V. P. Rotshtein

Pulsed electron-beam technology for surface modification of metallic materials

This article concerns the foundations of a new technology for surface modification of metallic materials based on the use of original sources of low-energy, high-current electron beams. The sources contain an electron gun with an explosive-emission cathode and a plasma anode, placed in a guide magnetic field. The acceleration gap and the transportation channel are prefilled with plasma with the use of spark plasma sources or a low-pressure reflected discharge. The electron-beam sources produce electron beams with the parameters as follows: electron energy 10–40 keV; pulse duration 0.5–5 μs; energy density 0.5–40 J/cm2, and beam cross-section area 10–50 cm2. They are simple and reliable in operation. Investigations performed with a variety of constructional and tool materials (steels, aluminum and titanium alloys, hard alloys) have shown that the most pronounced changes of the structure-phase state occur in the near-surface layers quenched from the liquid state, where the crystallization front velocity rea...

Use of low-energy, high-current electron beams for surface treatment of materials

Abstract This article describes the characteristics of original sources of low-energy (10–45 keV), high-current (up to 50 kA) electron beams of microsecond duration, designed for the surface thermal treatment of materials. Under the action of this type of beam, graded structures are formed which may impart improved physicochemicai properties and strength to the surface layers. This permits the use of these beams for improving the strength and electrochemical properties of pieces and tools, and for increasing the electric strength of vacuum insulation. Some technological operations, such as the deposition and removal of coatings and surface alloying, can be realized in the intense evaporation mode.

Pulsed electron-beam melting of high-speed steel: structural phase transformations and wear resistance

Abstract The structural and phase transformations occurring in the near-surface layers of pre-quenched high-speed steel subjected to pulsed electron beam melting have been investigated. Melting was induced by a low-energy (20–30 keV), high-current electron beam with a pulse duration of 2.5 μs and an energy density ranging from 3 to 18 J/cm2. Using electron microscopy and X-ray diffraction it has been revealed that with increasing beam energy density gradual liquid-phase dissolution of initial globular M6C carbide particles occurs in the near-surface layer of thickness up to ∼1 μm. This process is accompanied by the formation of martensite crystals (α-phase) and an increase of residual austenite (γ-phase) content. When the carbide particles are completely dissolved, martensitic transformation is suppressed. In this case, a non-misoriented structure is formed consisting predominantly of submicrometer cells of γ-phase separated by nanosized carbide interlayers. Irradiation of cutting tools (drills) in a mode corresponding to an abrupt decrease in the content of M6C particles due to their liquid-phase dissolution enhances the wear resistance of the drills by a factor of 1.7. This is associated with the fixation of undissolved particles in the matrix, the formation of residual compressive stresses and of dispersed M3C carbide particles as well as the high (∼50%) content of the metastable γ-phase in the surface layer.

The effect of pulsed electron-beam treatment of electrodes on vacuum breakdown

A method for preliminary treatment of electrodes by a microsecond low-energy intense electron beam is proposed. It has been demonstrated that such a beam melts off the electrode surface and cleans the surface layers from impurities and dissolved gases. In combination with subsequent conditioning of the vacuum gap with low-current pulsed discharges, high breakdown electric fields can be attained. >

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.

Increasing the electric strength of vacuum insulation by irradiating the electrodes with a low-energy high-current electron beam

The paper describes how irradiation of the electrode surface with a LEHCEB (low-energy high-current electron beam) affects the prebreakdown current and the electric strength of vacuum insulation. This study is an extension of a study described earlier. Experiments have been performed for 0.1 mm vacuum gaps formed by refractory metal electrodes and for millimeter vacuum gaps with a pulsed voltage of amplitude 250 kV and duration 30 to 100 ns, both in a high oil-free vacuum and in technical-grade oil vacuum. Based on the results obtained, it is stated that the LEHCEB irradiation of electrode surfaces is a promising technique for increasing the electric strength of vacuum insulation over a wide range of voltages and under varied vacuum conditions.

Mechanisms for Hardening of Carbon Steel with a Nanosecond High-Energy, High-Current Electron Beam

Abstract It has been demonstrated that in thin quenched-steel targets irradiated with a high-energy, high-current electron beam of moderate power density, in parallel with the near-surface microhardness maximum formed by a thermal mechanism (quenching from high temperatures), two other maxima appear. One of them is situated in the zone of reflection of the stress wave from the rear surface of the target, Since the material in this zone is not heated, it is hardened by a strainm stress-wave mechanism. Another maximum is situated in the zone of reflection of the stress wave from the target face. The steel structure in this zone is modified by a combined mechanism, such that the material is hardened by the stress wave and simultaneously tempered by the operative temperature field. It has been shown that the positions of the microhardness maxima can be calculated with a reasonable accuracy by solving numerically a set of thermoelasticity equations. The structure of the material at the microhardness maxima loc...

Effect of conditions of pulsed electron-beam melting for Al (film)/Ti (substrate) systems on phase formation and properties of Ti-Al surface alloys

Findings of comparative investigations are presented for phase formation, characteristics of hardening, tribological properties, and oxidation resistance of Ti-Al intermetallic surface alloys formed by multiple alternation of deposition of an Al film (0.1–1 μm) on a Ti substrate and pulsed liquid-phase mixing of Al and Ti by intense low-energy (∼15 keV) electron beams with microsecond (∼3 μs) and submillisecond (100 μs) duration. It is found that microsecond synthesis is effective for formation of γ(TiAl) oxidation-resistant surface alloys. In turn, submillisecond synthesis allows one to form Ti3Al surface alloys with enhanced wear resistance.

Bulk changes in the microhardness of a solid WC-110G13 steel alloy exposed to a low-energy, high-current electron beam

Bulk changes in the microhardness of a solid WC-110G13 steel alloy are studied as a function of the energy density of a low-energy, high-current electron beam, the number of pulses, and the target thickness. It is established that the beam energy density has a threshold at which quasiperiodic changes in the microhardness occur in the bulk of the alloy.

Application of the pulsed electron-beam treatment of electrode surfaces for increasing the electric strength of vacuum gaps

A method for preliminary treatment of electrodes with a low-energy, high-current electron beam of microsecond duration is proposed. This method, combined with subsequent conditioning of the vacuum gap by pulsed discharges, makes it possible to achieve high values of the breakdown electric field. Projected uses of the method for increasing the electric strength of high-power electrodynamic systems are described.