65G Steel Research Articles

Results of metallographic studies of cutting parts of cultivator paws made of 30MnB5 steel

Rationale. Cultivators are widely used in our country for surface tillage. Moreover, their most common working organ is the pointed paw. In recent years, foreign manufacturers of agricultural machinery have begun to use boron-containing steels in the manufacture of working parts of agricultural machinery, which can increase the wear resistance and durability of machine parts. The article presents the results of metallographic studies of the structure and properties of the cutting parts of pointed cultivator paws made of boron-containing steel 30MnB5. The purpose of the work is to study the structure and properties of boron-containing steels after surfacing relit and subsequent hardening. Materials and methods. When carrying out metallographic studies, we used the cutting parts of the paws of the KPIR-3.6 and KPU-5.4 cultivators, mass-produced according to OST 23.2.164-87 at the Buinsky Machine-Building Plant of the Republic of Tatarstan. These working bodies were made of steel grade 30MnB5 DIN EN 10083-3. To ensure heterogeneity of the structure, a layer of relit was fused to one side of the cutting blade of the cultivator paw, after which the entire working element was hardened. The macro- and microstructure of the metal part was studied using a microsection cut out to the cutting edge. For macrostructural studies, a stereoscopic microscope from MEIJI RZ with a magnification of up to 7 times was used. The microhardness of the part was measured using the Vickers method (GOST R ISO 6507-1-2007) at different loads on a MicroMet 5104 microhardness tester. Contamination of the base metal of the part with non-metallic inclusions was assessed using the “Ш4” method according to GOST 1778-70. Results. The proposed manufacturing technology for cultivator blades made of 30MnB5 steel made it possible to obtain a cutting part that is heterogeneous in structure and hardness, which ensures self-sharpening of the blade during the friction of the cultivator blade on the soil. The steel base of the cultivator paw after heat treatment has a troostomartensite structure with a microhardness of ~ 564 HV 0.3. The deposited layer of relit has a dendritic cast structure of tungsten with a microhardness of 900...1020 HV 0.05 and tungsten carbides with a microhardness of 2315...2460 HV 0.05. The wear of paws made of 30MnB5 steel turned out to be 9.5% less than that of working bodies made of 65G steel. The cost of manufacturing working parts using the proposed technology was reduced by 14.3%. Conclusion. The practical value of the study lies in the fact that the results of studies of the cutting parts of self-sharpening cultivator paws, made of 30MnB5 steel using the proposed technology, are used in the production process of Buinsky Machine-Building Plant OOO in the Republic of Tatarstan. The paws manufactured using the proposed technology are installed on cultivators KPIR-3.6 and KPU-5.4. The presence of the self-sharpening effect of the paws made it possible to increase the quality of products required by consumers and its high competitiveness.

TRIBOLOGICAL AND CORROSION PROPERTIES OF 45 AND 65G STEELS USED IN AGRICULTURAL MACHINERY AFTER ELECTROLYTIC-PLASMA HARDENING

The article examines the effect of electrolytic plasma hardening on the wear resistance and corrosion resistance of steels 45 and 65G, which are used in the production of agricultural machinery components. The presented results demonstrate the improvement of the surface properties of steel through the application of electrolytic plasma hardening. This technology provides rapid heating and cooling, which contributes to the formation of a fine-grained and hardened surface layer, as evidenced by microstructural studies conducted using an optical metallographic microscope. Tribological tests showed an improvement in wear resistance after electrolytic plasma hardening: the wear volume for steel 45 was 3,03×10-4 mm³, and for steel 65G it was 6,17×10-5 mm³, which is 7 and 4,5 times less than the wear volume for the initial samples, respectively. The analysis of polarization curves showed that the corrosion current density decreased compared to the initial sample. For steel samples 45 and 65G after three cycles of electrolytic plasma hardening, the corrosion current densities were 6,87×10^-6 A/cm² and 1,61×10^-7 A/cm², respectively. Additionally, a shift in the corrosion potential towards more positive values was noted, indicating an increase in corrosion resistance. The results of the study demonstrate significant improvements in the tribological and corrosion properties of steels 45 and 65G after electrolytic plasma hardening, providing valuable data for industrial applications.

