Vol. 25 No. 1 2023 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. WEB OF SCIENCE
OBRABOTKAMETALLOV Vol. 25 No. 1 2023 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 Affairs, 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. Gerasenko, Director, Scientifi c and Production company “Mashservispribor”, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Evgeniy A. Kudryashov, D.Sc. (Engineering), Professor, Southwest State University, Kursk; 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, Institute of Strength Physics and Materials Science, Russian Academy of Sciences (Siberian Branch), Tomsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary
Vol. 25 No. 1 2023 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Ryaboshuk S.V., Kovalev P.V. Analysis of the reasons for the formation of defects in the 12-Cr18-Ni10-Ti steel billets and development of recommendations for its elimination............................................................... 6 Lapshin V.P., Moiseev D.V. Determination of the optimal metal processing mode when analyzing the dynamics of cutting control systems................................................................................................................... 16 Gimadeev M.R., Li A.A., Berkun V.O., Stelmakov V.A. Experimental study of the dynamics of the machining process by ball-end mills.................................................................................................................. 44 Bratan S.M., Chasovitina A.S. Simulation of the relationship between input factors and output indicators of the internal grinding process, considering the mutual vibrations of the tool and the workpiece................... 57 EQUIPMENT. INSTRUMENTS Podgornyj Yu.I., KirillovA.V., Skeeba V.Yu., Martynova T.G., Lobanov D.V., Martyushev N.V. Synthesis of the drive mechanism of the continuous production machine......................................................................... 71 Lobanov D.V., Rafanova O.S. Methodology for criteria analysis of multivariant system................................ 85 MATERIAL SCIENCE Sokolov A.G., Bobylyov E.E., Popov R.A. Diffusion coatings formation features, obtained by complex chemical-thermal treatment on the structural steels............................................................................................ 98 Filippov A.V., Khoroshko E.S., Shamarin N.N., Kolubaev E.A., Tarasov S.Yu. Study of the properties of silicon bronze-based alloys printed using electron beam additive manufacturing technology................... 110 Lysykh S.A., Kornopoltsev V.N., Mishigdorzhiyn U.L., Kharaev Yu.P., Tikhonov A.G., Ivancivsky V.V., Vakhrushev N.V. The effect of borocoppering duration on the composition, microstructure and microhardness of the surface of carbon and alloy steels............................................................................................................. 131 EDITORIALMATERIALS 149 FOUNDERS MATERIALS 159 CONTENTS
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 The effect of borocoppering duration on the composition, microstructure and microhardness of the surface of carbon and alloy steels Stepan Lysykh 1, a, *, Vasily Kornopoltsev 2, b, Undrakh Mishigdorzhiyn 1, c, Yuri Kharaev 3, d, Aleksandr Tikhonov 4, e, Vladimir Ivancivsky 5, f, Nikita Vakhrushev 5, g 1 Institute of Physical Material Science of the Siberian Branch of the RAS, 6 Sakhyanovoy str., Ulan-Ude, 670047, Russian Federation 2 Baikal Institute of Nature Management Siberian branch of the Russian Academy of sciences, 6 Sakhyanovoy str., Ulan-Ude, 670047 Russian Federation 3 East Siberia State University of Technology and Management, 40V Kluchevskaya str, Ulan-Ude, 670013, Russian Federation 4 Irkutsk National Research Technical University, 83 Lermontov str., Irkutsk, 664074, Russian Federation 5 Novosibirsk State Technical University, 20 Prospekt K. Marksa, Novosibirsk, 630073, Russian Federation a https://orcid.org/0000-0002-1421-5251, lysyh.stepa@yandex.ru, b https://orcid.org/0000-0003-1970-2945, kompo@mail.ru, c https://orcid.org/0000-0002-7863-9045, undrakh@ipms.bscnet.ru, d https://orcid.org/0000-0001-6449-4175, kharaev@inbox.ru, e https://orcid.org/0000-0002-4917-9916, tihonovalex90@mail.ru, f https://orcid.org/0000-0001-9244-225X, ivancivskij@corp.nstu.ru, g https://orcid.org/0000-0002-2273-5329, vah_nikit@mail.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. 