Sergey V. Gnedenkov

Production of hard and heat-resistant coatings on aluminium using a plasma micro-discharge

Oxide structures were synthesized on aluminium alloy surfaces as the anode under plasma discharges conditions. Aqueous solutions containing ions of an organic acid were used as electrolytes. It was ascertained that the amorphous coatings obtained have a significant microhardness and heat-resistance up to 870°C. On the basis of experimental data obtained by thermogravimetric analysis, X-ray analysis and laser mass-spectroscopy methods, conclusions about the formed oxide layer compositions were made.

Composition and adhesion of protective coatings on aluminum

The composition, structure and homogeneity of oxide coatings formed by the microarc oxidation (MAO) method on aluminum alloy surfaces and possessing significant hardness and heat-resistance up to 870°C were investigated. On the basis of experimental data obtained by X-ray analysis, EPMA, XPS methods, the conclusions about oxide layers composition formations were made. The presence of finely dispersive aluminum oxide as a main component in the coating composition provides the hardness and heat-resistance of the layer obtained on the aluminum. This layer has a significant adhesion to aluminum substrate. The model ideas concerning construction and reasons of formation of thin friable top layer have been suggested.

Electrochemical impedance simulation of a metal oxide heterostructure/electrolyte interface: A review

The results of an analysis of the literature data obtained when investigating processes of charge transfer at interfaces of heterostructures formed by various methods, including the high-energy methods, are presented in this paper. The performed investigation of oxide layers at the titanium surface, with use made of impedance spectroscopy data made it possible to reveal the nature and influence of some processes and factors on the charge transfer mechanism realized at a metal oxide heterostructure/electrolyte interface. Simulating an oxide/electrolyte interface gives one a chance to identify, in a spectrum, the responses that characterize the behavior of porous and poreless layers, as well as the responses that are due to the space-charge region formed in the oxide material and to the corrosion and diffusion processes.

Composite Polymer Containing Coatings on the Surface of Metals and Alloys

It was shown that the Plasma Electrolytic Oxidation (PEO) treatment followed by coating the superdispersed polytetrafluoroethylene (SPTFE) Forum® on the developed mesoporous PEO-layer resulted in a composite coating on the surface of metals and alloys (e.g., titanium, nitinol, steel). The electrochemical properties including contact corrosion currents of the galvanic couples steel/titanium with composite coating were studied by means of electrochemical impedance spectroscopy and potentiodynamic polarization. In addition, mechanical properties were examined. It was ascertained that the combination of PEO-produced coating with SPTFE provided increased corrosion stability of metals and alloys making them suitable for implantation surgery.

Charge transfer at the antiscale composite layer-electrolyte interface

Properties of composite coatings based on oxide layers formed on a titanium surface using the plasmic electrolytic oxidation method and processed using Forum® superdispersed polytetrafluorinethylene were investigated. A combination of electrochemical impedance spectroscopy, differential thermal analysis, and thermal gravimetry methods allowed one to establish the change of the surface state as a result of heating that determines the charge transfer mechanism at the heterostructure-electrolyte phase interface and the difference in the thermodynamic stability of the temperature fractions of the employed polymer.

Formation of BaTiO3 coatings on titanium by microarc oxidation method

Barium titanate layers on a titanium surface have been formed with using of microarc oxidation (MAO) method. The formation process was carried out in the aqueous electrolyte containing barium ions. The formation conditions, composition and anomalous properties of surface layers obtained are discussed. Based upon the experimental results the mechanism of metal/dielectric/metal (MDM) structure formation is proposed.

Cyclic Strength of Titanium Alloys, Anodized under Micro-Arc Conditions, in Sea Water

The durability of titanium alloys having undergone micro-arc oxidation and then exposed to sea water is estimated based on experimental results and theoretical concepts. A beneficial effect of microplasma process on the cyclic strength of titanium and its alloy is explained.

Functional coatings formed on the titanium and magnesium alloys as implant materials by plasma electrolytic oxidation technology: fundamental principles and synthesis conditions

Abstract Metallic implants have been successfully used in medicine for the past 60–70 years. Historically, implants were designed only as mechanical devices, whereas the biological aspects of their application were beyond the researchers’ interest. The improvement of living conditions and the increase of the average life span have changed the situation. The clinical requirements for medical implants rise up substantially. Presently, it seems impossible to imagine the use of metallic implants in the human body without preliminary surface modification to modulate the interaction between the surrounding biological environment and the implant. The review highlights the most recent advances in the field of functional coatings formed on implants by the plasma electrolytic oxidation technology. Special attention is dedicated to the principles of surface modification of the commercially pure titanium, titanium nickelide, and Mg-Mn-Ce magnesium alloy. The advantages and disadvantages of the method and the characteristics of these materials are discussed from this point of view. Some aspects of this review are aimed at corrosion protection of implants with application of polymer materials.

Hydrophobic properties of composite fluoropolymer coatings on titanium

The results of studies of the hydrophobicity of composite coatings on titanium formed using the method of plasma electrolytic oxidation (PEO) with further treatment by superdispersed polytetrafluoroethylene and its low-molecular fractions are presented. The chosen regimes of application of fluoropolymer materials of different fractional composition onto oxide coatings allow enhancing significantly hydrophobic surface properties (the contact angle reaches 131°).

Protective oxide coatings on Mg-Mn-Ce, Mg-Zn-Zr, Mg-Al-Zn-Mn, Mg-Zn-Zr-Y, and Mg-Zr-Nd magnesium-based alloys

Protective coatings are formed on different magnesium-based alloys (Mg-Mn-Ce, Mg-Zn-Zr, Mg-Al-Zn-Mn, Mg-Zn-Zr-Y, and Mg-Zr-Nd) by plasma electrolytic oxidation. Electrochemical and mechanical properties of the coatings are studied, as well as their chemical and phase compositions and structures. Analysis of the data obtained revealed the reasons for the differences in the corrosion and mechanical characteristics between plasma electrolytic layers formed on different magnesium alloys used in aviation and space engineering.