Bulletin PNRPU. Mechanical engineering, materials science

The development of modern industry, aimed at reducing the consumption of materials, improving the technological properties of products. Products made of expensive metals and alloys scarce it is advisable to make combined, the base consists of the cheapest materials, and on the working surface of fusing alloys with special properties. Such bimetallic structure is many times cheaper than structures made entirely of metal with the desired properties. This paper presents the results of a study on the production of the layered composite material. The basis of the composite material is high-alloy corrosion- resistant steel and nickel alloy 10H18N10T 06H15N60M15. A promising method of manufacture of such structures - the use of a multi-layer deposition. The use of highly concentrated heat sources to simplify the manufacture of such structures. A study of the technological possibilities of manufacturing laminates plasma arc of direct action of reverse polarity. Plasma arc reversed polarity allows for a minimum penetration or dissolution of the base metal to provide a bimetal with unique combinations of properties. Researches laminate structure of the composite material obtained by using light microscopy. It is shown that the application of reverse polarity plasma arc current produces defect-free laminates in surfacing of steels and alloys of different classes. surfacing of the fine structure, a uniform transition from one layer to the homogeneous material and a clear interface between dissimilar materials. Mechanical testing specimens witnesses have shown that the material has good mechanical properties. It manages to combine such indicators as high tensile strength and maintaining a high yield strength and elongation of the resultant laminate is 22%.

During the operation, steel products are under various mechanical and thermal impacts, that can cause the growth of fatigue changes, and as a result, premature aging of the material can happen. It leads to technosphere disasters. That’s why, it is important to control the properties of steel and steel products. The method proposed as an additional means of control is based on the phenomenon of magnetic hysteresis and was tested on steel 34HN3M. This steel is used for manufacturing of different components operating at temperatures up to 500 °C and high pressure. It is suggested to use a magnetic hysteresis loop of ferromagnetic materials, obtained by quasi-static magnetization. In this case, the current magnetization and demagnetization and hence the magnetic field, is described sawtooth function of time. Then it becomes possible to provide a hysteresis loop in the form of a single-valued function of the field strength that is proportional to the time period. Discrete Fourier transformation is applied for the obtain the given functions. In this paper we study the correlations of the Fourier spectrum of the hysteresis loops of steel, dependent on a change of its structure and mechanical properties. The structural changes in the steel during its thermal processing may include, for example: stress relief, precipitation of carbides and their changing. The aforementioned changes in steel greatly affects the shape of the loop, out as a harmonic Fourier spectrum is sensitive to the waveform change, the method of Fourier analysis may provide an additional means of nondestructive inspection of structural changes in the steels, together with the measurement of coercive force, hardness and other parameters.

Physical and mechanical properties of coatings applied on a substrate made from a steel 40Х are investigated. The coatings are received by means of vacuum installation Unicoat 600SL, using magnetron dispersion in the environment of inert gas. The researching object is a wear-resistant antifrictional coating, sprayed on roller-screw mechanism details, working in hard conditions of lubrication absence or its limited application. At study and realisation of coating process by the basic factor influencing on stability of structure physical and mechanical properties is a generation of multicomponent metal plasma. The researching purpose is working out of the efficient PVD-coating providing reduction of a slippage friction coefficient in a kinematic knot screw-roller-nut, high wear-resistance of knot details and increasing in efficiency of roller-screw mechanism. In an article the analysis is made and the calculation algorithm of coating hardness is descript. The article describes the analysis and calculation algorithm of coatings hardness, implemented in software nanohardness Micro-Combi Tester (Switzerland). Coating has been was carried out on the 2D method at which was obtained a structure with alternating layers Cr, TiAlN, AlTiN, Ti, TiN. There was also a trying to get a gradient-layered coating structure with a define variation of components in a layer depth, which undoubtedly improves the coating mechanical characteristics. However, owing to a row of the specific reasons, which will be study in a future, positive result in this direction was not yet received. The spraying regimes of the strongest and wear-resistant nitrid coating aluminium-silicon-titan (AlSiTi)N which properties are investigated on the modern nano hardness gauge Micro-Combi Tester (Switzerland) are experimentally selected. As a result of the executed researching it is installed that the strongest and wearproof coating is nitride of the aluminium-silicon-titan (AlSiTi)N which it is recommended to put on working surfaces of roller-screw mechanism details.

The peculiarity of magnetic abrasive polishing is a continuous involvement of new cutting edges of the abrasive grains of the ferromagnetic filler in cutting which is related to the effect of self-sharpening. With time an irreversible degradation of polishing capacity associated with the destruction of the cutting grains and saturation of the portion of ferromagnetic abrasive filler with processing products takes place. Long-term retention of the cutting ability of the portion of ferromagnetic abrasive powder filler, as a special tool material, is the most important performance indicator influencing the technical and economic efficiency of production. It is found that long-term retention of polishing properties and high microcutting ability of the portions of ferromagnetic abrasive filler depends on many parameters: the type of abrasive material, macro- and microgeometrical parameters of grains, material and the initial parameters of roughness of the workpiece surface, the depth of the defect layer, processing scheme and other conditions of magnetic abrasive polishing. Determination of all parameters and the degree of their influence on the tool durability of a portion of ferromagnetic abrasive filler in working conditions is not possible. This is why for the experimental determination of tool durability of a portion of ferromagnetic abrasive filler proposed are criteria of quantitative assessment: the parameter of maximum allowable roughness and the minimum removal of workpiece material in the end of a specified period of time. The method described in this article was developed with the use of quantitative assessment criteria for durability. The given method presents determination of tool durability for two cases: when polishing several small workpieces by one portion of filler and when polishing a part of the surface of a large workpiece by one portion of filler. The proposed method of determination of tool durability can be used for technological preparation of production of magnetic abrasive polishing operations in the conditions of large-scale production to ensure stable parameters of the quality of processed surfaces with minimal expenditures for filler. The tool durability calculated by this method may be one of the comparative characteristics useful in selection of productive fillers.