2023 vol. 25 no. 1 pp. 131–148 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2023-25.1-131-148 ART I CLE I NFO Article history: Received: 15 December 2022 Revised: 09 January 2023 Accepted: 03 February 2023 Available online: 15 March 2023 Keywords: Thermochemical treatment (TCT) Borocoppering Diffusion layer Carbon steel Alloy steel Microhardness Roughness Funding The study of carbon Steel 45 (0.45% C) and Steel U10 (1.0% C) was carried out within the framework of the state task of the BINM SB RAS No. 02732021-0007. The study of 0.5C-Cr-Ni-Mn alloy steel was carried out with the financial support of a grant from the Russian Science Foundation (project 19-79-10163-P). Acknowledgements Research were partially conducted at core facility “Structure, mechanical and physical properties of materials” and the Science Center “Scientific Instruments” of the Dorji Banzarov Buryat State University. The authors express their gratitude to Ulakhanov Nikolay Sergeevich and Gulyashinov Pavel Anatolyevich for their help in coordinating experimental research. ABSTRACT Introduction. Borocoppering is one of the methods of thermochemical treatment (TCT) aimed at forming diffusion layers with high physical and mechanical properties on the surface of carbon and alloy steels. The thickness of the diffusion layer is the most important characteristic of the TCT, which determines the depth of hardening. Consequently, the intensity and main characteristics of the TCT (layer thickness, alloying element concentration profile) depend on the process conditions (temperature, duration, and amount of alloying element). The purpose of this work is to determine the temperature-time parameters of diffusion borocoppering, which contribute to the formation of diffusion layers with a maximum thickness. The paper considers the results of surface hardening of carbon and alloy steels (for example, Steel 45 (0.45% C), Steel U10 (1.0% C), and 0.5C-Cr-Ni-Mn steel) by high-temperature soaking in powder mixtures containing boron and copper. Borocoppering was carried out in sealed containers with the powder mixture consisting of boron carbide, copper oxide, and sodium fluoride as an activator at a temperature of 950 °C for 3–5 h. The resulting specimens with a diffusion layer were examined using an optical microscope and a scanning electron microscope (SEM); the microhardness, elemental and phase composition of the layers were also determined, as well as the roughness of the obtained surfaces. Results and discussions. The microstructure of the obtained diffusion layers is studied; diagrams of the changes in the layers’ thickness and the microhardness distribution over the layers’ thickness are shown. It is established that with an increase in the soaking time from 3 to 5 h, the thickness of the diffusion layer increases from 120 to 170 μm on Steel 45 (0.45% C); from 110 to 155 µm on Steel U10 (1.0% C) and from 130 to 230 µm on 0.5C-Cr-Ni-Mn steel. Agradual decrease in the concentration of boron and copper along the layer thickness from 15–16% and 2–3% on the surface, respectively, to zero values at the boundary with the base metal is revealed. It is established that borocoppering to the formation of more thick boride layers on the surface of carbon and alloy steels compared to pure boriding. Moreover, an increase in the duration of soaking during the process contributes to the greatest increase in the thickness of the layer on 0.5C-Cr-Ni-Mn steel. A study of microgeometry is carried out, microtopographies and profilograms of specimens’ surfaces are shown before and after borocoppering. It is established that the roughness after borocoppering increases by 2-3 times compared to the initial one, and an increase in the duration of the process does not have a significant effect on the roughness. For citation: Lysykh S.A., Kornopoltsev V.N., Mishigdorzhiyn U.L., Kharaev Yu.P., Tikhonov A.G., Ivancivsky V.V., Vakhrushev N.V. The effect of borocoppering duration on the composition, microstructure and microhardness of the surface of carbon and alloy steels. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2023, vol. 25, no. 1, pp. 131–148. DOI:10.17212/1994-6309-2023-25.1-131-148. (In Russian). ______ * Corresponding author Lysykh Stepan A., Junior researcher Institute of Physical Material Science of the Siberian Branch of the RAS, 6 Sakhyanovoy str., 670047, Ulan-Ude, Russian Federation Tel.: 8-924-397-24-76, e-mail: lysyh.stepa@yandex.ru
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Introduction The tasks of improving the reliability, operability and durability of machine parts, structures and tools are among the priorities in science and technology. To solve these problems, it is necessary to develop and implement effective methods that can improve many operational characteristics (corrosion resistance and wear resistance) by surface hardening. One of the most common methods of surface hardening is thermochemical treatment (TCT), which is aimed at improving a wide range of physical and mechanical properties during the operation of machine parts and tools. The essence of any TCT method consists in thermal and chemical effects on the material in order to change the composition, structure and properties of the surface layer. From the analysis of the literature data, it follows that one of the most common methods of TCT is boriding [1–6]. The boriding process has been known for more than