40Kh Steel Research Articles

On the physical-mechanical and tribotechnical properties of antifriction carbon fiber based on a modified thermosetting matrix

The physical-mechanical and tribological properties of anti-friction carbon fiber plastic UGET based on low-modulus carbon fabric “Ural T-15R” have been studied in order to increase the magnitude of the ultimate deformation and reduce the elastic modulus through the use of a modified thermosetting matrix ET-4 instead of the traditionally used ET-2.Modes of polymerization and of heat treatment of epoxy binders were selected considering the results of the experiments. Prototypes of prepregs were obtained by solution impregnation on the UPST-1000M line and then processed into PCM by hot pressing. Laboratory samples were made and physical and mechanical tests were carried out to determine the ultimate strength under compression, shear and bending stress under destruction, as well as Charpy impact strength. Steel 20Kh13 and oxidized titanium alloy PT-3V were used as counter body rollers to determine carbon fiber tribosets.It was shown that carbon fiber samples based on chemically modified binder ET-4 with two-stage polymerization and heat treatment mode in the range of 90°C to 180°C both have better physical-mechanical and tribotechnical properties, in contrast with the analogue with a three-stage mode and carbon fiber carbon heat at friction over 20Kh13 steel and oxidized titanium alloy PT-3V.

Tribological Characteristics of Ti–Al– N, Ti–Al– Ni–N, Ti–Cr–Ni–N, and Ti–Cr–Ni–Mo–N Strengthening Coatings on Steel 20Kh13 in a Friction Pair with Carbon Fiber and Their Corrosion Resistance

Tribological Characteristics of Ti–Al– N, Ti–Al– Ni–N, Ti–Cr–Ni–N, and Ti–Cr–Ni–Mo–N Strengthening Coatings on Steel 20Kh13 in a Friction Pair with Carbon Fiber and Their Corrosion Resistance

Electrofriction treatment of plow shares

This paper presents the results of research aimed at developing the technology of plow share hardening by means of electrofriction hardening. It is shown that in electrofriction hardening of plow shares a structure with microhardness gradient is formed along the depth of the hardened zone. After electrofriction hardening the microhardness of plow share increases in 3–3.5 times in comparison with the initial state. The reason for the gradient character of microhardness distribution along the thickness of the modified layer is the ultra-high cooling rate, which causes a high temperature gradient near the surface. On the basis of the results of scanning electron microscopy it is established that at electrofriction hardening of steel 40Kh the hardened surface layer is formed, consisting of two zones: the surface hardened zone with the structure of fine–needle martensite and austenite; the zone of thermal influence (transition layer) with martensite-perlite structure, smoothly passing into the initial ferrite-perlite structure. It is established that the phase composition of steel 40Kh in the initial state consists of α-Fe phase with BCC lattice, and after electrofriction hardening the hardening phases of residual austenite (γ-Fe) and martensite (α'-Fe) are formed. The obtained data allow us to conclude that electrofriction treatment is an effective method of plow share hardening from structural steel 40Kh.

Determination of tribotechnical properties of polymers depending on the test conditions

The paper presents the results of morphological and tribotechnical tests of samples of ultrahigh molecular weight polyethylene (UHMWPE), high molecular weight polyethylene (HMWPE), polyethylene terephthalate (PET), polyoxymethylene (POM). Tribotechnical tests were carried out on a friction machine with a vertical axis of rotation of the spindle according to the scheme: “the end of the annular surface of the counter–flange sleeve (steel 40Kh, 48-52 HRC) is a plane (wide side of the polymer sample).” The moment of friction and the load on the samples were determined using strain gauges placed in the friction machine in continuous mode. The effect of the surface roughness of a 40Kh steel counter-tile on the friction coefficients when tested without lubricant and in the presence of hydraulic oil MGE-10A at a constant sliding speed has been established. The maximum values of the friction coefficients were obtained during friction without lubrication after processing the end face of the counter-tile with sandpaper P180 and P1200. The minimum values of the friction coefficients were obtained by lubricating MGE-10A after processing with sandpaper P1200 of a 40Kh steel counterplate. According to the morphology of the friction surfaces, the main wear mechanisms for UHMWPE, micro-cutting, HWMPE and PET, micro-cutting and plowing and for POM, fatigue wear and plowing are determined.

