Chemical composition, structure and microhardness of multilayer high-temperature coatings

Vol. 24 No. 4 2022 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. We sincerely happy to announce that Journal “Obrabotka Metallov” (“Metal Working and Material Science”), ISSN 1994-6309 / E-ISSN 2541-819X is selected for coverage in Clarivate Analytics (formerly Thomson Reuters) products and services started from July 10, 2017. Beginning with No. 1 (74) 2017, this publication will be indexed and abstracted in: Emerging Sources Citation Index. 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. 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

OBRABOTKAMETALLOV Vol. 24 No. 4 2022 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; Sergey V. Kirsanov, D.Sc. (Engineering), Professor, National Research Tomsk Polytechnic University, Tomsk; 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. 24 No. 4 2022 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Dyuryagin A.A., Ardashev D.V. A study of the relationship between cutting force and machined surface roughness with the feed per tooth when milling EuTroLoy 16604 material produced by the DMD method...................... 6 Ulakhanov N.S., Tikhonov A.G., Mishigdorzhiyn U.L., Ivancivsky V.V., Vakhrushev N.V. The features of residual stresses investigation in the hardened surface layer of die steels after diffusion boroaluminizing............... 18 Rubtsov V.E., Panfi lov A.O., Knyazhev E.O., Nikolaeva A.V., Cheremnov A.M., Gusarova A.V., Beloborodov V.A., Chumaevskii A.V., Ivanov A.N. Development of plasma cutting technique for C1220 copper, AA2024 aluminum alloy, and Ti-1,5Al-1,0Mn titanium alloy using a plasma torch with reverse polarity................ 33 Amirov A.I., Moskvichev E.N., Ivanov A.N., Chumaevskii A.V, Beloborodov V.A. Formation features of a welding joint of alloy Ti-5Al-3Mo-1V by the friction stir welding using heat-resistant tool from ZhS6 alloy....... 53 EQUIPMENT. INSTRUMENTS Ardashev D.V., Zhukov A.S. Investigation of the relationship between the cutting ability of the tool and the acoustic signal parameters during profi le grinding..................................................................................................... 64 Bataev D. K-S., Goitemirov R. U., Bataeva P. D. Studies of wear resistance and antifriction properties of metalpolymer pairs operating in a sea water simulator........................................................................................................ 84 Zakovorotny V.L., Gvindjiliya V.E., Fesenko E.O. Application of the synergistic concept in determining the CNC program for turning............................................................................................................................................ 98 MATERIAL SCIENCE Sokolov R.A., Novikov V.F., Kovenskij I.M., Muratov K.R., Venediktov A.N., Chaugarova L.Z. The effect of heat treatment on the formation of MnS compound in low-carbon structural steel 09Mn2Si................................ 113 Burkov А.А., Krutikova V.O. Deposition of titanium silicide on stainless steel AISI 304 surface...................... 127 Pugacheva N.B., NikolinYu.V., BykovaT.M., Goruleva L.S. Chemical composition, structure and microhardness of multilayer high-temperature coatings..................................................................................................................... 138 Saprykina N.А., Chebodaeva V.V., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А., Guseva T.S. Synthesis of a three-component aluminum-based alloy by selective laser melting............................................................... 151 Gabets D.A., MarkovA.M., Guryev M.A., Pismenny E.A., NasyrovaA.K. The effect of complex modifi cation on the structure and properties of gray cast iron for tribotechnical application..................................................... 165 Ivanov I.V., Yurgin A.B., Nasennik I.E. Kuper K.E. Residual stress estimation in crystalline phases of highentropy alloys of the AlxCoCrFeNi system........................................................................................................... 181 Korosteleva E.N., Nikolaev I.O., Korzhova V.V. Features of the structure formation of sintered powder materials using waste metal processing of steel workpieces................................................................................. 192 EroshenkoA.Yu., Legostaeva E.V., Glukhov I.A., Uvarkin P.V., TolmachevA.I., Luginin N.A., Bataev V.A., Ivanov I.V., Sharkeev Yu.P. Effect of deformation processing on microstructure and mechanical properties of Ti-42Nb-7Zr alloy............................................................................................................................................. 206 Kutkin O.M., Bataev I.A., Dovzhenko G.D., Bataeva Z.B. The study of characteristics of the structure of metallic alloys using synchrotron radiation computed laminography (Research Review)................................ 219 EDITORIALMATERIALS 243 FOUNDERS MATERIALS 255 CONTENTS

