Vol 27, No 2 (2025)
TECHNOLOGY
Comparison of Ultrasonic Surface Treatment Methods Applied to Additively Manufactured Ti-6Al-4V Alloy
Abstract
Introduction. Selective Laser Melting (SLM) of metal powders enables the fabrication of parts with arbitrary geometries, which is unattainable through conventional manufacturing technologies. The main disadvantages of the method include high surface roughness, resulting from metal spattering, spheroidization, partial melting and powder adhesion, as well as difficulties with finishing complex surface areas. One effective approach for processing such parts is the application of ultrasonic liquid technologies, where cavitation bubbles act as working bodies, penetrating and performing work on any area of the surface. The purpose of this study is to determine the influence of different types of ultrasonic treatment on the surface properties obtained by selective laser melting through comparative testing. Materials and methods. Samples made from Ti-6Al-4V titanium alloy, manufactured using selective laser melting on an EOS M280 machine, were investigated. For ultrasonic treatment, a rod-shaped magnetostrictive vibratory system was used, with the end of the emitter positioned 20 mm from the side surface of the sample. A etching solution (3% HF + 5% HNO3 + H2O) was used as a liquid medium to remove the oxide film that hinders the effect of cavitation. Cavitation-erosion (CET) treatment, cavitation-abrasive (CAT) treatment, and additionally, ultrasonic surface plastic deformation (USPD) were performed. After treatment, the surface condition, roughness, and sub-microgeometry were assessed for all samples. The microstructure of the USPD-treated samples was also investigated. Results and discussion. A high-speed imaging method was used to compare the main mechanisms of interaction with the surface during CET and CAT. During CET, collapsing and pulsating cavitation clusters are observed, located at the points of highest peaks and valleys on the surface. During CAT, the micro-cutting action of abrasive particles is added. These particles receive shock waves generated by collapsing bubbles, hit the surface, and undergo oscillatory, rotational, and longitudinal movements. Comparison of the surface condition dynamics revealed that CET enables complete removal of surface defects down to the melt tracks. CAT removes some surface defects while deforming the remaining ones. During USPD, spherical defects are crushed, forming large flat areas. All types of ultrasonic treatment reduce surface roughness: Ra is reduced by 33% during CET, by 43% during CAT, and by 52% during USPD. However, Rmax is lowest with CAT. The microstructure after USPD is characterized by a hardened layer with a depth of approximately 100 µm and an increase in microhardness up to 35%. However, after USPD, defects in the form of cracks, partially deformed spheres, and the presence of untreated deep surface depressions are formed in the surface layer, which significantly reduces performance characteristics. Therefore, it is advisable to perform CET or CAT before USPD to remove surface defects.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):6-28
6-28
A comparative evaluation of friction and wear in alternative materials for brake friction composites
Abstract
Introduction: this study examines research and development efforts aimed at developing non-asbestos brake friction composites (BFCs) to improve the safety and performance of automotive brake systems. The evolution of BFCs from asbestos-based materials to safer alternatives is studied, and an analysis is performed to develop alternative material combinations. The critical roles of key components — fibers, binders, friction modifiers and fillers — in creating durable brake friction composites for brake systems is emphasized. A composite material based on basalt fiber with calcium carbonate filler is compared to a composite material based on aramid fiber with barium sulfate filler through pin-on-disc tribological testing. Based on the test results, it is determined that the alternative composite materials show promise for application in brake systems. This work also provides a foundation for further development of eco-friendly brake friction composites by selecting optimal formulations. The present work defines an approach for subsequent research aimed at varying the components and their ratios in the creation of composite materials. This research will further improve the functionality of automotive brake systems. Purpose of the work: this research is focused on the development of non-asbestos brake friction composites (BFCs) with the goal of improving the safety and performance of automotive brake systems. Eco-friendly alternatives to asbestos are investigated, and the roles of fibers, binders, friction modifiers, and fillers are analyzed. The objective of the research is to identify optimal formulations for creating durable, sustainable brake materials, paving the way for further implementation of innovative solutions in practice. Methods of investigation: a pin-on-disc tribological method is used to evaluate wear, friction, and durability, as well as to assess the suitability of the developed materials for use in brake systems. This research is dedicated to analyzing the influence of components (fibers, binders, friction