Cu-Ni Coatings Research Articles

Tribological Properties of Nanostructured Diffusion Layers of Metal Coatings

Copper nickel (Cu-Ni) coatings on products from instrumental steel H12M were drawn and they were subjected to subsequent intensive plastic deformation under stresses 3.0; 3.5; 4.0 and 4.5 GPa. The nanostructured surface, formation grains size of 13...173 nm with high-angle (at 3.0; 4.0; 4.5 GPa) and low-angle (dislocation) borders of grains (at 3.5 GPa), influencing redistribution of alloying elements and tribological properties was shown by means of methods of light and electronic microscopy, X-ray diffraction and micro-ray spectral analysis, and also tribological tests.

Effect of Heat Treatment Temperature on the Spectral Properties of Cu-Ni Coating.

Cu-Ni coatings were prepared on the surface of nickel by electrodeposition method, and Cu-Ni coatings were heat-treated in 25-900 °C. Heat-treated Cu-Ni coatings were characterized with scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX) and X-ray diffraction (XRD) techniques, respectively. Effects of heat treatment temperature on the spectral properties of Cu-Ni coatings were studied. The surface of Cu-Ni coating is composed of the nodules. The nodules of Cu-Ni coating surface become smaller with the increase in heat treatment temperature in 25-600 °C. The nodules of Cu-Ni coating surface become smaller and the dividing line between the nodules becomes more blurred with the increase in heat treatment temperature in 600-900 °C. The contents of copper in Cu-Ni coating decrease from 82.52 at % to 78.30 at % with the increase in heat treatment temperature in the range of 25-900 °C; the contents of nickel in Cu-Ni coating increase from 17.48 at % to 21.70 at % with the increase in heat treatment temperature in the range of 25-900 °C. The crystal structure of Cu-Ni coating is Cu0:8lNi0.19 cubic crystal structure. The crystal structure of the CuO0.81Ni0.19 becomes more complete with the increase in heat treatment temperature in 25- 300 °C. Part of crystal structure of the Cu0.81AlNi0.19 can turn Cu0.8lNi0.19 cubic crystal structure into Cu3.8Ni cubic crystal structure, and is advantageous to Cu3.8Ni (311) and Cu0.81Ni0.19 (311) growth with the increase in heat treatment temperature in 600-900 °C.

Microstructural analysis of high-pressure cold-sprayed Ni, NiCu and NiCu + Al2O3 coatings

Cold spraying has shown its potential to produce metallic and composite coatings with high quality and performance. For instance, the impermeability of the coatings is the criterion for the corrosion resistance and thus, fully dense coatings can act as real corrosion barrier coatings. Our previous study has demonstrated the good corrosion properties of high-pressure cold-sprayed (HPCS) Ni and NiCu coatings whereas the present study focuses on the analysis of structural characteristics behind the dense coatings. Microstructures of as-sprayed and heat-treated HPCS Ni, Ni20Cu and Ni20Cu+Al2O3 coatings have been evaluated with FESEM from top-view direction. This revealed clearly particle deformation and particle boundaries whereas particle bonding was evaluated with cavitation–erosion test. Density was proven with Corrodkote test and impermeable HPCS NiCu+Al2O3 coating structures were achieved. Furthermore, cavitation–erosion resistance of NiCu coating was improved by heat treatment.

The Effect of Current Density on the NiCu Coating Synthesized by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the current density on the as-plated NiCu coatings are systematically researched. It was found that the moderate current density is beneficial to the compactness of the coatings. The content of the copper decreased and that of the nickel increased with the increasing of the current density. When the current density is smaller than 40 mA/cm2, the contents of nickel and copper vary apparently. When the current density is larger than 40 mA/cm2, the contents of nickel and copper vary slightly. That means the copper is more easily deposited at low current density and the nickel is more easily deposited at high current density.

Electrodeposition of Cu-Ni Incorporated with Layered Silicates for Microbial Corrosion Protection

Electrodeposition of different metals and alloys has become popular for corrosion resistance and hardness in the oil and gas industry because of the major problems that persist with corrosion. The off-shore oil rigs in the ocean are exposed to highly corrosive spray zones and low flow submerged components. The cost of corrosion weighs a heavy burden of about $1.372 billion dollars on the oil and gas industries in the United States [1]. Breaking down the total amount, this accounts for $589 million in surface pipeline and facility costs, $463 million in down hole tubing expenses and $320 million in capital expenditures related to corrosion [1].Electrodeposition has become a popular technique to produce new materials for science and engineering applications. The technique has become favorable in synthesizing coatings because of low cost, convenience, and the ability to work at low temperatures. When determining the structure, morphology, and composition of the film; the pH, current, and applied potential play an important role [2]. For use in marine environments, copper alloys are used to defend against biofouling of materials by inhibiting microbial induced corrosion (MIC). Copper ions are able to eliminate bacteria, viruses, fungi, algae and other microbes. Copper alloys have been examined due to their increased feasibility, material strength, and cost as compared to pure copper coatings [3]. The two major copper alloys that are most commonly examined are Cu-Ni 90-10 and Cu-Ni 70-30. 90-10 Cu-Ni coatings show good protection in more stagnant conditions, where as the 70-30 Cu-Ni coatings are employed in higher flow conditions because of the increased hardness provided by the higher concentration of nickel. Copper alloys are usually employed when long term durability is needed. Incorporation of ceramics into the metal coating improve the mechanical properties. Layered silicates are the ceramic compounds being analyzed in this study, which hold many lucrative properties such as a high surface area, good chemical resistance, resistance to extreme temperatures, and resistance to pH. Scientists have been able to prove that layered silicates improve the resistance to corrosion when it comes to conductive polymer composite coatings, scientists have proved that layered silicates increase the resistance to corrosion [4]. With the addition of montmorillonite (MMT) into the Cu-Ni matrix, an increase in strength, adhesion, wear and fracture toughness of the coating occurs, which provides for better corrosion resistance and hardness.The Cu-Ni-MMT coatings were analyzed with many different instrumental and electrochemical techniques. Scanning electron microscopy (SEM) was chosen to analyze the morphology of the electrodeposited films. X-ray diffraction (XRD) was used to analyze the crystal structure of the films. The copper to nickel metal ratio was determined using atomic absorption spectroscopy (AAS) and the presence of the clay in the film; silicon, alumina, magnesium and iron was confirmed with energy dispersion x-ray spectroscopy (EDX). The corrosion resistance and hardness of the films were analyzed using Tafel polarization, immersion tests, impedance spectroscopy, and nanoindentation. Also, solution studies were performed with zeta potential, particle size, and viscosity to determine the optimum amount of loading for MMT into the Cu-Ni films.In conclusion, copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth. Two major alloys of copper-nickel, 90-10 and 70-30, were electrodeposited with a layered silicate, montmorillonite, for microbial corrosion protection in marine environments on a stainless steel substrate. The overall corrosion resistance and hardness was improved with the film in comparison to the bare stainless steel substrate, which proves to be advantageous for the off-shore drilling environment in the oil and gas industry.

