Vol. 26 No. 3 2024 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.
OBRABOTKAMETALLOV Vol. 26 No. 3 2024 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Ukraine: Sergiy V. Kovalevskyy, D.Sc. (Engineering), Professor, Vice Rector for Research and Academic Aff airs, Donbass State Engineering Academy, Kramatorsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary
Vol. 26 No. 3 2024 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sukhov A.V., Sundukov S.K., Fatyukhin D.S. Assembly of threaded and adhesive-threaded joints with the application of ultrasonic vibrations...................................................................................................................................... 6 Baraboshkin K.A., Adigamov R.R., Yusupov V.S., Kozhevnikova I.A., Karlina A.I. Thermomechanical rolling in well casing production (research review)......................................................................................................................... 24 Dwivedi R., Somatkar A., Chinchanikar S. Modeling and optimization of roller burnishing of Al6061-T6 process for minimum surface roughness, better microhardness and roundness................................................................................ 52 Ilinykh A.S., Pikalov A.S., Miloradovich V.K., Galay M.S. Experimental studies of rail grinding modes using a new high-speed electric drive...................................................................................................................................................... 66 Karlina Yu.I., Konyukhov V.Yu., Oparina T.A. Assessment of the possibility of resistance butt welding of pipes made of heat-resistant steel 0.15C-5Cr-Mo................................................................................................................................... 79 Gimadeev M.R., Stelmakov V.A., Shelenok E.A. Product life cycle: machining processes monitoring and vibroacoustic signals fi lterings.................................................................................................................................................................... 94 EQUIPMENT. INSTRUMENTS Zakovorotny V.L., Gvindjiliya V.E., Kislov K.V. Information properties of frequency characteristics of dynamic cutting systems in the diagnosis of tool wear....................................................................................................................... 114 Ablyaz T.R., Blokhin V.B., Shlykov E.S., Muratov K.R., Osinnikov I.V. Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products....................................................... 135 Sidorov E.A., GrinenkoA.V., ChumaevskyA.V., Panfi lovA.O., Knyazhev E.O., NikolaevaA.V., CheremnovA.M., Rubtsov V.E., Utyaganova V.R., Osipovich K.S., Kolubaev E.A. Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets..................................................................................................................................... 149 MATERIAL SCIENCE Semin V.O., Panfi lov A.O., Utyaganova V.R., Vorontsov A.V., Zykova A.P. Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing................................ 163 Dewangan R., Sharma B.P., Sharma S.S. Investigation of hardness behavior in aluminum matrix composites reinforced with coconut shell ash and red mud using Taguchi analysis............................................................................ 179 Saprykina N.А., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А. The eff ect of technological parameters on the microstructure and properties of the AlSiMg alloy obtained by selective laser melting......................................................... 192 Burdilov A.A., Dovzhenko G.D., Bataev I.A., Bataev A.A. Methods of synchrotron radiation monochromatization (research review).................................................................................................................................................................. 208 Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution..................................................................................................................................................................... 234 Pugacheva N.B., Bykova T.M., Sirosh V.A., MakarovA.V. Structural features and tribological properties of multilayer high-temperature plasma coatings........................................................................................................................................ 250 Sharma B.P., Dewangan R., Sharma S.S. Characterizing the mechanical behavior of eco-friendly hybrid polymer composites with jute and Sida cordifolia fi bers.................................................................................................................... 267 Kornienko E.E., Gulyaev I.P., Smirnov A.I., Plotnikova N.V., Kuzmin V.I., Golovakhin V., Tambovtsev A.S., Tyryshkin P.A., Sergachev D.V. Fine structure features of Ni-Al coatings obtained by high velocity atmospheric plasma spraying.................................................................................................................................................................... 286 EDITORIALMATERIALS 298 FOUNDERS MATERIALS 307 CONTENTS
