Vol 27, No 4 (2025)

Introduction. There is a growing demand for eco-friendly cutting fluids in machining due to their non-toxicity, sustainability, high performance, and ability to improve surface quality. These fluids support green manufacturing practices and promote a safe working environment. Copper oxide-based nanofluids offer the combined benefits of enhanced heat transfer, increased safety, and reduced tool wear and cutting forces. The purpose of the work. This research focuses on evaluating the performance of copper oxide-based cutting fluids in turning processes to support sustainable and eco-conscious manufacturing. The study investigates the turning of SS 304 steel using varying concentrations of copper oxide nanofluids. The methods of investigation. In this study, the turning process was tested under various machining conditions using different concentrations of copper oxide nanoparticles (0.3 %, 0.6 %, 0.9 %, 1.2 %, and 1.5 %). Corn oil was selected as the base oil, and the copper oxide nanoparticles were dispersed in the corn oil to prepare the nanofluid. Machining trials were conducted under different lubrication environments: dry, wet, minimum quantity lubrication (MQL), and nano-enhanced MQL (nMQL). A comparative study was performed to assess cutting temperature and cutting forces. Results and discussion. The results showed that the use of 1.2 % copper oxide nanofluid led to significant reductions in cutting force and cutting temperature, by approximately 17.54 % and 29.53 %, respectively, compared to traditional dry and wet machining environments. Furthermore, the nanofluid was observed to form a protective film at the tool-workpiece interface, reducing tool wear. These findings highlight the potential of copper oxide-based green cutting fluids to improve turning operation efficiency and promote environmentally sustainable practices.

Introduction. Hybrid metal matrix composites (HMMCs) are increasingly used in the aviation and automotive industries due to their low density, high stiffness, and exceptional specific strength. Among aluminum MMCs, Al7075-based composites are gaining wider acceptance. Continuous research and development in this field focuses on improving the durability and performance of these advanced materials. Purpose of the work. Machinability of Al7075 is a significant challenge because the abrasive reinforcement phase causes rapid tool deterioration, increased machining forces, and a poor surface finish. Moreover, the industrial focus on green manufacturing has led to a shift from traditional coolant-based machining to sustainable alternatives. In this context, researchers have optimized machining performance using advanced technological advancements and techniques. However, limited work is reported on modeling the machining performance of Al7075 nanocomposites during turning under compressed air cooling. Methods of investigation. Manufacturers can gain a better understanding of increasing the effectiveness of turning processes for Al7075 nanocomposites by creating a comprehensive model. Therefore, this work models the machining performance of hybrid Al7075 nanocomposites during turning under compressed air-cooling conditions with an artificial neuro-fuzzy inference system (ANFIS) to predict tool wear (TW), surface roughness (Ra), and cutting force (Fc) as a function of process parameters. Results and discussion. In this work, an ANFIS model was developed to predict the machining performance considering the effect of process parameters such as cutting speed, feed rate, and depth of cut for different Al7075-based nanocomposites. These nanocomposites were prepared using silicon carbide (30–50 nm) and graphene (5–10 nm) nanoparticles as reinforcements by the stir casting process. Reinforcement materials affect the mechanical and physical properties of composites. For engineering applications, SiC and graphene are preferred reinforcements with distinctive features. ANFIS models were developed to predict Ra, Fc, and TW based on the experimental results. The Sugino method was used to represent fuzzy rules and membership functions, as it utilizes weighted averages in the defuzzification process and offers better processing efficiency. The MATLAB ANFIS toolbox was used to design and tune fuzzy inference systems. The developed ANFIS model predicts machining responses effectively and offers a practical approach for optimizing process parameters with high reliability. The results of this research show good agreement between the experimental results and the predicted ANFIS outcomes, with an average prediction error below 8%. Specifically, the ANFIS model yielded errors of 5.1% for Ra, 13.45% for Fc, and 7.92% for TW. The model exhibited excellent agreement with experimental data, demonstrating high prediction accuracy and generalization capability. 3-D graphs are plotted for a better understanding of the effect of process parameters on Fc, Ra, and TW for different nanocomposites. The findings affirm the efficacy of compressed air cooling in improving machinability while minimizing environmental impact. Furthermore, the developed ANFIS model serves as a reliable tool for optimizing turning parameters for Al7075 composites, supporting the advancement of green manufacturing strategies. This research warrants further investigation into the application of ANFIS in machining processes, specifically exploring various metal matrix composite types and rigorously assessing the long-term effects of compressed air cooling on both environmental sustainability and tool life.