Energy features of friction thermomechanical handling (FTMH) of steel products and the effect on the state of their surface structure

Abstract. Problem. The article deals with the influence of energy and power characteristics of frictional thermomechanical handling of steel products (FTMH) on the state of their surface. Goal. The goal of this work is to study the relationship between the energy and power parameters of steel FTMР and the strengthening result. Methodology. To achieve this goal, the following tasks were solved: fabrication of samples from 65G steel, preliminary hardening heat treatment of samples, hardening of the working surface of samples using FTMO, measurement of the components of the cutting force arising from FTMO using a dynamometer, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness, and depth of hardening of the experimental samples, conclusions regarding the relationship between the effectiveness of hardening of samples during processing and the energy and power parameters of FTMH. Results. Changes in the structures and properties of samples made of steel, which is used for products requiring a hard and wearresistant surface under the influence of processing to form surfaces with altered properties, are shown. Originality. Measurements of the machining process at FTMH using a dynamometer were carried out and the circumferential (circular) cutting (machining) force was calculated, which made it possible to construct graphical dependencies that allow characterizing the surface hardening taking into account the thickness of the disk. It is shown that the microhardness of the surface of the prototypes was increased to 1300 kg/mm2, which is equivalent to 13000 MPa. Practical value. Recommendations on the optimal thickness of the hardening disk have been made, taking into account the results obtained. The research results can be used in production and research.

STRENGTHENING OF THE SURFACE BY FRICTION

The study is devoted to the application of the method of surface hardening by friction Object of study - the process of surface hardening by friction.Subject of study - samples of 65G steel the method allows achieving high values of hardness, strength and wear resistance of materials in a short time and at much lower cost compared to other processing methods. The aim and objectives of the study are to investigate the nature of surface hardening of steel samples by friction. To achieve this goal, the following tasks are envisaged: manufacturing samples from 65G steel in the form of plates, preliminary heat treatment of samples for their maximum thermal hardening, hardening of the surface of samples by friction, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness and depth of hardening of these samples, conclusions on the influence of processing factors on the hardening result. Based on the experimental data obtained, we constructed graphs of microhardness changes in the cross-section of the samples and studied the microstructures. It can be seen that after friction treatment, a layer with a modified structure is formed in the surface of the samples. The microhardness of the surface is significantly higher (approximately 2 times) than the microhardness of the main part in the samples. Metallographic analysis has shown that the layer formed in the samples has a martensitic structure characterized by a higher degree of dispersion and microhardness compared to the martensitic structure obtained during the previous heat treatment. Changes in the microstructure and microhardness of the samples that were surface hardened using different processing modes were compared. Certain differences in the characteristics of their hardened «white» layers were found. It is also shown that the hardened «white» layer is located along the entire length of the surface in the samples and is continuous and homogeneous.

УПРОЧНЕНИЕ РАБОЧИХ ОРГАНОВ СЕЛЬСКОХОЗЯЙСТВЕННЫХ МАШИН ВИБРОПЛАЗМЕННЫМ МЕТОДОМ

The task of increasing the service life of agricultural machinery by hardening the surfaces of its working parts has always been relevant. Currently, this problem is most successfully solved with the use of plasma technologies. In this paper, we present the results of some studies on the vibrating plasma treatment of the surface layer of samples made of steel 65G. (Research purpose) The research purpose is determining the possibilities of vibrating plasma methods for hardening the working parts of agricultural machinery and studying the physical and mechanical properties and structural changes in the surface layer of these products. (Materials and methods) Four samples of 65G steel were taken for research: the initial one; a sample with electric spark treatment; a sample with vibrating arc treatment with a single-rod electrode; a sample with vibrating arc treatment with a three-rod electrode. The morphology of the surface, the elemental composition of the samples and the microstructure of the coatings were studied using electron and metallographic microscopes. (Results and discussion) It has been shown that electric spark treatment in some modes increases the hardness of the surface of the material by more than four times. Vibrating arc treatment with a copper graphite electrode allows carburization of the surface layer of the material; the hardened layer has a hardness of more than three times the hardness of the base. (Conclusions) The results of the study are consistent with the results of studies by other authors on electric spark and vibrating arc discharges. The surface layer formed during the processing of the part with vibrating plasma is a new composite structure. Hardening of the base material along the depth of the part during electric spark processing occurs by 0.5-1.0 millimeters, during vibrating arc processing - up to 3-4 millimeters.