modifiers, and fillers) on the properties of friction composites for brake systems. Two compositions were experimentally studied: basalt fiber with calcium carbonate and aramid fiber with barium sulfate. Results and discussion: the results of the research demonstrate the effectiveness of using basalt fiber with calcium carbonate and aramid fiber with barium sulfate as components in friction composites for brake systems. It is shown that these materials provide high levels of wear resistance and friction performance. The potential for further optimization of compositions to improve eco-friendliness and enhance the operational properties of braking systems is emphasized. The obtained results also highlight the importance of component selection for the development of safe and sustainable brake friction composites.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):29-42
29-42
Microstructure and mechanical properties of Ti2AlNb-based alloy weld joints as a function of gas tungsten arc welding parameters
Abstract
Introduction. Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is a promising welding method for Ti2AlNb-based alloys, including Ti–Al–Nb–(Zr, Mo)–Si alloy, due to its accessibility and relative simplicity, making it attractive for aerospace applications. However, the application of GTAW to Ti–Al–Nb–(Zr, Mo)–Si alloy is limited by the formation of a coarse-grained microstructure in the weld, leading to reduced mechanical properties of weld joints. Purpose of the work. This study investigates the influence of GTAW modes (using direct current with low- and high-frequency pulses) on the microstructure and tensile properties of Al–Nb–(Zr, Mo)–Si alloy weld joints. Methods. GTAW of plates was carried out using welding currents ranging from 80 to 150 A, employing both low- and high-frequency (>100 Hz) pulses. The microstructure of the weld joints was examined using scanning electron microscopy (SEM). The tensile properties were evaluated through uniaxial tensile testing of the welded joints. The shielding gas flow rate was 12 L/min, while a separate gas flow of 2 L/min was used for blowing. The microstructure of the weld joints was examined using scanning electron microscopy (BSE-EBSD analysis). The tensile properties were evaluated through uniaxial tensile testing of the weld joints. Results and discussion. The weld joints microstructure is characterized by elongated, coarse dendrites in the central and weld bead regions and globular β-grains in the root part of the fusion zone. Tensile testing of the weld joints revealed a strength level approximately 90% of that of the base metal when using pulse mode (σu = 1100 MPa, δ = 1.1 %, 335–390 HV0.2) and not less than 80% when using direct current modes. This level of mechanical properties is achieved using high-frequency pulsed welding, where the maximum length and width of dendrites in the weld joint are 1.06 mm and 0.33 mm, respectively, and the average size of globular grains in the lower part of the weld joint is approximately 130 μm, which is less than that observed when utilizing the same modes, but direct current.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):43-56
43-56
Enhancement of EDM performance for NiTi, NiCu, and BeCu alloys using a multi-criteria approach based on utility function
Abstract
Introduction: Machining hard materials and shape memory alloys (SMAs), such as NiTi, NiCu, and BeCu, using conventional techniques is challenging due to excessive tool wear and poor surface finish. Non-conventional machining methods, particularly electrical discharge machining (EDM), offer improved precision and surface quality. However, the effectiveness of EDM is contingent upon the optimization of process parameters. The purpose of this study is to optimize EDM parameters to enhance the machining performance of SMAs by considering factors such as pulse-on time, pulse-off time, discharge current, gap voltage, and workpiece electrical conductivity. Methods. In this study, the Taguchi experimental design approach was employed to analyze the influence of key process parameters on the material removal rate (MRR), surface roughness (SR), and tool wear rate (TWR). Analysis of variance (ANOVA) was then applied to identify the most statistically significant factors affecting machining performance. A multi-objective optimization method, based on utility theory, was utilized to determine the optimal EDM settings that balance MRR, SR, and TWR. The results were validated through experimental trials. Results and Discussion. The experimental results indicated that Trial 15 achieved the highest MRR of 9.076 mm³/min, while Trial 1 produced the lowest SR of 2.238 µm. The minimum TWR of 0.041 mm³/min was observed in Trial 10, which contributes to increased tool lifespan. ANOVA revealed that gap voltage was the most influential factor, accounting for 85.98% of the variation in machining performance, followed by discharge current (4.76%) and pulse-off time (2.59%). The multi-objective optimization process successfully identified parameter configurations that optimize MRR while minimizing SR and TWR. The prediction model developed in this study demonstrated high accuracy, with an R² value of 93.3% and an adjusted R² of 89.7%. Validation experiments confirmed the effectiveness of the optimized parameters, resulting in an average MRR of 8.852 mm³/min, SR of 2.818 µm, and TWR of 0.148 mm³/min. The findings presented herein confirm that careful optimization of EDM parameters significantly enhances the machining performance of SMAs, considerably improving machining efficiency and tool longevity.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):57-88
