HV. Results showed that the Ni-10SiC and Ni-30SiC coatings suffered stable and initial wear phases. Several big grooves and spalling pits were noted on the sported surface of the Ni coating. While shallow scratches were observed on the wear surface of Ni-30SiC coating. In addition, the Ni-30SiC coating had the lowest corrosion current density (6.325 ×10−6 A/cm2), demonstrating the most efficient corrosion resistance among all three coatings.

Optimization of the corrosion performance of Ni-SiC coatings through flash heating

Flash heating is an effective thermal deposition technique for additively applying high performance coatings with the possibility of on-site coating application. This research analyzes the corrosion performance of coatings developed by flash heating using a two-cubed full factorial design of processing conditions such as gas flow rate, coating composition, and current on corrosion rate. Using a 95 % confidence interval, it was found that the gas flow rate and the combination of composition and current had statistically significant effects on corrosion performance with p-values of 0.0015 and 0.0067, respectively. The optimal corrosion performance was found to occur at a gas flow rate of 12–14 cfh, composition of 70 wt% Ni and 30 wt% SiC, and a plasma current of 140 A. These parameters resulted in a corrosion rate of 20.4 μA/cm2. This is a reduction of 96.6 % compared to the carbon steel substrate and 90.9 % compared to the worst-performing Ni-SiC coating in terms of corrosion rate. This research enables the prediction and optimization of corrosion performance of Ni-SiC coatings when fabricated by flash heating.

Process prediction of Ni–SiC coatings based on RBF-BP model

The preparation of Ni–SiC coatings using magnetic field-assisted jet electrodeposition under various plating settings is described in this study. A RBF-BP composite neural network with 4 × 4 × 4 × 7 × 10 × 1 was used to predict the corrosion resistance of Ni–SiC coatings prepared by employing different plating parameters. The results show that the fitting degree between the expected value and the actual value of the RBF-BP composite neural network is 0.97497. Moreover, the hybrid neural network can accurately predict the corrosion resistance of Ni–SiC coatings prepared under different process parameters. The corrosion weight loss of the coating is the lowest at the current density of 4 A/dm2, a jet rate of 3 m/s, a SiC particle concentration of 8 g/L, and at a magnetic field intensity of 0.8 T, demonstrating its corrosion resistance under these conditions. According to the coating characterization analysis, the coating's grain size was significantly refined, and the surface was smoother with a high amount of uniformly sized SiC nanoparticles.

High-Performance Ni-SiC Coatings Fabricated by Flash Heating

In this research, a novel flash heating coating application technique was utilized to create Ni-SiC coatings on carbon steel substrates with SiC contents much higher than is achievable using certain conventional coating techniques. Hardness profiles showed that the coatings improved the substrate by as much as 121%, without affecting the substrate. Tribotests showed that the wear performance was improved by as much as 4.7× in terms of the wear rate (mm3/N·m) for the same coating when using an Al2O3 counterpart. Pure SiC coatings as a reference were also fabricated. However, the SiC coatings experienced elemental diffusion of Fe from the carbon steel substrate into the coating during fabrication. This occurred due to the increased heat input required for pure SiC to fuse to the substrate compared to the Ni-SiC coatings and resulted in decreased tribological performance. Diffusion of Fe into the coating weakened the coating’s hardness and reduced the resistance to wear. It was concluded that ceramic–metallic composite coatings can successfully be fabricated utilizing this novel flash heating technique to improve the wear resistance of ceramic counterparts.

Effect of Ultrasonic Nanocrystal Surface Modification on Properties of Electrodeposited Ni and Ni-SiC Composite Coatings

In this study, pure nickel and Ni-SiC composite coatings were prepared by the conventional electrodeposition technique from nickel sulfamate electrolytic bath containing dispersed SiC particles. The samples obtained after the electrodeposition were subjected to the ultrasonic nanocrystal surface modification (UNSM) technique to improve the surface- and interface-related properties of the coatings. The surface morphology, elemental composition, surface roughness, microstructure, and crystallinity were observed and analyzed by using scanning electron microscope, energy-dispersive x-ray spectroscopy, roughness tester, and x-ray diffraction techniques, respectively. Electrochemical corrosion behavior of the obtained samples was evaluated in 3.5 wt.% NaCl solution by using three electrodes configuration. XRD result revealed the enhanced crystallinity of the UNSM-treated samples. A significant improvement in surface morphology, Vickers microhardness, wear and coefficient of friction, and anti-corrosion property was observed in the UNSM-treated nickel and Ni-SiC coatings compared to the UNSM-untreated samples.

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

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.

Effect of variation in SiC loading, current density and bath temperature on coating thickness and tensile strength of Ni-SiC nanocomposite coatings

The mechanical properties like hardness, tensile strength, wear resistance of electro-co-deposited Ni-SiC coatings are dependent on factors like bath temperature, current density, duration of deposition, amount of SiC particles etc. Ni-SiC nano composite coatings were prepared on a mild steel substrate by electro-co-deposition process. In this study, the effect of electrochemical bath parameters such as bath temperature, current density and SiC loading were varied and effect of this variation on the coating thickness and tensile strength of Ni-SiC composite coating was studied. The experimental results showed that, a uniform deposit thickness was obtained for 3 A/dm2 current density, temperature of 55°C and loading of 4 g/l. A peak value of coating thickness was observed at a current density of 4 A/dm2 from the experiment. The experimental results also showed that, the tensile strength of the composite coating containing SiC the is significantly higher than pure Ni coating and the tensile strength increases with an increase in the percentage of SiC particles in Ni-SiC coatings. The tensile strength of the composite coating increased by nearly about 52% with increasing SiC loading and then decreased.