half a century, but is not widely used compared to carburizing [7–10], nitriding and nitrocarburizing [11–14]. As a result of saturation of iron-carbon alloys with boron, layers with high hardness (1,600–2,000 HV) are formed on the surface. The widespread use of boriding in mechanical engineering is limited by high brittleness and tendency to cracking of surface layers after various chemical and thermal processing methods [15–17]. There are several ways to reduce the brittleness of the boride layer: 1) obtaining single-phase layers consisting of Fe2B phase; 2) obtaining thinner layers; 3) the use of such elements as chromium, copper, nickel, aluminum, etc. in the composition of the saturating mixture together with boron [21–24]. Of particular interest is one of the methods of TCT – borocoppering. This method is aimed at increasing the thickness of the diffusion layer, as well as increasing the plasticity of the diffusion layer. The authors of [21–23] found that an increase in the concentration of copper in the composition of the saturating mixture contributes to an increase in the thickness of the diffusion layer. The purpose of this work is to determine the temperature-time parameters of diffusion borocoppering, which contribute to the formation of diffusion layers with a maximum thickness. The paper considers the results of surface hardening of carbon and alloy steels (for example, Steel 45 (0.45% C), Steel U10 (1.0% C), and 0.5C-Cr-Ni-Mn steel) by high-temperature soaking in powder mixtures containing boron and copper. The purpose of this work is to study the structure of the diffusion layer depending on the duration of complex saturation of the surface of specimens made of Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel with boron and copper. Research methodology The diffusion saturation process was carried out in a powder medium. Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel were used as test specimens, the chemical composition of which is shown in Table 1. Ta b l e 1 Chemical composition of Steel 45 (0.45% C), Steel U10 (1.0% C), 0.5C-Cr-Ni-Mn, wt.% C Si Mn Ni S P Cr Cu Fe Mo Steel 45 (0.45% C) 0.42–0.5 0.17–0.37 0.5–0.8 up to 0.25 up to 0.04 up to 0.035 up to 0.25 up to 0.25̴ 97 – Steel U10 (1.0% C) 0.96–1.03 0.17–0.33 0.17–0.33 up to 0.25 up to 0.028 up to 0.03 up to 0.2 up to 0.25̴ 97 – 0.5C-Cr-NiMn steel 0.5–0.6 0.1–0.4 0.5–0.8 1.4–1.8 up to 0.03 up to 0.03 0.5– 0.8 up to 0.3̴ 95 0.15–0.3
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 The saturating mixture included powders of boron carbide, aluminum and copper oxide. Sodium fluoride acted as an activator of the saturation process. The composition of the saturating mixture had the following percentage of components: 47 % B4C + + 28 % CuO + 23% Al + 2 % NaF. The optimal amount of copper oxide was chosen based on the works [21–23], where diffusion layers with maximum thickness were obtained. The prepared specimens were placed in a container, filled with a saturating mixture (Fig. 1, a) and placed in a muffle furnace (Fig. 1, b). To prevent oxidative processes, the lid of the container was sealed with fusible glass. Diffusion saturation was carried out at a temperature of 950 °C, for 3, 4 and 5 hours. Further, the container was cooled in air; specimens were extracted, cleaned out of the remnants of the saturating mixture. This was followed by the preparation of specimens for metallographic studies. a b Fig. 1. Packed containers (a), muffle furnace EKPS-50 (b) The specimens were fixed in clamps, then grinding and polishing were carried out. To identify the microstructure of the studied specimens, a chemically active solution consisting of nitric acid (4 %) and alcohol (the rest) was used. Metallographic studies were carried out on an optical microscope Altami MET 2C. Microhardness measurements were carried out on a PMT-3M microhardness meter, the load on the diamond pyramid was 50 g. Elemental analysis was conducted on a JEOL JCM-6000 scanning electron microscope (SEM) with an elemental dispersion analyzer. To study the structure, the etched surface of the specimens was studied in the mode of secondary electrons. X-ray phase analysis was performed on a D2 PHASER diffractometer with a LYNXEYE linear detector. The measurement step was 0.02°, the processing time of one step was 1.2 s. The study of the topography with the determination of the surface roughness parameters of the obtained specimens was carried out on an optical profilometer Bruker Contour GT-K1 with Vision64 software [24, 25]. Results and discussion As a result of diffusion surface saturation of specimens with boron and copper for 3 hours, diffusion layers with a thickness of 110–130 µm were obtained (Fig. 2). After diffusion borocoppering for 4 hours, diffusion layers with a thickness of 140–220 µm were obtained on the surface of the specimens (Fig. 3). Fig. 2, a shows a 120 µm thick diffusion layer of Steel 45 (0.45% C) with a hardness of 1,800–1,600 HV. The diffusion layer has a needle-like structure typical of the boride layer. A characteristic feature is the deep insertion of needles into the steel base, which many authors point out as the reason for the strong adhesion of the diffusion layer to the metal base [26–29]. In this case, the needles at the ends have rounding. The carboboride phase is isolated directly from boride needles, the hardness of which was 1,200–1,750 HV. The transition zone between the layer and the steel base does not differ from the ferrite-pearlite structure of the base.