Introduction. Currently, many mathematical approaches exist for approximating surface profile curves. Most employ volumetric mathematical expressions to describe surface profile parameters after various types of processing. Purpose of the work is to select a mathematical apparatus that is simple enough from an engineering perspective to approximate the surface profile of VT22 titanium alloy samples after surface plastic deformation (SPD) and various electromechanical processing (EMP) modes, with the possibility of eliminating random technological errors. The paper investigates the effect of EMP modes using alternating and direct current at densities of 100, 300, and 600 A/mm2, considering both the application of force by the deforming tool-electrode (150 N) and its absence (10 N), on the surface geometry of VT22 titanium alloy samples. The electromechanical processing of metal alloys used in this work can significantly change the geometric profile, structure, and operational properties of the surface. Its distinctive feature is the creation of both microdeviations (roughness) and macrodeviations and relief (waviness, “oil pockets”, build-ups from metal surfacing to the repair size) on the surface. Research methods. Profilometric analysis was performed using a PM-7 device, followed by processing of the roughness measurement results using the fast Fourier transform (FFT) on the surface of a cylindrical sample made of VT22 titanium alloy with a diameter of 16 mm after electromechanical rolling with an tool-electrode, previously subjected to semi-finish turning. The error of the model curves of the surface profile was estimated using the Pearson correlation coefficient (R). Results and discussion. The use of high-density direct current helps to obtain a surface with a high relative support length of the profile (98.8%), a low arithmetic mean deviation of the profile (1.9 μm), and an average step of profile irregularities (56 μm). Based on the FFT, the considered modes of electromechanical processing contribute to the formation of profile waviness with different pitch and height. The greatest correlation is observed for modes 2, 4, and 9 (R > 0.7), while the lowest correlation coefficient was noted for EMP with a direct current density of 100 and 300 A/mm2 (modes 5 and 6, R < 0.25).

Introduction. Unlike traditional manufacturing processes, additive manufacturing (AM) offers improved efficiency while being environmentally friendly. A significant limitation hindering the adoption of wire-based electron beam additive manufacturing (EBAM) technology is the relatively low quality and high surface roughness of 3D-printed parts. The purpose of this study is to establish the optimal values of milling process parameters (rotational speed, feed rate, and milling width) based on the simultaneous evaluation of the surface roughness of the machined surface and the material removal rate. Methods and materials. This study investigated specimens fabricated using EBAM technology. Uniaxial tensile tests were conducted on an electromechanical testing machine. Cutting forces were determined with a Kistler 9257B dynamometer. Milling studies of EBAM 321 steel workpieces were performed on a semi-industrial CNC milling machine. Results and discussion. It was shown that in order to increase the material removal rate and reduce the cutting force on a milling machine without the use of coolant, it is recommended to increase the milling speed, but not to increase the feed rate. To investigate the relationship between material removal rate and surface roughness relative to milling parameters on a semi-industrial machine (with an average stiffness of the portal frame), multiple linear regression models and nonlinear models based on feedforward neural networks were employed. It was demonstrated that linear regression models are sufficient for predicting optimal milling parameters. However, it should be noted that the study was conducted within a narrow range of gentle machining conditions, with short processing times and without accounting for tool wear. Under these constraints, the optimal milling parameters for EBAM 321 steel were predicted as follows: spindle speed of 4,500 rpm, feed rate S = 404 mm/min, and cutting depth B = 0.43 mm, resulting in a predicted surface roughness (Ra) of 0.648 µm and a material removal rate of 695 mm³/min.

