Interfacial phenomena and reactions between tungsten semicarbide (W₂C) and corrosion-resistant steel melt have been studied using wetting experiments. This process was followed by the method of high­temperature contact heating of W₂C substrate and a metal sample made of 08Kh18N10T steel. It was established that wolfram carbide has good indicators of wettability by corrosion-resistant steel, wetting angle is 135 – 145°. Composition of the substrate surface has been studied by electron scanning microscopy to determine composition of reaction products. Analysis of the obtained results allows us to state that content of chemical elements varies over the entire contact area, but pattern of their distribution there is uniform. Due to the obtained data we can make an assumption about the applicability of combination of these components to create dispersed-hardened materials. To this end, experiments have been carried out to produce dispersedly hardened centrifugal cast blanks with various types of casting – horizontal and vertical. To obtain experimental materials, the horizontal and vertical type centrifugal casting was introduced into tungsten semicarbide ingots in an amount of 1 % wt. After producing experimental materials, a number of mechanical properties were studied, such as tensile strength, yield strength and hardness. The experimental results allow us to conclude that the use of dispersed hardening in process of centrifugal casting makes it possible to obtain metal materials with increased mechanical properties. Indicators of ultimate strength increase (for all samples on average) by 2.49 %, yield strength – by 2.27 %, hardness – by 5.02 %, which correlates with the provisions on metals physico-chemical properties when using dispersed hardening technologies.

The article presents analysis of magnetization and heating of ferromagnetic charge in crucibles of induction furnaces of two types. In inductor furnaces, the charge is magnetized by a vertical electromagnetic flow, and in electromagnetic furnaces with a curved U-, C-, or O-shaped magnetic circuit (MPr) – by a horizontal flow. Knowledge of these largely general magnetization processes is insufficient. B_i magnetic induction in charge material is rather important. There are difficulties in determining this parameter during magnetization of a single piece of charge and other magnetic quantities associated with it: B_m induction and N_m  strength of the demagnetizing field, N demagnetization coefficient, M magnetization, magnetic permeabilities of μ_i substance and μ_t body, k_m susceptibility, etc. Difficulties increase at magnetization, if it is a porous body with crucible volume of ~V _t and a factor of filling with ferromagnetic pieces of this volume of K_v ≤ 0.5. It also creates a demagnetizing field with B_mt induction and H_mt strength. Beyond that, pores have an additional demagnetizing effect. Therefore, the induction В_iт in a porous body is less than the induction В_i in a solid one. To compare magnetization of ferromagnetic charge with horizontal and vertical flows with frequency of 50 Hz, modeling experiments were carried out with the samples of DSL08 unconsolidated shot from high-carbon steel (GOST 11964 – 83) with K_v ≈ 0.53. The samples were placed in the inductor and between the poles of a U-shaped core piece. Induction was measured by a cylindrical and flat probe unit of Sh1-15 militeslameter in air and in the sample. An advantage of electromagnetic furnace over an inductor one is more uniform distribution of B_i induction in charge and its significant excess (1.7 times) over the B_e induction in a furnace working cavity, which indicates more efficient use of electromagnetic energy in this furnace during heating. The author proposed to control В_i induction when heating the charge by the ammeter-voltmeter method using measuring coil made of heat-resistant wire.

The article presents results of the fatigue tests of natural steel composite material for cyclic bending in a zero loading cycle. Natural ferritemartensite composite (NFMC) has a structure of alternating layers of viscous ferrite and strong martensite, which determines special mechanism of crack deceleration under loading. Zero loading cycle presumes presence of tensile forces directed only in one side, which makes it possible to avoid work hardening of crack edges during its growth. A diagram of fatigue fracture was constructed using data obtained on kinetics of fatigue crack propagation and its growth rate, depending on the number of vibration cycles. Comparison of test results for the samples made of steel of the same chemical composition was carried out. In one case, the secondary sorbite structure ran through the traditional heat treatment. In the other, quenching of the initial row ferrite-pearlite structure in intercritical temperature range, led to obtaining ferrite-martensite composite layered structure. These materials had the same hardness, but the difference in structure organization caused the NFMC structure steel advantage in terms of resistance to fracture under cyclic loading. When crack approaches the martensite-ferrite interface, delamination occurs in ferrite due to tensile stresses parallel to the crack plane. Growth of a crack stops before additional energy is supplied for a new crack generation under conditions close to the uniaxial stress state. Method for determining characteristics of kinetics of crack growth under fatigue loading is presented and recommended for testing steels and alloys under conditions of cyclic load changes.

