Papers by Vasily Efremenko
Lubricants
Multicomponent and high-boron cast alloys have been recognized as materials with excellent wear r... more Multicomponent and high-boron cast alloys have been recognized as materials with excellent wear resistance due to the formation of hard phases called carbides and borides. However, the wear performance of the combination of these two materials called hybrid multicomponent cast alloys (HMCAs) has not been comprehensively studied. Therefore, this study will evaluate the effect of C (0–0.9 wt.%) and B (1.5–3.5 wt.%) addition on the erosion wear behavior of an HMCA containing 2.5 wt.% Ti, 10 wt.% Cr, and 5 wt.% each of V, Mo, and W. Shot-blast erosion testing was used to evaluate the wear resistance of each alloy. The test was conducted for 3600 s using 2 kg of irregularly shaped steel sand as a scraper at impact angles of 30°, 60°, and 90°. The results showed that the highest wear rate in 0C and 0.45C with 1.5–3.5% B occurred at an impact angle of 60° due to gouging and indentation mechanisms occurring simultaneously. However, different results occurred in the case of 0.9C with the sam...
Microstructure-Properties Characterization of Selective Laser Melted Biomedical Co-28Cr-6Mo Alloy
Materials Science Forum
Co-28Cr-6Mo alloy (ASTM F75) is widely used in different biomedical applications (dental devices,... more Co-28Cr-6Mo alloy (ASTM F75) is widely used in different biomedical applications (dental devices, orthopedic implants, etc.). Casting and metal forming are the two conventional technologies for the fabrication of this alloy. Recently, additive manufacturing has also been adopted. Due to the peculiarities of this technological process, 3D-printed alloys differ from traditionally manufactured alloys in their structure and properties. In the present work, the features of selective laser melted Co-28Cr-6Mo alloy were studied in comparison with its wrought analogue. The study included microstructural characterization (optical and electron scanning microscopy), nanoindentation, and tribological testing. It was shown that the SLM alloy featured the “fish-scale” structure, characteristic of additively fabricated alloys. This structure was composed of fine columnar dendrites. SLM Co-28Cr-6Mo was found equivalent or superior to the wrought alloy in terms of properties, such as hardness, elast...
Materials
This paper is devoted to the evaluation of the “three-body-abrasion” wear behaviour of (wt.%) 5W–... more This paper is devoted to the evaluation of the “three-body-abrasion” wear behaviour of (wt.%) 5W–5Mo–5V–10Cr-2.5Ti-Fe (balance) multi-component (C + B)-added alloys in the as-cast condition. The carbon (0.3 wt.%, 0.7 wt.%, 1.1 wt.%) and boron (1.5 wt.%, 2.5 wt.%, 3.5 wt.%) contents were selected using a full factorial (32) design method. The alloys had a near-eutectic (at 1.5 wt.% B) or hyper-eutectic (at 2.5–3.5 wt.% B) structure. The structural micro-constituents were (in different combinations): (a) (W, Mo, and V)-rich borocarbide M2(B,C)5 as the coarse primary prismatoids or as the fibres of a “Chinese-script” eutectic, (b) Ti-rich carboboride M(C,B) with a dispersed equiaxed shape, (c) Cr-rich carboboride M7(C,B)3 as the plates of a “rosette”-like eutectic, and (d) Fe-rich boroncementite (M3(C,B)) as the plates of “coarse-net” and ledeburite eutectics. The metallic matrix was ferrite (at 0.3–1.1 wt.% C and 1.5 wt.% B) and “ferrite + pearlite” or martensite (at 0.7–1.1 wt.% C an...
Influence of Boron Addition on Erosive Wear Characteristics of Multi-component Cast Steel
Journal of the Reports of the Japan Foundry Engineering Society Meeting, 2018
Metals
TRIP-assisted C-Si-Mn steels are usually subjected to austempering with a preliminary intercritic... more TRIP-assisted C-Si-Mn steels are usually subjected to austempering with a preliminary intercritical annealing that is targeted at the multi-phase structure with 40–60 vol.% of proeutectoid ferrite. The kinetics and the mechanism of phase-structural transformations can be impacted due to the additional alloying of TRIP-assisted steel by the strong carbide forming elements, thus necessitating an alternative approach for the selection of intercritical annealing parameters. This issue is analyzed in the present work, which investigates the effect of the temperature of intercritical annealing on the “Structure/Properties” correlations in 0.2 wt.% C-Si-Mn-Nb steel additionally alloyed by 0.55 wt.% Cr, 0.20% Mo, and 0.11 wt.% V. The annealing temperature ranged from 770 °C to 950 °C, and austempering was performed at 350 °C for 20 min. It was observed that the addition of the (Cr, Mo, and V) complex significantly improved the steel hardenability. However, the annealing of steel at 770 °C (...