57-88
Ensuring hole shape accuracy in finish machining using boring
Abstract
Introduction. In modern manufacturing, hole processing is one of the more labor-intensive operations. The presence of a large number of body parts with high-precision holes, which are subject stringent accuracy requirements regarding parameters such as size, shape and axis location, contributes to the complexity of their machining. Achieving these accuracy specifications often requires a diverse range of tools and multipurpose machining. Currently, there are numerous methods for hole processing, and boring is a key one for achieving high levels of accuracy. However, despite the many advantages of this method in achieving diametrical size accuracy, the shape deviation of the resulting holes has not been sufficiently investigated. The subject. The paper analyzes the main technological parameters of the hole boring process, and establishes their relationship with hole shape indicators, such as deviation from roundness and cylindricity. The study includes the development of an approach to predict error magnitude, considering the kinematics and dynamics of the machining process. The purpose of the work is to predict the radial displacement of the tool axis and to develop methods for ensuring the accuracy of the hole shape in finishing operations using boring. The main tasks of the present study involve establishing dependencies between technological processing parameters and the values of deviations from roundness and cylindricity, as well as determining the magnitude of the radial displacement of the tool to enable error magnitude prediction. Method and methodology. Methods for measuring deviations from roundness and cylindricity are considered, and their advantages and disadvantages are presented. Special attention is given to determining the influence of key factors during machining using frequency analysis method, which allows for evaluation the quality and reliability of the measurements performed. The hardware used for the experimental studies, along with the selected materials and processing modes, is described. Results and discussion. This paper examines the main factors affecting the accuracy of the hole shape obtained by boring. The application of the developed algorithms and models enables engineers to select optimal processing parameters based on the specified functional accuracy requirements of the hole, thereby ensuring the required shape accuracy.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):89-102
89-102
EQUIPMENT. INSTRUMENTS
Experimental investigation of graphene oxide-based nano cutting fluid in drilling of aluminum matrix composite reinforced with SiC particles under nano-MQL conditions
Abstract
Introduction. Minimum Quantity Lubrication (MQL) is effectively employed as suitable cooling strategy. However, compared to flood cooling, which is widely used in the industry, MQL is characterized by a lower heat dissipation capacity. While thermal shock is reported in flood cooling, the use of MQL ensures a smoother chip removal and reduces the risk of thermal stress. Research methods. Within the scope of this study, experimental investigations were carried out on drilling of aluminum matrix composite (MMC) reinforced with silicon carbide (Al-SiC MMC) using AlCrN PVD-coated drills (drill diameter 8 mm). MMC samples were manufactured with varying volume fractions of SiC (10–30%). The aim of the experiments was to study the influence of non-edible vegetable oil with the addition of graphene oxide (used as a cutting fluid) on the drilling process of AlSiC MMC. The cutting speed (30–150 m/min), feed rate (0.05–0.25 mm/rev), volume fraction of SiC (10–30%), and MQL flow rate (60–180 ml/h) were selected as input process parameters. Their response parameters were cutting force, torque, surface roughness, hole circularity, and burr height during high-speed drilling of MMC. The undi (Calophyllum inophyllum) oil parameters were determined in accordance with the ASTM 6751 standard. The surface morphology and elemental analysis of graphene oxide were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX). The purpose of the work. The use of nano-cutting fluid in combination with MQL is one of the promising approaches for further improving the characteristics of MQL, especially when drilling difficult-to-machine materials. The introduction of nanomaterials into MQL contributes to reducing friction at the tool-chip interface, which leads to a decrease in cutting temperature. These methods facilitate the machining of lightweight and difficult-to-machine materials, in particular, aluminum-based metal matrix composites (MMCs), which are widely used in the automotive and aerospace industries. Results and Discussion. It was found that the use of graphene oxide nanoparticles dispersed in non-edible undi (Calophyllum inophyllum) oil represents a promising alternative to traditional cutting fluids in drilling MMC. The aim of the study was to develop semi-empirical models for predicting surface roughness and temperature for various compositions of MMC. Increased cutting efficiency is achieved by precisely determining the temperature in the machining zone. However, the practical determination of the cutting temperature in each specific case involves significant labor and financial costs. It was additionally found that graphene oxide nanoparticles mixed with non-edible undi (Calophyllum inophyllum) oil represent an effective alternative to traditional cutting fluids in drilling MMCs. The present work develops a comprehensive empirical formula for predicting the theoretical temperature and surface roughness. It was found that the majority of the power input into the machining process is transformed into thermal energy.