Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products

Vol. 26 No. 3 2024 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.

OBRABOTKAMETALLOV Vol. 26 No. 3 2024 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Ukraine: Sergiy V. Kovalevskyy, D.Sc. (Engineering), Professor, Vice Rector for Research and Academic Aff airs, Donbass State Engineering Academy, Kramatorsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary

Vol. 26 No. 3 2024 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sukhov A.V., Sundukov S.K., Fatyukhin D.S. Assembly of threaded and adhesive-threaded joints with the application of ultrasonic vibrations...................................................................................................................................... 6 Baraboshkin K.A., Adigamov R.R., Yusupov V.S., Kozhevnikova I.A., Karlina A.I. Thermomechanical rolling in well casing production (research review)......................................................................................................................... 24 Dwivedi R., Somatkar A., Chinchanikar S. Modeling and optimization of roller burnishing of Al6061-T6 process for minimum surface roughness, better microhardness and roundness................................................................................ 52 Ilinykh A.S., Pikalov A.S., Miloradovich V.K., Galay M.S. Experimental studies of rail grinding modes using a new high-speed electric drive...................................................................................................................................................... 66 Karlina Yu.I., Konyukhov V.Yu., Oparina T.A. Assessment of the possibility of resistance butt welding of pipes made of heat-resistant steel 0.15C-5Cr-Mo................................................................................................................................... 79 Gimadeev M.R., Stelmakov V.A., Shelenok E.A. Product life cycle: machining processes monitoring and vibroacoustic signals fi lterings.................................................................................................................................................................... 94 EQUIPMENT. INSTRUMENTS Zakovorotny V.L., Gvindjiliya V.E., Kislov K.V. Information properties of frequency characteristics of dynamic cutting systems in the diagnosis of tool wear....................................................................................................................... 114 Ablyaz T.R., Blokhin V.B., Shlykov E.S., Muratov K.R., Osinnikov I.V. Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products....................................................... 135 Sidorov E.A., GrinenkoA.V., ChumaevskyA.V., Panfi lovA.O., Knyazhev E.O., NikolaevaA.V., CheremnovA.M., Rubtsov V.E., Utyaganova V.R., Osipovich K.S., Kolubaev E.A. Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets..................................................................................................................................... 149 MATERIAL SCIENCE Semin V.O., Panfi lov A.O., Utyaganova V.R., Vorontsov A.V., Zykova A.P. Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing................................ 163 Dewangan R., Sharma B.P., Sharma S.S. Investigation of hardness behavior in aluminum matrix composites reinforced with coconut shell ash and red mud using Taguchi analysis............................................................................ 179 Saprykina N.А., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А. The eff ect of technological parameters on the microstructure and properties of the AlSiMg alloy obtained by selective laser melting......................................................... 192 Burdilov A.A., Dovzhenko G.D., Bataev I.A., Bataev A.A. Methods of synchrotron radiation monochromatization (research review).................................................................................................................................................................. 208 Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution..................................................................................................................................................................... 234 Pugacheva N.B., Bykova T.M., Sirosh V.A., MakarovA.V. Structural features and tribological properties of multilayer high-temperature plasma coatings........................................................................................................................................ 250 Sharma B.P., Dewangan R., Sharma S.S. Characterizing the mechanical behavior of eco-friendly hybrid polymer composites with jute and Sida cordifolia fi bers.................................................................................................................... 267 Kornienko E.E., Gulyaev I.P., Smirnov A.I., Plotnikova N.V., Kuzmin V.I., Golovakhin V., Tambovtsev A.S., Tyryshkin P.A., Sergachev D.V. Fine structure features of Ni-Al coatings obtained by high velocity atmospheric plasma spraying.................................................................................................................................................................... 286 EDITORIALMATERIALS 298 FOUNDERS MATERIALS 307 CONTENTS