Introduction. Pilot production plays an important role in modern mechanical engineering. Copy-piercing electrical discharge machining (CPEDM) technology has become widespread in machining pilot parts manufactured in flexible production flows. Manufacturing tool-electrodes (TE) is one of the main stages of the CPEDM technological cycle. Purpose of the work. Review of existing studies of modern methods of manufacturing tool-electrodes for electrical discharge machining. Research methods. A literature review of studies in the field of electrical discharge machining devoted to tool-electrodes, carried out mainly over the past 20 years, is presented. Various configurations of structural elements machined using CPEDM technology, as well as TE configurations for their machining, are described. The dependences of the influence of the geometric parameters of the simplest TE configurations on the output parameters of CPEDM are shown. The main groups of TE manufacturing methods are identified. The limitations, advantages, and disadvantages of alternative methods to traditional ones are described. The main trends in the development of modern TE manufacturing methods are revealed. Results and discussion. Based on the literature review of modern research in the field of electrical discharge machining, current trends in the development of tool-electrode configurations are presented, and problems in the manufacture of complex-shaped tool-electrodes using traditional methods are identified. It has been established that among the alternative methods for manufacturing tool-electrodes, investment casting, powder metallurgy, and additive methods are of greatest interest to modern scientists. It has been shown that each method has its own advantages and disadvantages, confirmed by a number of studies. The following current areas of development of complex-shaped tool-electrodes and methods for their manufacture are highlighted: topological optimization of tool-electrodes, use of modern high-tech casting methods; expansion of the range of tool-electrodes materials with improved electrical discharge properties; optimization of powder metallurgy modes, FDM printing, and selective laser melting; increasing the thickness and quality of tool-electrodes coatings obtained using rapid prototyping technologies.

Introduction. One of the crucial criteria for evaluating the effectiveness of the chosen strategy for machining blanks is the tool wear intensity. Reducing the intensity of tool wear leads to a reduction in production costs related to cutting tool expenditures and an improvement in overall productivity. The purpose of this work is to reduce tool wear intensity during the machining of a blank manufactured from the shape memory alloy titanium nickelide TN-1. Methods. As part of this research, a complete three-factor turning experiment was conducted on the alloy blank to determine the cutting insert wear intensity over a wide range of cutting conditions. During the tests, the geometric parameters of the resulting chips, specifically thickness and width, were measured. By constructing graphs representing the dependencies of the chip parameters, approximating these dependencies, and assessing the reliability of each approximation, a key parameter was identified for developing a methodology to predict tool wear intensity. Results and discussion. The study demonstrates that for predicting the cutting insert wear intensity when turning a titanium nickelide TN-1 blank, it is advisable to use the dependency on the resulting chip thickness. The established mathematical dependency is described by a system of equations that allows for the determination of the cutting insert wear intensity and the calculation error. The probability of accurately predicting the true value of tool wear intensity within the specified range is at least 87.5% at a 95% confidence level, which indicates sufficient practical accuracy. The essence of the methodology developed within this study for predicting the cutting insert wear magnitude lies in performing a test cut to obtain a chip whose thickness is then used to calculate the wear intensity magnitude and the most probable absolute error based on the established dependencies. Additionally, the study establishes that the wear intensity dependency exhibits a minimum point. This circumstance allowed for the establishment of the minimal possible wear intensity during TN-1 alloy machining, as well as the associated calculation error: δVmin = (0.432 ± 0.096)·10−3 mm−2. For an optimal chip thickness of a = 0.34 mm, the closest tested mode yielding a comparable wear intensity of 0.475⋅10−3 mm−2 is: cutting speed 5 m/min, feed rate 0.2 mm/rev, depth of cut 0.3 mm. The chip thickness for this mode was 0.4 mm.

