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To improve erosion resistance, strength, and other protective properties, a comprehensive modification of the surface layers of 25CrMoV steel, which is widely used in turbine construction, was performed. For comparative studies, modifications with different interlayer materials (Mo and Ti) and modifications without interlayer were used. The Mo and Ti layers were deposited on a nitrided ion plasma surface. The outer protective layer for all modifications was unchanged and consisted of a Mo2N coating. To determine the role of the deposition of interlayer metal coatings on the strength properties of the complex modified coatings, the distributions of hardness (H, GPa), Young's modulus (E, GPa), and other strength parameters (H/E and H3/E2) measured by cross sections (h, µm) were investigated. The hardness of the Mo2N coating was ~30 GPa, and the hardness of the nitrided layer was ~12 GPa. The modulus of elasticity for the Mo2N coating was ⁓415 GPa, and for the nitrided steel - ⁓270 GPa. It was found that the main factor influencing the strength properties of a multilayer structure is related to the different materials of the metal layers. For the Mo and Ti layers, the values of E differ significantly (⁓ 340 GPa and ⁓ 180 GPa, respectively), with almost identical values of H (⁓ 6.5 GPa). The distributions of elastic modulus E = f(h) measured in the modified layers correlate well with the distributions of nitrogen concentration CN = f(h). The distributions of H/E = f(h) and H3/E2 = f(h) for the modifications with Mo and Ti layers show a decrease in mechanical properties in the areas of the intermediate layers (Mo and Ti). For the modification without interlayer, the distributions of these indicators do not show such a drawback. The cavitation resistance of the comprehensively modified 25CrMoV steel is up to 2 times higher than that of the steel in the original condition. NSC KIPT performed extensive ion plasma modification on a pilot batch of turbine parts. These products, which are part of the steam distribution mechanisms, were manufactured by Ukrainian Power Machines JSC (Kharkiv) for the thermal power industry.

The equations for predicting the quality parameters of the coatings is proposed, which allow predicting structural parameters (thickness, continuity), mechanical properties (microhardness) and geometric parameters (roughness) based on the energy indicators of the electrospark alloying, such as discharge energy, as well as process productivity, and, therefore, to establish purposefully an algorithm for further governing of the surface properties of parts. The recommended algorithm allows determining the most rational way of forming of surface layers with a demand quality. The technique is tested for the fabrication of coatings on the cathode of steels 20 and 40 using aluminium as an anode. [ABSTRACT FROM AUTHOR]

The nature of the stress state arising under sliding friction loading is investigated on the model of a discretely processed material in which there is an annular transition zone between the inclusions (hardened area) and the matrix according to the known law of change in its mechanical properties. It is shown that local stresses in the material, depending on the type of loading of the elementary volume, can be predicted and calculated, taking into account the mechanical properties, appearance, and structure of the transition zone that occurs as a result of laser processing. The strength of the transition zone has a linear dependence and the stress concentration in the area after laser treatment decreases and smoothly transitions to the matrix, and then it decreases to the stresses in the matrix, which gives the advantage of discrete laser treatment of hardened steel. [ABSTRACT FROM AUTHOR]

The zone of stable immiscibility of liquid phases during the smelting of a copper alloy with 20% wt. Fe is obtained by using steel with 0.2% C; the research method is agree with the features of the state diagrams of Cu-Fe and Cu-Fe-C systems in the zone of low concentrations of C. In the induction crucible furnace, primary melting of steel is carried out with gradual saturation of the melt with copper with small solid additives in insignificant overheating of the melt above the liquidus temperature (up to 25 K) and laminar motion of metal. This ensures its constant presence in the state of pre-stratification (emulsion nucleuses that continuously nucleate and dissolve), which is characteristic of Cu-Fe melts. In the melt layers that surround the copper additives during their dissolution, the Cu content increases and they enter into the immiscibility zone of the Cu-Fe system alloyed with C. There spontaneous emulsification and acquisition of a stable structure by dispersed phases took place. During their subsequent transition to the mixing zone, the inherited constancy of the structure restrains the dissolution process of globularized formations. The cooling of the metal liquid is accompanied by competition between the processes of globularization and dendrites' formation. This manifests itself in the sizes of the melt volumes, which are characterized by the predominance of one of the types of phases or their parity depending on the temperature, concentration and time conditions, as well as the features of their nucleation and development. In the structure of the sheet obtained by casting in a roll crystallizer (cooling rate of ≅ 1000 K/s), 19 types of globularized formations (0.2-250 μm) are found, three of which (0.2-1.0 μm) are frozen microemulsions. Prospective directions for the application of sheet products made of copper-steel alloys with a microemulsified structure (manufacture of products by additive technologies for responsible equipment, shields from electromagnetic and thermal influences, and inserts in sliding bearings) are determined. [ABSTRACT FROM AUTHOR]