ОСОБЕННОСТИ ИЗНАШИВАНИЯ ВОССТАНОВЛЕННЫХ С ПОСЛЕДУЮЩИМ УПРОЧНЕНИЕМ КВДУ ЛЕМЕХОВ ОБОРОТНЫХ ПЛУГОВ

The widespread use of plows from foreign manufacturers has led to the need to develop a restoration technology with subsequent hardening of replacement parts of their working bodies, in particular plowshares, due to their intensive wear. The situation is aggravated by the fact that there are currently significant interruptions in the supply of spare parts for foreign tillage equipment and a significant increase in their cost. Existing technologies for restoring parts of this type do not provide them with a high service life, and therefore require improvement.The wear features of reversible plow shares restored using wear-compensating elements followed by carbide-arc hardening (CAH) were studied in this work. Production tests were carried out using the shares of the Lemken EurOpal reversible plow when plowing medium and heavy loamy soils. Spring sheets made of steel 65G, which had lost their elasticity, were used as the material of the compensating element. A multicomponent paste containing 65% matrix powder PR-Kh30SRNDYu, 25% boron carbide and 10% cryolite was used for CAH. The specific wear of the cutting surfaces of plowshares along the width was studied in three sections. The production tests carried out made it possible to establish that the increase in wear of the cutting surfaces of both serial shares in the delivery state and those restored with subsequent hardening of the highpressure unit with an increase in their operating time is subject to a linear relationship. The greatest wear, regardless of the operating time of the ploughshare, is in the heel area, the least wear is near the bit attachment area. Restoring the studied shares with subsequent CAH on the rear side makes it possible to increase their operating time to 76 hectares, which is on average 1.8 times higher than that of serial shares in the delivered state. The use of the proposed technology will help solve the problem of resource conservation and import substitution.

Composition, Structure, and Wear Resistance of Surface Nanostructures Obtained by Electric Spark Alloying of 65G Steel

Composition, Structure, and Wear Resistance of Surface Nanostructures Obtained by Electric Spark Alloying of 65G Steel

Macrostructure of hardened chisel opener with silicon-manganese-chromium based cladding

The study relevance is due to the fact that the wear of the working bodies of seeding machines leads to increased fuel consumption, deterioration of the quality of seed placement, and reduced yields. In this regard, this article is aimed at studying the condition of hardened working parts of the experimental grain-fertilizer-grass seeder. Based on the results of information search, the following hardening methods were adopted: electric arc cladding with hard-alloy electrodes and sormite; heating of the chisels by HFC quenching. Samples of experimental bits of coulter bits of a grain and grass seeder made of 65G steel were used for research. The state of worn surface layers of chisels was studied by ultrasonic flaw detector. Research has allowed to establish that among hardened samples the smallest equivalent area of wear has the sample, hardened full working surface by cladding with electrodes T590, and also according to the results of field experiments this sample had the greatest resistance to abrasive impact. On the basis of these results as the most rational method of chisel hardening for production conditions in agricultural enterprises it is recommended to replace the typical factory heat treatment with cladding of the full working part of chisel.

Stimulation of the Bainite Transformation Scenario by an External Magnetic Field

Introduction. It makes practical sense to change the properties of steels with a bainite structure, as with bainite transformation under the influence of a magnetic field, it is possible to improve the ductility of the steel while maintaining or even increasing its strength. Scientific research in this area has focused on the influence of the magnetic field on thermodynamics and on the change in the phase transformation scenario. However, there is no detailed description in open sources of the effect of a magnetic field on the structure and properties of the products of intermediate bainite transformation. The aim of the work is to study the peculiarities of the influence of an external magnetic field on the scenario and kinetics of phase transformation of steel.Materials and Methods. The study was conducted using samples made of 65G steel. Their chemical composition was monitored using a Magellan Q8 optical emission spectrometer. Heat treatment (resistive heating) was carried out in an IMASH 20–75 installation for high-temperature research. The heating temperature was approximately 1000 degrees 1000°C, and the holding time was 10 minutes. The sample was cooled down using water-cooled electrical contacts. An external magnetic field with a strength of 400 kA/m and 800 kA/m was created by an electromagnet integrated into the vacuum chamber of the installation.Results. The experiments confirmed the potential for altering the transformation pathway from pearlite into bainite in the presence of an external magnetic field of up to 1 MA/m. Images of the microstructure and surface relief of samples after cooling in a magnetic field were obtained. Kinetic changes and dependencies of the volumetric transformation rates on the duration of isothermal exposure were analyzed. It has been found that exposure to a constant magnetic field of 1.6 MA/m increased the volumetric transformation rate by 1.808 times (for 65G steel) and by 1.687 times (for 45H steel).Discussion and Conclusion. The results of observations of changes in the surface relief during cooling in the absence of a magnetic field, and in magnetic fields of various strengths, were recorded. This has allowed us to draw the conclusion that the external magnetic field stimulates the bainitic transformation instead of the original pearlitic one. Microstructural changes can be explained by the influence of the magnetic field on the initial phase magnetic state.