Introduction. Additive manufacturing (AM) technologies, particularly wire arc additive manufacturing (WAAM), offer a rapid and cost-effective approach for producing complex metal components. However, WAAM can induce anisotropy in the resulting material's physical and mechanical properties. This anisotropy must be considered in design and application to ensure reliable performance in service. The purpose of the work. This study aims to quantitatively assess the anisotropy of mechanical properties in materials produced by WAAM to enhance the reliability of components used in critical applications. Research methodology. Samples were fabricated from low-carbon alloyed steel (0.08 C-2 Mn-1 Si), stainless steel (0.04 C-19 Cr-9 Ni), and aluminum alloy (97 Al-3 Mg) using the WAAM process. These samples were then subjected to mechanical testing to determine their tensile and impact toughness and hardness. Results were compared to those of the materials in the initial state to determine the relative anisotropy of each property. Results and discussion. For 0.08 C-2 Mn-1 Si steel, the tensile strength of WAAM-fabricated samples exhibited minimal variation across different orientations, indicating relatively high isotropy (relative anisotropy of 1.3 %). A relative anisotropy of 33 % was observed for elongation, 21 % for impact toughness, and 16 % for hardness. The 0.04 C-19 Cr-9 Ni stainless steel exhibited a relative anisotropy of 15.1 % for tensile strength, 244 % for elongation, 33 % for impact toughness, and 4% for hardness. The 97 Al-3 Mg aluminum alloy showed a significant relative anisotropy in tensile strength (83.6 %) and relative elongation (513 %) due to differences in the “vertical” direction. Impact toughness exhibited only slight variations (28 %) depending on sample orientation, while hardness can be considered isotropic. In general, hardness demonstrated the lowest relative anisotropy, while elongation exhibited the highest.

Introduction. One of the most promising fields for the application of magnesium alloys is medicine. Their key advantages are bioresorbability and a low elastic modulus, comparable to that of human cortical bone (up to 30 GPa). Biocompatible Mg-Zn-Zr-Ce (MA20) system alloys are among the most promising for medical applications. Due to their relatively low mechanical properties, the development of severe plastic deformation (SPD) techniques for forming an ultrafine-grained (UFG) state in bulk billets of the Mg-Zn-Zr-Ce alloy to achieve optimal functional properties requires further research. Analyzing the conditions for forming a high-strength UFG state necessitates considering various strengthening mechanisms, including well-known ones related to the effect of UFG structures. Identifying the deformation and strain hardening mechanisms in magnesium alloys subjected to SPD is also highly relevant. The purpose of this work is to establish the mechanisms of strain hardening and to investigate the influence of heat treatment on the structure and properties of the MA20 magnesium alloy after combined SPD. Research methods. The study object was the MA20 alloy in a UFG state (wt. %: Mg – 98.0; Zn – 1.3; Ce – 0.1; Zr – 0.1; O – 0.5). The UFG state was achieved via a combined SPD process involving ABC-pressing followed by multi-pass rolling in grooved rolls. To study the effect of annealing on the microstructure and mechanical tensile properties, samples were annealed in air at temperatures of 200, 250, 300, and 500 °C for 24 hours. The microstructure and phase composition of the samples were investigated using optical and transmission electron microscopy. Results and discussion. It was established that applying a combined SPD method (ABC-pressing and multi-pass rolling) to the MA20 alloy results in the formation of an ultrafine-grained structure with an average grain size of about 1 μm. This leads to a significant increase in yield strength (σ_0.2) to 250 MPa and ultimate tensile strength (σ_u) to 270 MPa, while simultaneously reducing ductility to 3%. Annealing at 200 °C was found to preserve the UFG state in the MA20 alloy and to lead to a 100% increase in ductility, with an 8% decrease in σ_0.2 and a 4% decrease in σ_u compared to the initial UFG state (non-annealed). Conclusions. It was revealed that the grain boundary (σ_grain = 202 MPa) and dislocation (σ_dis = 69 MPa) strengthening contributions provide the most significant increase in the strength of the UFG MA20 magnesium alloy. For the magnesium alloy in the UFG and fine-grained (FG) states, a critical grain size interval of (1–7) μm was identified, corresponding to a sharp increase in the intensity of change for the calculated contributions of dislocation (dσ_dis/ dd), grain boundary (dσ_grain/ dd), overall strengthening (dσ_total/dd), and dislocation density (dρ/dd). For the coarse-grained (CG) state of the alloy in the grain size range (7–40) μm, these parameters stabilize.

