D. A. Romanov

Surface relief and structure of electroexplosive composite surface layers of the molybdenum-copper system

The surface topography and structure of copper layers exposed to multiphase plasma jets of products of electrical explosion of molybdenum and copper foils are studied using profilometry and scanning electron and light microscopy. Such treatment allows deposition of either layered coatings or alloyed composite layers. It is found that the surface layer roughness parameter is Ra = 3.2−4.0 μm. The thickness of some copper and molybdenum layers of coatings is 15–20 μm. Electroexplosive alloying produces layers 25 μm thick. Sizes of copper inclusions in the molybdenum matrix near the surface of such layers vary from 30 nm to 1–2 μm.

Structure and properties of surface layers obtained due to titanium-surface alloying by yttrium via combined electron-ion-plasma treatment

The surface layer of titanium is modified via a combined method involving electroexplosive alloying by yttrium and subsequent high-intensity electron-beam irradiation. The elemental and phase composition, defect substructure, and mechanical and tribological characteristics of the alloyed layers are investigated. The titanium-surface layer is revealed to be saturated with yttrium, oxygen, and hydrogen atoms, which give rise to the formation of a metal-ceramic layer hardened with titanium and yttrium oxides and carbides and stimulate a manifold increase in the microhardness and a decrease in the friction coefficient and wear rate of the modified layer.

The physical basics of structure formation in electroexplosive coatings

It is shown that, under an electroexplosive spraying of coatings of various systems, the dynamic rotation of the particles deposited is the basis for forming a vortex hierarchically organized structure in both the coating and upper layers of the substrate, including their interface. This causes dispersion of all the structural elements of the cover, their mutual penetration into each other, and the absence of a sharp interface between the coating and the substrate. The impact of multiple shocks on the deposited coating by a highenergy plasma jet from the discharge of a plasma accelerator creates the forged structure in the material, which is characterized by high strength, wear resistance, and relaxation capability.

Structure of electroexplosive TiC–Ni composite coatings on steel after electron-beam treatment

The phase and elemental compositions of the surface layer in Hardox 450 steel after electroexplosive spraying of a TiC–Ni composite coating and subsequent irradiation by a submillisecond high-energy electron beam are studied by the methods of modern physical metallurgy. The electron-beam treatment conditions that result in the formation of dense surface layers having high luster and a submicrocrystalline structure based on titanium carbide and nickel are found. It is shown that electron-beam treatment of an electroexplosive coating performed under melting conditions leads to the formation of a homogeneous (in structure and concentration) surface layer.

Structure of the molybdenum–carbon–copper composite coatings produced by electroexplosive spraying followed by electron-beam treatment

Electroexplosive Mo–C–Cu composite coatings are modified by a high-energy electron beam for the first time. Our studies demonstrate that the electron-beam treatment of the electroexplosive spraying layer that is performed under melting conditions leads to the formation of a structurally and concentration homogeneous surface layer.

Structural-phase states and tribological properties of electroexplosive composite coatings on copper after electron-beam treatment

The dislocation substructures of electroexplosive composite coatings deposited onto copper and modified by a high-intensity electron beam are analyzed. It is revealed that a highly defective multiphase structure is formed in the surface layer of the coatings and that molybdenum and tungsten nanoinclusions are generated in Mo-Cu and W-Cu coatings. Particles of carbides (Mo2C and WC) and titanium boride (Ti2B5) are observed in Mo-Cu-C, W-C-Cu, and TiB2-Cu coatings. Tribological tests are performed and the aver-age values of the friction coefficient and wear rate of the examined systems are determined.

Surface gradient structure-phase states formation under differentiated quenching of 100 meter rails

Using transmission electron microscopy methods the layer by layer analysis of rails differentially quenched in different regimes is carried out on different scale levels. It is shown that the differentiated quenching of rails is accompanied by the formation of morphologically different structure, being produced according to the diffusion mechanism of γ-α transformation and consisting of plate perlite grains, free ferrite grains and grains of ferrite-carbide mixture. The gradient character of the changing of structure, phase composition and dislocation substructure parameters in the surface layer of rails head is established. It is revealed that the interfaces between globular cementite particles-matrix are the most dangerous stress concentrators.

Temperature field calculation with allowance for heat of chemical reactions under electroexplosion nickel plating of aluminum

The analysis of stress-strained state at the boundary «faced surface layer – substrate» is performed by methods of elasticity theory of inhomogeneous media, on exposure to the load distributed in a circle. The fundamental aspects of Kelvin – Helmholtz and Richtmayer – Meshkov instabilities are considered. The following methods are used for the research. The analytical method of solution is used for finding the temperature distribution of substrate and coating material as well as distribution of speed of material motion in deposition of the coating. Finite element method is required in accounting for the parameters of convective mixing. For the analysis of the proposed thickness and dispersion of the coating the concepts of hydrodynamic Kelvin – Helmholtz and Richtmayer – Meshkov instabilities are used. Using the mass, energy and momentum conservation laws, with allowance for the possible exothermal reactions, the system of equations of the mathematical model of electroexplosion synthesis on the basis of t...

Elemental and phase composition of TiB2–Mo coating sprayed on a steel by electro-explosive method

The elemental and phase composition of the surface layer of Hardox 450 steel with a composite TiB2–Mo coating sprayed by an electro-explosive method are investigated after pulsed irradiation with an intense electron beam of submillisecond duration. Electron-beam treatment conditions leading to formation of a dense surface layer with high luster with a submicrograin structure on the basis of titanium diboride and nickel are ascertained. It is shown that an electron-beam treatment under melting rate leads to formation of a surface layer with homogeneous structure and uniform concentration distribution.

Structure and phase composition of wear-resistant coatings of the TiB2–Al system prepared by electroexplosion sputtering

The surface profile, structural features, and phase composition of coatings of the TiB2–Al system, which were fabricated by electroexplosion sputtering, are investigated by optical interferometry, scanning electron microscopy, and X-ray phase analysis. It is established that posttreatment surface roughness parameter Ra = 2.0 μm. The phase composition of formed layers includes Al, TiB2, and TiBC3. Coatings have a cohesion–adhesion bond with the surface-contact material.