Bulletin PNRPU. Mechanical engineering, materials science

As a result of these studies was an experimental locomotive brake pads microstructure consisting of ferrite and graphite, which easily and inexpensively can be obtained in the conditions of the manufacturer and conditions of repair facilities and comparative performance tests. The hardness varies from 100NV to 600НВ. Hardness is dependent upon the balance of graphite and of cementite in the structure, which is difficult to optimize, because any technological changes in the manufacturing process can dramatically change that balance. Based on the structural analysis of the investigated standard locomotive brake pads, the authors determined that the presence of all structural components under standard, their balance may vary within wide limits. This is confirmed by the hardness measurements on the surfaces of new and worn pads. The work contains the analysis of the results of the study of pathologic wear in the tribological pair "wheel tread of the locomotive - brake pad" derived from performance tests, the locomotive brake pads three groups - standard of low hardness, standard increased hardness and experimental (with the structure of ferrite-graphite) at the three locomotives freight traffic on the stretch of station Achinsk Krasnoyarsk railway. Analysis of the research material allowed to distinguish three classification groups gain metal bands on the brake shoes for thickness and structure. A significant number of pads have traces of abnormal wear on the tires of the wheels (fat), the influence of the structure of the cast iron pads on the magnitude of a gain. The suggested direction of reducing the gain by transforming the standard structure of cast iron in ferrite-graphite.

High-precision navigation devices are used in modern aircraft construction to transmit weak signals with high reliability. Previous studies of the characteristics of sliding contacts made of noble metals showed that the contact pair (CP) brush / ring has the highest performance if it is made of gold-copper alloys near equiatomic composition. Alloys of gold and copper are capable, with appropriate heat treatment, to acquire an ordered atomic structure characterized by a strictly defined arrangement of atoms of each kind in the crystal lattice. The ordering process is carried out by the diffusion movement of atoms, so the formation of an ordered structure is determined by the temperature-time processing conditions. Earlier it was shown that the high physical and mechanical characteristics of ordered gold-copper alloys ensure stable operation of the CP. In the present study, the kinetics of the formation of an ordered structure of the L10 type in a gold-copper alloy of a nonstoichiometric composition (Cu-80 wt. % Au) has been studied by resistometry. The results obtained in measuring the electrical resistivity during heating and cooling of samples in different initial states (disordered by quenching or plastic deformation) are described. The high thermal stability of the ordered CuAuII phase at low temperatures was revealed. In turn, it was established that the CuAuI phase is very rapidly rearranged in CuAuII when heated above 350 °C. It is confirmed that the preliminary plastic deformation does not lead to an increase in the rate of atomic ordering in comparison with the quenched state. As a result of prolonged heat treatment, an ordered state with a resistivity ρ = 7.71·10-8 Om m was obtained, which is significantly lower than the data given in the literature for the alloy of the chosen composition.

The paper describes the technique of automatic control of the welding process on the analytical model of heat propagation into the product. The technique is applicable for argon-arc welding of double-sided butt joints without edge preparation. The essence of this technique is to determine two coefficients of the structural model of a point heat source on the surface of a plate. To determine the coefficients, it is necessary to measure the temperature of the body at two points with their known coordinates. The data on standard values of the penetration and the weld width are taken as these points. The solution of the system of equations for the known coefficients is described graphically by constructing isolines for the penetration and the weld width. For control, the concept of the specific effective power per 1 A of arc current is used. It makes not to measure the effective welding power. The current and the welding speed are measured, and one parameter is used as the control parameter. In this case, the requirements to the accuracy of the control parameter are significantly reduced. An example of using the proposed technique for argon-arc welding of the first layer of a double-sided weld is given. The proposed method eliminates the inaccuracies of the mathematical model associated with the assumption that there is no temperature dependence of the thermophysical coefficients. The control method provides a significant reduction of the experiments to determine the coefficients of the mathematic dependence of the penetration against the welding parameters, to increase the accuracy of the penetration control by reducing the dependence of the coefficients determined experimentally on the welding parameters, and to take into account the influence of the temperature and the thickness of the welded parts on the penetration without additional experiments.