Creep behaviour of dissimilar weld joint between buttered Grade 91 steel and Alloy 800

Creep rupture behaviour of dissimilar weld joint (DWJ) between buttered Grade 91 steel (G91) and Alloy-800 fabricated by Shielded Metal Arc Welding (SMAW) process is investigated at 873 K over a stress range of 90–160 MPa. DWJ exhibited lower creep rupture strength than the G91 steel and the failure location of the DWJ shifted with applied stress. At high stresses (≥140 MPa) fracture occurred in the over-tempered region of base metal, whereas it shifted to HAZ at lower stresses. In contrast to interface failures being considered the life-limiting factor in DWJs, the ruptured specimens in the present study revealed a clear interface (between the buttering layer and G91) free from deleterious coarse carbides and insignificant cavitation even after creep exposure of ≈ 5800 h. It’s important to highlight that the buttered G91 DWJ exhibited higher rupture life and weld strength reduction factor compared to joints fabricated without buttering by the SMAW process.

Application of combined wave hardening and heat treatment for wear resistance increase

The article describes the results of studies on abrasive wear after combined hardening by wave strain and heat treatment of steels 65G and 30HGSA. Recommendations are given for combined hardening modes that contribute to an increase in abrasion resistance by 15—16 % compared to thermal hardening alone. It has been established that the highest wear resistance is achieved as a result of combined hardening, which provides a more homogeneously hardened structure.

Methods of structural surface engineering in solving problems of multifactorial improvement of materials performance

Problem. Structural surface engineering encompasses a complex of scientific disciplines and technological methods of directed change of physical and chemical properties of materials surface layers by modification, deformation, application of films, coatings, protective layers, with the help of various combined methods. In the course of the study several different methods of structural engineering of the surface are considered for solving problems of multifactor increase of the level of exploitation characteristics of materials. The methods described in the article are characterized by different physics of the process on the way to obtaining the result, but are aimed at modifying the structure and properties of the surfaces to which they are applied. Goal. Consideration of different methods of influence on the surface of ferrous and non-ferrous alloy objects, analysis of their influence on the modification of the structural state and properties of the surface layers that were investigated, discussion of the peculiarities of each of the considered technologies. Method. The first direction includes technologies that include a friction component, namely thermofriction treatment (TFT) for thermofriction hardening (TFH), supplementary thermofriction hardening (STH) or thermofriction welding (TFW). The second direction is the technology involving the use of anodic-cathodic electrolysis mode in alkali-silicate electrolyte – micro-arc oxidation (MAO). The third direction is the technology of vacuum-arc PVD-method, which involves obtaining chromium coatings. The article describes the features and results of application of such technologies, as well as the expediency of using this or that method for materials of different classes, schemes of the corresponding installations are presented. Results. The result of additional hardening of U8A steel surface from the microhardness level of 7.2 GPa to 14.7 GPa by DTFZ method after its thermal hardening practically to the maximum possible level is shown. The microstructure of the cross section of the pre-hardened U8A steel sample after DTFZ is presented, where the degree and character of surface hardening can be reliably seen. It is emphasized that in previous studies a consistently effective hardening of steels of various classes was achieved, up to a level of 22 GPa in 65G steel. The structure and properties of coatings on low-alloy aluminum alloys AB and AD1 formed in alkali-silicate electrolyte in the anodic-cathodic mode of MDO in the process of application of the microarc oxidation method have been studied. It is shown that the method of MDO in alkali-silicate electrolyte allows to obtain coatings with thickness up to 300 μm, coating growth rate ~ 2 μm/min and coating hardness 10-20 GPa. The coatings have high adhesion to the substrate, have a layered structure, the properties of the coatings are determined by the properties of the base layer. The coatings have a crystalline structure and consist of the following phases: γ-Al2O3, α-Al2O3, mullite (3Al2O3⋅2SiO2), the ratio between the phases depends on the electrolysis conditions. It is established that phase formation begins with the γ-Al2O3 phase, which in the process of further growth of the coating turns into the α-Al2O3 phase or interacts with silicon oxide to form the mullite phase. The possibility of obtaining high-quality chromium nitride-based hard coating by vacuum-arc sputtering is shown.