Analysis of micromechanical and tribotechnical properties of fluoropolymers during friction on 40Kh steel

The paper presents the results of micromechanical and tribotechnical tests of samples of polytetrafluoroethylene, radiation-modified (PTFE – RM according to modes A and B), coked in comparison with the PTFE standard (Fluoroplast -F4). The influence of the surface roughness of a 40Kh steel counter-tile on the coefficients of friction against time at a constant sliding speed is considered. Micromechanical tests were carried out using the method of instrumental indentation with a triangular Berkovich diamond pyramid. Tribotechnical tests were performed on a friction machine with a vertical axis of rotation of the spindle according to the scheme “the end of the sample of the fluoropolymer disk is the end of the counter-flange of the annular sleeve (steel 40Kh)” without lubrication and when the friction pair is lubricated with MGE-10A hydraulic oil. It was found that during friction without lubrication, PTFE samples had the maximum friction coefficients, and F4K20 samples had the minimum friction coefficients when working with 40X steel counter-tiles treated with P180 sandpaper. PTFE-RM (A) samples had the best wear resistance, followed by decreasing F4K20, PTFE – RM (B) and PTFE under friction without lubrication. In the presence of lubricant, the samples of the PTFE standard were inferior in wear resistance to the F4K20 samples, but were 5-7% better than the samples of PTFE-RM (B) and (A), respectively.

Determination of tribotechnical properties of composite samples during friction on 40Kh steel

The paper presents the results of tribotechnical tests of samples of ornamental textolite (OT), ornamental structural textolite (OST) and oxafen. The influence of the surface roughness of a 40Kh steel counter-tile on the coefficients of friction from sliding speed, friction moments from pressure and jamming load from sliding speed is considered. The tests were performed on a friction machine with a vertical axis of rotation of the spindle according to the “plane-ring” scheme when the friction pair was lubricated with MGE-10A hydraulic oil. The test loads and sliding speeds were changed stepwise. It has been found that with a decrease in the surface roughness of steel counter-tiles, the friction coefficients decrease when friction occurs on polymer composite materials. OST samples had the best indicators for reducing the coefficient of friction from the sliding speed and the moment of friction from pressure, followed by OT and oxafen samples. The bully resistance of OT samples is higher than that of OST and oxafene samples. Oxsofen samples had the highest resistance to abrasive wear by loose grain, followed by OST and OT samples.

Study of the resistance of plugs when piercing billets made of 20Kh13 steel on the MISIS-130D screw rolling mill

Study of the resistance of plugs when piercing billets made of 20Kh13 steel on the MISIS-130D screw rolling mill

Study of wear resistance of plugs when rolling 20Kh13 steel pipes

Study of wear resistance of plugs when rolling 20Kh13 steel pipes

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.

Influence of combined electromechanical processing modes of 40Kh steel on its structure and hardness

The paper considers the effect of combined electromechanical processing in three different modes on the structure and hardness of the surface layers of 40Kh steel, which was in a normalized state (the original structure). The modes differ from each other by the different applied load and the number of pulses. The applied load in modes 1 and 2 (current strength 39 kA, pulse time 0.02 s, number of pulses 1) is 100 and 250 MPa, respectively. A distinctive feature of mode 3 compared to mode 2 is a greater number of pulses (two). Metallographically it was established that in all three cases a hardened surface layer of different thickness (from 300 to 1200 μm) with a hardness of 593 – 598 HV is formed, consisting of two zones (a surface zone with a structure of fine-needle martensite; a transition zone smoothly transitioning into the initial ferrite structure). The transition zone (treatment according to mode 1) in its structure contains martensite and ferrite. The transition zone (mode 2 processing) consists of a Widemannstett structure. A more substantial surface heating zone according to this mode (700 μm) in comparison with the processing according to mode 1 (300 μm) in combination with intensive heat removal contributed to the formation of a Widmanstett structure, which is defective and unacceptable for operation. The transition zone with the processing according to mode 3 has the structure of martensite and ferrite. The formation of a defective Widmanstett structure in the transition zone does not occur, since 2 times more pulses are used during processing than in mode 2. This contributes to the heating of the surface layer to a greater depth (1200 μm), and, consequently, the structure formation in the transition zone occurs from the intercritical interval Ag3 – Ag1 .

