Russian Metallurgy (Metally)最新文献

The study is dedicated to the process of electromagnetic stirring of liquid metal containing solid conductive particles and the effect of forced stirring during metal solidification on the redistribution of impurities in the ingot. Stirring is achieved by non-contact influence of traveling and pulsating magnetic fields of varying topologies. The research was conducted experimentally using a low-melting point gallium alloy (for flow structure analysis) and a tin-lead alloy (for solidification studies). The flow structures generated in the liquid metal under external force application, as well as the impurity concentration fields after crystallization under the influence of external electromagnetic forces, were obtained. Stirring flow velocity field measurements were performed using the optical particle image velocimetry method, while concentration field measurements were carried out via local conductivity measurements of the ingot. A homogeneity parameter for impurity distribution was introduced, and the dependence of this coefficient on the stirring regime was determined.

In continuation of the search for new materials for the development of all-solid-state lithium and lithium-ion batteries, we have synthesized solid electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ having lithium-cation conduction and a NASICON-type structure by glass crystallization and lithium–vanadium bronze Li_1.3V₃O₈ by the interaction of lithium carbonate and NH₄VO₃ in an aqueous solution followed by heat treatment at 400°C. The thermal stability of the synthesized materials and their chemical resistance toward each other are investigated. For this purpose, mixtures of the solid electrolyte and the bronze are held for 15 h at various temperatures from room temperature to 500°C, and their phase compositions are then studied by X-ray diffraction (XRD). XRD shows no chemical interaction between the electrolyte and the bronze up to 300°C inclusive. At higher temperatures (350°C), reflections of lithium metavanadate first appear on X-ray diffraction patterns; after isothermal holding at 470–500°C, the phase compositions of the mixtures include a number of interaction products, the main of which is Li₂PVO₆. Thus, according to the obtained results, the materials under study can be recommended as components for the development of medium-temperature all-solid-state lithium-ion batteries.

The problems of the existing technological methods of high-velocity thermal spraying of powder materials are analyzed. A comparative characteristic of these methods and the properties of the formed coatings is given. Trends toward the development of new effective and economical technologies are characteristic of a wide range of research objects using supersonic coating deposition methods. The prospects for using high-velocity thermal spraying methods in repair production for restoring worn machine parts are shown.

The basic principles of deposited metal formation during arc surfacing with flux-cored wires, one of which is a filler wire, are considered. The influence of the filler wire feed rate on the weld bead formation is investigated. The limiting values of additional filler feed rate as a function of wire introduction site are determined. The influence of the filler wire on the stability indicators of the arc process is studied. In the arcing modes under study, a filler wire feed rate of up to 2.4 m/min is shown not to destabilize the surfacing process when the wire is fed along the front of the weld pool. However, when the filler wire is fed at the rear part of the weld pool, its feed rate cannot exceed 2.0 m/min. An increase in the feed rate is found to break the stability of the surfacing process.

Comparative tribological tests of titanium alloy VT6 samples with arc-sprayed NiCrBSi coatings under fretting wear conditions in the gross slip regime demonstrate the effectiveness and potential of electric arc spraying for improving the performance characteristics of friction pair parts made of the titanium alloy.

Effect of K₂CO₃, TiO₂, and CaF₂ on the stability of surfacing, when these components are introduced into the composition of flux-cored wire charge of the C–Cr–B alloying system intended for the deposition of abrasion-resistant coatings, is studied. Oscillograms of the deposition of the fabricated flux-cored wires are obtained under various conditions ensuring electrode metal transfer with and without short circuits. The oscillograms are used to reveal the effect of the components of flux-cored wires charge on the stability of the process. The effect of the introduced components on the coefficient of burnout and splashing losses and the fraction of participating the base metal are detected under various surfacing conditions.

The use of supersonic flame spraying on a mass scale is limited because of insufficient information on the properties of protective coatings formed by this method from various types and systems of powder materials. Here, we substantiate the possibility of using supersonic flame spraying to create protective coatings on machine parts for various functional purposes. The characteristics of the coatings are determined and compared; they demonstrate the advantages of this method compared to subsonic gas-thermal coating formation methods. The aim of this work is to study the physical and mechanical properties of coatings formed by high-velocity flame spraying under various conditions. The coatings are deposited onto samples using the Plakart-HV2 robotic complex for high-velocity flame (HVOF) spraying. WC–Co–Cr 86-10-4 and PR‑Kh14N7S3R3 powder materials are used to form the coatings. Metallographic examination of the sprayed coatings is carried out according to generally accepted methods. Dense, wear-resistant coatings with a maximum hardness of 1475 HV are found to be formed from the WC–Co–Cr 86-10-4 powder by supersonic flame spraying under rational conditions. The high microhardness of the coatings made from this powder mixture is caused by the presence of WC in their structure. When the PR-Kh14N7S3R3 powder material is used, the maximum microhardness is about 927 HV. The properties of the coatings produced by supersonic flame spraying depend on the powder material composition and their formation conditions. The characteristics of the formed layers can be changed over a wide range by varying the process conditions and the content of elements in the sprayed powder material, which enables the production of coatings with the required physical and mechanical properties.

The influence of thermomechanical heredity on the physicomechanical properties of 08Kh18N10T steel, which is used in the manufacture of the furnace coils for diesel fuel hydrotreating units, is studied. Preliminarily deformed samples are shown to change their strength, plasticity, and creep characteristics. The features that determine the behavior of steel under thermomechanical treatment are revealed. The application of various loading cycles combined with thermal treatment is found to significantly increase the mechanical characteristics. Thermomechanical heredity also significantly affects the microstructure of the steel, which determines its performance characteristics and guarantees the reliability and safety of oil refining units.

The architecture and capabilities of a computer system being developed for analyzing the weldability of steels, the demonstration version of which is available at weldability.ru, are presented. This system consists of modules for inputting and verifying user-provided initial data, analyzing the main physical and metallurgical processes, optimizing technological parameters according to specified criteria, as well as modules for interaction with external software and output of final results. The system enables calculations of key weldability indicators for typical and geometrically unique welded structures and joints, significantly simplifying the design and technological preparation of welding of critical components.

Modern gas turbine engines operate under changing temperature loads; therefore, one of the important characteristics of the protective coatings used on turbine blades is their high resistance to the initiation and propagation of cracks under mechanical and thermal loads. The effective internal heat removal systems used in cooled turbine blades lead to an increase in their thermal intensity. Currently, thermal fatigue cracks are common defects found in the protective coatings used on turbine blades. The heat resistance of the coatings at high temperatures is determined by three factors: the shape of the part on which a coating is deposited, the coating thickness, and the phase composition of the surface layers or the maximum aluminum content in a coating. Therefore, when choosing a protective coating for these operating conditions, it is important to know the influence of these factors on the heat resistance of a coating. We perform a comparative study of the cracking resistance of various coatings under cyclic temperature changes. The dependence of the heat resistance of the coatings under study on their deposition method and phase-structural state is determined. The revealed mechanism of formation and propagation of thermal fatigue cracks as a function of the phase composition of the initial coating is particularly important. The life of protective coatings under cyclic temperature changes is shown to depend on the chemical composition of a coating and the method of its formation. The dependence of thermal fatigue crack formation on samples with the coatings under study on the number of temperature change cycles is found.