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):103-125
103-125
Prediction of surface roughness in milling with a ball end tool using an artificial neural network
Abstract
Introduction. Milling stainless steel with a ball-end tool is a complex technological process that requires precise control of processing parameters to ensure high surface quality. In this regard, it is an urgent task to develop methods for predicting roughness parameters, such as Rz. The aim of this work is to develop a predictive neural network model that can estimate surface roughness when milling stainless steel using a ball-end tool. Method and methodology. The main focus is on error backpropagation and gradient descent methods, as well as hyperparameter tuning, which are necessary to prevent overfitting and underfitting of the model. Experimental studies include the analysis of both controlled variables, such as feed per tooth, angle of inclination and diameter of the tool, and uncontrolled, including coolant supply and tool wear. Results and discussions. The use of coolant for milling austenitic steel has reduced the roughness parameters Rz by an average of 14%. A strong negative correlation has been established between the dimensional wear of the tool and the parameter Rz (−0.95). At the same time, wear in the range of 2…4 μm affects an increase in the Rz parameter by 21% compared to the minimum values. The data obtained were used to train eight configurations of artificial neural networks, which were used to predict roughness using the Rz parameter. The results show that the 3-16-16-1 network configuration showed the lowest MSE (0.0313), followed by 3-20-14-1 (0.0470) and 3-64-64-1 (0.0481), respectively. In addition, these configurations also demonstrated the lowest average absolute error values, which demonstrate the average of the absolute differences between predicted and observed values (0.1014; 0.1251 and 0.1155, respectively), and the coefficient of determination, which is a statistical measure indicating the proportion of data variability explained by the model (0.9944; 0.9916; 0.9904). A comparison of the experimental data with the predictions of various models allowed us to determine the average value of the absolute differences for the models according to the parameter Ra ≈ 0.074. The study suggests approaches to training neural network models for accurate prediction of roughness parameters, which makes a significant contribution to the methods of modeling machining processes.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):126-141
126-141
Manufacturing conditions of bimetallic samples based on iron and copper alloys by wire-feed electron beam additive manufacturing
Abstract
Introduction. Wire-feed electron beam additive manufacturing (EBAM) is a promising production technology, offering unprecedented control over interface design in composite materials, which is challenging to achieve using conventional methods. The ability to control localized metallurgical processes within the melt pool is a key advantage of EBAM technology. This study investigates the influence of key EBAM parameters (wire feed configuration, scanning strategies, and linear energy input) on achieving diverse interface designs in bimetallic samples composed of copper and iron-based alloys. Establishing the relationship between microstructure evolution and 3D printing parameters is of great importance for the development of EBAM. The purpose of this study is to elucidate the effects of fundamental EBAM process parameters (beam current, wire feed rate, heat input, scanning strategy, and intrinsic material properties) on the fabrication of high-quality copper-iron bimetallic samples exhibiting both sharp and smooth interfaces, as well as heterogeneous material distributions. Research Methods. This study heavily emphasizes experimental investigations to optimize the EBAM process. Bimetallic samples featuring sharp interfaces, smooth interfaces, and heterogeneous microstructures, based on copper and iron alloys, were fabricated using wire-feed EBAM. The study analyzed the values of heat input depending on the layer being deposited; the wire feed rate depending on the material used, and the types of printing strategies depending on the ratio of dissimilar materials in bimetallic samples. A Pentax K-3 digital camera, equipped with a 100 mm focal length lens, was employed for high-resolution visual inspection and quality assessment of the fabricated bimetallic samples with varying interface designs. Results and