Analytical studies of both the influence of chemical elements on the mechanical properties of steels and their influence on the stability of austenite are carried out. The experience of creating low-alloyed and microalloyed steels is analysed that made it possible to determine the influence of individual alloying elements (Mn, Si, Cr, Ni, Mo, V, etc.) on the structural condition and set of operational properties of wheels. Smelting of steel ingots of experimental composition is carried out in laboratory conditions. As shown, the use of steel with alloying carbide-forming elements for the production of railway wheels leads to the need to adjust the modes of thermal strengthening in order to obtain the best set of mechanical properties. To increase the wear resistance of solid-rolled wheels, it is necessary to carry out their heat treatment in such a way that, in all layers of the rim, dispersed lamellar products of austenite decomposition and fine-grained structure of steel are obtained. When heating the wheels for hardening, it is necessary to achieve a uniform austenitic state of steel, which ensures the given amount of rim strengthening, satisfactory values of impact viscosity in the wheel disc. At the same time, the size of the austenite grain depends on the heating temperature for hardening, which significantly affects the value of the viscosity of the rim metal. The goal of the work is to determine the rational heating temperature before strengthening heat treatment of experimental steel for railway wheels microalloyed with vanadium (up to 0.11 wt.%) and molybdenum (up to 0.15 wt.%), with an increased content of silicon (up to 0.57 wt.%), chromium (up to 0.9 wt.%) and nickel (up to 0.7 wt.%). An experiment is performed to determine the heating temperature for strengthening heat treatment of railway wheels made of experimental steels by the method of hardening at different temperatures. According to the results of metallographic studies, it is established that, for steel samples No. 1 (comparative carbon steel) and No. 2 (0.9% Cr and 0.41% Ni) at a heating temperature of 900°C, some changes in the morphology of the microstructure are already observed. For samples made of steel No. 4 containing 0.89% Cr and 0.11% Ni, when heated to 900°C and subsequently quenched, the structural heterogeneity is strongly pronounced. For samples made of steel No. 3 containing 0.21% Cr and 0.70% Ni, the formation of a homogeneous dispersed structure is observed during quenching from 900°C. As established, the rational heating temperature for strengthening heat treatment for steel compositions No. 1, No. 2 and No. 4 is of 850°C; for steel composition No. 3, the heating temperature is of 900°C. The optimal heating temperatures for experimental steels are established. [ABSTRACT FROM AUTHOR]

The article analyses technologies for the formation of coatings to protect machine and equipment parts from corrosion and wear in aggressive environments. The study considers plasma electrolytic oxidation (PEO) regimes of valve metal materials on the core, microstructure, and physical and mechanical properties of oxide coatings. To solve this problem, it is promising to develop a combined technology: application of a layer of aluminium on the surface of steel parts followed by its PEO. The purpose of this work is a theoretical study of the temperature distribution in a steel cylinder covered with a layer of aluminium during PEO to substantiate the thickness of the layers of the two-layer aluminium–aluminium oxide coating. An installation for PEO and a technological process of forming a two-layer Al–Al2O3 coating on long-dimensional parts are developed. A mathematical model is created for an infinite three-layer cylinder with an internal coaxial surface cylindrical source of heat that moves at a constant speed in the radial direction deep into the aluminium layer of the cylinder. It is based on solving the boundary value problem of thermal conductivity with the condition of ideal thermal contact between the layers. During PEO, a solid oxide layer is formed, but the thickness of the unoxidized aluminium layer decreases. The thermophysical characteristics of such a cylinder are functions of both the radial co-ordinate of the cylinder and the time. During the construction of a two-layer coating, it is advisable to use the results of thermal calculations to justify the thickness of the unoxidized aluminium layer adjacent to the surface of the steel under the condition of ensuring the flow of mutual diffusion processes at the interface between aluminium and steel to increase the adhesion strength of the coating to the base due to heating by instantaneous heat sources caused by the action of electric-spark discharges in the PEO process. The thickness of the outer solid layer of aluminium oxide is chosen based on the condition of ensuring the necessary service life of machine parts for wear with a certain reservation. The results of mechanical, tribological, and corrosive cracking tests for steel samples with the developed two-layer Al2O3 coating show its high operational properties.

The structure, phase and chemical composition, microhardness, and microbrittleness of the surface zones of P6M5 steel after chemical and thermal treatment: nitriding followed by titanium and chromium plating are considered. Metallographic and micro-X-ray spectral analyzes of wear surfaces of P6M5 steel with different types of coating were carried out. It is shown the dependence of physical and mechanical properties of complex coatings and discrete laser treatment on wear-resistance. The analysis of the obtained data showed that azochromic coatings with additional strengthening by laser treatment of steel, which serves as a substrate for coatings, increase its performance in extreme operating conditions, excluding its crushing, chipping and peeling. [ABSTRACT FROM AUTHOR]

17G1S steel is widely used in pipelines. Change in the physical properties of this material with time depends on the conditions of gas pipeline operation and pipe environment. Material damage due to operating time by far not always leads to a change of such standard characteristics of the material as σt, σy, К1С and a number of others. At the same time, such material can be significantly damaged, but the traditional methods do not allow determining it. The objective of this work is to demonstrate the sensitivity of acoustic emission method to changes in 17G1S steel properties after 15 years of the main gas pipeline operation. Testing results show that the analyzed acoustic emission parameters change essentially under the impact of operating time, and they can be the characteristics for evaluation of the current state of the damaged material. [ABSTRACT FROM AUTHOR]

A review of recent foreign research literature is given, dedicated to the choice of welding consumables and relevant approaches to welding of combined joints between martensitic and austenitic steels, which are widely used at the moment and in the domestic power machine building. The typical representatives of martensitic and austenitic steels are considered; the problems arising in the joints of dissimilar steels during high-temperature operation, in particular, the process of diffusion of carbon from less alloyed steel to more alloyed and arising of thermal stresses due to the difference in the coefficients of thermal expansion of the combined steels are mentioned; technological approaches to reduce the negative impact of the abovementioned factors are described, as well as the promising welding consumables used in the manufacture of such joints and their comparative analysis are given. At the end of the review, a table is given in which literary references are classified depending on the grade of combined steels and welding consumables used in the manufacture of welded joints in relevant literary references. [ABSTRACT FROM AUTHOR]