Modeling of operational reliability of running wheels of overhead cranes of seaports

Overhead cranes are widely in operation in sea and river ports for cargo transshipment in open and closed storage areas. Since they are the main link in technological processes, the productivity of Port production lines depends on their reliable and continuous operation. It is known that during the operation of cranes, 90% of the running wheels fail and are replaced with new ones due to intensive wear of the edges, and 60-70% of crane rails due to wear of their side faces. Since the service life is the main indicator of the durability of parts and assemblies, therefore, increasing the installation of wheel life is an urgent task, which will reduce the cost of repair and operation of cranes. As the experience of operation shows, running wheels have the most worn elements of movement mechanisms. Thus, their service life ranges from several months to 2-3 years. This is due to the fact that replacing the wheels is cheaper compared to replacing the crane track. Since the service life is the main indicator of the durability of parts and assemblies, therefore, increasing the installation of wheel life is an urgent task, which will reduce the cost of repair and operation of cranes. Analysis of studies of complex technical systems shows that the reliability of overhead crane mechanisms operated for more than 30 years in the Seaport is not fully understood, the nature of wheel damage depends on the operating conditions. For research, 4 identical overhead cranes with a lifting capacity of 10 tons were selected, which operate in Hook mode in seaports. Crane wheels are made of 65g steel by casting. Crane mechanisms were visually examined and wheel wear was measured after 3 months during 4 years of operation. Based on the research results, the parameters of the Wear model from time to time in the form of a step function are calculated. The obtained values of the correlation coefficient indicate that there is a fairly tight relationship between wear and operating time. The average error value for the proposed model does not exceed 6.1%, which is quite acceptable for engineering calculations. It is established that the service life of Crane wheels does not exceed 3.3...3.4 years of operation, which is less than 4 years specified by the manufacturer.

Composition, Structure, and Wear Resistance of Surface Nanostructures Obtained by Electric Spark Alloying of 65G Steel

By a combination of the X-ray phase and fluorescence analyses, it was shown that a hardened layer formed during electric spark alloying of 65G steel using a processing electrode made of T15K6 hard alloy is a nanocrystalline material. The ratio of the crystalline and the amorphous phases in it was achieved by changing the discharge energy. Since an increase in the discharge energy leads to an increase in the surface roughness and its amorphization, there is an optimal value of the discharge energy at which the maximum wear resistance of the resulting nanocomposites is achieved. At E = 0.2 J, the wear resistance of the hardened layer is 7–10 times higher than that of an untreated surface.

Changes in structure, hardness and crack resistance of plasma-strengthened steel 65G

The present paper describes the research of structure, hardness and crack resistance indicators before and after plasma treatment of 65G steel of a ploughshare part. As a result of plasma treatment, we obtained the modified layer with increased hardness in the range of 980 – 3558 HV with increase in 3.6 times. Metallographic studies showed that pearlitic-ferritic structure of the original metal transforms into needle martensite with high hardness and strength due to plasma hardening. It is recommended to determine the impact toughness by the Drozdowski method, in which a fatigue crack is pre-created on a special vibrator. Also, before the fatigue crack was grown, lateral V-shaped notches of different depths were made on the sample lateral surface. The relative crack length, λ, varied from 0.27 to 0.65. According to the results of compression tests, it was found that there was a small movement of cracks in the hardened samples in the range from 1.3 to 5.6 mm. The initial unstrengthened samples are in a more brittle state than the quenched ones, and accordingly, significant fracture is observed in the conditions of artificial cracking. The evaluation of 65G steel samples for crack resistance by impact bending tests with subsequent oscillographing showed that plasma hardening inhibits crack growth by increasing impact toughness. Thus, the use of plasma hardening is effective in surface hardening of 65G steel, in particular ploughshares which are constantly exposed to mechanical stresses, friction and wear.