discussion. Based on an in-depth understanding of the factors governing electron beam-material interactions, this work systematically details the potential for creating components with controlled sharp or smooth interfaces, as well as heterogeneous material architectures. Furthermore, the study briefly outlines process control methodologies aimed at minimizing defects, considering factors influencing melt pool dynamics, including the precise regulation of thermal conditions during 3D printing process. A fixed heat input was prescribed for each material to achieve a sharp interface morphology: specifically, 0.09 kJ/mm for the deposition of M1 copper layers, which is 2.5 times lower than the heat input used for depositing Cu-9 Al-2 Mn copper alloy layers. Similarly, a heat input of 0.17 kJ/mm was used for 0.12 C-18 Cr-9 Ni-Ti stainless steel layers, which is 1.5 times lower than that for 0.09 C-2 Mn-Si steel alloy layers. In contrast, the fabrication of smooth interfaces relied on dynamically adjusting the heat input and wire feed rates as a function of the layer being deposited and the target composition. The formation of heterogeneous structures required the use of tailored scanning strategies during EBAM, depending on the volume fraction of dissimilar alloys deposited via the wire feedstock. The successful fabrication of defect-free copper-iron bimetallic samples was achieved through careful control of the EBAM process.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):142-158
142-158
Performance of Y-TZP-Al2O3 composite ceramics in dry high-speed turning of thermally hardened steel 0.4 C-Cr (AISI 5135)
Abstract
Introduction. Analysis of contemporary data in the fields of materials science and the application of ceramic cutting tools for machining difficult-to-machine iron- and nickel-based alloys reveals a limited amount of experimental data concerning the use of the promising Y-TZP-Al2O3 ceramic, which is based on submicron yttria-partially-stabilized zirconia and reinforced with alumina. Purpose of the work. To study the performance of RNGN 120400-01 removable cutting inserts made from Y-TZP-A12O3 ceramic during dry high-speed (200 m/min) cutting of 0.4 C-Cr (AISI 5135) steel (HRC 43…48). Research Methods. Characterization of the initial powders and the sintered ceramic, both before and after cutting tests, was performed using X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses, as well as scanning electron microscopy (SEM) in BSE mode. The physical and mechanical properties of the sintered ceramic were determined using the hydrostatic weighing method, three-point bending, and Vickers microhardness and fracture toughness measurements. Cutting tests were conducted on a high-rigidity lathe in a production shop conditions, involving dry high-speed turning of hardened 0.4C-Cr steel (AISI 5153) (HRC 43…48) in two stages. The first stage involved establishing the allowable variation limits for cutting modes (cutting speed and feed rate) and investigating the wear and failure characteristics of the cutting insert rake and flank faces. The second stage utilized ceramic cutting inserts with a chamfered cutting edge. Results and discussion. It was established that for Y-TZP-A12O3 ceramic, the use of cutting modes V > 200 m/min, S > 0.4 mm/rev, and t > 0.2 mm is not advisable due to the short service life of the cutting edge. A chamfer on the cutting edge is necessary to provide controlled edge blunting. The observed wear patterns and analysis of failure areas indicate a dominant brittle fatigue failure mechanism, caused by the thermal effects of high-speed friction combined with tangential stresses from the chip flow. It is concluded that the Y-TZP-Al2O3 ceramic composite is promising for use as a cutting tool material for dry high-speed turning of both hardened steels and, potentially, wear-resistant cast irons. Based on the conducted research and described observations, recommendations are formulated for the use of Y-TZP-Al2O3 ceramic in future studies.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):159-173
159-173
MATERIAL SCIENCE
Morphological changes of deformed structural steel surface in corrosive environment
Abstract
Introduction. Internal factors, including phase heterogeneity, crystallographic texture, residual stress amplitude and the concentration of non-metallic inclusions, exert a nonlinear, multi-parametric effect on the corrosion resistance of metallic systems in aggressive environments. This complex interaction significantly complicates the prediction of corrosion degradation kinetics and the assessment of the operational life of metal structures. These parameters modulate the spatial distribution of corrosion defects, their morphology and penetration depth, necessitating a systematic approach to establish quantitative correlations. To gain a more accurate understanding and account for the influence of internal factors on the corrosion process, comprehensive research and analysis are required. The use of mathematical processing methods in the analysis of influence will reveal stronger regularities applicable to the process of corrosion damage. This will enable the development of methods and approaches for optimizing the design, production and operation of metal structures and products, as well as improving their reliability and