Deposition of titanium silicide on stainless steel AISI 304 surface

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 Deposition of titanium silicide on stainless steel AISI 304 surface Alexander Burkov 1, a, *, Valeria Krutikova 2, b 1 Institute of Materials Science of the Khabarovsk Scientific Center of the Far-Eastern Branch of the Russian Academy of Sciences, 153 Tikhookeanskaya, Khabarovsk, 680042, Russian Federation 2 Institute of Tectonics and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, 65 Kim Yu Chen street, Khabarovsk, 680000, Russian Federation a https://orcid.org/0000-0002-5636-4669, burkovalex@mail.ru, b https://orcid.org/0000-0001-9977-2809, nm32697@gmail.com 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. 127–137 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2022-24.4-127-137 ART I CLE I NFO Article history: Received: 02 August 2022 Revised: 06 September 2022 Accepted: 08 September 2022 Available online: 15 December 2022 Keywords: Coating Electrospark deposition Stainless steel AISI 304 Titanium silicide Ti5Si3 Coefficient of friction Corrosion Oxidation resistance Wear rate Microhardness Funding The work was carried out within the framework of the state task of the Federal state budgetary institution of science Khabarovsk Federal Research Center of the Far Eastern Branch of the Russian Academy of Sciences (FSBIS KhFRC FEB RAS), 153 Tikhookeanskaya, Khabarovsk, 680042, Russian Federation, subject number FWUW-2022-0006 Acknowledgements Research were partially conducted at core facility “Structure, mechanical and physical properties of materials”. ABSTRACT Introduction. Metal-ceramic coatings based on titanium silicide are promising for protecting stainless steel AISI 304 from wear, corrosion and high-temperature oxidation. Purpose of the work: to investigate the stainless steel AISI 304 surface layer structure after electrospark deposition in a mixture of titanium granules with silicon powder, and to study oxidation resistance, corrosion resistance and tribotechnical properties of the obtained coatings. Research methodology. Fe-Ti-Si coatings on the stainless steel AISI 304 samples were obtained by electrospark machining with a non-localized electrode consisting of titanium granules and 2.6-6 vol.% mixture of titanium and crystalline silicon powders. Results and discussion: it is shown that a stable positive gain of the cathode is observed when the proportion of silicon in the powder mixture does not exceed 32 vol.%. The phase composition of the coatings includes: a solid solution of chromium in iron, titanium silicide Ti5Si3, titanium and silicon, which is confirmed by the energy dispersion analysis data. The microhardness of Fe-Ti-Si coatings ranges from 10.05 to 12.86 GPa, which is 5-6 times higher than that of uncoated steel AISI 304. The coefficient of friction of the coatings is about 20% lower compared to steel AISI 304 and hovers around 0.71-0.73. Wear tests in dry sliding mode show that Fe-Ti-Si coatings can increase the wear resistance of steel AISI 304 up to 6 times. The oxidation resistance of the coatings at a temperature of 900 ̊С is 7-12 times higher as compared to steel AISI 304. The conducted studies have shown that new electrospark Fe-Ti-Si coatings can increase corrosion resistance, oxidation resistance, microhardness, as well as reduce the coefficient of friction and wear rate of the stainless steel AISI 304 surface. For citation: Burkov А.А., KrutikovaV.O. Deposition of titanium silicide on stainless steelAISI 304 surface. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2022, vol. 24, no. 4, pp. 127–137. DOI: 10.17212/1994-6309-2022-24.4127-137. (In Russian). ______ * Corresponding author Burkov Alexander A., Ph.D. (Physics and Mathematics), Senior researcher Institute of Materials Science of the Khabarovsk Scientific Center of the Far-Eastern Branch of the Russian Academy of Sciences, 153 Tikhookeanskaya, 680042, Khabarovsk, Russian Federation Tel.: 8 (914) 1618954, e-mail: burkovalex@mail.ru

