Properties Of Chromium Coatings Research Articles

The Mechanism for the Effect of Nanocarbons Added to Electroplating Electrolytes on the Tribotechnical Properties of Chromium Coatings

The Mechanism for the Effect of Nanocarbons Added to Electroplating Electrolytes on the Tribotechnical Properties of Chromium Coatings

Characteristics and Properties of Chromium Coatings with Diamond Nanoparticles Deposited Directly on Aluminum Alloys

Characteristics and Properties of Chromium Coatings with Diamond Nanoparticles Deposited Directly on Aluminum Alloys

Structure and Tribological Properties of Chromium Coatings Formed by Electrodeformation Cladding with Flexible Tools

The paper contains results of investigations on structure and tribotechnical properties of chromium coatings formed by a method of electrodeformation cladding with flexible tools (EDCFT). The purpose of these investigations is to assess prospects for application of the coatings as an alternative to galvanic chrome plating which is widely used in manufacturing hydraulic cylinder rods of metal-cutting machines. Rotary metal brushes with a wire pile made of 65Г-steel and 03Х17Н14М2-stainless steel have been used as a flexible tool. A compacted bar obtained by sintering a mixture of pure chromium powders and a nano-sized diamond-graphite blend UDDG has been employed as a donor material for EDCFT. According to results of the research it has been established that alloying elements of wire pile such as chromium and nickel are added to a coating composition while forming coatings a stainless steel brush. So in the case of using brushes with wire pile of 03X17H14M2-stainless steel the amount of chromium and nickel in a clad coating layer is 5.3 and 9.6 times higher in percentage, respectively, in comparison with the coating formed by a 65Г-steel brush that can contribute to improvement of coating corrosion resistance. At the same time, surface relief of the coating has a developed rough structure consisting of chromium microparticles having various size that are tightly packed and elongated in the direction of brush rotation and there are no flaws in the form of discontinuities and delaminations. Tribological tests have been performed under conditions of “boundary lubrication” on a rotary friction machine that implements friction of a rubber indenter on a flat surface of a rotating disk. According to data of the tribotechnical tests it has been ascertained that under conditions of “boundary friction” for such paired samples as “coated disc – rubber roller” chromium coatings formed by the EDCFT method, have the lowest values of a sliding friction coefficient (fтр = 0.023) which are 7.5 times lower than chromium coatings obtained by electroplating. At the same time the wear of rubber rollers in pairs with electroplated chromium coatings has turned out to be less than in pairs with the coating formed by the EDCFT method.

Effects of PEG, PVP and SDS on the Properties of Chromium Coatings Prepared from Trivalent Chromium Chloride Baths Using Experimental Design and Multi-Response Optimisation

Effects of PEG, PVP and SDS on the Properties of Chromium Coatings Prepared from Trivalent Chromium Chloride Baths Using Experimental Design and Multi-Response Optimisation

Effect of alumina nanoparticles on the structure and physicochemical properties of chromium coatings

The results of research into the structure, chemical composition, and main functional properties of electrodeposited chromium-based nanocomposite coatings are described. The nanodispersed phase that provides an increase in the microhardness, wear resistance, and corrosion stability of the resulting coatings is determined. The percentage of the main chemical elements in the electrodeposited chromium-based nanocomposite coating are found.

Effect of a high-frequency electromagnetic field on the properties of chromium coatings

The results of studying the effect of high-frequency magnetic-pulse treatment of electrodeposited chromium coatings on their structure are described. It is shown that the effect of magnetic-pulse treatment depends on the deposition conditions, which are responsible for significant changes in the initial structure and microhardness of the coatings.

Chemometrics applied to functional chromium electroplating by pulse plating techniques

Electrodeposited chromium coatings offer high levels of mechanical and tribological properties that justify their use in many industrial and engineering applications. However, one problem of these functional coatings is their limited corrosion resistance and the low current efficiency of their electrodeposition process. Reverse pulse plating can lead to an improvement in the characteristics of chromium deposits, but the high number of variables involved and the interactions among them make the selection of operating parameters difficult. In this paper, a chemometric approach was used in order to design the experiments and study the effect of pulse plating parameters on the properties of chromium coatings. Multivariate analysis was proposed to establish a relationship among structural and physical characteristics of chromium deposits and to determine the pulse parameters required to achieve certain properties. The results indicated that by reverse pulse electrodeposition, it is possible to obtain crack free chromium coatings, with similar hardness values as those obtained from direct current electrodeposited coatings, but with an improved corrosion resistance.