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 After borocoppering of Steel 45 (0.45% C) for 4 hours, the layer thickness was 140 µm, which is 20 µm greater compared to the soaking this steel for 3 hours (Fig. 3, a). The microhardness was 2,000 HV at the surface, followed by a decrease to 1,600 HV at the layer/base interface. There is a fusion of needles at the base with the formation of a continuous layer. There is no carboboride phase adjacent to the boride needles. The transition zone is more clearly represented in the form of a light ferrite layer, where the maximum concentration of boron reaches 4 %, and then it gradually decreases towards the core of the specimen. The steel structure retains proeutectoid ferrite (light inclusions); martensite with a small content of residual austenite is also observed. On the surface of the carbon tool Steel U10 (1.0% C), after 3 hours of TCT, a diffusion layer with a thickness of 110 µm was obtained, the hardness of which was 1,975–1,575 HV (Fig. 2, b). The layer consists of tightly pressed needles with an unexpressed transition zone, which is represented by perlite with low boron content. The steel structure consists of a plate-like perlite surrounded by a thin cementite mesh. It is necessary to note the presence of light coagulated inclusions, apparently being austenite. After borocoppering of Steel U10 (1.0% C) for 4 hours, a diffusion layer with a thickness of 140 µm was obtained, which is 30 µm greater compared to the soaking this steel for 3 hours (Fig. 3, b). The microhardness also increased slightly to 2,050 HV at the surface, followed by a decrease to 1,600 HV at the layer/base interface. The microstructure indicates the fusion of needles and the formation of a continuous layer in the upper and middle part of the layer with the preservation of the needle structure at the layer/base interface. The presence of a transition zone is not observed, and the microstructure of the base metal is represented by a lamellar perlite with a cementite mesh. a b c Fig. 2. Microstructure of the diffusion layer after complex surface saturation with boron and copper for 3 hours of soaking: a – Steel 45 (0.45% C), layer thickness is 120 µm; b – Steel U10 (1.0% C), layer thickness is 110 µm; c – 0.5C-Cr-Ni-Mn steel, layer thickness is 130 µm a b c Fig. 3. Microstructure of the diffusion layer after complex surface saturation with boron and copper for 4 hours of soaking: a – Steel 45 (0.45% C), layer thickness is 160 µm; b – Steel U10 (1.0% C), layer thickness is 140 µm; c – 0.5C-Cr-Ni-Mn steel, layer thickness is 220 µm
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Metallographic studies of the structure and diffusion layer of 0.5C-Cr-Ni-Mn steel showed the presence of a diffusion layer with a thickness of 130 µm and 220 µm at 3- and 4-hour borocoppering, respectively (Fig. 2, b, Fig. 3. b). The microhardness was 1,800–1,500 HV at 3-hour soaking and 2,000–1,650 HV at 4-hour soaking. When conducting diffusion saturation with boron and copper of specimens from Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel for 5 hours, an increase in the thickness of the diffusion layer by 10–15 µm is observed (Fig. 5). Fig. 4, a shows the structure of Steel 45 (0.45% C), where, in contrast to the previous borocoppering modes, the layer has a pronounced needle-like structure in the form of enlarged needles with a rectilinear direction to the core of the specimen. There is an increase in microhardness in the near-surface part of the layer, where its maximum value is 2,100 HV (Fig. 6, a). a b c Fig. 4. Microstructure of the diffusion layer after complex surface saturation with boron and copper for 5 hours of exposure: a – Steel 45 (0.45% C), layer thickness is 170 µm; b – Steel U10 (1.0% C), layer thickness is 155 µm; c – 0.5C-Cr-Ni-Mn steel, layer thickness is 230 µm Fig. 5. The thickness of the diffusion layer formed after borocoppering of Steel 45 (0.45% C), Steel U10 (1.0% C), and 0.5C-Cr-Ni-Mn steel for 3, 4 and 5 hours On the surface of the specimens from Steel U10 (1.0% C), after 5 hours of borocoppering, the diffusion layer loses its needle-like structure and takes the form of a continuous layer, as evidenced by Fig. 4b. The increase in thickness was 15 µm, and the maximum value of microhardness was equal to 2,000 HV (Fig. 6, b).