The article presents data on studies of iron borides synthesis during induction heating to 1000 °C for 5 min of steel 20 samples with a coating from a charge containing Fe – H₃BO₃. Content of boric acid in the charge varied from 25 to 75 % wt. Charge in the experiments could be diluted with a solution of liquid glass in water with addition of small amount of ammonium hydroxide and coal. Study of the surface layer microhardness showed that during saturation of the surface layer of carbon steel 20 with boron, a macroscopically extensive diffusion zone 900 – 1000 μm in size is formed, in which the boride content gradually decreases when moving deeper into the matrix. Such a size of the diffusion zone indicates an anomalously high mass transfer during boriding of steel 20. Indeed, the calculated diffusion coefficient during boriding under induction conditions (about 1.35·10^–9 m²/s) is two orders of magnitude higher than the diffusion coefficient in the classical boriding. X-ray studies showed that, under the considered conditions, Fe₂B and FeB borides are synthesized, and a solid solution of boron in α­iron is also formed. An analysis of phase composition of the diffusion zone structural components indicates that, from the surface to the matrix, formation of boride phases occurs in the following sequence: FeB → Fe₂B → (α­phase + B) → base metal. Microstructure of the diffusion zone consists of more or less pronounced layers consisting of FeB and Fe₂B boride phases. On the whole, especially deep-ying regions of the diffusion zone are a composite material consisting of plastic α-phase and iron boride crystals. Crystals in FeB and Fe₂B in the layer are oriented mainly perpendicular to the diffusion front. Perhaps, this is due to the rapid predominant growth of the boride phase under conditions of high diffusion mobility of boron atoms in one direction and hindered in others.

The effect of impurity carbon and oxygen atoms on the migration rate of the tilt boundaries with the misorientation axis <110> in γ-Fe with fcc crystal lattice was studied by the method of molecular dynamics. Dependences of energy of the considered boundaries and rate of their migration at a temperature of 1600 K on the misorientation angle were obtained. The migration rate of <110> tilt boundaries under the same conditions turned out an order of magnitude lower than the migration rate of <111> and <100> boundaries, which is primarily due to the relatively low energy of <110> boundaries. In addition, the low-angle <110> tilt boundaries are unique compared to other tilt boundaries – grain­boundary dislocations in them are ordinary perfect edge dislocations with even cores that do not contain jogs periodically located on them as in <111> and <100> boundaries. The introduction of impurity carbon and oxygen atoms led to a significant decrease in migration rate of the grain boundaries. The binding energies of impurity carbon and oxygen atoms with grain-boundary dislocations in the austenite were calculated. The obtained values correlate well with the dependences of migration rate of <110> boundaries on the impurities concentration. Effect of impurities on migration of the boundaries in austenite turned out to be stronger than in the previously studied nickel and even more so in silver, which can be explained by the relatively low value of the electronegativity of iron atoms in comparison with nickel and silver. A higher value of the binding energy with dislocations in austenite and, accordingly, a greater effect on the migration rate of grain boundaries were obtained for carbon atoms.

The work is devoted to the research of cracks causes in welded joints of high­strength steel for arctic purposes based on the study of the structure and mechanical properties of the weld metal and the zone of thermal influence. Consumers of machine­building products make increasingly high demands on welded joints of metal structures. This necessitates the use of rolled steels for their production, which have increased mechanical and special properties. When welding MAGSTRONG W700 type steels, cracks are observed in local sections of welded joints. It was established that the structure of the weld metal of welded joints of MAGSTRONG W700 steel is characterized by the presence of columnar crystals with a hardness of 312 – 323 HV. The metal structure in the overheating area of thermal influence zone is characterized by the presence of enlarged primary grain, as well as batch formations of bainite and bainite-martensite with hardness of 338 – 352 HV. The level of temporary resistance to rupture of the metal in thermal influence zone is 618 – 627 MPa. Depending on the test temperature, values of the impact strength of the metal in thermal influence zone vary from 62 to 86 J/cm². MAGSTRONG W700 steel has good resistance to the formation of hot cracks during welding (UCS = 20,3), however, it has an increased tendency to form cold cracks (C_E = 0,48). Analysis of the data obtained showed that destruction of welded joints of the studied steel occurs due to its unsatisfactory weldability. Such weldability is due to a complex chemical composition, as well as a whole set of factors (such as the formation of unfavorable structures in the metal of welded joints under the influence of thermal welding cycles, a complex picture of welding stresses, the level of which exceeds the temporary resistance to metal rupture). Also, the structure of the weld metal has a large­crystalline structure, which significantly weakens the connection.