durability. Purpose of work is to develop a multi-criteria model linking the depth of corrosion damage (an integral indicator of environmental aggressiveness) with microstructural, mechanical, and topographic characteristics of low-carbon steel St3. The objects of the study are samples from rolled sheet metal with varying degrees of residual plastic deformation (ε = 0–7%). Methods of investigation. Grain size, texture, and dislocation density were assessed through microstructural analysis using optical microscopy (Olympus GX53) and scanning electron microscopy (JEOL 6008A). Quantitative morphometry of corrosion damage was performed using digital image analysis (AXALIT software), with median depth determined as a key parameter. X-ray diffraction analysis of residual stresses was implemented to construct tensor stress fields. Results and discussion. Experimental data demonstrates a non-linear increase of the median depth of corrosion damage with the degree of deformation: at ε = 6.6%, a twofold increase in the median depth is observed compared to the undeformed state. Multivariate regression analysis revealed the dominant influence of internal residual stresses on the kinetics of the corrosion damage process (R² = 0.89). The scatter of the determined values for internal stresses is ±5 μm. The observed regularities are associated with the behavior of the material structure during plastic deformation, which occurs most significantly in the {111} <110> directions, leading to the generation of reverse residual stresses. The median depth of corrosion damage reflects the rate of corrosion. The group method of data handling (GMDH) allowed for the synthesis a complex parameter combining various parameters of steel structure. Polynomial approximation of the dependence of the median depth of corrosion damage in 5% HCl on the complex parameter shows high convergence (R² = 0.99) with a determination error of ±1 μm. The developed model confirms that residual stresses are one of the key factors modulating the corrosion activity of deformed St3 steel. The results obtained allow for the optimization of cold treatment of steel to increase the corrosion resistance of metal structures. Further studies are planned to focus on the influence of dynamic loads and temperature gradients on the evolution of dislocation substructures.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):174-188
174-188
Effect of heterogeneous structure on mechanical behavior of austenitic stainless steel subjected to novel thermomechanical processing
Abstract
Introduction. The low yield strength of austenitic stainless steels is a factor significantly limiting their industrial applications. In turn, the formation of a heterogeneous structure is a promising method for achieving a synergy of mechanical properties. At the same time, an effective way to obtain a bulk heterogeneous structure is cold radial forging. However, the underlying mechanisms for the improved mechanical properties of materials with a heterogeneous structure formed in the process of cold radial forging are currently poorly understood. Purpose of the work is to investigate the effect of a heterogeneous structure obtained by deformation and heat treatment on the mechanical properties of austenitic stainless steel 0.08 C-17 Cr-13 Ni-2 Mn-Ti. Methods. Uniaxial tensile tests were performed on specimens obtained by cold radial forging followed by heat treatment at 600–700°C, using an Instron 5882 testing machine at room temperature with a strain rate of 1.15 × 10–3 s–1. A VIC-3D visual inspection system was used to measure elongation during testing. The fine structure was examined on perforated foils with a diameter of 3 mm using a JEOL JEM-2100 transmission electron microscope at an accelerating voltage of 200 kV. Results and discussion. It was shown that, after thermo-mechanical treatment, a twin-matrix austenite structure was obtained in the center of the rod, while an ultrafine-grained structure with isolated recrystallized austenite grains of approximately 1 μm in size was obtained at the edge. It was established that a two-component axial austenite texture <001>/<111> is formed in the center of the rod, which transformed into a shear texture B/B? towards the rod surface. It was determined that the formation of a heterogeneous structure led to additional strengthening due to back stresses. It was found that, after heat treatment at 700°C, the specimen with a heterogeneous structure exhibited the highest yield strength, equal to 1054 MPa, with a relative elongation of 16%. Thus, the employed thermo-mechanical treatment may be a promising method for obtaining large-sized rod stocks from austenitic stainless steel 0.08 C-17 Cr-13 Ni-2 Mn-Ti with high mechanical properties.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):189-205
189-205
Effect of cold radial forging on structure, texture and mechanical properties of lightweight austenitic steel
Abstract