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Fig. 6. Microhardness distribution: a – for Steel 45 (0.45% C); b – for Steel U10 (1.0% C); c – for 0.5C-Cr-Ni-Mn steel; d – microstructure of Steel 45 (0.45% C) after 4 hours of soaking with points of indentation a b c d
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Minor changes in the structure of the diffusion layer after 5-hour borocoppering undergo specimens of 0.5C-Cr-Ni-Mn steel (Fig. 4, c). The thickness of the layer was increased by 10 µm (Fig. 5). The needle-like structure of the layer remains unchanged, but the needles’ growth is observed. It is also worth noting that directly adjacent to the boride needles are some secretions, presumably of a carboboride structure, which have a direction at some angle relative to the needles themselves. The microhardness and the nature of its distribution remain unchanged (Fig. 6, c). An increase in the carbon content in Steel 45 (0.45%C) and Steel U10 (1.0%C) reduces the average layer thickness at both soaking modes. The thickness of the layer is greatest on 0.5C-Cr-Ni-Mn steel specimens, despite the intermediate carbon content (Fig. 4). It is likely that alloying elements in steel take part in the intensification of diffusion during borocoppering. As can be seen in Fig. 6, the distribution of microhardness after borocoppering for 3, 4 and 5 hours on all steels is similar and is characterized by a gradual decrease in values from the surface to the base metal. It should be noted that the microhardness of all specimens over the entire thickness of the layer after 5-hour borocoppering is higher by 100–150 HV, compared with the microhardness of specimens after borocoppering for 3 and 4 hours. Presumably, this is due to an increase in the content of the harder phase of FeB after a 5-hour borocoppering. The data given in Table 2 (Fig. 7, a) confirm the presence of boron and copper in the diffusion layer on the test specimen made of Steel 45 (0.45% C). There is a decrease in the concentration of boron and copper in the direction from the surface to the interface with the base metal. Carbon is pushed into the transition zone, where its concentration is maximum – 0.56%. Nickel and manganese are almost evenly distributed over the entire thickness of the diffusion layer. The presence of chromium was detected in the transition zone. Consequently, the elemental analysis shows the nature of the distribution of alloying elements corresponding to the chemical composition of Steel 45 (0.45% C). The results presented in Table 3 (Fig. 7, b) for Steel U10 (1.0% C) indicate the presence of boron on the surface in the amount of 16.81 % and a gradual decrease in its concentration to 0.68 %. The maximum amount of copper is observed on the surface of the diffusion layer and directly under the boride needles. Carbon is pushed under the boride layer, where its content reaches 1.69 %. Chromium and manganese are evenly distributed over the entire thickness of the diffusion layer. Table 4 shows the elemental composition of 0.5C-Cr-Ni-Mn steel after borocoppering for 4 hours (Fig. 7, c). As in the previous specimens, the maximum concentration of boron is observed on the surface, followed by its decrease towards the boundary with the base. The maximum carbon concentration is visible on the surface and in the transition zone. Aluminum, chromium, nickel, molybdenum and copper are concentrated in the same zones as carbon. X-ray phase analysis performed on the surface of Steel 45 (0.45% C) (see Fig. 8) after borocoppering demonstrates the presence of phases FeB, Fe2B. The inability to determine copper is most likely due to its small amount. Ta b l e 2 The elemental composition of the diffusion layer on Steel 45 (0.45% C) after 4 hours of borocoppering (Fig. 7, a) Points of the spectrum Chemical elements, mass % B C Mn Ni Cr Cu Fe 1 16.73 0.2 0.29 0.41 – 2.39 79.98 2 11.37 0.06 0.38 0.44 – – 87.75 3 6.2 0.32 0.22 0.51 – – 92.75 4 – 0.56 0.24 0.31 – 0.36 98.53 5 – 0.47 0.35 0.51 0.12 0.17 98.38