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products Timur Ablyaz a, Vladimir Blokhin b, Evgeniy Shlykov c, *, Karim Muratov d, Ilya Osinnikov e Perm National Research Polytechnic University, 29 Komsomolsky prospekt, Perm, 614990, Russian Federation a https://orcid.org/0000-0001-6607-4692, lowrider11-13-11@mail.ru; b https://orcid.org/0009-0009-2693-6580, warkk98@mail.ru; c https://orcid.org/0000-0001-8076-0509, Kruspert@mail.ru; d https://orcid.org/0000-0001-7612-8025, Karimur_80@mail.ru; e https://orcid.org/0009-0006-4478-3803, ilyuhaosinnikov@bk.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2024 vol. 26 no. 3 pp. 135–148 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.3-135-148 ART I CLE I NFO Article history: Received: 11 June 2024 Revised: 25 June 2024 Accepted: 28 June 2024 Available online: 15 September 2024 Keywords: Additive technologies Selective laser melting Copy-piercing electrical discharge machining Current Voltage Pulse on time Surface roughness Tool electrode wear Funding The research was financially supported by the Russian Science Foundation under grant No. 23-29-00104. https:// rscf.ru/project/23-29-00104/ Acknowledgements The authors express their gratitude to Associate Professor of the department. ITM FSAOU VO “PNRPU” Morozov E.A. for assistance in the manufacture of samples of electrode-tools using the SLS method from maraging steel MS1. ABSTRACT Introduction. The paper presents the results of a study of the use of a tool electrode (TE), manufactured by selective laser alloying from MS1 maraging steel powder for copy-piercing electrical discharge machining (EDM). Purpose of the work: experimental study of the features of the use of additively manufactured TE in the EDM of critical products. Research methods. The specimens were prepared using a ReaLizer SLM 50 system. The starting material was spherical MS1 powder with an average particle size of 30 μm. To test the modes and select a TE sample with the least number of surface defects, four manufacturing modes were tested, and the best TE sample was selected for further research. The EDM was carried out on EMT Smart CNC equipment in a dielectric oil environment. The specimens were installed in a clamp with straight polarity and were used as TE; a 0.12C-18Сr-10Ni-Тi steel plate served as the workpiece electrode. The study was conducted using a factorial experiment (type 23) with a central design. The input data of the factorial experiment is the current I (A), voltage U (W), pulse on time Ton (μs). The output parameters were the roughness parameter Ra and tool electrode wear γ. The roughness parameter Ra was measured using a Mahr Perthometer S2. Results and discussion. TE samples were made from MS1 powder using the SLS method; the highest quality TE sample No. 4 was selected for EDM. Empirical equations are obtained that describe the relationship between the roughness parameter Ra and tool electrode wear γ, depending on the EDM modes. At the minimum mode with a current I = 4 A and a voltage U = 50 V, the tool electrode wear is γ = 0.0063875 g. The maximum tool electrode wear is γ = 0.13938 g with a current I = 8 A and a voltage U = 50 V. It is established that at a constant pulse on time Ton = 75 μs, the smallest roughness Ra = 2.83 μm is obtained at a current of I = 4 A and a voltage U = 100 V, and the maximum roughness is Ra = 4.1568 μm at I = 8 A and U = 100 V. For citation: Ablyaz T.R., Blokhin V.B., Shlykov E.S., Muratov K.R., Osinnikov I.V. Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 3, pp. 135–148. DOI: 10.17212/1994-6309-2024-26.3-135-148. (In Russian). ______ * Corresponding author Shlykov Evgeniy S., Ph.D. (Engineering), Associate Professor Perm National Research Polytechnic University, 29 Komsomolsky prospect, 614990, Perm, Russian Federation Tel.: +7 961 759-88-49, e-mail: Kruspert@mail.ru

OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Introduction The relevance of the use of additive technologies in the manufacture of electrodes for electrical discharge machining (EDM) has arisen due to the increased requirements for the accuracy and quality of manufacturing of complex-profile products [1–3]. It has been established that one of the most rational additive methods for producing tool electrodes (TE) is the technology of selective laser melting (SLM) [4–8]. It is noted that the use of additive technologies allows to provide the required parameters of repeatable geometry of complex-profile elements, as well as to provide increased performance and durability of TE through the use of new compositions of powder materials. In the works [9–13] the efficiency of composite tool electrodes obtained using additive technologies is noted. The principle of SLM technology is to split the product into layers and then print the product with cyclic repetition of operations. Increased requirements to accuracy, quality and reliability of product manufacturing require the use of high-quality TE repeating the surface profile. The required dimensional accuracy of products machined by the EDM method varies from 12 to 6 grades of accuracy, and the required roughness in terms of Ra from 3.2 to 0.8 μm. Increased requirements of accuracy and roughness are connected with operational peculiarities; machined surfaces are in conjunction with kinematic units and mechanisms. The works [14–18] consider the SLM method for the production of metal tool electrodes. The authors note that the use of additive technologies for growing TE allows not only to provide the required parameters of repeatable geometry of complex-profile elements of products, but also to obtain increased performance and durability of TE by using new powder materials. The main parameters of the SLM process are laser power, scanning speed, hatch type and distance, layer thickness and powder characteristics. These parameters affect the formation of defects in the process of TE growing. Porosity is the most frequent and difficult defect to eliminate in selective laser melting. Pore formation is influenced by the properties of the initial powder material, machine parameters and growth modes [19–21]. Another defect arising in the application of powder additive technologies is nonfusion, which occurs when single tracks do not overlap sufficiently with each other. Incorrectly selected modes for a certain material lead to increased porosity. At insufficient power value in the SLS process, the powder layer is not completely melted, which leads to the effect of spheroidization or non-melting with the previous layer due to the presence of unmelted particles in the track [22]. Increasing the power value leads to intensive evaporation of the material or the most fusible components of the powder, this contributes to the formation of pores. The presence of such defects contributes to the intensification of TE destruction in the EDM process. Also the presence of instability in the TE structure can negatively affect the formation of a stable spark formation process during copy-piercing machining, which will negatively affect the quality of processing. At present, the formed approaches to the design of TE configuration and assignment of machining modes rely on the methods of design of loaded critical products. These approaches do not include the peculiarities of the physical side of the EDM process. It is necessary to optimize the dimensions and shape of TE not only taking into account mass and mechanical characteristics, but also taking into account its physical properties (electrical resistance and the possibility of forming a stable spark generation channel). Initial parameters of TE influence the formed surface and directly the TE flow rate. Structural defects intensify the process of TE consumption in the process of EDM. The required surface quality is affected by the roughness of the TE not only before EDM, but also in the process itself. On this basis, it is established that ensuring the requirements of the TE quality is an urgent scientific and technological task. The purpose of the work is an experimental study of the application peculiarities of additively manufactured TE in the copy-piercing EDM of critical products. Objectives of the study are as follows: 1) to develop a rational technique for manufacturing tool electrodes from maraging steel MS1 using the selective laser melting method. These tool electrodes should have a minimum number of structural defects for further copy-piercing EDM; 2) to establish an empirical dependence of the surface quality parameter of the additively manufactured TE from maraging steel MS1 depending on the modes of copy-piercing EDM;

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 3) to establish an empirical dependence of the wear of the additively manufactured TE from maraging steel MS1 depending on the modes of copy-piercing EDM; 4) to assess the effect of the modes of copy-piercing EDM on the surface quality of the additively manufactured TE from maraging steel MS1. Research methodology The research was carried out on the basis of the center of collective use “Center of additive technologies” of the Federal State Educational Institution of Higher Professional Education “Perm National Research Polytechnic University”. Manufacturing of TE prototype was carried out by the additive technology method (SLM). Tool electrodes were made of MS1 maraging steel powder. The powder particles had an average size of 20–40 μm and were spherical. Maraging steel are unique low-carbon martensitic steels that gain strength from intermetallic precipitates formed during the aging heat treatment process. Low carbon content provides good weldability, and significant alloying additives allow achieving high strength due to precipitation hardening mechanism. The following defects occur during the SLS process: cracks, pores, rather rough surface with the presence of melted powder particles. It is necessary to work out fusion modes on this MS1 powder. Carrying out trial modes will allow obtaining TE with a minimum number of defects. The fusion modes were studied using the Realizer 50 machine (Fig. 3a). This machine operates according to the SLM technology. It is used primarily for producing small-sized parts from various powders. The machine has a pulsed fiber laser. This laser has the ability to adjust the beam trajectory, as well as the duration of illumination. One of the main advantages of the Realizer SLM 50 is the high level of detail in the products. Argon was used as a protective gas for sintering. Four modes (Table 1) of fusion of MS1 powder material were used to obtain TE and the best quality one was selected. Ta b l e 1 Technological modes of manufacturing the tool electrode No. t, μs I, mA S, μm Pav, W Filling step, μm h, μm V, m/s 1 40 1,400 20 35 0.05 30 1 2 40 1,400 30 35 0.05 30 0.75 3 20 1,200 20 30 0.05 30 1 4 20 1,400 20 35 0.05 30 1 The parameters varied during manufacturing of TE from the powder of MS1 maraging steel by SLM method were exposure time for each point t, μs; operating current I, mA; distance between points of the laser trajectory S, μm; average power of laser radiation Рav, W; filling step, μm; thickness of a single layer h, μm; scanning speed V, m/s. The samples of tool electrodes were made in the form of parallelepipeds with a length of 30 mm and a cross section of 5×5 mm. Fig. 1 shows the obtained samples on the growth substrate. The high energy density of the SLM process leads to excessive material evaporation and spattering, resulting in the formation of a large number of pores. The pores reduce the fatigue characteristics and mechanical properties of the resulting products by acting as stress concentrators. Cracks on the surface of the products obtained by SLM methods are caused by a large temperature gradient be- Fig. 1. Samples of tool electrodes

OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 tween the melt bath and the solidified metal. On samples No.1–3 (Fig. 2a–c) there are chaotically arranged pores with a diameter of 40–65 μm. The surface of sample No.4 is characterized by the smallest number of structural defects (pores with a diameter of 20–28 μm, cracks up to 2–3 μm wide). When examining these samples for the presence of defects (pores, microcracks), it was found that the most suitable sample for EDM is No.4 (Fig. 2d). Copy-piercing electrical discharge machining was carried out on an Electronica Smart CNC machine (Fig. 3b) in a transformer oil environment. The workpiece to be processed was made of stainless steel 0.12C-18Сr-10Ni-Тi. The values and range of input parameters are presented in Table 2. A Mahr Perthometer S2 profilometer (Fig. 3c) was used to evaluate the surface quality parameter Ra. The evaluation was carried out according to the GOST 2789-73 methodology. The surface topography of the samples and the number of defects on its surface were assessed using an inverted metallographic microscope of the NIM900 research class (Fig. 3d) at magnifications of ×300 and ×500. In order to determine the dependencies of the formation of the roughness parameter Ra of TE, as well as the wear of the working surface of TE, made of MS1 maraging steel, obtained using selective laser melting Fig. 2. Surfaces of sample: а – No.1; b – No.2; c – No.3; d – No.4 а b c d Ta b l e 2 Modes of copy-piercing EDM machining Mode Current I, A Pulse activation time Тon, μs Voltage U, V Minimum level 4 50 50 Medium level 6 75 75 Maximum level 8 100 100

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 technology, a full factor experiment (FFE) of type 23 with the center of the plan was carried out. The factor values were coded into a matrix using transformation coordinates. The planning matrix of the experiment is shown in Table 3. The output parameters are the TE roughness parameter Ra, μm and TE wear γ, g. The detailed methodology of FFE is presented in papers 23–24. According to this technique, 9 experiments were carried out and the results were obtained on the dependence of TE roughness Ra and electrode wear depending on the modes of EDM using TE manufactured by SLS technology from MS1 maraging steel (Table 4). а b Fig. 3. Facilities for conducting the experiment and evaluating the results: а – ReaLizer SLM 50; b – NIM900 microscope; c – Electronica Smart CNC copy-piercing EDM machine; d – Mahr Perthometer S2 profilometer c d Ta b l e 3 Coded planning matrix Exp. No. X0 X1 X2 X3 X1X2 X1X3 X2X3 X1X2X3 1 1 -1 -1 -1 1 1 1 -1 2 1 1 -1 -1 -1 -1 1 1 3 1 -1 1 -1 -1 1 -1 1 4 1 1 1 -1 1 -1 -1 -1 5 1 -1 -1 1 1 -1 -1 1 6 1 1 -1 1 -1 1 -1 -1 7 1 -1 1 1 -1 -1 1 -1 8 1 1 1 1 1 1 1 1 9 1 0 0 0 0 0 0 0

OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Ta b l e 4 Matrix of experimental results Exp. No. Ra, µm γ, g 1 2.9475 0.0062 2 4.33693 0.01 3 3.0374 0.0059 4 3.34163 0.0172 5 2.8057 0.0082 6 3.8035 0.0021 7 3.016 0.0161 8 4.6673 0.0156 9 3.50183 0.001 Results and discussion As a result of the FFE empirical dependencies were obtained. These dependencies establish the relationship between output parameters and processing modes. The linear relationship between the independent variable and input factors is assumed in the paper. The empirical model of the dependence of the TE wear parameter on the machining modes (current I (A), voltage U (W), pulse on time Ton (μs)), has the following form (1): γ = + × + × - × - 0.002997 0.00214325 0.00010806 0.00027248 on I U T - × × + × × + × × 0.00005425 0.0000028992 0.00003276 . on on I U T U I T (1) Fisher criterion was used to test the adequacy of the mathematical model: = < 2 2 , adeq calc table y S F T S (2) where Fcalc and Ftable are the values of the Fisher criterion (respectively, calculated and tabulated); S 2 adeq is the variance of adequacy; S2 y is the variance of reproducibility. = < = 0.003 3.24. calc table F T (3) Based on the fact that Fcalc < Ftable at the level of dependence α = 0.05, we can conclude that the model satisfies the criterion of adequacy. The obtained mathematical model reliably reflects the dependence of the output parameter (wear and tear) on the modes of copy-piercing EDM. Fig. 4 presents the graph of the response hypersurface. The graph establishes the dependence of input data (processing modes: I, U, Ton = 75 μs) on the TE wear (γ). It is established that in the minimum mode at current of I = 4 A and voltage of U = 50 V the wear of TE is γ = 0.0063875 g. At current of I = 8 A and voltage of U = 50 V the maximum wear of TE is fixed and is γ = 0.13938 g. Physical features of the character of material destruction as a result of EDM influence directly depend on the value of energy of a single discharge. The value of the pulse (discharge) energy increases in direct proportion with the increase of current strength. Further there is an electroerosive destruction of TE. At high current values, the temperature in the spark formation zone increases, which also leads to intensive wear of TE. The empirical model of dependence of the surface quality parameter (roughness, Ra) of TE on processing modes (current I (A), voltage U (W), pulse on time Ton (μs)), has the form (4):

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 = - + × + × + × - - × × - × × - × × + 0.7004 1.070300415 0.03421764 0.04854912 0.0106517 0.0006473216 0.01304028 on on on Ra I U T I U T U I T + × × × 0.0001738704 . on I T U (4) Fig. 5 presents a hypersurface plot showing the influence of such parameters as voltage and current on the formation of surface quality. It was found that at constant pulse turn-on time Ton = 75 μs, the smallest TE roughness Ra = 2.83 μm was obtained at current I = 4 A and voltage U = 100 V, and the maximum TE surface roughness was Ra = 4.1568 μm at I = 8 A and U = 100 V. The values of the dimensions of the wells parameters change with the change of the power of single discharges acting in the interelectrode gap. The formation of a more accurate and clean surface of TE occurs at the minimum value of the power of discharges, which depend on the value of current. Increasing the current is accompanied by an increase in the depth of wells and obtaining a greater roughness of the TE surface. Figures 6–8 show images of the TE surface after SLM and after copy-piercing EDM processing in the minimum and maximum modes. Areas of melted MS1 powder units are observed on the surface of TE Fig. 4. The regression model hypersurface of electrode flow rate at constant pulse duration Ton = 75 μs; γ is a tool electrode wear (g); I is a current (A); U is a voltage (V) Fig. 5. The regression model hypersurface of the TE surface roughness at constant pulse on time Ton = 75 μs; Ra is the roughness parameter (μm); I is a current (A); U is a voltage (V)

OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 a b Fig. 6. Electrode surface before machining (after 3D printing) at magnifications of ×500 (а) and ×300 (b) a b Fig. 7. Electrode surface after electrical discharge machining at minimum mode at magnification ×500 (а) and ×300 (b) a b Fig. 8. Electrode surface after electrical discharge machining at maximum mode at magnification ×500 (а) and ×300 (b) (Fig. 6) made of maraging steel MS1 by SLM method. It was found that the melted areas are located chaotically on the TE surface. Pores between the melted areas are also observed. After EDM, the surface of TE acquires a smooth and even morphology. With copy-piercing EDM in the maximum modes at I = 8 A, Ton = 100 μs, U = 100 V, hollows and chaotic cracks are formed, accompanied by zones of melted material