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Introduction Austenitic stainless steel AISI304 is used in the chemical and aerospace industries, atomics, medicine and other fields, due to its high corrosion resistance [1]. However, it is highly susceptible to wear due to its relatively low hardness (~200 HV) [2]. In addition, AISI304 steel is also subjected to pitting corrosion in electrolytes and begins to oxidize actively at temperatures above 800 °C in air [3]. The application of hard and anticorrosive coatings on the surface of AISI304 stainless steel is designed to reduce these disadvantages and expand its scope of application. Metal-ceramic (MC) materials are a kind of metal matrix composites, and combine in its composition a metal matrix reinforced with ceramic particles. Ceramic phases provide high hardness, and a relatively soft matrix holds the ceramics and gives such a composition high crack resistance and strength. MC materials are highly resistant to abrasion [4]. There are two ways to obtain a MС structure: the introduction of ceramic particles into a metal matrix or the crystallization of solid phases from the melt [5]. MC coatings attract a lot of attention of researchers because of its high hardness, wear resistance and corrosion resistance [6]. One of the promising reinforcing compounds is titanium silicide Ti5Si3, which has a high melting point, high-temperature resistance and oxidation resistance [7, 8]. Thus, in [9] it was shown that the coating with Ti5Si3 was preserved under cyclic oxidation conditions at 900 °C for 1,000 hours. Due to the strong covalent atomic bond, Ti5Si3 has high hardness and is stable under conditions of abrasive and adhesive wear [10]. Earlier, we showed the possibility of single-stage coating based on titanium silicide Ti5Si3 by electrospark deposition (ESD) of a titanium alloy with a non-localized anode made of titanium granules with the addition of crystalline silicon powder [11]. The deposited coatings had advanced high-temperature resistance at 900 oC and high wear resistance. It was shown that the Ti 5Si3 phase is formed by the interaction of silicon with titanium melt in the discharge microbath. Moreover, this interaction can occur both on the surface of the granules and on the titanium cathode. In the case of processing steel AISI304, only the first option can be implemented, so the transfer of Ti-Si material from titanium granules to the stainless steel surface plays a key role. As is known, the ESD is based on the phenomenon of polar material transfer from the anode to the cathode. It consists in the release of very hot microparticles of the electrode material into the melt microbath at the cathode, mixing of these materials and rapid solidification after the discharge [12]. Polar transfer is observed if the erosion of the anode exceeds the erosion of the cathode during the ESD process. The proportion of anode elements in the coating and its thickness depend on the polarity degree. The polarity criterion positively correlates with the thermophysical properties of the materials of the electrode pair; however, it is influenced by many factors [13]. Therefore, the establishment of polar transfer and its degree is achieved empirically. The purpose of this work is to study the structure of AISI304 stainless steel surface layer after ESD in a mixture of titanium granules with silicon powder, and to study the hightemperature resistance, corrosion and tribotechnical properties of the deposited coatings. Materials and methods Preliminary experiments have shown that in the case of an anode mixture of titanium granules with silicon powder, a positive cathode weight gain was not observed. To achieve a positive cathode weight gain, titanium powder was gradually added to the anode mixture, since it has better electrical conductivity compared to silicon. Titanium particles act as contact bridges among silicon particles, reducing the resistance of the system. The content of titanium powder in the mixture was gradually increased until a stable of the cathode weight gain began to be observed. So, the silicon concentration in the powder mixture was 31.6 vol.%. Granules from titanium alloy VT1-00 and powder mixture in various ratios (Table 1) were poured into a metal container connected to the positive output of the pulse generator; therefore, the granules acted as an anode. The silicon powder had an average particle size of 10 µm. The coatings were applied to a stainless steel AISI304 substrate in the form of a cylinder with a diameter of 12 mm and a height of 10mm(Table 2). The substratewas connected to the negative of pulse generator. The IMES-40 pulse generator

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 1 Composition of anode mixtures, designations and characteristics of coatings Designation of samples Composition of powder mixture, vol.% Charge content in the anode mixture, vol.% The content of ERTi-1 granules, vol.% Thickness, μm Si Ti Si2.6 31.6 68.4 2.633 97.367 24.8 ± 7.9 Si6.0 6.048 93.952 21.7 ± 11.2 Ta b l e 2 Chemical composition of AISI304 steel Element Fe Cr Ni Mn Cu P C S Concentration, wt. % 66.374 18 8 ≤ 2 ≤ 1 ≤ 0.045 ≤ 0.03 ≤ 0.03 generated discharge rectangular current pulses with an amplitude of 110 A, at a voltage of 30 V, with a duration of 100 μs and a period of 1,000 μs. Argon was filled into the working volume of the container at a rate of 10 L/min to prevent titanium nitriding. The setup for electrospark deposition of coatings with a non-localized electrode is described in detail in [14, 15]. The structure of the coatings was studied using a Vega 3 LMH (Tescan, Czech Republic) and an X-max 80 energy dispersive spectrometer (EDS) (Oxford Instruments, UK). The phase composition of the coatings was determined using a DRON-7 X-ray diffractometer in Cu-Kα radiation. The microhardness of the coatings was measured on a PMT-3M hardness tester at a load of 0.5 N according to the Vickers method. The wear resistance and coefficient of friction of the coatings were studied according to the ASTM G99 – 17 using “pin-on-disk” scheme. The tests were carried out in dry sliding mode using a counterbody in the form of a disk made of high-speed steel M45 at speed 0.47 ms– at a load of 10 N for 600 s. Polarization tests were carried out in a three-electrode cell after 30 minutes of holding samples in a 3.5% NaCl solution under natural aeration conditions at room temperature until a stationary value of the corrosion potential was established. Scanning was performed using a P-2X potentiostat (Elins, Russia) at a rate of 10 mV∙s–1 in the range of –1.5 – 0.5 V. The contact area of the samples with the electrolyte solution was 1 cm2. The counter electrode was a paired ETP-02 platinum electrode, the reference electrode was a standard silver chloride electrode, and the coated samples and AISI304 steel served as the working electrode. The test for cyclic high-temperature resistance was carried out in a furnace at a temperature of 900 °C. The total testing time was 100 hours. The samples were kept at a given temperature and after some time intervals (~6 hours) were removed and cooled in a desiccator to room temperature. During the test, all samples were placed in a corundum crucible to account for the mass of exfoliated oxides. The weight change of all samples was measured using a laboratory balance with an accuracy of 0.1 mg. Results and discussion The coatings were deposited within 180 s, since the mass of the substrate began to decrease during further processing due to the accumulation of defects and the onset of the threshold of brittle fracture of the coating, which is characteristic of ESD [16]. The X-ray analysis of the coatings showed the presence of ferrochrome (Fe-Cr) and hexagonal titanium (αTi) phases forming the coating matrix (Fig. 1). Titanium silicide Ti5Si3 and silicon act as a reinforcing ceramic. The Ti5Si3 phase is formed during the interaction of silicon with titanium melt on the granule’s surface, which is accompanied by heat release (ΔHo 298 = = –581.2 kJ/mol), according to reaction 1: 5Ti + 3Si = Ti5Si3. (1)