The Effect of Temperature on the NiCu Coating Prepared by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the temperature on the as-plated NiCu coatings are systematically researched. It was found that the lower of the temperature, the more compact of the coatings. With the increasing of the temperatures, the content of the nickel decrease and that of the copper increase. When the temperature is lower than 35 °C the contents of nickel and copper do not vary apparently. When the temperature is larger than 40 °C, there are significant increases of the copper content while apparent decreases of the nickel content.

The Influence of pH Value on the NiCu Coating Synthesized by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the pH value on the as-plated NiCu coatings are systematically researched. It was found that the weak acid environment was beneficial to the deposition of nickel copper alloy. With the increasing of the pH value, the content of the copper decrease and that of nickel increase.

High-Pressure Cold-Sprayed Ni and Ni-Cu Coatings: Improved Structures and Corrosion Properties

Cold spraying is a promising technique for the production of dense metallic coatings. In cold spraying, coating formation is through high velocity impacts of solid particles with high kinetic energy. During impact, particles deform plastically and adhere to the substrate, gradually building-up the coating. This makes it possible to form pure and dense coating structures. These impermeable coatings are advantageous in many applications such as those where corrosion protection is required. Nickel and nickel-copper alloys have good corrosion resistance and therefore, as dense coatings, have high potential for employment as corrosion barrier layers. In this study, the structural and corrosion properties of high-pressure cold-sprayed (HPCS) Ni and NiCu coatings are characterized. NiCu alloys are known to have good corrosion resistance in sulphuric and hydrochloric acids, whereas Ni is resistant to caustic soda and alkaline salt solutions. This study also shows the effect of heat treatments on coating properties. FESEM studies of cross-sectional samples reveal structural details of the HPCS coatings while corrosion properties are evaluated with polarization measurements. The corrosion behavior of both the bulk and substrate material is determined in order to assess the real corrosion protection potential of the coatings.

CHARACTERIZATIONS OF CU-BASED COATED AL7075 VIA PLASMA-SPRAY METHOD — A WEAR CASE STUDY

Despite of its poor tribological properties (low hardness and low resistance to friction, wear and abrasion as well as poor seizure resistance), aluminum has become a potential material in automotives, particularly in the engine areas. To overcome these weaknesses and increase the engine lifetime, a good surface treatment can be one of the best options. In this work, Cu-Ni alloy that has such excellent properties like ductility, corrosion and wear resistance, good electrical and thermal conductivity as well as it can be easily joined or fabricated into useful shapes, was chosen. The work aims to study the wear behavior of Cu-Ni coatings deposited on Al7075 substrates using an atmospheric plasma spray (APS) with different level of plasma powers. Lubricated wear test were carried out on a pin-on-disc tester under an applied load of 100 N with a fixed sliding speed of 0.851 ms-1 at room temperature (~ 23°C). It was found that a decrease in plasma power from 40 kW to 30 kW promoted finer microstructures and higher hardness of the coatings, up to 39%. At 30 kW, the splats formation involved high degree of flattening and solidification without many splashes within the structure. At higher power (40 kW), both velocity and temperature of droplets were noted to be increased, resulting rougher coating structures which were most likely due to overlapped splats. In turn, this weakened the bonding strength between splats. In the case of wear, the resistance of Cu-Ni coated Al7075 was found to be increased from ~6 to 18 × 10-5 mm3/Nm, indicating a mild wear regime that was attributed to an increase in the coating hardness.

The stability of hydrogen evolution activity and corrosion behavior of NiCu coatings with long-term electrolysis in alkaline solution

In this study, NiCu composite coating was electrochemically deposited on a copper electrode (Cu/NiCu) and tested for hydrogen evolution reaction (HER) in 1 M KOH solution for long-term electrolysis with the help of cathodic current–potential curves and electrochemical impedance spectroscopy (EIS) techniques. The bulk and surface composition of the coating was determined using atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) analysis. The surface morphology was investigated by scanning electron microscopy (SEM). The effect of electrolysis on the corrosion behavior of the Cu/NiCu electrode was also reported. It was found that the NiCu coating had a compact and porous structure with good time stability. The HER activity of the coating was stable over 120 h electrolysis and the HER mechanism was not modified during the operation. The corrosion tests showed that the corrosion resistance of the Cu/NiCu electrode changed when a cathodic current was applied to the electrolysis system.