Introduction. Aluminum alloys of the Al-Cu-Mn system, alloyed with 23% copper and 1–2% manganese (ALTEK), are distinguished by heat resistance and high mechanical properties due to the formation of nano-dispersed particles of the Al20Cu2Mn3 phase. When exposed to high temperatures (up to 400°C), the particles block the processes of polygonization and recovery, hindering the movement of grain boundaries. A promising direction for improving these alloys is the modification of the cast structure with transition metals (TMs). An insufficient content of TMs does not provide a modifying effect, while an excessive amount leads to a reduction in strength due to the formation of a large number of coarse intermetallic particles. The subject of this work a ALTEK alloys alloyed with Mg, Zr, Sc, and Hf. The purpose of the work is to determine the optimal concentrations of scandium, hafnium, and zirconium required for effective modification of the cast structure of ALTEK alloys during complex alloying. The effect of complex additions of transition metals (Zr, Sc, Hf) on the formation of the cast structure of Base0.15Zr0.05Sc0.05Hf, Base0.1Zr0.14Sc0.16Hf, Base0.1Zr0.2Sc0.16Hf, and Base0.1Zr0.25Sc0.16Hf alloys is investigated in comparison to the base alloy. The research methods were optical and scanning electron microscopy, and X-ray diffraction analysis. Results and discussion. Modification of the grain structure in alloys with a scandium content of less than 0.20% is not observed, and the average grain structure size is 350 μm. The addition of scandium in the amount of 0.20% and 0.25% leads to a decrease in the average grain diameter to 41.8 μm and 29.7 μm, respectively. Scanning electron microscopy showed that particles of the Al6Mn and Al2CuMg phases are present in all the alloys studied. Particles of the Al3(Sc,Hf,Zr) phase are found in the Base0.1Zr0.2Sc0.16Hf and Base0.1Zr0.25Sc0.16Hf compositions. X-ray diffraction analysis revealed the Al20Cu2Mn3 phase and small amounts of Al6Mn and Al2CuMg in the base alloy and in the Base0.1Zr0.25Sc0.16Hf alloy. The structural modification is explained by the precipitation of primary Al3(Sc, Zr, Hf) particles. Application of the results. The obtained results are promising for the development of new materials for the manufacture of aerospace products. Conclusions. The addition of 0.20–0.25% scandium with a zirconium content of 0.1% and hafnium of 0.16% is the most effective.

Introduction. During the recrystallization annealing of cold-rolled electrical and automotive steels, the formation of pickups on the surface of furnace rolls presents a significant issue, as they lead to surface damage of the steel strip in the form of indentations. The focus of the present study is the evaluation of this defect. Methods. To this end, a laboratory-based methodology was developed to assess the tendency of furnace rolls to form pickups. The method replicates the contact interaction between the furnace roll and the steel strip under real annealing conditions, taking into account the applied contact pressure, a temperature range of 700–900 °C, the (H2–N2) furnace atmosphere, and a humidity level arising from the presence of oxygen adsorbed on the steel strip. To validate the method’;s reliability, a comparative analysis was conducted between pickups formed on the roll surface after industrial operation and those generated under laboratory conditions in the contact zone between steel samples made of roll and strip materials. The analysis employed optical microscopy, X-ray diffraction, and scanning electron microscopy. Results and discussion. The study confirmed that the developed methodology produces pickups on the specimen surfaces with morphology, chemical composition, and phase structure closely resembling those observed on the furnace rolls. A comparative assessment of the pickup formation rate between a typical furnace roll material (EI 283 steel) and a NiCrAlY coating applied by plasma spraying revealed that the pickup formation rate for the EI 283 steel was an order of magnitude higher. The validated methodology can thus be used to evaluate the effectiveness of strategies aimed at mitigating pickup formation on furnace rolls under long-term high-temperature contact conditions.