Yu. F. Ivanov

Increase in the fatigue durability of stainless steel by electron-beam surface treatment

The structure, phase composition and dislocation substructure of 20Cr23Ni18 steel subjected to electron-beam treatment and subsequent multicycle fatigue loading until destruction were studied by scanning and transmission electron microscopy. It was shown that electron-beam treatment with an energy density of 20 J/cm2 increases the fatigue durability by a factor of 2.1. The cause of steel fatigue destruction is analyzed and a way of further increasing the fatigue durability is proposed.

Magnetic properties and structural parameters of nanosized oxide ferrimagnet powders produced by mechanochemical synthesis from salt solutions

The phase composition, the structural parameters, and the basic magnetic characteristics of a number of nanosized powders of simple spinel ferrites produced by the method of mechanochemical reactions from salt systems were studied. The influence of size and surface effects on the saturation magnetization and magnetic anisotropy was determined. The applicability of the shell model to the description of the magnetic properties of nanosized spinel ferrites is discussed.

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.

Effect of elastic excitations on the surface structure of hadfield steel under friction

The structure of the Hadfield steel (H13) surface layer forming under dry friction is examined. The deformation of the material under the friction surface is studied at a low slip velocity and a low pressure (much smaller than the yields stress of H13 steel). The phase composition and defect substructure on the friction surface are studied using scanning, optical, and diffraction electron microscopy methods. It is shown that a thin highly deformed nanocrystalline layer arises near the friction surface that transforms into a polycrystalline layer containing deformation twins and dislocations. The nanocrystalline structure and the presence of oxides in the surface layer and friction zone indicate a high temperature and high plastic strains responsible for the formation of the layer. It is suggested that the deformation of the material observed far from the surface is due to elastic wave generation at friction.

Structural-phase states and properties of coatings welded onto steel surfaces using powder wires

Structural-phase states and mechanical properties of coatings welded onto Hardox 400 steel using En-DOtecDO*30, EnDOtecDOtec*33, and SK A 70-G weld wires are investigated via X-ray structural analysis, optical and scanning electron microscopy, and measuring microhardness, wear resistance, and friction coefficients. It is shown that the coatings had microhardnesses and wear resistances were higher than those of their substrate by factors of 2–3 and 2, respectively, while the friction coefficients of coatings were lower than those of the substrates by a factor of 1.2. Hardening was due to the formation of disperse structures containing up to 40 vol % of Fe3C, Fe23(C, B)6, NbC, Fe3B, and Fe3Si0.97 particles.

Formation of surface gradient structural-phase states under electron-beam treatment of stainless steel

The structural-phase states of steel 08X18H10T (0.08% C, 18% Cr, 10% Ni, 1% Ti) subjected to pulse electron beam treatment in the regime of surface layer melting is investigated using the methods of optical and electron microscopy. The regularities of variations in the phase composition and the state of the defect substructure moving away from the irradiation surface up to a 200-μm depth are revealed.

Evolution of the structure and phase states of rails in prolonged operation

The transformation of the structural and phase states and defect substructure of the surface layer (depth up to 10 mm) in rails during prolonged operation (with a total load amounting to 1000 million t) is analyzed on the basis of metal physics. The microhardness is plotted, and decrease in strength of the rail’s contact surface after prolonged operation is noted. In rail operation, a multilayer structure is formed. The surface layer (about 20 μm) has a multiphase submicrocrystalline and nanocrystalline structure; it contains micropores and microcracks. The structure at a distance of 2 mm from the contact surface is morphologically similar to the steel structure before operation: it consists primarily of pearlite grains (mainly plates), mixed ferrite-carbide grains, and structure-free ferrite grains. The density of the flexural extinction contours increases at a distance of 2 mm from the contact surface. The amplitude of the stress field is greatest at the phase boundary between a globular particle and the matrix.

Melt nonstoichiometry and defect structure of ZnGeP2 crystals

The defect structure of ZnGeP2 crystals grown from a melt by the vertical Bridgman method has been investigated. A deviation of the melt composition from stoichiometric leads to the formation of striations and the inclusions of other phases which are observed as structures (chains) oriented parallel to the growth axis. According to the microanalysis data, the inclusion composition corresponds to a mixture of ZnGeP2, Zn3P2, and Ge. Nanoinclusions of germanium phosphide are detected by transmission electron microscopy. X-ray topography reveals defects of four types. The main defects in the central part of an ingot are related to the composition fluctuations, and the newly formed dislocations are basically single ones. Most dislocations are formed at the crystal periphery.

Structural and phase transformations in nanostructured 0.1% C-Mn-V-Ti steel during cold deformation by high pressure torsion and subsequent heating

The structural and phase transformations which take place in low-carbon 0.1% C-Mn-V-Ti steel during deformation by high pressure torsion (HPT) and subsequent heating have been studied using transmission electron microscopy and X-ray structural analysis methods. Whatever the initial state, be it ferritic-pearlitic or martensitic (obtained by quenching from 950°C and 1180°C), HPT at room temperature leads to the formation of a nanosized oriented grain-subgrain structure. The average size of the elements of the grain-subgrain structure in the 0.1% C-Mn-V-Ti steel after severe plastic deformation is larger in the initially ferritic-pearlitic state (95 nm) than in the initially martensitic states (65 and 50 nm after quenching from 950°C and 1180°C, respectively). It is shown that quenching from 950°C and 1180°C causes the formation of the martensite of different fineness, providing, in turn, nanostructures of different dimensions and different levels of the strength properties after HPT. Quenching from 1180°C is conducive to a higher thermal stability of the HPT-induced nanocrystalline structure of the 0.1% C-Mn-V-Ti steel on account of the larger amount of vanadium carbide precipitates. It is found that HPT leads to a considerable increase in the microhardness of the 0.1% C-Mn-V-Ti steel as compared to its microhardness in the initial state (more than 3 times as high in the ferritic-pearlitic state and more than 2 times as high the initially martensitic states).