Materials
The structural features and nanoindentation/tribological properties of 316 stainless steel fabric... more The structural features and nanoindentation/tribological properties of 316 stainless steel fabricated by conventional rolling and laser-based powder bed fusion (LPBF) were comparatively investigated regarding the effect of surface-pulsed plasma treatment (PPT). PPT was performed using an electrothermal axial plasma accelerator under a discharge voltage of 4.5 kV and a pulse duration of 1 ms. Optical microscopy, scanning electron microscopy, X-ray diffraction, nanoindentation measurements and tribological tests were applied to characterize the alloys. The LPBF steel presented almost the same modulus of elasticity and double the hardness of rolled steel. However, the LPBF steel manifested lower dry-sliding wear resistance compared with its wrought counterpart due to its porous structure and non-metallic inclusions. Conversely, LPBF steel showed three times higher wear resistance under sliding in simulated body fluid (SBF), as compared with wrought steel. PPT led to steel modification ...
Radiothermometric Measurements of Biological Objects Deep Temperature
2019 IEEE 39th International Conference on Electronics and Nanotechnology (ELNANO)
The new approach for measuring deep temperature of human body is proposed based on radio-thermome... more The new approach for measuring deep temperature of human body is proposed based on radio-thermometry. The novel design of radio-thermometer is developed and described containing microstrip antennas as an radio-thermometer applicator/receiver with significantly reduced coefficient of standing waves. The high efficiency of radio-thermometer is clinically proved for diagnostic of inflammatory processes in human body.
Computer Modeling and Intelligent Systems
The article outlines the theoretical and practical aspects of the development of new approaches f... more The article outlines the theoretical and practical aspects of the development of new approaches for improving the effectiveness of health care based on information computational technologies. A medical information system for the process of rehabilitation and rehabilitation of post-stroke patients was designed and implemented, based on structuring each of the levels according by relevant criteria, which allows to take into account the effect of endogenous and exogenous risks of patients' therapy in residual period.
Kovove Materialy-Metallic Materials
The structure and mechanical properties of two 0.2 wt.% C TRIP-assisted steels (Transformation In... more The structure and mechanical properties of two 0.2 wt.% C TRIP-assisted steels (Transformation Induced Plasticity) were compared to evaluate the effect of additional (Cr, Mo, V)-alloying on transformation kinetic and tensile/impact behavior after isothermal bainite transformation (bainitizing) and Q&P (Quenching-and-Partitioning) treatment. The work was performed using SEM, XRD, tensile/impact testing, and computer simulation. It was found that adding 0.55 wt.% Cr, 0.2 wt.% Mo, and 0.11 wt.% V into Mn-Si-Nb steel increased the incubation time in pearlite and bainite temperature ranges by 5.6 and 4.4 times, respectively. More heavily alloyed steel performed an improved combination "Strength/Ductility/Impact Toughness": its maximum PSE (Product of Strength and Elongation) value of 24 GPa• % referred to bainitizing treatment, whereas the highest KCV 20 • C values (220-225 J cm −2) corresponded to Q&P treatment. Improved mechanical properties of (Cr, Mo, V)-alloyed steel were attributed to a higher amount of retained austenite and a slower rate of TRIP-effect.
Three-body abrasive wear behaviour of metastable spheroidal carbide cast irons with different chromium contents
International Journal of Materials Research, 2018
The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of sph... more The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of spheroidal carbide cast iron (9.5 wt.% V) was studied using optical and scanning electron microscopy, X-ray diffractometry, dilatometry and three-body abrasive testing. It was found that quenching from 760 °C and 920 °C improved the alloys’ wear resistance compared to the as-cast state due to the formation of metastable austenite transforming into martensite under abrasion. The wear characteristics of alloys studied are 1.6 – 2.3 times higher than that of reference cast iron (12 wt.% V) having stable austenitic matrix. Chromium addition decreases surface damage due to the formation of M 7C3 carbides, while it reduces wear resistance owing to austenite stabilization to abrasion-induced martensite transformation. The superposition of these factors results in decreasing the alloys’ wear behaviour with chromium content increase.