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing Viktor Semin a, Aleksander Panfilov b, Veronika Utyaganova c, Andrey Vorontsov d, Anna Zykova e, * Institute of Strength Physics and Materials Sciences SB RAS, 2/4, pr. Akademicheskii, Tomsk, 634055, Russian Federation a https://orcid.org/0000-0003-0410-3667, viktor.semin.tsk@gmail.com; b https://orcid.org/0000-0001-8648-0743, alexpl@ispms.ru; c https://orcid.org/0000-0002-2303-8015, veronika_ru@ispms.ru; d https://orcid.org/0000-0002-4334-7616, vav@ispms.ru; e https://orcid.org/0000-0001-8779-3784, zykovaap@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. 2024 vol. 26 no. 3 pp. 163–178 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.3-163-178 ART I CLE I NFO Article history: Received: 18 April 2024 Revised: 15 May 2024 Accepted: 01 June 2024 Available online: 15 September 2024 Keywords: Aluminum bronze Stainless steel ElectronBeamAdditiveManufacturing Composite Corrosion Funding The work was performed according to the Government research assignment for ISPMS SB RAS, project FWRW2024-0001. ABSTRACT Introduction. The development of novel materials based on copper alloys and stainless steel, as well as the determination of the optimal parameters for its processing make it possible to expand the area of its implementation, increase efficiency and service life of tools and constructions. The load-bearing parts of marine equipment (bearing constructions, piston cylinders, pumps, valves, gears, rotary instruments, etc.), made of austenitic steels or aluminum bronze, are in direct contact with sea water, so the problem of increasing its corrosion resistance in the presence of strong oxidizing agents (Cl–, F– anions) is relevant. One of the advanced and actively researched methods for producing copper/steel composites is additive manufacturing that allow fabricating complex parts through layerby-layer growth. In particular, the synthesis of composites based on aluminum bronze and steel can be realized by wire-feed electron beam additive manufacturing. In order to implement composite materials produced via additive technologies in a humid (marine) climate, it is necessary to ensure not only high strength, but also corrosion properties. The purpose of this work is to study the corrosion resistance of composites, based on aluminum bronze CuAl9Mn2 and stainless steel ER 321 produced by dual-wire-feed electron beam additive manufacturing. Research methods. Examination of the surface of CuAl9Mn2/ER 321 composites before and after corrosion tests was carried out by methods of voltammetry and electrochemical impedance spectroscopy using a potentiostat-galvanostat. Results and discussion. Using a complex of electrochemical methods, it is revealed that the developed composites with a volume fraction of steel ≥ 25 % demonstrate a significant decrease in anodic current densities and a simultaneous increase in charge transfer resistance. Composites with a steel content of 75 vol. % are characterized by the highest corrosion properties in 3.5 wt. % NaCl solution, which is referred to a reduction in corrosion rate by 9.5 times compared to aluminum bronze. It is shown that the main processes occurring on the surface of the composites (CuAl9Mn2 + + ER 321) are anodic oxidation of copper and iron, leading to the formation of corrosion products – Cu2O and FeCl2. For citation: Semin V.O., PanfilovA.O., Utyaganova V.R., VorontsovA.V., ZykovaA.P. Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 3, pp. 163–178. DOI: 10.17212/1994-6309-2024-26.3-163-178. (In Russian). ______ * Corresponding author Zykova Anna P., Ph.D. (Physics and Mathematics), Head Laboratory Institute of Strength Physics and Materials Sciences SB RAS, 2/4, pr. Akademicheskii, 634055, Tomsk, Russian Federation Tel.: +7 3822 286866, e-mail: zykovaap@ispms.ru Introduction It is well known that aluminum bronzes are distinguished among copper alloys by its high mechanical, corrosion and anti-friction properties [1, 2]. These alloys are widely used in the marine industry (valves, fittings, ship propellers, pump shafts, valve rods, water chambers of heat exchangers etc.) [3]. Bronze alloyed with ~10 wt. % Al, exhibits the best comprehensive properties and is considered to be the most widely used materials in the aluminum bronze group of alloys. When Al content reaches a solubility limit (9.4 wt. %), the friction coefficient decreases, but a wear loss during wear on steel increases [4, 5]. The microstructure, corrosion resistance and wear resistance of aluminum bronze alloys are complex and