Electroplating of Compound Ni–SiC Coatings and Improvement of Wear Resistance

Ni-SiC nano-composite coatings with various contents of SiC nano-particulates were prepared by means of the conventional electrodeposition in a nickel-plating bath containing SiC nano-particulates to be co-deposited. The surface morphology and structural constituent in the electrolyte layer were observed by SEM and EDS. The dependence of SiC nano-particulates amount in the nano-composite coatings was investigated in relation to the SiC concentration in bath. The effect of SiC nano-particulate incorporation content on micro-hardness as well as wear-resistance was studied too. The results showed that the nano-Ni-SiC plating layer had smooth and flat surface, uniform microstructure as well as higher micro-hardness and wear-resistance than pure Ni coating. The optimum experimental parameters were derived at condition of, addition of 6g/L SiC nano-particulates in the bath, 40°C temperature, current density of 4A/dm2 , and a stirring rate of 250rpm.

Tribocorrosion behaviour of Ni–SiC nano-structured composite coatings obtained by electrodeposition

The combined corrosion-wear degradation of nano-structured Ni–SiC coatings in sliding contacts immersed in electrically conductive solutions is investigated in situ by electrochemical techniques (open-circuit potential measurements, E OC, the potentiodynamic polarization measurements, PD, and the electrochemical impedance spectroscopy). The coating thickness was 50 μm, with an average volume of dispersed phases inside nickel of 20%. The samples were tested in a cell, containing the electrolyte and electrodes, and mounted on a pin-on-disk tribometer, with the working surface of the specimen facing upwards. Both continuous and intermittent friction tests were carried out. In the intermittent tests, friction was applied periodically: during each cycle, friction was first applied for 2 s at constant sliding speed under constant normal load and then stopped during a latency time of 20 s or 0.5 s. Without friction, the free potential reaches a passive value after immersion in the test solution. When friction force is applied the free potential is shutting down to active values. Under friction the measured current, I can be considered as the sum of two partial currents: one generated by the wear track areas, where the passive film is destroyed and the surface is active; the other one linked to the surface not subjected to friction and that remains in the passive state. A localised corrosion process when subjected to friction in 0.5 M K 2SO 4 was not observed on nano-structured Ni–SiC composite coatings. The mechanical destruction of the passive film occurs in the wear track by friction and subsequent restoration of the film (repassivation) when friction stops. The wear volume loss increases with sliding forces.

Improved corrosion resistance through microstructural modifications induced by codepositing SiC-particles with electrolytic nickel

Micron and submicron-sized SiC-particles (5 and 0.3 μm respectively) were codeposited with nickel from a Watts electrolyte. The Ni–SiC composite coatings showed a better corrosion resistance in a 0.6 M NaCl solution than nickel electrodeposited under the same conditions. The corrosion rate of Ni–SiC decreases by two orders of magnitude with respect to pure Ni coatings. This improved corrosion resistance is quite independent of the size and amount of embedded particles, except for the smallest SiC-particles investigated. In that case, the pitting corrosion potential shifts to more noble values indicating a notable reduction of the localized corrosion susceptibility. This improved corrosion resistance of Ni–SiC coatings containing submicrometric SiC-particles is linked to a change in grain morphology and texture of the coatings. That morphology evolves from columnar grains to small and equiaxed grains.

The influence of B 4C and SiC additions on the morphological, physical, chemical and corrosion properties of Ni coatings

Microhardness, internal stresses, Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) measurements were used to compare nickel matrix composite coatings — NiB 4C and NiSiC — with a pure nickel coating. The influence of incorporated carbides on Ni electro-co-deposition, the surface morphology, physical and chemical strength and corrosion ability of Ni coatings has been studied. Ni coating properties differ from those of NiSiC and even more from NiB 4C properties. Their microhardness is lower than that of NiSiC coatings but their corrosion resistance is twice higher than that of NiB 4C coating. The correlation between physical properties of the surface of incorporated carbides and coating surface properties exists: due to the conductive B 4C the activity of the surface increased and its stability decreased. As a result, the corrosion resistance ability of hydrophobic metallic Ni surface decreases, hard and corrosion resistant compact matrix is formed with non-conductive SiC particles. High temperature does not change the integrity of Ni composites.

Influence of Dispersion Particles Present in the Solution on the Kinetics of Deposition of Ni-SiC Coatings

SummaryThe influence is discussed of the silicon carbide powder present in suspension on the polarisation curves of the cathodic reduction of nickel ions The importance is emphasized of the powder properties especially their impurities and the magnitude of their specific area. The effect is also considered of brightening and wetting agents on the kinetics of deposition of Ni-SiC dispersion coatings.On account of the great technlogical interest in high-hardness and wear resistance coatings on aluminium substrates a part of the investigations was performed on aluminium alloy cathodes.

An electrochemical investigation of corrosive wear of as-plated and heat-treated nickel and Ni-SiC coatings

Electrochemical studies on as-plated Ni-SiC coatings have shown that the applied load has little influence on tribomechanical behaviour since hard inert SiC particles protrude above the surface of the nickel matrix and carry most of the load. Appropriate heat treatments (200–400 °C) can improve the tribochemical behaviour of nickel and Ni-SiC coatings. Temperatures above 400–450 °C are deleterious because of loss of hardness and decomposition of SiC in Ni-SiC coatings.