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Ta b l e 3 The elemental composition of the diffusion layer on Steel U10 (1.0% C) after 4 hours of borocoppering (Fig. 7. b) Points of the spectrum Chemical elements, mass % B C Al Si Cr Mn Ni Fe Cu 1 14.81 0.83 0.22 0.16 0.34 0.57 – 81.18 1.89 2 12.73 0.43 0.19 0.17 0.15 0.08 – 85.68 0.57 3 6.91 0.61 0.06 0.11 0.09 0.55 – 83.34 – 4 0.68 1.22 – 0.34 0.23 0.32 0.11 95.91 1.19 5 – 1.69 – 0.28 0.12 0.3 – 97.61 – b c Fig. 7. The points of the spectra counting in the diffusion layer on the sample during elemental analysis: a – Steel 45 (0.45% C); b – Steel U10 (1.0% C); c – 0.5C-Cr-Ni-Mn steel after 4 hours of borocoppering a The X-ray obtained on Steel U10 (1.0% C) (see Fig. 9) demonstrates the presence of the Fe2B phase and the Fe3C carbide phases. It is worth paying attention to the absence of the FeB phase. The presence of copper is also not observed. As a result of X-ray phase analysis of a 0.5C-Cr-Ni-Mn steel specimen (see Fig. 10) the phase composition of the boride layer was established, which consists of three borides: FeB, Fe2B and Cr5B3. It should be noted
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Ta b l e 4 The elemental composition of the diffusion layer on 0.5C-Cr-Ni-Mn steel after 4 hours of borocoppering (fig. 7, c) Points of the spectrum Chemical elements, mass % В C Al Cr Ni Cu Mo Fe 1 16.43 0.35 0.3 0.66 0.67 2.6 0.57 78.42 2 14.77 0.15 0.51 0.66 0.67 - 0.14 83.1 3 12.05 0.06 – 0.53 0.51 0.51 0.27 86.07 4 5.98 0.03 – 0.62 0.31 – 0.34 92.72 5 1.35 0.41 – 0.63 0.46 – 0.25 96.9 6 0.21 0.37 0.56 0.59 0.57 0.09 0.07 97.54 7 – 0.4 0.58 0.4 0.56 0.54 – 97.52 Fig. 8. XRD pattern of the specimen of Steel 45 (0.45% C) after borocoppering for 4 hours that copper was detected in free form, which confirms the assumptions indicated in [21], where it does not form thermally stable compounds with boron, iron and carbon. As a result of the study of microgeometry, three-dimensional microtopographs were obtained, as well as profilograms of the surfaces of the specimens after TCT (see Fig. 11–13). Roughness was estimated by the parameter Ra (Table 5). The roughness of Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel in the initial state before the TCT was comparable and the Ra values are in the range of 0.06–0.084 µm (Fig. 11, a, 12, a, 13, a). After TCT, there is an increase in the heights of micro-dimensions compared to the initial specimens for all the materials under consideration and the processing time (Fig. 11, b–d, 12, b–d, 13, b–d). After borocoppering, an increase in the Ra parameter was established by 2–3 times compared to the initial specimens
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Fig. 9. XRD pattern of the specimen of Steel U10 (1.0% C) after borocoppering for 4 hours Fig. 10. XRD pattern of the sample made of 0.5C-Cr-Ni-Mn steel after borocoppering for 4 hours before treatment, while an increase in the TCT time from 3 to 5 hours does not lead to a further increase in roughness (Table 5). The resulting roughness after borocoppering (Ra 0.16–0.2 µm), with an initial Ra of 0.06–0.08 µm, meets the requirements for surface roughness of most mechanical engineering products and does not require additional subsequent machining.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Fig. 11. Microtopography of the surface of Steel 45 (0.45% C) specimens: a – initial, without treatment; b – after borocoppering for 3 hours; c – after borocoppering for 4 hours; d – after borocoppering for 5 hours а b c d
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Fig. 12. Microtopography of the surface of Steel U10 (1.0% C) specimens: a – initial, without treatment; b – after borocoppering for 3 hours; c – after borocoppering for 4 hours; d – after borocoppering for 5 hours а b c d