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 significantly depend on the composition and cooling rate during the alloy production. Ordered structures, martensitic transformations and intermetallic compounds may form in this group of alloys [6–8]. Multiphase composition and microstructure of the copper alloys greatly affect both tribological and corrosion characteristics [3], therefore, increased attention is paid to studies of the microstructure and properties of these materials. One of the high-tech and extensively developed methods for producing composite copper- and steelbased materials is additive technologies, which make it possible to fabricate complex parts through a layerby-layer growth and have many advantages over traditional metallurgical technologies [1, 9–12]. In general, coatings or bimetallic alloys composed of aluminum bronze and steel are studied [10–12]. For example, in the paper [1], the tribocorrosion properties of additively produced stainless steel 316 (316SS), impregnated with bronze in seawater were studied. Tribological test showed that the resulting composite had yield strength and friction characteristics comparable to the conventional 316SS steel, while significant improvement in wear resistance was achieved at the test loads up to 80 N and reciprocating frequencies up to 20 Hz. It is assumed that the bronze smeared along the wear track serves as a solid lubricant, so the resulting passive oxide film seems to be a tribofilm that inhibits an abrasive wear at high loads. At the same time, an assessing the corrosion properties of various types of bronzes [1, 2] do not allow to unambiguously conclude about the nature of the corrosion damage, as well as the mechanisms of formation of corrosion products (CuO, Cu2O, etc.) in copper alloys during immersion into chloride-containing solutions. To date, the fabrication of composites based on aluminum bronze and steel could be performed using modern metallurgical methods of additive manufacturing, for example, electron beammelting. In particular, this technology is realized using a dual-wire-feed electron beam additive manufacturing (EBAM) method [13–15]. Earlier, the authors of this work produced composites based on aluminum bronze (CuAl9Mn2) and stainless steel (ER 321) using EBAM [13, 16]. It was found that depending on the “CuAl9Mn2 : ER 321” ratio the structural-phase states of the obtained composites were different and its mechanical characteristics could be improved. Our ongoing study aims to reveal the operating characteristics of the “CuAl9Mn2/ ER 321” composites. The kinetics of a charge transfer at the interfaces and the factors responsible for the resistance to the appearance of the corrosive currents between microgalvanic elements (copper- and ironbased phases) remain poorly studied issues. The purpose of the work is to study the corrosion resistance of the composites based on CuAl9Mn2 aluminum bronze and ER 321 stainless steel, produced by a dual-wire-feed electron beam additive manufacturing. The scientific objectives of this study include (i) a comprehensive assessment of the electrochemical behavior of CuAl9Mn2/ER 321 composites in marine solution (3.5 wt. % NaCl); (ii) a determination of the phase composition of corrosion products and type of corrosion damage; (iii) an identification of the predominant corrosion mechanism. Methodology In order to fabricate composites, the wires ∅1.6 mm of CuAl9Mn2 aluminum bronze and ER 321 stainless steel were used as raw materials. A stainless steel plate with a thickness of 10 mm was chosen as a substrate. To produce the bronze-steel composites, an EBAM installation, equipped with two wire feeders, was used (Fig. 1). The following parameters of the EBAM process were used: beam accelerating voltage 30 kV, beam current from 44 to 77 mA, print speed (movement of the working stage) was 400 mm/min. The required volume ratio of bronze and steel was maintained constant during processing by automatically adjusting the appropriate ratio of the wire feed speeds. As a result, the composites with a size of 80×120×8 mm3 and a volume ratio CuAl9Mn2 : ER 321 = 90 : 10, 75 : 25, 50 : 50 and 25 : 75 were obtained. A more detailed method for producing composites is presented in early works [13, 16]. For metallographic studies, the specimens were cut out by means of an electrical discharge machine, according to the Fig. 1. Then, the specimens were subjected to mechanical polishing using an abrasive sandpaper, followed by polishing with a diamond paste. To assess the mechanical properties, the specimens were tested for uniaxial static tension, and the microhardness was measured by the Vickers method [13, 16].