Additive technologies (AT) or layer-by-layer synthesis technologies are one of the most dynamically developing areas of "digital" production. The common problem of additive technologies is to ensure the proper microstructure of the synthesized material and eliminate defects. The use of a filler wire as a working material allows to get rid of the problems associated with the low productivity of existing methods, the high cost of the equipment used, the limited types of materials used due to the use of powder systems. The paper presents the results of studying the features of the formation of the structure and properties of 04Cr18Ni9 steel in additive processes, namely, in the case of СМТ (Сold Меtal Тransfer) surfacing, plasma surfacing with reverse polarity current and plasma surfacing with a consumable electrode (Plasma MIG). Products made of stainless chromium-nickel steels are widely used in a wide variety of industries. The main problem with additive technologies is to ensure the properties of laminates no lower than those obtained by traditional methods. Typical defects of laminates obtained by surfacing are increased porosity, nonmetallic inclusions, reduced plasticity, and for high-alloy steels, loss of special properties. A comparison is made between the structure and mechanical characteristics of materials obtained by SMT surfacing, plasma surfacing by reverse polarity current, and plasma surfacing by a consumable electrode. It is shown that the use of a hybrid method of plasma surfacing by a consumable electrode is promising for additive technologies. It is established that the mechanical characteristics of samples made of 04Х18Н9 steel obtained by surfacing are not lower than for steel of similar composition in the deformed state.

To develop pilot production into serial production, it is necessary to identify the material-science characteristics of the potassium-phlogopite material for compliance with the technological regulations. For this, raster electron microscopy was used with X-ray spectral microprobe analysis, petrographic, X-ray phase and silicate analyzes. In the course of petrographic analysis, refractive indices, the nature of cleavage and the general interference of light were determined. Additionally, the morphometric parameters of the structural components were evaluated by the image analysis method. As a result, the following attributes of potassium fluorophilic acid have been identified: refractive indices equal to 1.597 and 1.550; perfect cleavage - ((001), parallel bands along the grains, interference of 2-3 orders of magnitude (multisyllabic color transitions on the photo), change in color when moving the microscope stage. It is established that the morphometric characteristics of the components vary in size, but the proportional structure of the components is preserved, as evidenced by the stable value of the sphericity coefficient. Using the methods of scanning electron microscopy and microprobe X-ray spectral analysis, the structure of the microstructure and the elemental composition of the individual constituents were established. A joint analysis of X-ray diffraction and silicate analysis revealed that the composition of sample material, %: SiO2 - 39.00-41.10; TiO2 - 0.04-0.06; Al2O3 - 9.00-9.70; Fe2O3 (total) - 0.05-0.15; P2O5 no more than 0,01, Na2O - 0,04-0,47; K2O - 7.20-8.90; CaO - 0.80-3.20; MgO - 27.2-29.2; S (sulfur sulfide) not more than 0.01; SO3 (sulfur sulfate) - 0.07-0.20; CO2 - 0.11-0.31, F - 9.35-11.67. Phase composition, wt. %: fluorophlogopite - 86.7-89.9 %, accompanying phases (ortho- and clinopyroxenes, humite mineral phases and plagioclase) - 5.0-7.0 %, glass-phase - 5.1-7.2 %. Samples of potassium fluorophlogopite have been identified meet the requirements of the technological regulations of the enterprise and correspond to TU 5714-489-05785388.

In this article, the most effective technologies for the additive manufacturing of metal products, using the methods of layer-by-layer deposition of the material are considered. The principles of operation of such technologies as GMAW, GTAW, PAW, CMT, DMD, LBDMD, EBAM, FDM are described. A summary table of key characteristics of these processes and their comparative analysis are presented. The advantages and disadvantages of these methods, main applications and development tendencies are revealed. The most promising direction of development of technologies for creating metal products by the method of layer-by-layer deposition of the material is determined. It is concluded that FDM technology has not fully revealed its potential due to a wide range of technical problems. Current research is considered aimed at overcoming existing technological barriers that impede the development of FDM 3D printing technology. The range of issues to be solved for the successful manufacture of metal products using this technology is considered. Hypotheses and ways of solving problems are being put forward. Prospects of this technology are considered, as well as an assessment of its utility in production and for society. The initial stage of development by the scientific team of Perm National Research Polytechnic University of a more mobile and easily accessible technology for printing metal products of complex geometric shapes based on FDM technology of 3D printing is presented. A number of technical solutions have been described that allow to avoid or solve existing problems and limitations in this area. For example, heating the hot-end of the extruder to 1000 ° C for several tens of seconds and previously impossible rapid and accurate temperature control, which allows to fully control the extrusion process of the material.