Electrofrictional Hardening of the 40Kh and 65G Steels

This study investigated the influence of electrofrictional treatment on the structure and hardness of the surface layers of the 40Kh and 65G steels. Based on the results of scanning electron microscopy, it was determined that during the electrofrictional hardening (EFH) of 40Kh steel, a hardened surface layer, with a microhardness of 873 ± 37 HV0.1, was formed. This layer consisted of two zones: a surface-quenched zone, with a structure of fine needle-like martensite and austenite; and a heat-affected zone (transition layer), with a structure of martensite and high-dispersion pearlite (troostite), smoothly transitioning into the original ferrite–pearlite structure. After EFH, a layer with a thickness of ~150 μm containing carbides in the martensite was formed on the surface of the 65G steel, which smoothly transitions into the heat-affected zone with a structure of needle-like martensite. The microhardness of the 65G steel in its initial state was 277 ± 20 HV0.1, and after EFH, it reached 811 ± 23 HV0.1. The results of the microstructure analysis of the 40Kh and 65G steels after EFH were consistent with the results of X-ray phase analysis. It was established that the phase composition of the 40Kh and 65G steels in their initial states consisted of an α-Fe phase with a body-centered cubic (BCC) lattice, and after EFH, both steels formed strengthening phases: residual austenite (γ-Fe) and martensite (α′-Fe). During EFH, under high temperature and pressure conditions, carbon from the cast iron electrode was alloyed with iron, contributing to the formation of cementite on the surface of the 65G steel. These obtained data allowed us to conclude that electrofrictional treatment is an effective method for the surface hardening of 40Kh and 65G steels.

Methods of Structural Engineering of Surface in Solving the Problems of Multifactorial Increase of the Level of Operational Characteristics of Materials

In the course of the study, several different methods of surface structural engineering are reviewed. The methods described in this paper are characterized by different process physics on the way to obtaining the result, but they are aimed at modifying the structure and properties of the surfaces to which they are applied. Among them, two different technological directions are considered. The first area involves technologies that include a friction component, namely thermofriction treatment (TFT) for thermofriction strengthening (TFS), additional thermofriction strengthening (ATFS) or thermofriction welding (TFW). The second direction is a technology that involves the use of an anode-cathode electrolysis mode in an alkaline-silicate electrolyte – micro-arc oxidation (MAO). The paper describes the features and results of the application of such technologies and the feasibility of using this or that method for materials of different classes, and presents schemes of the corresponding installations. The result of additional hardening of the surface of U8A steel from a microhardness level of 7.2 GPa to 14.7 GPa using the ATFS method after its thermal hardening to almost the maximum possible level is shown. The microstructure of the cross-section of a prehardened specimen of U8A steel after ATFS is presented, where the degree and nature of surface hardening are reliably visible. It is emphasized that in previous studies, consistently effective hardening of steels of various classes has been achieved, even up to the level of 22 GPa in 65G steel. Regarding the method of microarc oxidation, the structure and properties of coatings on low-alloy aluminum alloys AB and AD1 formed in an alkaline-silicate electrolyte in the anode-cathode MAO mode were investigated. It is shown that the method of MAO in alkaline-silicate electrolyte allows to obtain a coating thickness of up to 300 μm, a coating growth rate of ~ 2 μm/min, and a coating hardness of 10-20 GPa. The coatings have high adhesion to the substrate; they have a layered structure. The properties of the coatings are determined by the properties of the base layer. The coatings have a crystalline structure and consist of the following phases: γ-Al2O3, α-Al2O3, mullite (3Al2O3·2SіO2), the ratio between the phases depends on the electrolysis conditions. It has been established that phase formation begins with the γ-Al2O3 phase, which in the process of further coating growth turns into the α-Al2O3 phase or interacts with silicon oxide to form the mullite phase.