Special Features of Structural Changes in Quenched Steel 40Kh Under Conditions of Friction Loading

Special Features of Structural Changes in Quenched Steel 40Kh Under Conditions of Friction Loading

Corrosion Cracking of 40Kh Steel with Oxygen Depolarization

Corrosion Cracking of 40Kh Steel with Oxygen Depolarization

ИССЛЕДОВАНИЕ И МОДЕЛИРОВАНИЕ ПРОЦЕССА ПЛАЗМЕННОЙ ЗАКАЛКИ СТАЛИ 40Х

In this paper, the results of research and modeling of the process of plasma hardening of specimens from steel 40Kh are presented. Using experimental data on the size of hardening zones within the framework of thermophysical modeling, the effective radius and efficiency of the plasma arc are determined. The simulation of plasma surface hardening was carried out depending on the speed and current of the plasma arc. Based on the analysis, nomograms are proposed for determining the depth and width of the hardening zone of steel 40Kh depending on the speed and current of the plasma arc. Thermal cycles are constructed in the steel heating zone. The cooling rates of the material are determined depending on the speed of movement and the depth of hardening in comparison with the critical rate of steel hardening.

Effect of the composition of multicomponent powders on the mechanical and tribotechnical properties of coatings obtained by laser additive technologies

The paper presents the results of metallographic studies and tribotechnical tests of samples of medium-carbon steel 34KhNi3MoA and coatings obtained by laser surfacing of a powder multicomponent charge based on iron and cobalt in a ratio of 3:1 with additives of nano particles of tantalum carbide. The samples were processed with a circular defocused beam and with transverse beam oscillations normal to the scanning speed. Comparative tests for friction and wear were carried out in a pair with a hardened 40Kh steel counterplate. The load and sliding speed during the tests varied discretely. Turbine oil TP 22C was used as a lubricant. It is shown that the introduction of additives of nano-tantalum carbide into the charge reduces friction losses, increases the wear resistance of coatings compared to the charge without carbides and the base material. The wear resistance of coatings with an increase in the amount of the hardening phase increases compared to the original steel. It has been established that the technology of laser surfacing with multicomponent coatings with nano particles of tantalum carbide can be used to restore worn surfaces of shaft necks, turbine blades, thrust discs, shut-off valves and other parts operating at high temperatures and in corrosive environments.

Evaluation of Internal Stresses in Modified Near-Surface Layer of 20Kh13 Steel during Incubation Period of Water Droplet Impact Erosion

This study investigates the change in internal stresses of ion nitrided and Cr–CrC ion-plasma-coated 20Kh13 steel samples during the incubation period of the droplet impact erosion. To obtain internal stress values, a method based on measuring the deformation (curvature) of the sample along the surface profiles before and after its modification/coating, as well as during the subsequent droplet impact has been applied. The results suggest that the initial droplet impact on the uncoated, nitrided and coated material leads to a sharp increase in the initial internal stress values. The rate of increase in internal stress decreases with the surface damage development and accumulation. The proposed method of stress evaluation can be used in selecting a criterion for comparing the erosion resistance of a material and a method for modifying its surface.