Electrodeposition and physico-mechanical properties of chromium coatings modified with disperse particles

Chromium electroplates from Cr(III)-baths modified with disperse phases of CeO2, Cr2O3, graphite, and ultradisperse diamond are studied. Mechanical properties of the composite coatings are investigated. The Cr2O3-particles present in the bath are found to cause the destruction of the coatings already during the plating. When modifying with CeO2-particles, good coatings with enhanced microhardness can be obtained at their concentration in the bath of no more than 15 g/l. The deposition rate in such cases exceeds that in the blank baths. The optimum range of the CeO2-particle concentration, allowing to obtain the maximal microhardness, is 5–8 g/l. The self-lubricating chromium-graphite composite coatings can be deposited at a graphite concentration in the bath of up to 4 g/l. The microhardness of the chromium coatings is most strongly affected by ultradisperse diamond particles that increase the microhardness by a factor of 1.4; they also decrease the coatings’ brittleness. When the ultradisperse diamond concentration in the solution is as high as 30 g/l, the diamond content in the composite coating reaches its limiting value of 12–14 vol % (or 6.4–7.2 wt %). The optimum ultradisperse diamond concentration was found to be 17 g/l in the baths and 10.5 vol % (or 5.6 wt %) in the composite coating. At these concentrations, the coatings with the maximum microhardness and lowest brittleness are obtained.

Composition, Structure, and Corrosion–Electrochemical Properties of Chromium Coatings Deposited from Chromium(III) Electrolytes Containing Formic Acid and Its Derivatives

To study electrocatalytic properties of chromium, its deposits are obtained from Cr(III) electrolytes containing formic acid and its four derivatives (formaldehyde, methyl alcohol, formamide, dimethylformamide) and comprehensively examined. Amorphous structure of the deposits is established with an x-ray diffraction analysis. The valence state of chromium and major extrinsic elements is studied by x-ray photoelectron spectroscopy. The carbon reduction degree and the organization of carbon particles in deep layers of the deposits (chainlike or graphite-like structures) is shown to depend on the nature of organic compounds added into the chromium-plating electrolyte. The corrosion–electrochemical behavior of the obtained deposits in 0.5 M H2SO4 is compared to that of polycrystalline chromium and deposits plated from sulfate–oxalate Cr(III) electrolytes.

Properties of Chromium Coatings Deposited from “Sulpho-Chromispel-I” Electrolyte of Standard Concentration

SUMMARY The most important properties of reflectivity, internal stress, hardness and surface morphology of chromium coatings deposited from “Sulfo-Chromispel-I” electrolytes (250 g dm−3 CrO3) are studied The effects of operating parameters and electrolyte composition are evaluated. It is established that chromium coatings depositedfrom “Sulpho-Chromispel-I” electrolytes exhibit low internal stress. The current density and thickness of the coating affect the latter. Internal tension is reduced with the increase in coating thickness at current density of 50 A dm−2, which is very favourable for depositing thick functional chromium layers. The reflectivity is affected by the concentration of iodide and cathodic current density. At current densities up to 35 A dm−2 the higher the iodide concentration, the brighter the coating. With increased current densities the coatings produced are coarser and their brightness is reduced. Small amounts of sulphuric acid (4–20 cm3 dm−3) improve the brightness. The hardness of the coatings deposited from the electrolytes studied is less than that of coatings deposited from a standard sulphate bath—300–400 kg mm−2. The roughness grade is 0.5-0.6 mm. The coatings deposited from “Sulpho-Chromispel-I” electrolytes are bright with low tensile stress and moderate hardness. They are deposited at ambient temperature over a wide interval of current density, which is rather advantageous from a technological point of view.

Effect of electrolyte circulation on gas content and mechanical properties of chromium coatings

Effect of electrolyte circulation on gas content and mechanical properties of chromium coatings