The analysis of domestic and global regulatory and technical documentation for railway rails shows that pre-eutectoid medium-carbon and high-carbon as well as post-eutectoid steels are used for the production of serial rails in world practice. According to the degree of alloying, both carbon and microalloyed, alloyed alloys are used. Thus, the issue of developing railway rails of a new generation with the use of boron microalloying and the effect of heattreatment regimes on the structural component of steel to obtain a high complex of mechanical properties is an actual direction of research. Boron dissolved in the matrix increases the incubation period of the nucleation of a new phase, decreases the temperature of the beginning of ferrite formation, as a result, suppressing the decomposition of austenite by the diffusion mechanism. The goal of the work: the study of the microstructure and fine structure of finely dispersed pearlite in steels for high-strength rails with hardness at the level of world requirements. Samples of test steel, which were pre-deformed and heat-treated according to test regimes, which differed in terms of cooling from 0.52 to 5.1°C/s, are studied. Based on the results of xray phase analysis after heat treatment of the experimental steels, the presence of Fe3C, Mn7C3, and FeCr formation is revealed, which have maxima at the same angles as α-Fe (matrix). When comparing and analysing the obtained data, it is established that the formation of MnSi, CrMn is present in all experimental steels, thus, they do not have a significant effect on the mechanical properties. As established, during accelerated cooling from a temperature of 900°C followed by tempering at 200°C for 120 min in laboratory test steels, internal stresses are relieved. At the same time, the microstructure corresponds to a highly-dispersed pearlite that meets the requirements of foreign standards. Experimental rail steel with 0.90% С, 0.39% Si, 0.89%Mn, 0.09% Cr, 0.010% Mo, 00035% B, 0.0123% N and with an increased carbon content has the following mechanical properties: σв = 1295 MPa, σ0.2 = 816 MPa, δ5 = 9.8%, ψ = 11.4%, KCU = 17.25 J/cm², which meet the requirements of EN 13674:1-2011 (R400НТ). [ABSTRACT FROM AUTHOR]

The adhesion of electric-spark chromium coatings on 30ХГСA steel parts is studied. As shown, the adhesion of coatings depends on internal stresses of different nature: the difference of coefficients of thermal expansion of contact materials, mismatch of crystal lattices of the coating and substrate, generating mismatch stresses, and the presence of structural defects in the coating and substrate. [ABSTRACT FROM AUTHOR]

The improvement of the quality of railway rails is associated with the use of steels of a new generation, which differ from known steels, DSTU 4344:2004 and EN 13674:2011, with a higher level of alloying. The operational properties of railway rails made of structural steels primarily depend on the mechanical properties. In steels of the pearlite class, wear resistance is ensured due to the small distance between the pearlite plates that contributes to the increase in hardness. The development of railway rails of a new generation and the determination of the effect of heat-treatment regimes on the structural component of steel to obtain a high complex of mechanical properties is an actual direction of research. The goal of this work is the study of the microstructure and fine structure of finely-dispersed pearlite in steels for high-strength rails with hardness at the level of world requirements. Samples of experimental steel are studied, which were previously deformed and heat-treated according to experimental regimes, which differed in cooling rates from 0.52 to 5.1°С/s. Based on the analysis of the interlamellar distance, as established, all steels have a structure of sorbitol-like pearlite with an interlamellar distance of 0.09-0.20 μm. This result meets the NTD requirements for the structure of thermally strengthened rails (DSTU 4344:2004 and EN 13674:1-2011). Based on the results of the analysis after heat treatment of the test steels, as established, the microstructure is a highly-dispersed pearlite that meets the requirements of foreign standards. Test rail steel with 0.90% C, 0.39% Si, 0.89% Mn, 0.0003% B, 0.0006 Ca with increased carbon content has mechanical properties meeting the requirements of EN 13674:1-2011 (R400HT). [ABSTRACT FROM AUTHOR]

This study was centered on improving the mechanical properties of AISI 8620 steel using the carburization technique. The failure in service conditions of many steel components such as cams, gears, and shafts necessitated the research as it demands that they possess both high wear-resistant surfaces and tough shock-resistant cores. Standard test samples prepared from the steel material were subjected to a pack carburization process using rice husk and charcoal as carburizers, and the energizer – calcium trioxocarbonate (IV) at temperatures of 800, 850, 900, and 950 °C, and held for 60, 90, and 120 minutes. The samples were quenched in water and tempered at 500°C for 60 minutes. After the pack hardening process, the test samples were subjected to tensile, impact, and hardness tests. From the data obtained, ultimate tensile strength (UTS), Hardness, Young’s Modulus, engineering strain, and impact strength were calculated. The case and core hardness of the carburized samples were noted, and an optical microscope was used to observe the microstructural features of the case-hardened, quenched, and tempered samples. The responses (mechanical properties of steel) were optimized using response surface methodology to obtain the optimum carburizing conditions-temperature and holding time. Results showed that the sample’s microhardness core and microhardness case increased from 253 to 327 HV and from 243 to 339 HV as the holding time increased from 60 to 120 minutes, indicating an appreciable increase in the mechanical property of the samples. The optimum carburizing conditions were at a temperature of 885 °C and a holding time of 120 minutes. Hence, the carburization of AISI 8620 steel using rice husk and charcoal as carburizers improved the steel material’s case, core, and mechanical properties.