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Fig. 13. Microtopography of the surface of 0.5C-Cr-Ni-Mn steel specimens: a – initial, without treatment; b – after borocoppering for 3 hours; c – after borocoppering for 4 hours; d – after borocoppering for 5 hours а b c d
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Ta b l e 5 Roughness of the specimens after TCIT (Fig. 11-13) Type of teatment Steel 45 (0.45% C) Steel U10 (1.0% C) 0.5C-Cr-Ni-Mn steel Ra, мкм Original, without teatment 0.06 0.062 0.084 Borocoppering for 3 hours 0.2 0.187 0.175 Borocoppering for 4 hours 0.16 0.201 0.273 Borocoppering for 5 hours 0.176 0.189 0.211 Conclusion Based on the conducted studies, it is found that saturation of specimens from Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel for 3, 4 and 5 hours leads to the formation of diffusion layers, the thickness of which varies from 110 to 230 µm. It is found that the increase in the thickness of the diffusion layer on Steel 45 (0.45% C) is 41%, with an increase in the time of treatment by 2 hours. On Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel, the values of the layer thickness increase were 40 and 77 %, respectively. For these grades of steels, a longer soaking time during borocoppering is recommended. It is established that during the diffusion boromedning for 4 hours, the greatest increase in the thickness of the diffusion layer is observed. The study of microtopography revealed that the roughness after borocoppering increases to Ra 0.16–0.2 µm at the initial Ra 0.06–0.08 µm for Steel 45 (0.45% C), Steel U10 (1.0% C) and 0.5C-Cr-Ni-Mn steel, while the duration of the process does not affect the increase in roughness. References 1. Busby P.E., Warga M.E., Wells C. Diffusions and solubility of boron in iron and steel. JOM, 1953, vol. 5, pp. 1463–1468. DOI: 10.1007/BF03397637. 2. Prince M., Surya Raj G., Yaswanth Kumar D., Gopalakrishnan P. Boriding of steel: improvement of mechanical properties – a review. High Temperature Material Processes, 2022, vol. 26 (2), pp. 43–89. DOI: 10.1615/ HighTempMatProc.2022041805. 3. Shevchuk E.P., Plotnikov V.A., Bektasova G.S. Diffuziya bora pri borirovanii uglerodistoi stali [Boron diffusion during carbon steel boriding]. Izvestiya Altaiskogo gosudarstvennogo universiteta = Izvestiya of Altai State University, 2021, no. 1 (117), pp. 64–65. DOI: 10.14258/izvasu(2021)1-10. 4. Yu L.G., Chen X.J., Khor K.A., Sundararajan G. FeB/Fe2B phase transformation during SPS pack-boriding: Boride layer growth kinetics. Acta Materialia, 2005, vol. 53, pp. 2361–2368. DOI: 10.1016/j.actamat.2005.01.043. 5. Bernal-Ponce J., Irvin-MartinezA., Vera-Cardenas E., Garcia-BarrientosA., Medina-FloresA., Bejar-Gomez L., Borjas-Garcia S. A microstructure comparison of Iron borides formed on AISI 1040 and D2 steels. Microscopy and Microanalysis, 2015, vol. 21, suppl. 3, pp. 1759–1760. DOI: 10.1017/S1431927615009575. 6. Mishustin N.M., Ivanaiskii V.V., IshkovA.V. Sostav, struktura i svoistva iznosostoikikh pokrytii, poluchennykh na stalyakh 65G i 50KhGA pri skorostnom TVCh-borirovanii [Composition, structure and properties of wearresistant coatings obtained on steels 65G and 50KhGAwith high-speed high-frequency boriding]. Izvestiya Tomskogo politekhnicheskogo universiteta = Bulletin of the Tomsk Polytechnic University, 2012, vol. 320, no. 2, pp. 68–72. 7. Balanovskii A.E., Vu V. Plazmennaya poverkhnostnaya tsementatsiya s ispol’zovaniem grafitovogo pokrytiya [Plasma surface carburizing with graphite paste]. Pis’ma o materialakh = Letters on Materials, 2017, vol. 7, no. 2, pp. 175–179. DOI: 10.22226/2410-3535-2017-2-175-179. 8. Kolosov A.D., Gozbenko V.E., Shtayger M.G., Kargapoltsev S.K., Balanovskiy A.E., Karlina A.I., Sivtsov A.V., Nebogin S.A. Comparative evaluation of austenite grain in high-strength rail steel during welding, thermal processing and plasma surface hardening. IOP Conference Series: Materials Science and Engineering, 2019, vol. 560. DOI: 10.1088/1757-899X/560/1/012185.
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