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Chemical composition, structure and microhardness of multilayer high-temperature coatings Nataliya Pugacheva 1, а, *, Yuri Nikolin 2, b, Tatiana Bykova 1, c , Larisa Goruleva 1, d 1 Institute of Engineering Science, Ural Branch, Russian Academy of Sciences, 34 Komsomolskaya str., Yekaterinburg, 620049, Russian Federation 2 Solid Flame Ltd., 54 Lenin Ave., box. 5, Yekaterinburg, 620075, Russian Federation a https://orcid.org/0000-0001-8015-8120, nat@imach.uran.ru, b https://orcid.org/0000-0003-1070-2076, sf.ekb@mail.ru, с https://orcid.org/0000-0002-8888-6410, tatiana_8801@mail.ru, d https://orcid.org/0000-0001-8635-5213, sherlarisa@yandex.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. 2022 vol. 24 no. 4 pp. 138–150 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2022-24.4-138-150 ART I CLE I NFO Article history: Received: 29 July 2022 Revised: 29 August 2022 Accepted: 15 September 2022 Available online: 15 December 2022 Keywords: Plasma spray Powders Coating Microstructure Dendrites Microhardness Funding The work was carried out on the equipment of the Plastometriya Shared Use Center of the IMASH UB RAS in accordance with the state assignment on the topic No. АААА-А18-118020790145-0. ABSTRACT Introduction. Plasma spraying is one of the modern and effective methods for coatings application for various purposes and compositions. With the help of thermal plasma flows, it is possible to spray almost any powder materials (ceramic, metal, metal-ceramic). Plasma spraying of multilayer protective coatings can be successfully used to increase the durability of pierced mandrels, which are the main tool in the production of hollow billets. The purpose of this work is to study the chemical composition, structure, and microhardness of multilayer hightemperature coatings of two different compositions deposited by plasma spraying, which are supposed to be used to increase the durability of pierced mandrels. Materials and research methods. The deposition of multilayer coatings of two compositions was carried out on a plasma-powder spraying unit with contact excitation of an arc discharge UPN-60KM TSP2017. Coatings were obtained by sequential deposition of three layers with different powder compositions. After deposition of all three coating layers, oxidative annealing was carried out at a temperature of 900°C to form a dense scale layer of FeO + Fe2O3 + Fe3O4 on the surface. The chemical composition of the coatings was studied by X-ray microanalysis using a TESCAN scanning electron microscope with an OXFORD attachment. The microstructure of the coatings was studied using a NEOPHOT metallographic microscope. Phase X-ray diffraction analysis was performed on a SHIMADZU diffractometer in Kα-chromium radiation. Microhardness was measured on a LEICA hardness tester at a load of 50 g. Results and discussion. The nature of the distribution of chemical elements over the thickness of the coating, consisting of four layers, is established: an inner metal layer that provides protection against high-temperature corrosion; a transitional metal layer designed to equalize the thermal properties between the layers; α-Fe metal oxide layer and iron oxides and external thermal barrier oxide layer FeO + Fe2O3 + Fe3O4. Coatings are characterized by a non-uniform distribution of structural components and microhardness over its thickness. The microhardness of the inner layer reaches 1,400 HV0.05, the transition layer is 800 HV0.05, and the metal oxide layer is 300 HV0.05. For citation: Pugacheva N.B., Nikolin Yu.V., Bykova T.M., Goruleva L.S. Chemical composition, structure and microhardness of multilayer high-temperature coatings. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2022, vol. 24, no. 4, pp. 138–150. DOI 10.17212/1994-6309-2022-24.4-138-150. (In Russian). ______ * Corresponding author Pugacheva Nataliya B., D.Sc. (Engineering), Associate Professor, Chief Researcher Institute of Engineering Science, Ural Branch, Russian Academy of Sciences, 34 Komsomolskaya str., 620049, Yekaterinburg, Russian Federation Tel.: 8 (343) 362-30-23, e-mail: nat@imach.uran.ru Introduction Plasma spraying is one of the advanced and effective methods for applying coatings of various purposes and compositions. By means of thermal plasma flows, it is possible to spray almost any powder materials (metallic, ceramic, cermet, etc.) [1–3]. Plasma spraying for applying self-fluxing powders is the most widely used technology [4, 5]. The self-fluxing process consists in spontaneous removal of oxides from the surface of particles during its fusion. For this to happen, oxides must have low melting temperature,