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Characteristically, silicon reflections are observed in the X-ray spectrum of the coatings, but there are no iron silicides. This may indicate unfavorable conditions for the formation of ferrosilicon under conditions of a low-voltage electric discharge. This also explains the halo visible in the diffraction patterns of the coatings in the angle range 2θ 35 – 50°, which indicates the presence of an amorphous phase in the coatings. As consequence, according to the results of X-ray phase analysis, it is impossible to judge reliably the effect of silicon concentration in the anode mixture on the content of titanium silicide in coatings. Figure 2, a shows a cross section image of the Si2.6 coating. The coating has a darker shade compared to the substrate due to the enrichment with silicon and titanium, which have a lower atomic weight compared to AISI304 steel elements. There are no clear boundaries and longitudinal cracks between the deposited layer and the substrate, which indicates good adhesion of the Fe-Ti-Si coating to steel AISI304. According to the EDS data (Fig. 2, b), the composition of the coating is dominated by iron and chromium from the substrate, which corresponds to the of X-ray data (Fig. 1). The concentrations of titanium and silicon dissolved in the coating matrix ranged from 5 to 20 at.%. There are dark inclusions in the coating structure (Fig. 2, c). According to its EDS analysis, the ratio of titanium to silicon is 49.3 to 31.8, which corresponds to titanium silicide Ti5Si3 (Fig. 2, d). The microstructure of inclusions is represented by columnar crystallites, which corresponds to the microstructure of Ti-Si coatings on a titanium alloy [11]. With an increase in the powder charge concentration in the anode mixture from 2.6 to 6 vol.%, the average coating thickness decreased from 24.8 to 21.7 µm (Table 1). Figure 3 shows polarization diagrams of Fe-Ti-Si coatings and AISI304 steel in 3.5 % NaCl solution at room temperature. Based on these data, the corrosion current density Icorr, the corrosion potential Ecorr and the polarization resistance Rp were calculated (Table 3). Rp was calculated using the simplified expression (2): corr 2.3 3 ( ) 0 a c p a c b b R I b b = + , (2) where ba and bc are the slopes of the Tafel section of the anode and cathode curves, respectively. It follows from Table 3 that the corrosion potentials were similar for both coatings and significantly greater than for AISI304 stainless steel. This suggests that Fe-Ti-Si coatings can reduce the activity of the stainless steel surface to spontaneous corrosion. The corrosion current density of the coatings was 1.8 to 2.1 times lower than that of AISI304 stainless steel (Table 3). The Si2.6 sample showed the highest corrosion potential and Fig. 1. X-ray diffraction patterns of deposited coatings

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b c d Fig. 2. SEM image of the cross-section of the Si2.6 coating in the back scattered electrons mode at magnifications of 4.7X (a) and 20X (c); EDS distribution of elements over the coating depth (b) and EDS spectrum of point 1 (d). The black arrows indicate inclusions of titanium silicide Fig. 3. Tafel polarization diagrams of coatings compared to AISI304 stainless steel