The technological features of producing brass-steel joint by the method of autovacuum heating are considered. The thickness of the brass layer after mechanical treatment was 10 mm. Studying the structures and chemical composition of various joint zones confi rmed the solution-diff usion nature of interaction of liquid brass with steel. The measurements of microhardness showed the absence of hard and brittle structures. A high quality of the joint was confi rmed by mechanical tests of the two-layer joint on static bending, rupture and shear. 17 Ref., 2 Tabl., 8 Fig. [ABSTRACT FROM AUTHOR]

Coercimetric testing revealed essential differences in metal structure in the subsurface layer of experimental caterpillar tracks. Obtained experimental results of 4-point bend testing of experimental caterpillar tracks from steels which somewhat differ by their chemical composition, confirmed the possibility of application of nondestructive coercimetric testing for assessment of the initial structural state and level of loading of the metal, which characterizes the degree of sustained damage after loading. Metal of a sound track from steel of 110G13L type in the initial condition should have negative values of the coercive force that is ensured by its optimal structural state. This circumstance can provide substantiation for introducing coercimetric testing for express-evaluation of the quality of castings and their heat treatment. 7 Ref., 4 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

Regularities of the effect of strength and ductility of steel (σ0.2 = 140...2100 MPa, ψK = 3...83%) on degree of embrittlement of prismatic pre-cracked specimens in three-point bending is analysed. Instead of plasticity (ψK), it is proposed to analyse the characteristic of deformation resistance (break resistance), Br = SK/σ0.2 which is responsible for the resistance of steel to brittleness in inhomogeneous fields created by stress raisers (SR--notches, cracks). As shown, in this type of test the criterion value of brittle fracture of steels at a temperature of 293 K can be a critical value of the parameter of break resistance Brc = 1.65. Deviation Br/Brc > 1 can be used as a measure of protection of steel from brittleness, while at Br/Brc ≤ 1 the ratio serves as a quantitative measure of the manifestation of brittleness of steel in bending pre-cracked specimens. The possibility of predicting the characteristic of embrittlement of steel Br/Brc by the calculated method according to the basic mechanical characteristics σ0.2 σB, SK, which were obtained during tensile tests of standard specimens, is shown. [ABSTRACT FROM AUTHOR]

In article we present the results of studies of the local x-ray spectral analysis of coatings formed by the electrospark alloying (ESA) method at the discharge energy Wp = 0.13, 0.52 and 0.9 J by anodes from nickel and stainless steel X10CrNiTi18-10 on the cathode surface from X10CrNiTi18-10 steel. During ESA by stainless steel X10CrNiTi18-10 anode with an increase Wp in characteristic points and from the entire investigated surface of the coating, the quantitative elemental composition is not changed. The analysis of elements distribution over the depth of the formed layer is showed that when using the electrode tool from steel X10CrNiTi18-10 with an increase in Wp, there are a slight decrease in chromium and an increase in nickel and titanium in the surface layer. When steel X10CrNiTi18-10 is replaced by nickel with an increase in Wp, the concentration of nickel on the coating surface decreases from 95.38 to 89.04%. As the recession deepens from the coating surface, the concentration of nickel gradually decreases, respectively, at Wp = 0.13, 0.52 and 0.9 J from 96.29, 90.29 and 89.04% on the surface to 9.0, 10.30 and 9.9% at depth: 120, 165 and 240 µm. At the same time, the concentration of chromium, titanium and iron gradually increases. [ABSTRACT FROM AUTHOR]

The article presents the results of research on a new method of restoration by means of electrospark alloying (ESA) of X10CrNiTi18-10 steel details, which operates under radiation conditions. The method can be used to repair machine details of nuclear power plants. The technology includes coating the worn surface of the detail with an ESA electrode, which is made of steel X10CrNiTi18-10 or nickel, which does not contain special additives of cobalt and other elements that form long-lived isotopes in the active working environment. ESA is carried out in two stages. Before the first stage, a layer of graphite electrode coating is applied to the worn steel surface by the ESA method--a tool with a discharge energy Wp = 0.02 J and a productivity 0.3 sm²/min. At ESA by the electrode tool from steel X10CrNiTi18-10 the first and second stages are car- ried out, accordingly at Wp = 0.20 J with productivity 1.6 sm²/min; and Wp = 0.55 J with a productivity 2.5 sm²/min. As a result, the coating thickness is ΔH = 0.19 mm, the continuity is S = 100% and the roughness is Rz = 57 µm. During ESA the first and second stages are carried out by nickel electrode tool respectively at Wp = 0.55 J with a capacity 2.5 sm²/min and Wp = 0.90 J with a capacity 3.4 sm²/min. As a result, ΔH = 0.20 mm, S = 100 % and Rz = 38 µm. The increase in discharge energy in ESA is accompanied by a decrease in yield strength and tensile strength and an increase in the relative elongation and relative narrowing of the sample. During the ESA of the sample with Wp = 0.90 J, compared with the undoped sample, the yield strength and tensile strength decrease with alloying by steel X10CrNiTi18-10, respectively, to 11.7% and 8.3%, and the relative elongation and relative narrowing increases, respectively, to 15% and 14.7%. During the ESA by nickel yield strength and tensile strength decreases to 13.3% and 8.6%, respectively, and the relative elongation and relative narrowing increase to 14.7% and 16.7%, respectively. [ABSTRACT FROM AUTHOR]

Results of experiments on electrostag remelting of used small tools from high-speed steel of R6MS grade are considered. Rationality of application of remelting by a double-circuit scheme is shown, which allows producing an ingot with a high quality surface and chemical composition, corresponding to that of R6MS steel. During experiments, remelting of electrodes, formed from used drills (broaches), mills and cutters of up to 0.2 m size was performed. Remelting into a current-supplying T-shaped mould with forming part diameter of 0.18 m was conducted. Shown is the possibility of performing remelting of consumable electrodes with the cross-sectional area, changing along the electrode length, while maintaining a stable electric mode at distribution of the supplied power between the current-supplying mould and consumable electrode (75 and 25 %) and obtaining high-quality ingots without surface defects under such conditions. [ABSTRACT FROM AUTHOR]

