Search

Using the methods of modern physical materials science, the structural phase state, the defect substructure and the fracture surface of low-carbon alloy steel welds formed with and without carbon-containing additionы are studied. A quantitative analysis of the structure and dislocation substructure parameters of the weld metal is performed. The contributions from the scalar and excess dislocation density to the weld metal strength are estimated. It is noted that for a weld formed without any carbon-containing addition the level of internal stress fields is higher, which may result in the material embrittlement. [ABSTRACT FROM AUTHOR]

The aim of this work is to analyze the structure and properties of a coating of the SnO2–In2O3–Ag–N composition formed on copper by a complex method combining electroexplosive spraying, irradiation with a pulsed electron beam, followed by nitriding in the plasma of a low-pressure gas discharge. It is shown that the thickness of the coating is ≈100 μm. The wear resistance of a coated copper specimen exceeds that of uncoated copper by a factor of 2.8. The friction coefficient of the coated specimens is μ = 0.479, which is a factor of 1.4 lower than that of uncoated copper μ = 0.679 ± 0.048. It is found out that hardness of the coating increases closer to the substrate and reaches a maximum value of ≈ 1400 ± 98 MPa (the substrate hardness is 1270 MPa). According to the micro X-ray spectral analysis, the main chemical element of the coating is silver; copper, tin, indium, oxygen and nitrogen are present in much smaller amounts. It is revealed by the XRD analysis that the main phases of the coating are copper- and silver-based solid solutions. [ABSTRACT FROM AUTHOR]

By the methods of transmission electron microscopy, the quantitative transformations of a structure at depths of 0, 2, 5, and 10 mm along a central axis and the axis of symmetry of a head fillet of lengthy differentially quenched rails after a severe plastic deformation (passed tonnage 1770 million tons of gross weight) are revealed on the micro- and nanoscale levels. On the microscale level, the transformation of a pearlite colony by cutting cementite plates with moving dislocations and subsequent dissolution with the escape of carbon to dislocation lines, low- and large angle boundaries are established. On the nanoscale level, the subgrain structure, being formed in surface layers, contains nanodimensional cementite particles, located at dislocations, in junctions and along the subgrain boundaries. The formation of the subgrain structure is the result of dynamic recrystallization under megaplastic deformation realized in the process of extremely long operation of rails. The formation of so-called "channels of deformation" is detected. [ABSTRACT FROM AUTHOR]

The structural-phase state and the fracture surfaces of low-carbon alloy steel coatings formed by arc surfacing are studied by scanning and transmission electron microscopy. A quantitative analysis of the structure and dislocation substructure parameters of the coatings is performed. The contributions of the scalar and excess dislocation densities to the hardening of the coatings are estimated. [ABSTRACT FROM AUTHOR]

WN–WC–W2C0.84–Ag coatings are fabricated by a combined method, which combines electroexplosive spraying, nitriding, and electron-beam treatment. The structure, phase composition, nanohardness, Young's modulus, wear resistance under dry sliding friction conditions, friction coefficient, electrical conductivity, and electroerosion resistance of the coatings are investigated. [ABSTRACT FROM AUTHOR]

Surface treatment by an electron beam is a method of improving the mechanical properties of metals. Rapid heating, vaporization, recrystallization, and plastic deformation in the surface produce dislocations with high density. That results in increase in physicomechanical properties such as the hardness and wear resistance. Since high-entropy alloys are a relatively new class of materials, the influence of a high-intensity pulsed electron beam on the dislocational structure has yet to be established. In the present work, a nonequiatomic high-entropy Co–Cr–Fe–Mn–Ni alloy produced by additive wire-arc technology undergoes surface treatment using a high-intensity pulsed electron beam (energy density 30 J/cm2). Investigation of thin foil by means of a transmission electron microscope indicates that this treatment has no effect on the chemical composition of the alloy. However, the dislocational substructure is profoundly changed. The scalar dislocation density varies nonmonotonically, reaching a maximum of 5.5 × 1010 cm–2 at a distance of 25 μm from the irradiated surface. At this distance, a somewhat oriented cellular dislocation substructure (cell size 400–600 nm) is formed. At greater distances from the surface (up to 45 μm), the dislocation substructure changes from cellular to cellular–reticular. At a distance of 120–130 μm, no effect of the electron beam is seen: the substructure corresponds to that of the initial alloy with a chaotic distribution of the dislocations. [ABSTRACT FROM AUTHOR]

In this paper, we study the regularities of surface-relief formation, the elemental and phase composition distribution over depth, and an increase in the surface microhardness of steel 45 depending on the parameters of electroexplosive boron-copper plating and subsequent electron-beam processing. The structure of the region of electroexplosive alloying with a thickness of up to 25 μm in depth is shown to include a coating, and surface, intermediate, and boundary layers. At an increase in the absorbed power density and the boron powder weight, the surface roughness of the electroexplosive boron-copper plating region increases while the microhardness increases up to 1400 HV. Subsequent processing by a pulsed electron beam leads to unification of the coating with the surface layer, an increase in the depth of the hardening region to 80 μm and a decrease in the surface roughness and microhardness to 800 HV. Improvement in the physical and mechanical properties of the alloying region is due to the formation of submicrocrystalline and nanocrystalline quenching structures containing hardening phases. [ABSTRACT FROM AUTHOR]