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 (Fig. 7–8). With copy-piercing EDM at I = 8A, Ton = 100 μs, U = 100 V, the presence of chaotic cracks up to 1–3 μm wide was found (Fig. 8). Cracks on the TE surface arise due to rapid heating of the surface (with the increase of the current value and pulse on time the temperature in the processing zone increases) and rapid cooling by dielectric liquid. Hollows on the surface of the electrode after copy-piercing EDM are associated with the accumulation of sludge from the products of destruction of the electrode material and detail electrode (DE). With the increase of current and pulse activation time the intensification of the fracture process occurs. Material melt zones appear with increasing energy of single pulses (with an increase in current). The EDM process is accompanied by high temperatures at the breakdown spot. Rapid heating and subsequent cooling cycles cause thermal stresses on the TE surface. These stresses contribute to the formation of cracks on the TE surface. The presence of microcracks and other surface defects leads to macro-defects of the surface layer and to a decrease in the operational properties of the TE. The topology of the machined surface of additively grown TE, shown in Fig. 7a at magnification ×500, shows that to exclude surface defects of TE it is required to use the minimum mode of copy-piercing EDM at current of I = 4 A, voltage of U = 100 V. Conclusions Tool electrodes were produced by selective laser melting from MS1 maraging steel powder. It is found that tool electrode sample No.4 contains a minimum number of pores and cracks. It was produced using a single point exposure time of 20 μs; operating current of 1,400 mA; distance between points of 20 μm; average laser power of 35 W; filling step of 0.05 μm; thickness of a single layer of 30 μm; scanning speed of 1 m/s. A regression dependence between modes of copy-piercing EDM and wear of tool electrode when machining TE from maraging steel is obtained. In the minimum mode with a current of I = 4 A and a voltage of U = 50 V the wear of the electrode is minimal and amounts to γ = 0.0063875 g. The maximum wear of the electrode-tool amounts to γ = 0.13938 g with a current of I = 8 A and a voltage of U = 50 V. A regression dependence between modes of copy-piercing EDM and the surface roughness quality parameter of the additively grown TE made of MS1 maraging steel is obtained. It is shown that at constant pulse on time Ton = 75 μs the smallest roughness of TE Ra = 2.83 μm is obtained at a current of I = 4 A and a voltage of U = 100 V, and the maximum roughness of the TE Ra = 4.1568 μm is obtained at I = 8 A and U = 100 V. It is established that on the surface of additively grown TE from MS1 maraging steel there are chaotically located surface defects (microcracks, hollows, broken sections and remelting zones), reducing the strength characteristics of ET. To exclude surface defects and to form a homogeneous surface it is necessary to use finishing modes with the value of current I = 4 A, voltage U = 100 V and pulse turn-on time Ton = 75 μs. It is established that with increasing values of current up to 8 A in the interelectrode gap there is an increase in temperature and the value of pulse discharge, which leads to structural defects. References 1. Rajurkar K.P., Sundaram M.M., Malshe A.P. Review of electrochemical and electrodischarge machining. Procedia CIRP, 2013, vol. 6 (2), pp. 13–26. DOI: 10.1016/j.procir.2013.03.002. 2. Dimla D.E., Hopkinson N., Rothe H. Investigation of complex rapid EDM electrodes for rapid tooling applications. The International Journal of Advanced Manufacturing Technology, 2004, vol. 23 (3), pp. 249–255. DOI: 10.1007/s00170-003-1709-8. 3. Ho K.H., Newman S.T. State of the art electrical discharge machining (EDM) // International Journal of Machine Tools and Manufacture. 2003. Vol. 43 (13), рр. 1287–1300. DOI: 10.1016/S0890-6955(03)00162-7. 4. Ayesta I., Flaño O., Izquierdo B., Sanchez J.A., Plaza S. Experimental study on debris evacuation during slot EDMing. Procedia CIRP, 2016, Vol. 42, pp. 6–11. DOI: 10.1016/j.procir.2016.02.174. 5. Uhlmann E., Polte J., Bolz R., Yabroudi S., Streckenbach J., BergmannA. Application of additive manufactured tungsten carbide-cobalt electrodes with interior flushing channels in S-EDM. Procedia CIRP, 2020, vol. 95, pp. 460– 465. DOI: 10.1016/j.procir.2020.03.136. 6. Uhlmann E., Bergmann A., Bolz R., Gridin W. Application of additive manufactured tungsten carbide tool electrodes in EDM. Procedia CIRP, 2018, vol. 68, pp. 86–90. DOI: 10.1016/j.procir.2017.12.027.

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