The article deals with tribochemical influence of the surface activity of biosynthetic oils on the operational efficiency and reliability of lubricated friction nodes under the critical conditions. It is proved that the oil surface activity is caused by the structure and properties of their molecules and interactions with steel surfaces. Evaluating criteria of oil tribochemical activity influence on the steel surface modification has been studied. The significant influence of biooils on the steel surface nanolayer phase transformations, friction and steel wearing is claimed. It has been established that the effect of the steel crystal structure deformation and strengthening its surface depends on activity of composition of lubricant. It is proved that biooils lead to improved friction and wear indicators of lubricated samples. X-structural analysis of the steel surfaces showed that during friction the austenite is destroyed and ferrite is formed. Penetration in the lubricated steel nanolayers shows increasing the ferrite and decreasing the austenite content, that cases reducing the deformation degree of metal crystals, which leads to the strengthening of its surface under the plasticized layer and to decreasing the level of friction and wear due to the formed intersurface servitotribopolymer film, which is stable under critical friction.

The paper presents the results of the study of the influence of chemical composition, temperature, stress and operating time on the creep and durability of structural steels. It is shown that the efficiency of structural steels in conditions of elevated temperatures and loads depends on the chemical composition, stress level, operating time and temperature. The influence of alloying elements is associated with the inhibition of the process of weakening of heat-resistant steels due to the reduction of their diffusion mobility and intensity of redistribution between the ferrite and secondary phases, their coagulation and reduction of structural defects. Mathematical models of relative elongation and fracture time in the process of creep from operating conditions and degree of alloying of steel are constructed. It is established that the efficiency of heat-resistant structural steels depends on 61 - 64% of the degree of alloying, 18 - 21% - the value of external stress, 7 - 18% - temperature and 11% of operating time. It is shown that the coagulation of carbides and nitrides in steels doped with nitrogen and vanadium is slower than carbides in steels doped with molybdenum, which more effectively shifts the softening process of heat-resistant steel in the region of higher temperatures and time.

The results of researches on steel 4H4N5M4F2 modes thermo-deformation processing optimization are given. It is established that incomplete annealing (750 °С ± 20 °С in comparison with full annealing 860 °С) in cast and forged condition promotes to improve the machining of blanks for the manufacture of matrices. It is shown that the use of incomplete annealing, namely partial recrystallization promotes the formation of spheroidized rather than lamellar carbide phase, which leads to a decrease in the characteristics: strength threshold, yield strength, hardness 900 MPa, 800 MPa, 32 33 HRC in the cast state and 1200 MPa, 1050 MPa, 38 39 HRC in forged condition, respectively. This increases the fracture toughness: 180 J/cm2 in the cast state and 130 J/cm2 in the forged state. The optimized mode of forging at the temperature of 1170 ± 20 °С and heat treatment (hardening at 1100 ± 5 °С and tempering at 595 ± 5 °С) of steel 4H4N5M4F2 allowed to increase impact strength five times in comparison with cast experimental steel, and also to increase strength threshold of 100 MPa. Forged steel 4H4N5M4F2 has slightly lower heat resistance compared to cast, which hardens at temperatures above 630 °C during operation of the die steel tool. After operation of the extruder wheels made of investigated forged steel and forged steel 4H5MF1S, which was used at the enterprise in copper processing, the properties of both steels were determined. The investigated forged steel 4H4N5M4F2 is characterized by an increase in the strength threshold by 200 MPa and hardness by 6 HRC. After operation (production of 60 tons of copper products of M1 grade) the tool (wheel extruder) from H13 steel (analog 4H5MF1S) had micro and macrocracks on the side and inner parts, and in the investigated steel 4H4N5M4F2 such defects were absent. Thus, the studied steel is characterized by increased stability.

Magnetic pulse welding is an innovative joining method that allows combining dissimilar metals. The article discusses weldability of copper rings with steel rods in order to study the possibility of using single-turn inductor. All specimens were welded with a discharge energy of 18 kJ. Significant deformations of copper rings were observed. Metallographic examination of welds revealed no defects. High-quality joining of metals in the welding zone with a characteristic wavy boundary interface was noted. However, to obtain more information on the exact mechanisms of weld formation, it is recommended to carry out numerical modeling of the process. [ABSTRACT FROM AUTHOR]

Ensuring trouble-free operation of structures and constructions is an extremely important and urgent task. That is why scientists pay a lot of attention to development of new methods, equipment and procedural materials for their implementation in industry. Particular attention is given to the state of material of the structures and constructions for timely decision taking and avoiding accidents or emergencies. Investigation of changes of acoustic emission (AE) parameters at different stages of testing material samples is conducted. Development of approaches to analysis of the distribution of AE event parameters is presented in the work. Informative parameters the distributions of which need to be studied, were tentatively determined, proceeding from analysis of the data of numerous investigations of different materials. Developed algorithms and determined means for setting up analysis of distribution of AE event parameters were introduced into the working part and visual interface of EMA-3.92 program. It is established that changes of AE parameters have certain regularities which is demonstrated by the results of testing samples from 17GS steel, and they can be used for assessment of the state of materials, when performing AE control and monitoring. Ref. 15, Tabl. 1, Fig. 11. [ABSTRACT FROM AUTHOR]