Study of Resistivity Distribution in Modified Surface Steel

This work focuses on making and studying steel conductors with inhomogeneous surface conductivity. Employing such materials (structures) for engineering the high-field pulsed magnets can provide them with enhanced durability. In this work, monotonically changing resistivity was realized by pack chromizing the medium-carbon steels, 30KhGSA and 40Kh, which were treated at 1000 °C in argon for 150 h under the Cr-load of 20 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to obtain a diffuse layer with minimal carbides at the surface. An approach to investigate the resistivity distribution across a diffuse layer after steel chromizing is suggested and involves a stepwise surface grinding, resistance measurement, and analytical processing of experimental data. The resistivity profile obtained by this method is well described by the complementary error function. At the near-surface layer, 30KhGSA and 40Kh steels have almost the same values of resistivity, about 110– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$115 ~\mu $ </tex-math></inline-formula> Ohm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm, which is 2.9–4.3 times higher than that in the bulk depending on steel. A strong correlation, almost a linear dependence, of resistivity with the depth-derived chromium concentration in the material was found. The proposed method allows one to measure the depth-varied resistivity for ferrous alloys with proper accuracy, while it does not require complex measuring equipment compared with other ones.

Microhardness and wear resistance of a high-entropy coating FeCrNiTiZrAl

In this article, the microhardness and wear resistance of the high-entropy FeCrNiTiZrAl alloy are studied on model specimens and on turbine blades made of 20Kh13 steel. The alloy was made by mechanical alloying and subsequent annealing in a vacuum furnace. The study showed that the obtained alloy is a high-entropy alloy with a microhardness μ = 740 HV, which is at the level of the microhardness of metallic glasses, but 2-3 times higher than the microhardness of stainless steels. The friction coefficient of the FeCrNiTiZrAl coating is k = 0.06, which is 10 times less than the friction coefficient of the titanium nitride coating (k = 0.65). The wear resistance of the high-entropy FeCrNiTiZrAl coating is much higher than that of stainless steels, and it leads to the fact that the cost of titanium nitride coating on turbine blades is 2 times higher than the cost of FeCrNiTiZrAl coating, that is, the economic effect is obvious.

Experimental Study of Material Structure in the Processing of Ball Pins

The article presents a technique for experimental studies of microstructure of microsections during rolling of ball pins made of 38KHGNM and 40KH steels. Moreover, photographing was carried out in the pole and equatorial parts of the ball pin head, as well as at the cross-cut end. When analyzing the photographs of microsections, it was concluded that after the final rotary rolling, deformation grinding of the grains occurred in the structure of ball pins.

A Comparison of the Effects of Ultrasonic Cavitation on the Surfaces of 45 and 40Kh Steels

The ultrasonic treatment of metal products in liquid is used mainly to remove various kinds of contaminants from surfaces. The effects of ultrasound not only separate and remove contaminants, they also significantly impact the physical–mechanical and geometric properties of the surfaces of products if there is enough time for treatment. The aim of this study was to compare the dynamics of ultrasonic cavitation effects on the surface properties of 45 (ASTM M1044; DIN C45; GB 45) and 40Kh (AISI 5140; DIN 41Cr4; GB 40Cr) structural steels. During the study, changes in the structure, roughness, sub-roughness, and microhardness values of these materials were observed. The results showed significant changes in the considered characteristics. It was found that the process of cavitation erosion involves at least 3 stages. In the first stage, the geometric properties of the surface slightly change with the accumulation of internal stresses and an increase in microhardness. The second stage is characterized by structure refinement, increased roughness and sub-microroughness, and the development of surface erosion. In the third stage, when a certain limiting state is reached, there are no noticeable changes in the surface properties. The lengths of these stages and the quantitative characteristics of erosion for the considered materials differ significantly. It was found that the time required to reach the limiting state was longer for carbon steel than for alloy steel. The results can be used to improve the cleaning process, as well as to form the required surface properties of structural steels.

Study of qualitative characteristics of surface layer of steels after electromechanical treatment with dynamic deformation

The results of studies of the qualitative characteristics of the hardened surface layer of normalized medium-carbon steels after electromechanical treatment with the dynamic application of the deformation force (electromechanical coinage EMC) are presented. The influence of the dynamic electromechanical treatment current density on the structure, microhardness, and thickness of the hardened surface layer has been established. An increase in current density during EMС leads to a significant increase in the depth of hardening, and an increase in the maximum hardness of steels 40Kh, 45, 50Kh. The results obtained can be used to establish the connection between the qualitative characteristics of the surface layer and the electromechanical coinage modes for a targeted effect on the structure of the treated surface.