For the protection of components and machine parts from various types of wear apply a surface treatment technologies designed for improve their service characteristics. The sprayed coating of Fe-C-Cr-Ti-Al system widely used to protect against abrasive wear, but their lamellar-porous structure leads to decrease in wear resistance, which limits area of their application. In order to improve the performance characteristics of coatings a various methods of their post-treatment are used. In this paper, the effect of plasma remelting (PR) on wear resistance of arc sprayed coatings was examined. Fe-C-Cr-Ti-Al cored wires were used as a feedstock. For coating deposition was used the device of active arc spraying ADM-10. Remelting of sprayed coatings was carried out on the universal installation for plasma treatment of materials, developed by welding department of PNRPU. The plasma treatment was done on a direct current polarity with using argon as a protective and plasma gas. The surfacing of cored wire was carried out by TIG method. Sprayed coatings before and after PR and arc surfaced layer were compared by two-body wear test, chemical composition and structure study. It was found that in the process of PR due to intense oxidative processes, there was a significant change in the chemical composition of the coating, promotes by formation of the medium-martensite structure, having high hardness and fracture toughness. The results by fixed abrasive tests of coatings showed the increase of wear resistance after plasma remelting in 2.5 times.

The paper presents the research lapping mineral ceramics CM-332 (HRC 90-93). During the investigations it was established that the performance synthetic diamond and more than 8 times higher compared to the performance of the abrasive based on corundum and silicon carbide green. When processing mineral ceramics is preferable to use a cast-iron lap marks SCH-28, which showed the best performance, as value the total removal material and value specific consumption of diamond and the surface roughness. To obtain the necessary roughness parameter Rz = 0.8, it is recommended to use a micropowder of diamond grit size of 10 microns. The optimum amount of micropowder on surface lap diameter 220-250 mm for grain ASM10 - 20-40 mg, for grain ASM20 - 40-80 mg. Increasing the surface pressure of 25 to 50 kPa increases the total removal material, reducing the specific consumption of diamond, and reduces the surface roughness. The optimal time for lapping of the mineral ceramics without changing diamond micropowder 6-8 minutes. The amplitude and frequency of lap are the main parameters for lappingmachine “Raster 220”. Lapping mineral ceramics more preferably carried out at a frequency of oscillation lap (tool) 270 1/min. and an amplitude of 10 mm. Flatness of lapping surfaces depends on the geometrical accuracy of the working surface of lap. To ensure a high surface flatness of lap is necessary to periodically carry them by three plates editing method.

The aerosol particles with a diameter less than 0.1 mm become prevalent in air pollution of working area of modern engineering production. Such ultrafine aerosol pollutions are caused by the use of new technologies of the engineering operations (for example, new types of welding and metal cutting). In addition the emissions of ultrafine aerosol are caused by more increased speed, complexity and precision of material processing as well as the more extensive usage a plastic, polymer or composite materials and workpieces of high-strength alloys, including those obtained by using nanotechnology. Because investigation of fine aerosol particles is technically challenging process the full monitoring of aerosol particle distribution is often impossible or time-consuming. Therefore the study for new ways to estimation of wide range size of aerosol particle is of current interest. The studies of the stability of particulate composition of aerosols have allowed developing a series of mathematical models for aerosol particle size distribution. However for all of known models the additional and complex researches to determine the parameters of aerosol particle size distribution are often required. Meanwhile fine aerosol particle contamination is interconnected and influences on the known air parameter of the working area - the air ion composition. Under influence of manufacturing operations air ion composition is modified and the concentration changes of small air ion (mostly decreasing) are determined by aerosol size distribution especially ultrafine particulate fraction. In the article a model of interrelation between fine aerosol particles distribution and air ion concentration of working area is presented. On the basis of this model and proposed method of ultrafine aerosol fraction assessment taking into account the parameters of air ion composition the algorithm for aerosol particle size distribution modeling is designed. On the example of the widespread industrial operations of engineering companies - grinding products from different materials - the proposed approach has been tested. The aerosol distributions in processing of parts made of steel are described by two size modes, same in cases machining of aluminum, ceramic and Teflon - by three size modes. Finely grinding of aluminum parts is characterized by greatest aerosol pollution. Under treatment of parts from ceramics the maximum concentration of respirable fraction of the aerosol particles (particle diameter more 0.5 mm) compared with all test materials is observed. In the treatment of parts from ceramic and Teflon the distribution in the area of fine (less than 0.1 mm) particles was reduced to a single size mode. Evaluation of ion generation intensity and comparability with intensity on industrial workplace without additional sources of generation of air ions are confirmed the authenticities of the presented model “aerosol particles - air ions” and of its theoretical and empirical basis.