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 3 Corrosion parameters of coatings calculated from the slopes of polarization curves Parameters Samples AISI304 Si2.6 Si6.0 Ecorr., V –0.68 –0.57 –0.603 Icorr, µA 27.5 13.1 15.1 Rp, kΩ 2.5 10.1 10.7 the lowest corrosion current density. The calculated polarization resistance of the deposited coatings was four times higher than that of the original AISI304 steel. Despite the high corrosion resistance of AISI304 steel, due to the high chromium content (Table 2), it can be concluded that the use of electrospark Fe-Ti-Si coatings can significantly improve its anti-corrosion properties. Figure 4, a shows the average values of microhardness measured on the surface of the coatings. The hardness of the coatings decreased from 12.86 to 10.05 GPa with the growth of powder charge in the anode mixture. Thus, the application of Fe-Ti-Si coatings can significantly increase the surface hardness of AISI304 steel (1.9 GPa). The high hardness of the coatings is primarily due to the presence of the Ti5Si3 phase, which hardness is 9.5 GPa [17, 18]. The higher hardness of the deposited coatings is explained by the structure refinement up to the amorphous state, due to the high cooling rates of the material after the completion of the discharge during ESD [19]. Figure 4, b shows the dynamics of the friction coefficient of the coatings compared to stainless steel AISI304. It follows from this that the application of Ti-Si coatings makes it possible to reduce the friction coefficient of AISI304 steel by 20 % from 0.9 to 0.73. With an increase in the powder content in the anode mixture, the average values of the friction coefficient slightly decreased from 0.73 to 0.71. With an increase in the silicon content in the anode mixture, the average values of coating wear rate increased from 1.07∙10–6 to 1.45∙10–6 mm3/Nm, which is consistent with the hardness data (Fig. 4, a). In general, the application of Fe-Ti-Si coatings makes it possible to increase the wear resistance of the AISI304 steel surface from 4.6 to 6.2 times. a b Fig. 4. Microhardness (a), coefficient of friction and wear rate at a load of 10 N (b)

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b Fig. 5. High-temperature oxidation resistance of samples at a temperature of 900 oC in air (a) and X-ray patterns of its surface after high-temperature oxidation resistance test (b) Figure 5, a shows the change in the mass of samples with Fe-Ti-Si coatings and AISI304 steel at a temperature of 900 °C. The weight gain of samples with coatings for 100 hours of testing ranged from 23.3 to 37.9 g/m2. The smallest weight gain was observed for the Si2.6 sample, which also showed the best corrosion resistance. Coated specimens were damaged by corrosion in 7–12 times less than AISI304 steel. The weight gain is due to the fixation of oxygen on the surface of the samples in the form of oxides of iron, titanium and chromium in the modifications of hematite, rutile and iron (II) chromite FeCr2O4 (Fig. 5, b). In contrast to AISI304 steel, on X-ray patterns of the coating’s surface, the reflections of ferrochrome, which is resistant to oxidation, are observed. The high oxidation resistance of coated samples is due to the limited contact of oxygen with the substrate, primarily due to the Ti5Si3 phase, which is resistant to oxidation at temperatures up to 1,000 °C. This is explained by the formation of a thin silicon dioxide barrier layer on the surface of Ti5Si3 particles [20]. Conclusions A technique is proposed for obtaining Fe-Ti-Si coatings by electrospark treatment of stainless steel AISI304 with an anode consisting of titanium granules and 2.6 – 6 vol.% of a mixture of titanium and crystalline silicon powders. It is shown that a stable positive weight gain of the cathode is observed when the fraction of silicon in the mixture of powders does not exceed 32%. The phase composition of the coatings included: a solid solution of chromium in iron, titanium silicide Ti5Si3, titanium, and silicon, which is confirmed by the energy dispersive analysis data. Titanium silicide Ti5Si3 is present in the coatings as separate inclusions. The thickness of the coatings ranged from 21.7 to 24.8 µm. The conducted studies have shown that Fe-Ti-Si coatings, prepared by a new method of electrospark deposition with a non-localized electrode with silicon and titanium powders, can increase corrosion resistance, oxidation resistance and hardness, as well as reduce the friction coefficient and wear of the AISI304 stainless steel surface. References 1. Rybalka K.V., Beketaeva L.A., Davydov A.D. Opredelenie skorosti korrozii stali AISI 304 v rastvorakh HCl metodom izmereniya omicheskogo soprotivleniya issleduemogo obraztsa [Determination of AISI 304 steel corrosion rate in the HCl solutions by the method of measuring specimen ohmic resistance]. Elektrokhimiya = Russian Journal of Electrochemistry, 2019, vol. 55, no. 9, pp. 1147–1152. DOI: 10.1134/S0424857019080139. (In Russian).

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