Electron-beam modification of coating-aluminum substrate systems

Multiphase surface alloys with improved strength and tribological characteristics have been synthesized by exposing coating/A7 substrate systems to a pulsed electron beam. Optimum modes of electron-ion-plasma treatment of commercially pure aluminum have been found at which the wear resistance and hardness of the surface layer were observed to increase by a factor of about 7.5 and up to 18, respectively

Formation of the surface alloys by high-intensity pulsed electron beam irradiation of the coating/substrate system

The results of the analysis of the structure and properties of the surface layer of aluminum A7 subjected to alloying by the intense pulsed electron beam melting of the film / substrate system. Fold increase in strength and tribological properties of the modified surface layer due to the formation of submicro - nanoscale multiphase structure have been revealed

Fractography of the fatigue fracture surface of silumin irradiated by high-intensity pulsed electron beam

The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 μm located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 μm in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life

The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance

Features of formation of structural-phase states on the surface of titanium alloy VT1-0 after electron-ion-plasma treatment

Complex modification of a surface of commercially pure titanium is realized. Firstly plasma is created by electrical explosion of a carbon-graphite fiber, of which surface was placed nanosized TiB2 powder. Then the surface of technically pure titanium is processed with this plasma. Finally, the modified surface was irradiated by an electron beam. Formation of multi-layer multiphase nanosized structure is revealed. It is shown that the maximum microhardness reached in a near-surface layer exceeds microhardness of a initial material more than by 10 times. Wear resistance of a blanket increases in 7.5; the friction coefficient decreases by 1.15 times

Features of formation of structural-phase states on the surface of titanium alloy VT1-0 after electron-ion-plasma treatment

Complex modification of a surface of commercially pure titanium is realized. Firstly plasma is created by electrical explosion of a carbon-graphite fiber, of which surface was placed nanosized TiB2 powder. Then the surface of technically pure titanium is processed with this plasma. Finally, the modified surface was irradiated by an electron beam. Formation of multi-layer multiphase nanosized structure is revealed. It is shown that the maximum microhardness reached in a near-surface layer exceeds microhardness of a initial material more than by 10 times. Wear resistance of a blanket increases in 7.5; the friction coefficient decreases by 1.15 times

Electron-ion plasma modification of Al-based alloys

The paper reports on the study where we analyzed the surface structure and strength properties of coated Al alloys modified by electron-ion plasma treatment. The Al alloys were deposited with a thin (≈0.5 μm) TiCu film coating (TiCu-Al system) and with a hard TiCuN coating (TiCuN–AlSi system) on a TRIO vacuum setup in the plasma of low-pressure arc discharges. The temperature fields and phase transformations in the film–substrate system were estimated by numerical simulation in a wide range of electron energy densities (5–30 J/cm2) and pulse durations (50–200 μs). The calculations allowed us to determine the threshold energy density and pulse duration at which the surface structure of the irradiated Al-based systems is transformed in a single-phase state (solid or liquid) and in a two-phase state (solid plus liquid). The elemental composition, defect structure, phase state, and lattice state in the modified surface layers were examined by optical, scanning, and transmission electron microscopy, and by X-ray diffraction analysis. The mechanical characteristics of the modified layers were studied by measuring the hardness and Young’s modulus. The tribological properties of the modified layers were analyzed by measuring the wear resistance and friction coefficient. It is shown that melting and subsequent high-rate crystallization of the TiCu–Al system makes possible a multiphase Al-based surface structure with the following characteristics: crystallite size ranging within micrometer, microhardness of more than 3 times that in the specimen bulk, and wear resistance ≈1.8 times higher compared to the initial material. Electron beam irradiation of the TiCuN–AlSi system allows fusion of the coating into the substrate, thus increasing the wear resistance of the material ≈2.2 times at a surface hardness of ∼14 GPa

Combined treatment of steel, including electrospark doping and subsequent irradiation with a high-intensity electron beam

A thermodynamic analysis of phase transformations taking place during doping of steel with tungsten and titanium has been performed. The studies on the surface layer of steel modified using the combined method (electrospark doping and the subsequent electron-beam treatment) have been carried out. Formation in the surface layer of a multi-phase submicrocrystalline structure with high strength properties has been revealed

Experimental Study and Mathematical Modeling of the Processes Occurring in ZrN Coating/Silumin Substrate Systems under Pulsed Electron Beam Irradiation

This paper presents a study of a combined modification of silumin, which included deposition of a ZrN coating on a silumin substrate and subsequent treatment of the coating/substrate system with a submillisecond pulsed electron beam. The local temperature on the samples in the electron-beam-affected zone and the thickness of the melt zone were measured experimentally and calculated using a theoretical model. The Stefan problem was solved numerically for the fast heating of bare and ZrN-coated silumin under intense electron beam irradiation. Time variations of the temperature field, the position of the crystallization front, and the speed of the front movement have been calculated. It was found that when the coating thickness was increased from 0.5 to 2 [mu]m, the surface temperature of the samples increased from 760 to 1070 °C, the rise rate of the surface temperature increased from 6×107 to 9×107 K/s, and the melt depth was no more than 57 μm. The speed of the melt front during the pulse was 3×105 [mu]m/s. Good agreement was observed between the experimental and theoretical values of the temperature characteristics and melt zone thickness