Zur Festigkeit niedriglegierter Stähle mit erhöhtem Kohlenstoffgehalt gegen abrasiven Verschleiß (Abrasive wear resistance of high-carbon low-alloy steels)
Tribologie und Schmierungstechnik
A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial s... more A comparative study of abrasive wear resistance of a thermomechanically strengthened commercial steel and a new 120Mn3 steel was performed. It could be demonstrated, that wear resistance of the proposed 120Mn3 steel is 2 to 5 times higher than that of the commercial steel. This improvement results from formation of martensite at the contact surface induced by plastical deformation during contact of abrasive particles for the case that the steel has been thermically treated to be in metastable austenite structure state by quenching from high temperatures. After wear testing the hardness of the contact surface increased up to 1200-1250 HV. Usage of the proposed material in bulk or as surface welded or surface heat treated layers in different machine parts working under abrasive
Key Engineering Materials, 2020
The present article is aimed at studying the austenite transformation kinetics and tensile proper... more The present article is aimed at studying the austenite transformation kinetics and tensile properties of constructional 0.2 wt%C-Si2Mn2CrMoVNb TRIP-assisted steel subjected to isothermal holding in the subcritical temperature range (350-650 °C with the step of 50 °C) after intercritical annealing at 770 °C. The study was fulfilled using optical microscopy (OLYMPUS GX-71), electron scanning microscopy (JEOL JSM-), dilatometric analysis, tensile testing, Vickers hardness measurements. The critical temperatures of the steel were found to be Ac1=750-760 °C and Ac3=930 °C. The results showed that austenite demonstrated increased stability to pearlite and bainite transformations with an incubation period of decades of seconds at any of the mentioned temperatures. The bainitizing treatment at 400 °C with holding of 300-600 s resulted in ferrite/bainite/retained austenite structure with precipitates of nanosized carbide (V,Nb)C providing an improved combination of mechanical properties as c...
Metals, 2022
The deposition of a thin (several tens of microns) protective coating in atmospheric conditions i... more The deposition of a thin (several tens of microns) protective coating in atmospheric conditions is a challenging task for surface engineering. The structural features and tribological properties of a particle-reinforced metal matrix composite coating synthesized on middle-carbon steel by air pulse-plasma treatments were studied in the present work. The 24–31 µm thick coating of “24 vol.% (TiC + WC)/Hardened steel matrix” was produced by 10 plasma pulses generated by an electro-thermal axial plasma accelerator equipped with a consumable cathode of novel design (low-carbon steel tube filled with “TiC/WC + Epoxy resin” mixture). The study included optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD, microhardness measurements, and dry “Ball-on-Plate” testing. The carbides were directly plasma-transferred to the substrate (steel of AISI 4145H grade) from the cathode without substantial melting. The hard (500–104...
Abstract. High-carbon low-alloyed steels are promising materials to increase abrasive wear resist... more Abstract. High-carbon low-alloyed steels are promising materials to increase abrasive wear resistance of machine parts working under severe wear caused by hard particles. These steels being quenched from 900-1000 oC possess mostly retained austenite structure which is capable to transform to martensite in the course of abrasive wear. The isothermal holding is known to serve as very beneficial yet long operation which provides bainite transformation with significant improvement of mechanical properties. The goal of present work was to investigate the changes in microstructure on very beginning of isothermal holding. Samples of high-carbon low-alloyed steel (1,21 % C; 2,56 % Mn; 1,59 % Si mass.) were quenched from 900 оС to obtain in microstructure mostly residual austenite and minor quantity of martensite. Isotermal holdings at 250 oC and time frame from 1 to 12 hrs were made to initiate bainite transformation and investigate the accompanying changes of microstructure. The first inve...
Optimal Parameters of Q Heat Treatment for High-Si Steels Found by Modeling Based on “Constrained Paraequilibrium” Concept
Lecture Notes in Mechanical Engineering
The article is dedicated to designing the regime of Q&P (Quenching and Partitioning) heat tre... more The article is dedicated to designing the regime of Q&P (Quenching and Partitioning) heat treatment for middle-carbon high-silicon steels 60Si2CrVA and 55Si3Mn2CrVMoNbA in order to improve their mechanical properties. The temperature of suspense of quenching cooling during Q&P treatment was calculated by modeling based on the concept of “Constrained Paraequilibrium” proposed by J. Speer. The values of Ms temperature as well as the kinetics of martensitic transformation for both steels were experimentally found to be incorporated into the model. It was derived from the modeling that quenching stage should be finished when reaching the steel temperature within the range of 150–220 °C which guarantees the highest volume fraction of retained austenite in the microstructure (together with tempered martensite). The results of calculations were verified by XRD measurements of retained austenite in Q&P treated specimens being found as 17 vol% for steel 60Si2CrVA and 28.5 vol% for steel 55Si3Mn2CrVMoNbA which are lower then predicted values. The probable reasons of this discrepancy are outlined.