Introduction. Lightweight austenitic steels, exhibiting high mechanical properties combined with cost-effective alloying and low density, are promising materials for automotive and airspace industries. The purpose of this work is to study the evolution of the structure and properties of Fe-21Mn-6Al-1C lightweight austenitic steel after cold radial forging (CRF) under various modes. Methods. Microstructural studies were performed using transmission and scanning electron microscopy (TEM) on JEOL JEM-2100 and FEI Nova NanoSEM 450 microscopes, respectively. Microhardness was determined in the cross-section using a Wolpert 402MVD microhardness tester with a load of 200 g and a dwell time of 15 s. Uniaxial tension testing of samples cut from the edge and center was performed on an Instron 5882 machine at room temperature and a strain rate of 1×10-3 s−1. Results and discussion. The stages of structure formation were determined: after deformation (ε) of up to 20%, the formation of deformation microbands in the center and parallel deformation microbands at the rod edge takes place; after ε = 40–60%, the formation of single mechanical twins in the center and packets of twins/lamellas at the edge occurs; after ε = 80%, the intensive twinning in the center and formation of a fragmented structure at the edge takes place. Increasing the degree of CRF leads to the development of a sharp two-component axial texture <111>// rod axis (RA) and <100>//RA in the center, which is blurred towards the edge. At the edge of the rod, a shear texture B/B? is observed after CRF with ε = 40% and higher. After CRF with ε = 20%, the material in the center of the rod exhibits higher strength and hardness and lower ductility compared to the edge. Further CRF is accompanied by a change in this strength/hardness and ductility ratio between the center and the edge of the rod to the opposite. Thus, CRF is a promising method for producing industrial blanks from lightweight austenitic steels.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):206-218
206-218
Integrated numerical and experimental investigation of tribological performance of PTFE based composite material
Abstract
Introduction. One of the most significant phenomena in every industrial sector is friction and wear, which inevitably occurs when there is relative motion between similar or dissimilar materials. A substantial portion of global energy production is estimated to be expended in overcoming friction and wear, making them critical factors in energy efficiency and sustainability. Recently, advances in materials science, lubrication technologies, and innovative design approaches have facilitated a significant reduction in friction and wear, leading to considerable energy savings and extended component lifespan. Polytetrafluoroethylene (PTFE), among other materials, has revolutionized the tribological field, emerging as a highly effective synthetic polymer. This is attributed to its exceptional properties, including a low coefficient of friction, chemical inertness, thermal stability, non-stick characteristics, and biocompatibility. These unique properties make PTFE an ideal material for various industrial applications, spanning from aerospace to biomedical sectors. The purpose of work. This study aims to conduct a comprehensive numerical and experimental investigation into the tribological properties of PTFE-based composites. The materials selected for investigation include pure PTFE, PTFE with 25% carbon (C) filler, and PTFE with 20% glass filler. Testing was performed using stainless steel (SS 304) as the counterbody. Tribological testing and subsequent evaluation were conducted under dry sliding friction conditions, considering key parameters such as load, sliding speed, and temperature. Response surface methodology (RSM) was employed to develop an empirical model, utilizing experimental data to predict the wear resistance of these materials. Empirical models were developed to understand the influence of process parameters on wear behavior and to optimize operating conditions for minimizing material loss. Method of investigation. Archard's wear model was used as the theoretical framework for predicting volume loss and specific wear rate based on numerical simulations. The wear coefficient (K) was determined through experimental testing and used as an input parameter in the numerical models. Numerical simulations were developed using the finite element analysis (FEA) software ANSYS, enabling the simulation of complex tribological interactions between the composite materials and the counterbody. A central composite rotatable design (CCRD) within the framework of RSM was used to structure the experiments. The experiments were conducted under dry sliding friction conditions using pin on disc tribometer. The input parameters for the experiments were load (ranging from 15 N to 200 N), sliding speed (ranging from 400 rpm to 1000 rpm), and temperature (ranging from 60 °C to 200 °C). Each experiment was conducted for a sliding distance of 5 km to ensure sufficient wear for analysis. A total of 20 experiments were performed for each material, providing a comprehensive dataset for statistical analysis and model validation. Result and discussion. The results of the study highlight the effectiveness of numerical simulation in predicting the wear resistance of PTFE-based composites under dry sliding friction conditions. Experimental investigations reveal that pure PTFE exhibits low mechanical strength, leading to a high wear rate, whereas PTFE with carbon and glass fillers demonstrates improved wear resistance characteristics. The addition of carbon to PTFE enhances the composite's performance by forming a stable transfer film on the counterbody, while the addition of glass promotes increased hardness and, consequently, reduced material loss. Empirical models developed using response surface methodology (RSM) confirm that the applied load on the pin is the most significant parameter affecting wear, followed by sliding speed and temperature. Numerical simulations based on Archard's wear model exhibit good agreement with experimental data, validating the accuracy of the numerical simulations. This research contributes to a deeper understanding of the application of PTFE-based composites in extending the service life and enhancing the reliability of industrial products.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):219-237