The diffusion model of the austenite transformation in hypoeutectoid alloyed steel during isothermal holding is received further development. The model which is developed provides ability to determine the volume fraction of the structural components, the quantity of which are depends on the magnitude of the steel overcooling. The model is considers the degree of the overcooling of austenite, the contents of carbon and structural components in the steel, the size of the nucleus, the volume fraction of the phases, the quantity of the carbon, which are running through a unit area over a period of time, the balance of thermal energy, etc. As shown, in the hypoeutectoid alloyed steel there are two maximum of the austenite stability in the temperature ranges of the existence of upper and lower bainite. The amount of retained austenite is minimal between these temperature diapasons. As established, the residual austenite, depending on the value of the steel overcooling and the temperature range of the holding during subsequent cooling, can decompose by diffusion or shear mechanisms. [ABSTRACT FROM AUTHOR]

In connection with the need to reduce the negative impact of the main defects of the forging ingots, the changes in their thermal state due to endogenous vibrational processing of the melt during crystallization are studied. Vibration processing of an ingot of steel 40XH weighing 7.6 tons was carried out in the upper part for 13 min after the completion of casting of steel at a frequency of 50 Hz and an amplitude of 1.5 mm. Based on the results of temperature measurements of the side surfaces in the upper, middle and bottom parts of the vibrated and control ingots, the regression equations were obtained for the change in their thermal state during crystallization for 200 minutes. A regular increase in temperature was established under conditions of endogenous vibration processing up to 30 °С in the upper part of the ingot with its gradual decrease over 100 minutes, and in the middle part by 10-15 °С over 50 minutes. In the bottom part, no temperature differences were noted during the first 25 minutes. In the next time interval, the temperature of the research ingot steadily decreases by 35-50 °C compared with the control. The obtained results indicate an increase in temperature in the upper part of the experimental ingot due to endogenous vibration treatment of the solidifying melt and a regular redistribution of temperature fields along the height of the ingot. An increase in the temperature gradient in the indicated volumes of the ingot as a result of endogenous vibration processing leads to an increase in convection and mixing of the melt, advancement of the crystallization front mainly in the direction of the upper part, the formation of a fine-crystalline structure and a greater length of the bottom cone without contamination with non-metallic inclusions, a decrease in the manifestation of axial segregation and an increase in mechanical properties metal ingot. The use of endogenous vibration treatment of steel ingots during their crystallization is a promising technological solution that opens new opportunities for controlling the processes of crystallization and structure formation, improves the quality of metal properties of large forged ingots.

The influence of additional heat hardening with the use of fast heating during austenitization on the armour resistance of high-strength sheet metal of protective purpose, made of medium-alloyed steel, is investigated. As established, the high-speed heat treatment by hardening and low tempering of slabs from rolled sheet with a thickness of 6 mm increases its ductility with unchanging the 4th class of leaves armour resistance. In addition to the possible inheritance of the deformation substructure, the increase in ductility after high-speed heat treatment while maintaining strength is due to significant grinding of the grain structure of steel. [ABSTRACT FROM AUTHOR]

According to the developed method of calculating the resource of cylindrical metalpolymer sliding guides, the resource of the guide at different loads and radial clearances is performed. The method is based on the known methodology for studying the kinetics of wear of materials during sliding friction. The slider of the guide is made of antifriction polymeric epoxy composite material DK6 of high hardness, and its base is made of steel. Quantitative and qualitative regularities of dependence of friction path on load and radial clearance are established. It is shown that increasing the load four times causes a decrease in the friction path by 5.61... 9.20 times, depending on the radial clearance ε and the diameter of the base. And doubling the radial clearance causes a decrease in the friction path by 2.40... 3.40 times depending on the load and the diameter of the base. [ABSTRACT FROM AUTHOR]

The paper presents a phenomenological model of the ductile-to-brittle transition in steels due to the action of low temperatures and stress raisers (SR)--notches, cracks, etc. Regularities of the effect of strength and toughness of steel on the critical temperature of brittleness Tc for specimens with an annular notch in tension or pre-cracked specimens in three-point bending are considered. As shown, the excessive (supercritical) low-temperature hardening of steel, unbalanced with the required margin of its toughness, when real strength of the steel, σ0.2, exceeds critical strength for a given type of SR, σ0.2c, is the reason for brittleness of specimens with SR. Physical essence of the quantity σ0.2c is explained in terms of specific characteristics of the steel resistance to break, Br, reflecting its margin of toughness. Recommendations are formulated for optimising a set of mechanical properties for products such as fastening bolts with SR in the form of a screw thread, to prevent their cold brittleness during low-temperature operation. [ABSTRACT FROM AUTHOR]

The results of studies on the effect of tempering regimes on the parameters of fine structure, stress and hardness of 25Cr2Mo1V steel are presented. It is shown that the secondary hardness of steel 25Cr2Mo1V, tempered at a temperature of 550 °C, maximum after 5 hours release and is due to the smallest block size of the crystal lattice. It is established that in the initial stages of decay of the supersaturated solid α-solution of hardened 25X2M1F steel at 550 °C, the crystal lattice parameters increase. During the next tempering time, the bonding of the crystal lattices of these phases is broken, due to the separation of the carbide particles from the α-phase and the parameter and the crystal lattice of the α-phase decreases.

Crystal-geometrical features of the structure of cast and normalized steel with 0.62 % of C content were studied using EBSD method. Inheritance link between the formation of pearlitic and ferritic-pearlitic structures with the structure of intercrystalline boundaries in cast and normalized steel were demonstrated. It was found that the austenite of cast and normalized steel undergoes plastic deformation in conformity with the mechanisms of sliding, twinning and grain boundary slippage. 72 % of low-angle (3... 15 ºС) and 28% of high-angle (20...60 ºС) intercrystalline boundaries are formed in cast steel. Normalization of cast steel leads to the formation of 23 % low-angle (5...15 ºС) and 77 % high-angle (20...60 ºС) intercrystalline boundaries. After normalization of steel the number of special boundaries Σ3…Σ13 increases from 1% to 7 % comparing to its cast state. The number of special boundaries is approximating the number of proeutectoid ferrite in cast and normalized steel.