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 low density, and high fluidity. Nickel-based Ni-Cr-B-Si alloys are most often used for this purpose; during plasma spraying of the alloys, B2O5-Cr2O3-SiO2 oxides form a fusible slag, which, when fusing, comes to the surface in the form of a thin glassy coating [6–8]. Coatings applied by plasma spraying have some disadvantages. First of all, its porosity ranges between 8 % and 15% [3–5]. In order to reduce porosity, special plasma surfacing techniques were developed, such as high-speed plasma surfacing, applying multilayer coatings, nanostructuring of sprayed coatings, rare-earth doping, repeated laser surface melting, and a combination of the techniques [9–11]. However, the presence of pores in a coating can be functionally advantageous in some cases. At high operating temperatures, oxygen easily penetrates through the pores deep into the coating, thus causing massive oxidation throughout its thickness, with the formation of a protective film of Cr2O3 or Al2O3 oxides [12–14]. A combination of several differently applied protective layers is successfully used to reduce the disadvantages of coatings [15– 19]. When a single application method is used, the layers may differ in the chemical and phase composition and perform different protective functions. In fact, functional gradient coatings are formed. Plasma spraying of multilayer protective coatings can be successfully used to increase the durability of piercing mandrels, which are the main tools used to produce hollow billets [20–22]. During operation, piercing mandrels are affected by cyclic heating (20 to 1100 °C) and by the pressure of the metal being deformed (up to 170 MPa) as it moves relative to the mandrel at a speed of up to 1 m/s [20, 23]. The durability of mandrels can be effectively increased by oxidizing the nose surface and the spherical surface in order to form an oxidized layer, which prevents the billet metal from sticking to the mandrel and is a heat-insulating layer [21–23]. The formation of an oxide layer on the surface increases the wear resistance of mandrels by a factor ranging from 1.5 to 2.0 [23]. The oxide layer provides additional thermal resistance, the value of which depends on the thickness of the scale layer, its thermophysical and mechanical properties [24–26]. As the temperature increases, the scale softens, and very soon it starts to act as a lubricant during contact. As is known [27, 28], under high-temperature oxidation (900-1000 °С), a layer consisting of FeO (wustite), Fe2O3 (hematite), and Fe3O4 (magnetite) is formed on a metal surface. The FeO film is an inner layer, and it peels off easily; therefore, when forming an oxide layer, one should reduce the amount of wustite as much as possible and make it turn into magnetite (Fe3О4). To increase the service life of piercing mandrels, protective coatings containing iron oxides can be successfully used. The development of various combinations of differently functioning layers is of interest. The aim of this paper is to study the chemical composition, structure, and microhardness of plasmasprayed multilayer high-temperature coatings of two different compositions, which are supposed to be used to increase the service life of piercing mandrels. Materials and research methods The coatings were applied by means of a UPN-60KMTSP2017 plasma powder spraying unit with contact initiation of an arc discharge (NPP TSP LLC, Ekaterinburg). All the layers of the multilayer coatings were sprayed onto 20CrNi4V (3310) chromium-nickel steel specimens under the same following conditions: a current of 310 A and a voltage of 57…60 V, with argon as the main plasma-forming gas and hydrogen as a high-enthalpy gas. Multilayer coatings with two different compositions were studied. The coatings were produced by successive overlaying of three layers. The first layer is meant for protection against hightemperature oxidizing and wear, it is produced by spraying self-fluxing powders of compositions 1 and 2 (see Table 1). This layer is required to prevent rapid fracture of mandrels in the case of the wear of the upper layers. It will enable one to remove the mandrel from operation in due time and to reapply the fractured outer layers, thus restoring the protective properties of the mandrel. The second layer is transitional, and it is produced by spraying a 50:50 mixture of high-temperature powders of compositions 1 or 2 with Fe powder. This layer is designed for a smooth variation of properties from the outer layer to the inner one, and it delivers iron to form an oxide film at high operating temperatures. The third metal-oxide layer is produced by spraying Fe powder in an oxidizing environment. It serves to restore the outer oxidized layer at the operating temperatures of piercing mandrels. The morphology of the particles of the sprayed powders is shown in Fig. 1.