High-chromium cast irons containing high amount of chromium (12-20 % Cr) are widely used in indus... more High-chromium cast irons containing high amount of chromium (12-20 % Cr) are widely used in industry as tribological materials, operating under abrasive, impact-abrasive, erosive and adhesive wear. The effectiveness of the application of high-Cr cast irons is largely dependent on the method of hardening treatments. The bulk heat treatment is traditionally offered for these alloys. Surface treatment using concentrated heat sources is almost not applied for strengthening of high-Cr cast iron, so this treatment remains as an important reserve in improving of their wear resistance. In this work the plasma jet heating was used to improve the wear resistance of 15%Cr-Mn-Ni-V-Ti cast iron. The plasmotron of indirect action with Ar-plasma gas and W-electrode was applied. We varied the initial structural condition of cast iron and the regimes of plasma processing. The initial structural conditions were: as-cast, quenched and tempered (200 o C or 700 o C), annealed (650 o C, 6 hours). The pla...
The present paper is aimed at the study of the kinetics of Mn, Si, Cr partitioning in 0.2wt%C-Si2... more The present paper is aimed at the study of the kinetics of Mn, Si, Cr partitioning in 0.2wt%C-Si2Mn2CrMoVNb TRIP-assisted steel under the annealing at 770 oC and 830 oC to be within the intercritical temperature range. The work was fulfilled using SEM, EDX, dilatometry, and hardness measurements. It was found that under heating a redistribution of the alloying elements between ferrite and austenite took place. Specifically, silicon partitioned to ferrite while chromium diffused to austenite with distribution coefficient values of 1.12-1.21 (KSi) and 0.75-0.86 (KCr). Manganese was found to partition to a much greater extent resulting in a distribution coefficient of KMn=0.38-0.50 and 2.6 times higher concentration in austenite as compared to ferrite. As annealing temperature raised from 770 oC to 830 oC the elemental partitioning was accelerated, followed by the decrease in manganese content in austenite (by 1.44 time) and ferrite (by 1.34 time) caused by an increase in austenite vol...
Materials
A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenchi... more A high-carbon, high-silicon steel (1.21 wt% C, 2.56 wt% Mn, 1.59 wt% Si) was subjected to quenching from 900 and 1000 °C, resulting in microstructures containing 60 and 94% of retained austenite, respectively. Subsequent abrasive wear tests of quenched samples were performed using two-body abrasion and three-body abrasion testing machines. Investigations on worn surface and subsurface were carried out using SEM, XRD, and microhardness measurement. It was found that the highest microhardness of worn surface (about 1400 HV0.05) was achieved on samples quenched from 900 °C after three-body abrasion. Microhardness of samples after two-body abrasion was noticeably smaller. with a maximum of about 1200 HV0.05. This difference correlates with microstructure investigations along with XRD results. Three-body abrasion has produced a significantly deeper deformed layer; corresponding diffractograms show bigger values of the full width at half maximum parameter (FWHM) for both α and γ alone sta...
Materials
The structural and tribological properties of a protective high-chromium coating synthesized on g... more The structural and tribological properties of a protective high-chromium coating synthesized on gray cast iron by air pulse-plasma treatments were investigated. The coating was fabricated in an electrothermal axial plasma accelerator equipped with an expandable cathode made of white cast iron (2.3 wt.% C–27.4 wt.% Cr–3.1 wt.% Mn). Optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, microhardness measurements, and tribological tests were conducted for coating characterizations. It was found that after ten plasma pulses (under a discharge voltage of 4 kV) and post-plasma heat treatment (two hours of holding at 950 °C and oil-quenching), a coating (thickness = 210–250 µm) consisting of 48 vol.% Cr-rich carbides (M7C3, M3C), 48 vol.% martensite, and 4 vol.% retained austenite was formed. The microhardness of the coating ranged between 980 and 1180 HV. The above processes caused a gradient in alloying elements in the coating and t...
Materials
The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carb... more The purpose of the research was to obtain an arc welded joint of a preliminary quenched high-carbon wear resistant steel without losing the structure that is previously obtained by heat treatment. 120Mn3Si2 steel was chosen for experiments due to its good resistance to mechanical wear. The fast cooling of welding joints in water was carried out right after welding. The major conclusion is that the soft austenitic layer appears in the vicinity of the fusion line as a result of the fast cooling of the welding joint. The microstructure of the heat affected zone of quenched 120Mn3Si2 steel after welding with rapid cooling in water consists of several subzones. The first one is a purely austenitic subzone, followed by austenite + martensite microstructure, and finally, an almost fully martensitic subzone. The rest of the heat affected zone is tempered material that is heated during welding below A1 critical temperature. ISO 4136 tensile tests were carried out for the welded joints of 120...
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Papers by Vasily Efremenko