219-237
Effect of impact processing on the structure and properties of nickel alloy ZhS6U produced by casting and electron beam additive manufacturing
Abstract
Introduction. Nickel alloys are widely used in the aerospace industry, but their operational characteristics require improvement through surface modification. A relevant challenge is to conduct a comparative analysis of mechanical impulse processing methods for cast and additively manufactured ZhS6U alloy to optimize their properties. The purpose of this work is to investigate the influence of low-frequency (LF) and high-frequency (HF) impact processing on the structural-phase state and surface properties of nickel alloy ZhS6U, produced by electron beam additive manufacturing (EBAM) and casting. The research methods include microstructural analysis using optical microscopy, X-ray diffraction analysis of the phase composition, microhardness measurements, and tribological testing via scratch testing of ZhS6U alloy samples after various processing modes. Results and discussion. It is established that LF processing of the cast alloy increases the volume fraction of the strengthening γ' phase, while HF processing forms an additional Ti2O phase. The processing of the additive alloy demonstrates more significant changes: micro-strains in the crystal lattice are 1.71…2.18 times higher, micro-stresses in the surface layer are 2.09…2.73 times higher, and the microhardness of the processed surface of the additively manufactured ZhS6U alloy is 8…16% higher compared to the cast material. Optimal processing modes are identified to be: 40 seconds for LF and 20 minutes for HF, providing a minimum friction coefficient of 0.075. Conclusions. Mechanical impulse processing effectively hardens the surface of nickel alloy ZhS6U fabricated by different methods. The application of the developed approaches is recommended to improve the performance characteristics of parts in the aerospace and mechanical engineering industries. Further research is required on the cyclic stability of modified structures after mechanical impulse processing in various frequency ranges.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):238-254
238-254
Martensitic transformations in TiNi-based alloys during rolling with pulsed current
Abstract
Introduction. Shape memory alloys based on TiNi possess a set of properties, including biocompatibility, corrosion resistance, low density, high specific strength, thermal stability, shape memory effect, and superelasticity. A significant number of studies are currently dedicated to various deformation methods of processing such materials, aiming to enhance their mechanical properties and shape memory characteristics. One such method is plastic deformation with the simultaneous application of pulsed current. Since the shape memory properties in TiNi-based alloys are due to the presence of thermoelastic martensitic transformations, the combined effect of deformation and current on these transformations is of particular interest. The purpose of this work is to investigate the characteristics of thermal and deformation-induced martensitic transformations in Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys during rolling with simultaneous application of pulsed current. Research methods. The paper analyzes samples of Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys after rolling with pulsed current at a density of 100 A/mm², a pulse duration of 100 μs, a pulse ratio of 10 to various strain levels (ε=0; 0.4; 0.8; 1.2). The study of the staging of martensitic transformations was carried out using differential scanning calorimetry at a heating/cooling rate of 10 °C/min in the temperature range of −150 to +150 °C. The phase composition was studied by X-ray diffraction analysis using Cu-Kα radiation at U=40 kV and I=40 mA in the angular range of 2θ=15 to 100 ° with a step size of Δθ = 0.05° and an exposure time of 5 s. Results and discussion. The results show that current-assisted rolling leads to the manifestation of a two-stage direct martensitic transformation during cooling in both alloys. Furthermore, increasing the strain level broadens the temperature range of the R-phase existence. The possibility of stabilizing the high-temperature austenitic B2 phase in the Ti49.2Ni50.8 alloy, as well as the emergence of a cyclically occurring deformation-induced “martensite-austenite-martensite” transformation in the Ti50.0Ni50.0 alloy, are demonstrated. Possible mechanisms for these features are discussed.
Obrabotka Metallov / Metal Working and Material Science. 2025;27(2):255-269
255-269