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 1 Composition of powders being sprayed Powder composition 1, wt. % C Cr Si B Mn V Fe 1.2 3.8 2.3 3.6 1.0 1.0 Bal Powder composition 2, wt. % C Ni Si B Mn Fe 0.5 9.0 1.2 2.7 4.0 Bal Fig. 1. Morphology of powder particles for multilayer coating spraying: a – powder of composition 1; b – powder of composition 2; c – Fe powder а b c The structural features and thickness of the obtained coatings were studied on the cross cuts by means of a Tescan Vega II XMU scanning electron microscope, equipped with an Oxford HKL Nordlys F+ energy dispersive attachment, and a Neophot-21 microscope at 100- to 1,000-fold magnification. By means of a Shimadzu X-ray diffractometer using Kα Cr radiation, phase X-ray diffraction analysis of each layer was performed on the specimen surface immediately after layer application. Microhardness was measured in a Leica hardness tester with a load of 50 g. After spraying of all the three coating layers, oxidizing annealing was performed at 900 °С in order to create a dense layer of FeO+Fe2O3+Fe3O4 scale on the surface. It is this oxide layer that will act as a lubricant in the operation of piercing mandrels and as a thermal barrier decreasing the surface temperature. The average size of the powder particles ranged between 60 and 100 μm for the coating of composition 1 and between 70 and 90 μm for the coating of composition 2; the size of the Fe powder particles was 40 to 60 μm. Results and discussion As was supposed, the sprayed coatings consist of four layers (Fig. 2). The thicknesses of each layer are presented in Table 2. According to the results of the phase X-ray diffraction analysis, the surface oxide layers on both studied coatings are identical and consist of a mixture of the oxides FeO, Fe2O3, and Fe3O4 (Fig. 3). The surface layer is denoted by 4 in Fig. 2; it should play the role of a lubricant, which decreases the friction coefficient and prevents the base metal from overheating. Obviously, the presence of diffraction peaks from the Fe-based α-solid solution is due to the fact that the metal oxide layer (3 in Fig. 2) got into the analysis of the specimen surface. The structure and element distribution of this layer are shown in Fig. 4.

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 2 Thickness of coating layers Coating Composition 1, µm Composition 2, µm 1st layer 200 150 2d layer 250 250 3d layer 350 370 4th layer 50 30 Total thickness 850 800 a b Fig. 2. The microstructure of the multilayer high-temperature coating: a – the coating of composition 1; b – the coating of composition 2 a b Fig. 3. A fragment of the diffraction pattern of the outer oxide layer: a – coating of composition 1; b – coating of composition 2

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b c Fig. 4. Distribution of elements in the metal-oxide layer (3 in Fig. 2): a – image in secondary-electron mode; b – in the characteristic X-ray radiation of iron; c – in the characteristic X-ray radiation of oxygen The inner layer (1 in Fig. 2) has a complex phase composition. Areas formed from molten undeformed and plastically deformed particles of the initial powder, as well as from deformed particles that have not had time to melt, are clearly distinguishable in its structure (Table 3). The particles of the first kind have managed to solidify before impact on the substrate; therefore, it has a practically initial round shape and a pronounced dendritic structure (1 in Fig. 5). The second-type particles have solidified directly on the substrate under deformation, and it has a polygonal structure without dendrites (3 in Fig. 5). The third grain type in the coatings studied (2 in Fig. 5) is represented by unmolten initial powder particles heated and deformed during collision with the substrate surface. The phase X-ray diffraction analysis has shown that the matrix in the coatings is constituted by solid solutions, namely, chromium ferrite for the coating of composition 1 (Fig. 6а) and ferrite + austenite for the coating of composition 2 (Fig. 6b). Fine carbides, silicides, and borides are the strengthening phases (Fig. 6). The second layer consists of the same phases as the first one, but with a higher content of ferrite formed during Fe powder spraying. In these ferrite grains there are no strengthening phases; therefore, it plays a role of dampers relaxing the arising thermal stresses. This layer provides smooth variation of the properties from layer to layer in the coatings. In this case, the porosity of the second layer is a positive factor since, during operation, under conditions of friction forces, the outer oxide layer penetrates into the pores of the Ta b l e 3 The chemical composition of the grains of the high-temperature coating marked in Figs. 5, at.% Coating of composition 1 (Fig. 5, a) Grain No. B C Si V Cr Mn Fe 1 13.5 2.0 4.5 1.1 4.5 2.6 71.7 2 9.9 0.9 3.1 1.4 6.5 3.5 74.3 3 14.9 1.3 7.4 0.8 14.2 1.5 59.7 Coating of composition 2 (Fig. 5, b) Grain No. B C Si V Mn Fe Ni 1 13.5 2.2 3.6 0.3 3.6 69.1 7.5 2 6.8 1.3 4.5 0.3 4.1 75.2 7.5 3 7.3 0.6 5.2 0.3 3.3 75.6 7.6