The authors have studied the elemental and phase compositions of electric arc coating with a flux-cored wire of Fe – C – Si – Mn – Cr – Ni – Mo system. Formation of electric arc coating was carried out using ASAW-1250 welding tractor with fabricated flux-cored wire on plates made of 09G2S steel. Aluminum production gas cleaning dust has been introduced into the composition of flux cored wire (instead of amorphous carbon). Chemical composition of the deposited metal was determined by X-ray fluorescence method on XRF-1800 spectrometer and by the atomic emission method on DFS-71 spectrometer. Microstructure of the electric arc coatings was studied using OLYMPUSGX-51 optical microscope. Analysis of phase and elemental compositions was performed by scanning electron microscopy using LEO EVO 50 instrument. Segregation of tungsten and molybdenum was revealed in electric arc coating. Concentration of tungsten changes more than 3 times, and molybdenum – more than 2 times. Fractures of the samples are formed as a result of ductile fracture of the material. There are surface layers on the samples fractures, thickness of which is determined by chemical and elemental composition of the electric arc coating. The layer under consideration is characterized by a relatively small diameter of fracture pits compared to the samples volume. Their diameter ranges from tenths to tens of micrometers. The largest pits are formed on particles of the second phase with micron sizes (2 – 3 µm). Contamination of metal of electric arc coatings with non­metallic inclusions was studied. It was established that chemical composition of flux-cored wire of the studied system does not significantly affect the level of contamination with non-metallic inclusions in electric arc coatings. Parameter a of crystal lattice and values of areas of coherent scattering of Fe and CrC phases formed as a result of hardfacing were determined by X-ray phase analysis.

In the industry of most developed countries, complex alloying as a surface layer saturation with metal and gas atoms in a certain sequence is extensively used. This study identifies and analyzes the changes in the elemental and phase composition, defect substructure, mechanical (microhardness), and tribological (wear resistance and friction ratio) properties of alloyed carbon steel after complex treatment, consisting of surface layer saturation with Al atoms and subsequent nitriding. We studied 40Cr steel. Its initial structure contains plate-like ferrite and pearlite grains. A TRIO system with a 600×600×600 mm3 vacuum chamber was used for complex alloying. The system was equipped with a control module for electron-ionic treatment. Aluminizing lasted for 4 hours at 963 K. The electric arc evaporator cathode was made of A7 aluminum alloy (98.8  %  Al). Subsequent nitriding of the aluminized layer lasted for 2 hours at 803 K. It was found that such treatment results in a modified surface layer up to 70 µm thick. The complex alloying of steel forms multiphase submicro- and nanostructures with Al nitrides, Fe and Cr nitrides, and aluminides. We found that steel hardness is greatest at the modified surface. It exceeds the initial hardness by 300 %. Complex alloyed steel is less resistant to dry friction.

The article considers quantitative estimation of the relative carbon content in the structure elements of rail head after passed tonnage of 1411 and 1770 mln tons. In the initial state carbon is mainly located in cementite particles and after the operation the defects of crystal structure together with cementite are the places of carbon location. It is shown that the processes of carbon redistribution take place more intensive in surface layers up to 2 mm. Increase in passed tonnage is accompanied by intensive carbon movement on the defects of working fillet structure compared to the tread surface.

The process of evolution of the stress-strain state (SSS) of a multilayer shell mold (SM) is modeled at properties change between layers during cooling of poured steel casting. A mathematical model was constructed and a theoretical study of the stress state of the SM was carried out in absence of connection between the layers in a multilayer composite. The article describes a complex three-component system: liquid metal, solid metal, and ceramic SM. Solid metal and SM are considered to be isotropic. To solve this problem, the authors used the theory of small elastic-plastic deformations and equations of thermal conductivity, as well as proven numerical methods. Evolution of SSS in SM was traced by time steps. Thickness of the solidifying metal was determined through the equation of interphase transition. The article considers the process of heating an axisymmetric SM when pouring liquid metal into it. Stress state was estimated by stresses and displacements that occur in SM. At SM contact with support filler (SF), SM surface move away from the SF is possible during cooling of liquid metal. In this case, contact problem is solved. Taking into account the compiled algorithm for solving the problem, calculations were performed for the case of complete sliding of layers using developed numerical schemes and software complexes. Obtained results of numerical calculations are clearly displayed by graphic illustrations in form of plots and graphs. Detailed analysis of the obtained results is given. There is inconsistency of the previously expressed idea about the applicability of sliding between layers in a multilayer composite from the position of reducing its stress state. The research results can be useful in calculations of other functional multilayer shell systems.

All industrial metallurgical enterprises produce and use milled materials obtained by crushing. In the global energy balance, the share of produced energy consumed for crushing is more than 5 %. This paper considers a scheme of the crusher with stops on a roll, the structure of which forms a complex stress state in a crushed piece under one­time action of normal and tangential stresses. It is shown that when generating a complex stress state in a fragmented piece of brittle material, the energy consumption is less by 30 – 40 % than when acting in a piece of linear normal stress. The authors developed a method for determining capacity of the drive electric motor of an energy-saving crusher with stop on a roll at design stage.