The results of the study by multiple regression analysis of the effect of additional alloying with cerium, vanadium, copper and boron on the start and finish temperature of the α → γ phase transformation, the content of ferrite and austenite in the structure of cast steel and after its quenching, the austenite grain size, the bonding energy of atoms alloying elements with the grain boundary. The quantitative laws of such influence are established.

The effect of the overheating temperature of steel melts above equilibrium liquidus (20…170 °C) and cooling rate at crystallization (5…650 °C/c) on characteristics of cast structure and mechanical properties of structural steels 25Л, 25ХГСТФЛ, 45Л, 45ХГСТФЛ was researched. The regular increase in the dispersion and mechanical properties of their cast structure under conditions of rapid cooling and an increase in the temperature gradient during crystallization was established. Based on the results of experiments, interpolation equations of the effect of melt overheating and cooling rates on the structural and mechanical properties of steels are obtained. The obtained equations allow to predict the properties of castings within the studied factor space.

The results of studies confirming the feasibility of using low-carbon steels for the manufacture of hot deformation tools of the metal are given. These steels have high heat resistance under thermal cycling conditions with water rapid cooling. The efficiency of alloying of steel depends on the type of tool and its working conditions. The developed heat treatment significantly increase the tool life of low-carbon alloyed steels under working conditions.

The resistance of gas-thermal coatings based on intermetallic compounds and steels under hydroabrasive wear conditions is determined. Recommended composite coating Ni-Ti – 30% Cr-B2 to improve the reliability of machine parts that work in conditions of aggressive exposure to abrasive in aqueous media.

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A mathematical physical-based semi-empirical model and a corresponding computer program are developed for describing recrystallization process and carbonitrides particles precipitation in deformed austenite. The model is suitable for alloyed steels of a wide range of compositions. The model allows calculate a thermodynamic equilibrium for excess carbonitride phases with solid solution, the kinetics of their nucleation and growth, and their effect on recovery and recrystallization. A detailed description is given for each aspect of the model and its physical nature. Verification of the simulation results with the experimental data from published sources confirms the sufficient reliability of the proposed computer model for evaluative calculations. The model's features are demonstrated by an example that simulates influence of Nb content on recristallization, recovery and nucleation, growth and Ostwald ripening of Nb and Ti carbonitride particles. The simulation shows and allows numerically evaluate the effect of slowing down recrystallization and recovery with increasing in Nb content. This indicates a significant effect of dispersed carbonitrides on recrystallization and recovery. The simulation theoretically predicts an intensification of Ti(C, N) particles precipitation and growth with an increase in the Nb concentration. Another result is an increase of dispersion and number of Nb(C, N) particles with an increase in the Nb concentration owing to more rapid transition to the Ostwald ripening stage, which is characterized by much more slowly average particle size growth than from a supersaturated solid solution. [ABSTRACT FROM AUTHOR]

Проблематика. Нині основними тенденціями розвитку металургійного виробництва в нашій країні є боротьба за підвищення якості металу в умовах загострення конкуренції як на внутрішньому, так і на світовому ринку. Одною з головних вимог, що ставляться до якісної сталі, є низький вміст неметалевих включень у готовій продукції, а також рівномірний їх розподіл по перетину металевої заготівки. З деякого часу отримання якісного металу стало можливим за рахунок рафінування його в рідкому стані на останньому етапі розливання у проміж­ному ковші. При цьому проведення досліджень у розливальному пристрої у промислових умовах обмежене внаслідок фізичних умов проведення процесу, а саме завеликого розміру розливального пристрою та високої температури. Ці обмеження можна подолати завдяки переміщенню експериментів з реального пристрою на фізичні моделі та подальшому дослідження якості отриманого металу металографічними методами. Видалення неметалевих включень на останньому етапі розливання є актуальною задачею. Однак проведені раніше дослід­ження не враховують впливу термодинамічних факторів на гідродинаміку проміжного ковша. Мета дослідження. Підвищення якості безперервнолитих заготівок. Методика реалізації. Термодинамічний аналіз процесів коагуляції та видалення неметалевих включень у шлак. Дослідження гідродинамічних процесів, які відбуваються у проміжному ковші у процесі безперервного розливання сталі і які сприяють видаленню неметалевих включень. Металографічні методики дослідження готового металу. Результати дослідження. Проведений термодинамічний аналіз дисперсної системи розплав сталі–неметалеві включення показав, що на частинках неметалевої фази утворюються металеві плівки. Фізичне моделювання гідродинамічних потоків показало, що найбільш ефективною структурою потоків, яка сприяє коагуляції неметалевих включень, є вихороподібна. Промислові випробування показали, що зразки металу, які були отримані при застосуванні реакційної камери, містять на 40–80 % менше неметалевих включень. Висновки. Для створення найбільш сприятливих умов для коагуляції неметалевої фази у проміжному ковші необхідно, щоб він був обладнаний реакційною камерою. Дані термодинамічного аналізу та фізичного моделювання узгоджуються з даними промислових випробувань.