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b Fig. 5. The microstructure of the inner layer of the coatings (1 in Fig. 2): a – composition 1; b – composition 2 a b Fig. 6. Fragments of diffraction patterns of the inner layer of the coatings under study: а – composition 1; b – composition 2 second layer and even the third one. Under severe operating conditions, which are typical for piercing mandrels, the outer oxide layer will gradually fail. At high temperatures, the recovery of the oxide layer due to iron oxidation in the third (metal-oxide) layer of the coatings is to be expected. The oxide layer can be restored by additional heat treatment, e.g., by surface heating with a gas or plasma torch. The porosity of the third layer will intensify oxygen penetration into the coating and increase the surface participating in the oxidation reaction. As the outer layers wear, nickel and chromium contained in the second and first inner layers become involved in the oxidation process. A decrease in the coating wear rate with transition to the inner layers is to be expected. This will be owing to the strengthening phases (carbides, silicides, and borides) having high hardness and increasing the hardness of the first inner layer (Fig. 7). The dendritic structure of the molten initial powder particles that have solidified before colliding with the substrate surface (Fig. 8) should help to slow down the wear of piercing mandrels during operation. In the coating of composiFig. 7. Microhardness distribution through the coating thickness

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b Fig. 8. Microstructure and chemical composition of non-deformable particles of type 1: a – coating of composition 1; b – coating of composition 2 tion 1, dendrites have a fine structure with closely spaced secondary branches, and this testifies to high solidification rates (Fig. 8, a). The dendritic branches are enriched with silicon and carbon, and the interdendritic spaces are enriched with boron (Table 4 and Fig. 8, a). Most likely, the dendritic branches consist of chromium ferrite with dispersed particles of Cr23C6 carbides, CrSi, Cr3Si, and (Cr,Fe,Mn)5Si3 silicides, and the interdendritic spaces consist of chromium ferrite with disperse FeB and Fe2B boride particles. In the coating of composition 2, the particles that have solidified before collision with the substrate are characterized by a coarser dendritic structure (Fig. 8, b). Ta b l e 4 The results of local chemical analysis of the areas, marked in Fig. 8, at.% Coating composition 1 (Fig. 8, a) Area No. B C Si V Cr Mn Fe 1 3.39 0.23 2.40 1.28 5.70 3.70 83.30 2 7.52 0.00 1.10 1.47 6.12 3.53 80.26 Coating composition 2 (Fig. 8, b) Area No. B C Si V Mn Fe Ni 1 8.55 2.11 3.91 0.30 4.58 73.65 6.90 2 17.16 2.42 3.59 0.24 3.63 66.17 6.80 In austenite, in the dendritic branches, a larger number of disperse nickel, manganese and iron silicide particles are formed, with Fe2B iron borides concentrated in the interdendritic spaces (Fig. 8, b and Table 4). The presence of silicon and chromium in the inner layer will ensure the formation of a Cr2O3 + SiO2 protective film during oxidation, which is known to be a reliable protection from high-temperature oxidation. Conclusion Compositions of layers in multilayer high-temperature coatings protecting the surface of piercing mandrels are proposed. The first layer, 150 to 200 μm thick, is produced by plasma spraying of self-fluxing Fe-Cr-Mn-V-SiC-B and Fe-Ni-Mn-Si-C-В powders and characterized by high hardness (up to 1400 HV 0.05) due to the