Investigation of changes in phase composition and tribological properties of 65G steel during electrolyte-plasma hardening

This paper presents the results of studies of phase composition and tribological properties of 65G steel, before and after electrolytic-plasma hardening at different regimes. The technology of electrolyte-plasma hardening and laboratory installation for implementation of electrolyte-plasma hardening are described. It was found that after electroplasma hardening a modified layer consisting of α'-phase (martensite) and cementite M3C is formed. The developed technological process of hardening of a part made of 65G steel makes it possible to obtain layers on the surface of the part that provide an increase in wear resistance by 2 times and in resistance to abrasive wear by 1.7 times. The carried out investigations have shown perspective and expediency of application of the developed method to increase operational properties of parts working in conditions of friction and wear. This technology can be used to increase the service life of working elements of agricultural machinery.

Plasma Coatings Based on Self-Fluxing NiCrBSi Alloy with Improved Wear Resistance Properties

The structure and properties of plasma coatings sprayed with a composite material based on a self-fluxing NiCrBSi alloy (PG-10N-01 alloy) modified with a composite material obtained by self-propagating high-temperature synthesis were studied. Titanium powders, carbon black, aluminum, iron oxide, PT-NA-01 thermosetting powder and PGOSA-0 refractory clay were used as the initial components of modified with a composite material. Mixing and mechanical activation of the initial powders was carried out in a BM-1 ball mill for 15 minutes at 130 rpm in a ratio of 1 to 40 of the mass of the charge to the mass of the falling bodies (steel balls with a diameter of 6 mm). Initiation of the self-propagating high-temperature synthesis was carried out using a special device by introducing a heated nichrome spiral. The process of coatings spraying was performed on the MPN-004 microplasma spraying unit at a current of 45 A, a voltage of 30 V with a distance of 100 mm on samples made of 65G steel with a thickness of 3 mm. Argon was used as a plasma-forming and shielding gas. In order to substantiate the feasibility of the self-propagating high-temperature synthesis, a part of the samples was sprayed with a self-fluxing alloy PG-10N-01 with the addition of a mechanical mixture of starting powders. It was established that as a result of plasma spraying of the PG-10N-01 alloy and the composite material of the modified with a composite material + PG-10N-01 composition, coatings with a dense and multiphase structure are formed. The microstructure of the PG-10N-01 alloy coating consists of a solid solution based on nickel (γ-Ni) with inclusions of nickel borides Ni3B and chromium carbides Cr3C2. When adding modified with a composite material in a nickel-based solid solution, in addition to the phases indicated above, borides of titanium TiB2, carbides of titanium TiC and silicon SiC were detected. Their presence leads to an increase in the microhardness of such coatings and their greater wear resistance under conditions of abrasive wear in comparison with the spraying coating of the PG-10H-01 alloy.

INVESTIGATION OF CUTTING EDGE RADIUS OF HARDENED FLAT KNIVES AFTER PRODUCTION TESTS

One of the important characteristics of flat knives is the radius of rounding of the cutting edge. The smaller the radius of rounding, the more efficient the cutting process is. With the help of various hardening methods, it is possible to reduce the wear of flat knives, so that the radius of rounding of the cutting edge will remain small for longer, and the knife will mow grass crops more efficiently. The most promising methods of knife hardening are HDPE boring, HDPE surfacing FeSi, as well as a combined method including HDPE boring and electric spark treatment. (Research purpose) The research purpose is studying the changes in the radius of the cutting edge of flat knives depending on the hardening technology and the time of their operation. (Materials and methods) Knives made of 65G steel with a length of 125 and 150 millimeters, hardened by HDPE boration, HDPE surfacing by FeSi, a combined method consisting of HDPE boration and electric spark treatment, as well as hardened by HDPE quenching at the manufacturer, were studied. The radii of rounding of the cutting edge of flat knives were measured according to the developed technique, consisting in the production of knife casts made of silicone, viewing the resulting casts on a microscope and calculating the radius using special software. (Results and discussion) It was shown that all three technologies contribute to reducing the dynamics of changes in the radii of rounding of the cutting edges. It was revealed that the best hardening technology was combined processing, and the worst was HDPE surfacing FeSi. (Conclusions) The radii of rounding of the cutting edges were measured. Histograms of the average radii of hardened knives were constructed depending on the hardening technology and the beveled area. It was determined that the hardening of the knives reduces the dynamics of changes in the radii of the rounding of the cutting edges.