The possibility is considered of producing a steel-titanium joint which forms at complex spray-deposition of a layer of aluminium oxide and a layer of iron powder PZh-1 on titanium with subsequent deposition by a consumable electrode or plasma of a layer of steel using filler wire Zv-08G2S. A new combined method was developed for joining steel to titanium with deposition of protective layers of Al2O3 and iron powder PZH-1 on titanium, with further deposition of a layer of filler wire Zv-08G2S by the plasma process. Ref. 8, Tabl. 2, Fig. 8. [ABSTRACT FROM AUTHOR]

Проблематика. Під час експлуатації литих деталей машин і механізмів найінтенсивнішим зовнішнім впливам піддаються поверхневі шари, тому саме їх структура й властивості визначають працездатність виробів у цілому. Для досягнення високої поверхневої міцності та зносостійкості деталей у промисловості використовують різні технологічні процеси, проте більшість із них не дають змоги одержати поверхневий шар із потрібними властивостями необхідної товщини. У цьому разі перспективним може бути технологічний процес поверхневого легування, тобто виготовлення виробів із диференційованими властивостями поверхні. Мета дослідження. Розроблення технологічного процесу виробництва виливків із заданими властивостями поверхні. Методика реалізації. На кожний стрижень наносили легувальне покриття. Стрижні з нанесеним покриттям протягом доби підсушували на повітрі. Форму та стрижні підігрівали та складали безпосередньо перед заливанням їх металом. Результати досліджень. Для виготовлення зносостійких деталей слід використовувати феромарганець, феротитан і ферохром, які дають змогу одержувати на поверхні виливків легований шар товщиною до12 мм із твердістю до 68 НRА. Такі параметри процесу повною мірою відповідають експлуатаційним вимогам до виробів, які працюють в умовах абразивного або гідроабразивного зносу. Висновки. Для підвищення твердості робочих поверхонь як наповнювачі легувальних покриттів можна використовувати окремі хімічні елементи, феросплави та хімічні сполуки: карбіди, бориди і нітриди.

The ‘soft’ nitriding of the suspension axle surface of the T150K tractor at the depth of 0.08 mm enables us to enhance its constructive strength, to increase its service life by 25 % and have a considerable economic effect.

In the article on the basis of mechanical, metallographic and X-ray spectral studies, the cause of accidental destruction of CHP pipelines is established. Metallurgical investigations have established that the surface of the pipelines is affected by corrosive ulcers, characteristic of products of corrosive influence of the chemically active process medium, pumped by pipelines. It is shown that corrosion of metal pipes of pipelines is accompanied by its active flooding and venting, which results in decrease of plastic properties and stability of the material against corrosion-mechanical destruction of pipelines, especially after 3-5 years of operation. Concentric distribution of elements on separate sections of corrosive impressions of pipe walls was studied using secondary ion mass spectrometry. Metallographic studies found that the surface of the pipelines was affected by corrosive ulcers, characteristic of products of corrosive influence of the chemically active process medium, which is pumped by pipelines. The scan was done horizontally, in the middle part of each plot. The construction of the distribution curves of the alloying elements present in the steel, in particular chromium, was performed to clarify the boundaries of these defects. In the cavities of the ulcers, the maxima of carbon concentrations and the oxygen distribution similar to it are recorded, indicating carbon-carbon corrosion of the metal in the presence of chemically aggressive technological environments. Microhardness was determined according to GOST 9450-80 using a diamond pyramid together with a metallographic microscope. Samples for hardness measurements were prepared in the same way as macrosplights. The change in the level of stresses of steel steels with different operating life was determined on standard cylindrical specimens with a diameter of 5 mm, which were cut from the blanks of these steels, and subjected to uniaxial stretching type MI-12 [6]. [ABSTRACT FROM AUTHOR]

The weapon has always been not only a means of warfare, but also the subject of the historical, cultural, technological heritage of any nation. Scientific achievements, technological and cultural innovations are realized in the weapon. Medieval Europe is rich in technological invention in the field of gunsmiths. Especially a lot of inventions relate to the manufacture of cold blade weapons. Through attempts and mistakes, medieval gunsmiths found the best possible variants of the material from which the weapon was made. Perhaps in the greatest degree this concerns the production of swords. In the Middle Ages, the sword was something more than a weapon. It was still a subject of status, prestige and art. Therefore, the gunner paid special attention to its manufacture. The sword provides the key to understanding the emergence and further evolution of all medieval weapons, and even more– phenomenon of European militaristic cultures. [ABSTRACT FROM AUTHOR]

The car industry uses a tremendous number of materials to build cars, including iron, aluminum, steel, glass, rubber, petroleum products, copper, steel and others. These materials have evolved greatly over the decades, becoming more sophisticated, better built, and safer. They've changed as new automotive manufacturing technologies have emerged over the years, and they're used in increasingly innovative ways. This article is devoted to systematization information on the introduction and application of modern materials in the automotive industry. Given both domestic and foreign sources of information, it follows that car manufacturers are constantly pushing to create the lightest cars possible to increase speed and power. Research and development into lightweight materials is essential for lowering their cost, increasing their ability to be recycled, enabling their integration into vehicles, and maximizing their fuel economy benefits. Light weighting without loss of strength and speed properties is the present, and the future, of the automotive manufacturing industry. It brings innovative materials to the frontline of design.

The dependence of physical and mechanical properties of manganese steel grade 110H13L on the effect of electrical activity during crystallization of the casting is considered. Treatment of the melt by electric current increases the speed of dissolution of metallic impurities and other components in the melt many times, providing not only finely crystalline structure, but also improving the homogeneity of metal casting. Improvement of mechanical properties is a consequence of crushing those which constitute microstructure. Processing by electric current does a beneficial effect on the process of crystallization of metal melts during casting, which significantly improves the structure of the ingot and its mechanical properties.