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 strengthening phases of carbides, silicides, and borides chaotically located in the ferritic (for coating 1) and austenitic (for coating 2) matrices. The aim of this layer is to provide high wear resistance and thermal oxidation resistance due to the formation of protective SiO2 and Cr2O3 oxide films. The second layer is produced by plasma flux spraying of a mixture of heat-resistant self-fluxing powders and an iron powder in the 1:1 ratio for providing a smooth transition of properties from the oxygencontaining to metallic layers. The thickness of this layer is 250 μm, and its microhardness is 800 HV 0.05. It consists of the same phases as the first layer, but with an additional number of ferrite grains free from strengthening phases. The third (metal-oxide) layer formed by plasma spraying of iron powder in an oxidizing environment is meant for the recovery of the surface oxide layer after wear at operating temperatures of piercing mandrels. It has a thickness of 350 μm and a microhardness of 300 HV 0.05. The layer is a mechanical mixture of ferrite grains and iron oxides. The fourth (surface) layer of the FeO+Fe2O3+Fe3O4 oxide mixture is produced by oxidizing the surface of the metal oxide third layer by means of a plasma torch. The aim of this layer is to reduce the friction coefficient of piercing mandrels during operation and to decrease their surface temperature. References 1. Baldaev L.Kh., Borisov V.N., Vakhalin V.A., Gannochenko G.I., Zatoka A.E., Zakharov B.M., Ivanov A.V., Ivanov V.M., Kalita V.I., Kudinov V.V., Puzryakov A.F., Sborshchikov Yu.P., Khamitsev B.G., Shkol’nikov E.Ya., Yaroslavtsev V.M. Gazotermicheskoe napylenie [Thermal spray]. Moscow, Market DS Publ., 2007. 344 p. ISBN 978-5-7958-0146-9. 2. Budinovsky S.А., Muboyadzhyan S.A., Gayamov A.M., Matveev P.V. Development of ion-plasma refractory metallic layers of heat-insulating coatings for cooled turbine rotor blades. Metal Science and Heat Treatment, 2014, vol. 55, pp. 652–657. DOI: 10.1007/s11041-014-9684-2. 3. Tarasenko Yu.P., Tsareva N.N., Berdnik O.B. The structure and physical-mechanical properties of the heatresistant Ni-Co-Cr-Al-Y intermetallic coating obtained using rebuilt plasma equipment. Thermophysics and Aeromechanics, 2014, vol. 1, no. 5, pp. 641–650. DOI: 10.1134/S0869864314050138. 4. Cherepanov A.N., Orishich A.M., Malikov A.G., Drozdov V.O., Ovcharenko V.E., Pshenichnikov A.P. Influence of modifying nanoadditives on the properties of a multilayer composite coating obtained by laser surfacing. The Physics of Metals and Metallography, 2019, vol. 120, iss. 1, pp. 101–106. DOI: 10.1134/S0031918X190100225. 5. Chen L., Wang H., Zhao C., Lu S., Wang Z., Sha J., Chen S., Zhang L. Automatic remelting and enhanced mechanical performance of a plasma sprayed NiCrBSi coating. Surface and Coatings Technology, 2019, vol. 369, pp. 31–43. DOI: 10.1016/j.surfcoat.2019.04.052. 6. Guzanov B.N., Kositsyn S.V., Pugacheva N.B. Uprochnyayushchie zashchitnye pokrytiya v mashinostroenii [Hardening protective coatings in mechanical engineering]. Ekaterinburg, Ural Branch of the RAS Publ., 2004. 244 p. ISBN 5-7691-1405-3. 7. Shevchenko O.I., Trekin G.E., Farber V.M. Distribution of chemical elements in structural components of a facing of a self-fluxing nickel alloy. Metal Science and Heat Treatment, 1997, vol. 39, iss. 6, pp. 233–235. DOI: 10.1007/bf02467225. 8. Otsubo F., Era H., Kishitake K. Structure and phases in nickel-base self-fluxing alloy coating containing high chromium and boron. Journal of Thermal Spray Technology, 2000, vol. 9, iss. 1, pp. 107–113. DOI: 10.1361/10599 6300770350131. 9. Du H., Lee S.W., Shin J.H. Study on porosity of plasma-sprayed coatings by digital image analysis method. Journal of Thermal Spray Technology, 2005, vol. 14, iss. 4, pp. 452–461. DOI: 10.1361/105996305X76450. 10. Odhiambo J.G., Li W., Zhao Y., Li C. Porosity and its significance in plasma-sprayed coatings. Coatings, 2019, vol. 9 (7), pp. 460–479. DOI: 10.3390/coatings9070460. 11. Zhou C.G. Yu Q.H. Nanostructured thermal barrier coatings. Thermal Barrier Coatings. Cambrige, UK, Woodhead Publishing, 2011, pp. 75–96. 12. Kornienko E.E., Nikulina A.A., Bannov A.G., Kuz’min V.I., Mildebrath M., Bezrukova V.A., Zhoidik A.A. Vliyanie temperatury oplavleniya na strukturu i svoistva samoflyusuyushchikhsya pokrytii na osnove nikelya [The influence of flowing temperature on the structure and properties of the self-fluxing coatings]. Obrabotka metallov

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