A. D. Teresov

Effect of Intensified Emission During the Generation of a Submillisecond Low-Energy Electron Beam in a Plasma-Cathode Diode

The effect of the intensification of electron emission in a plasma-cathode diode with a grid-stabilized plasma boundary has been investigated. For a pulsed (100-mus) electron beam of 15-20-keV energy that passes through the plasma formed as a result of gas ionization by an electron beam, it has been revealed that an increase in pressure increases the emission current at a fixed plasma-cathode discharge current, and the emission current can become greater in magnitude than the discharge current. It has been shown that a significant increase in electron-beam current is provided by the secondary ion-electron emission that results from the bombardment of the emission electrode surface by the accelerated ions coming from the boundary of the anode plasma.

Synthesis of Ti3Al and TiAl based surface alloys by pulsed electron-beam melting of Al(film)/Ti(substrate) system

Phase formation and surface hardening in the 100-nm-thick Al(film)/Ti(substrate) system under conditions of pulsed electron-beam melting (∼15 keV, ∼3 μs, 3–4 J/cm2) have been studied depending on the number of film deposition-melting cycles. Using this method, submicrocrystalline and nanocrystalline surface alloys with thicknesses ≥3 μm based on Ti3Al and TiAl intermetallics have been obtained on the titanium substrate.

Evolution of the phase composition and defect substructure of rail steel subjected to high-intensity electron-beam treatment

The morphology, structure-phase states, and defect substructure of annealed rail steel subjected to electron-beam treatment in the surface-layer melting mode are studied by scanning and transmission electron microscopy methods. The formation of the lath martensite structure, as well as cellular and dendritelike structures, containing nanoscale martensite crystals, is revealed.

Adhesion properties of a silicon-containing calcium phosphate coating deposited by RF magnetron sputtering on a heated substrate

Silicon-containing hydroxyapatite coatings 400–700 nm in thickness are prepared by means of radio-frequency (RF) magnetron sputtering on a heated (to 200°C) titanium substrate chemically etched and treated with a pulsed electron beam. The morphology and phase composition of the coating are studied. The morphology and roughness of the composite “calcium-phosphate coating-titanium substrate” differ depending on the treatment procedure of the substrate before deposition. The scratch test method is used to assess the adhesion strength of the coatings formed at different values of bias potential applied to the substrate. It is observed that the adhesion strength of the coating changes with decreasing crystallite size.

Surface Modification of TiC–NiCrAl Hard Alloy by Pulsed Electron Beam

The mechanisms by which nanostructural states are realized in e-beam-irradiated TiC-NiCrAl cermet depending on the irradiation mode have been revealed. Mechanical testing and tribotesting have yielded criteria for a substantial (a factor of 1.5-3) increase in performance characteristics of the cermet alloy (micro- and nanohardness, cutting resistance, coefficient of friction, and bending resistance).

Structural phase changes in a titanium-silicon system modified by high-current electron beams and compression plasma flows

Structural phase changes in a titanium-silicon system treated by low-energy high-current electron beams (HCEBs) and compression plasma flows (CPFs) with the duration 100 μs and the energy density 12–15 J/cm2 are studied. Scanning electron microscopy, X-ray diffraction and electron microprobe analysis are used in this work. The formation of a titanium-doped silicon layer 10–25 μm thick, titanium silicides (TiSi2 under HCEBs and Ti5Si3 under CPF treatment), silicon dendrites, and needle-like eutectics (typical size of precipitates is about 50 nm) is revealed. It is shown via the results of numerical simulation that the thickness of the metal-doped layer is mainly controlled by the power density value and the surface nonuniformity of the heat flow over the target surface. The thermodynamic regularities of phase formation are discussed, taking into account heat transfer between the silicide nuclei and solid silicon.

Structure of the surface layer of a wear-resistant coating after treatment with a high-intensity electron beam

Transmission electron microscopy is used to investigate the carbon extraction replicas of a wearresistant surface layer formed on Hardox 400 steel and its phase composition. The formation of a multiphase state is revealed, which includes a-iron grains and inclusions of carbide phases based on iron, chromium, and niobium. The surface layer is additionally treated by a high-intensity pulsed electron beam. The relative position of α-iron grains and particles of carbide phases is examined by the electron-diffraction microscopy of thin foils. The main carbide phase is iron carbide located as extended interlayers which separate a-iron grains. Nanoscale particles of chromium and niobium carbides are located at the interfaces of the a-iron–iron-carbide system and in the body of the a-iron grains. It is established that the surface layer is in the elastic-stress state during pulsed electron-beam treatment due to ultrahigh heating and cooling rates. It is shown that stress concentrators are the interphase boundaries between the carbide and the a-phase of iron.

Structure of electroexplosive TiB 2 –Ni composite coatings after electron beam processing

High-intensity electron beam modification of electroexplosive TiB2–Ni composite coatings is conducted for the first time. The phase and elemental composition of the surface layer of steel Hardox 450 subjected to electroexplosive spraying (EES) of the TiB2–Ni composite coating and subsequent irradiation with a submillisecond high-intensity pulsed electron beam are studied. Electron beam processing (EBP) modes that provide the formation of dense glossy surface layers based on titanium diboride and nickel with a submicrocrystalline structure are revealed. It is shown that EBP of a layer subjected to EES conducted in a melting mode leads to the formation of a surface layer with homogeneous structure and concentration.

Structure and phase composition of a chromium-silicon system modified by high-current electron beams

The results of studies of the structure-phase state of a chromium-coated silicon substrate system’s subsurface layer treated with low-energy high-current electron beams, 50–200 μs in duration and with an energy density of 15 J/cm2, are reported. The data of raster electron microscopy and X-ray structural and spectral microanalysis revealed the formation of a chromium-doped silicon layer with a thickness of 2–38 μm, chromium-enriched silicon dendrites, chromium disilicide CrSi2, and an amorphous eutectic layer (the characteristic cross-section size of the chromium-enriched phase extrusions is ∼50 nm). The structure-phase transformations are discussed taking into account the peculiarities of the distribution of temperature, diffusion and convective mass-transfer in the modified layer.

A high-current electron beam application for the surface modification of iron, stainless steel, and heat resistant alloys

The structure and strength of the surface coating layer of iron, stainless steel, and the heat-resistant alloy after being processed by a high-current low-energy electron beam have been considered. The methods of optical metallography, X-ray structural analysis, and transmission electronic microscopy have been used. The formation of a submicrocrystal structure of the fritted coating with a high density of dislocations has been established.