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 The studies of the electrochemical (corrosion) properties of the specimens were carried out by voltammetry and electrochemical impedance spectroscopy (EIS) using a potentiostat-galvanostat PalmSens 4. The electrochemical cell was a three-electrode system in which the specimen under study served as the working electrode. A silver chloride electrode filled with 1 M KCl was used as a reference electrode. The auxiliary electrode was a graphite electrode. In the method of a linear polarization, the following parameters were set: potential range varied from -0.5 to 0 V, scan rate was 1 mV/s. In the cyclic voltammetry (CV) method, the scan rate was 20 V/s, and the potential varied from -1.2 V to +1.2 V. Using the electrochemical impedance spectroscopy (EIS) method, the electrochemical processes associated with a charge (ions, electrons) transfer and diffusion of charges in the electrical double layer were identified. Processing of EIS results was carried out by modeling equivalent electrical circuits that describe the impedance behavior of the “electrolyte/composite” system. For impedance measurements, the DC voltage (Edc) was set equal to the open circuit potential. The amplitude of the sinusoidal signal (Eac) was 0.01 V. The frequency range was varied from 0.1 to 105 Hz. All measurements were performed at 3.5 wt. % NaCl. Pearson’s criterion (χ2), used to fit the raw data, ranged from 10-3 to 10-4, and the fitting errors did not exceed 10 %. PSTrace 5.8 software was used to calculate corrosion parameters. Quantitative assessment of the polarization resistance (Rp) of the composites was done by the Stern-Geary equation: ( ) = β β β + β p a c corr a c ( ) 2.303 ( ) , R i where βa is the slope of the anodic branch; βc is the slope of the cathodic branch; icorr is the corrosion current density. The surface morphology of the specimens after CV measurements was analyzed using a LEO EVO 50 scanning electron microscope (Zeiss, Germany) equipped with an energy dispersive spectrometer INCA Energy (Oxford instruments, UK). Results and Discussion Structural-phase state and mechanical characteristics of the CuAl9Mn2/ER 321 composites Previously, the authors found out the features, associated with formation of the structural-phase states in the aluminum bronze, stainless steel and CuAl9Mn2/ER 321 composites obtained by the EBAM method. It has been observed that aluminum bronze produced by the EBAM method is characterized by a columnar dendritic structure [8]. The martensitic β′ phase is located along the boundaries of the α-Cu grains (Fig. 2, a). The microstructure of the additively manufactured stainless steel ER 321 is characterized by elongated austenite grains exhibiting long and straight dendritic colonies (Fig. 2, b) [17]. Along the grain boundaries of the γ-Fe phase the δ-Fe phase is revealed (Fig. 2, b). When the volume ratio CuAl9Mn2 : ER 321 of the composite is 90:10, the structure of the composite, in comparison with the aluminum bronze, possesses a smaller size of the α-Cu grains, while the volume fraction of the β′ phase decreases significantly. Also, a precipitation of the globular α-Fe(Cr) particles and dispersed particles of the κiv-phase (Fe3Al) are observed (Fig. 2, c) [13]. The α-Cu solid solution contains Fig. 1. Scheme of EBAM process for composites and test specimens cut-up sketch: 1 – electron beam gun; 2 – electron beam; 3 – wire feeders; 4 – ER 321 wire; 5 – CuAl9Mn2 wire; 6 – melt pool; 7 – specimen for structural studies; 8 – specimens for tensile test; 9 – specimen for corrosion testing
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 ~1 at. % Ni. Increasing the concentration of steel ER 321 to 25 and 50 vol. %, leads to complete suppression of the β′-phase, α-Fe(Cr) grains are formed, within which fine particles with a β′/AlNi core/shell structure are observed (Fig. 2, d, e). In this case, in the α-Fe(Cr) solid solution, the precipitation of the dispersed particles of the κiv-phase is observed, the average size of which increases with increasing concentration of steel in aluminum bronze [13]. If the ratio CuAl9Mn2 : ER 321 reaches 25 : 75, a three-phase structure is formed, consisting of 44 vol. % of γ-Fe phase, 32 vol. % of the α-Fe phase and 24 vol. % of the α-Сu phase (Fig. 2, f). Nonequilibrium cooling conditions lead to the precipitation of the dispersed secondary particles of copper and NiAl in the γ-Fe and α-Fe grains, respectively [16]. Static tensile tests have shown that yield strength and an ultimate strength for CuAl9Mn2 and ER 321 are 148 and 440 MPa, and 300 and 610 MPa, respectively (Table 1). Acomposite produced using a volume ratio CuAl9Mn2 : ER 321 = 90 : 10 shows the values of the yield strength and ultimate strength that are comparable to the steel, but much greater than those of the aluminum bronze (Table 1). Addition of the stainless steel up to 50 vol. % into the aluminum bronze during EBAM processing leads to the higher values of the yield strength and tensile strength than those of the CuAl9Mn2 and ER 321 (Table 1). At the same time, in the composite with the ratio CuAl9Mn2 : ER 321 = 25 : 75, a decrease in the yield strength and strength is observed by 240 and 160 MPa, respectively, compared to the composite CuAl9Mn2 : ER 321 = 50 : 50. However, the ER 321 steel, diluted with aluminum bronze, shows improved mechanical characteristics compared to the pure ER 321 steel (Table 1), that are similar to the properties of the composites based on 316SS and tin bronze [1]. The microhardness of the CuAl9Mn2/ER 321 composites increases from 1.4 GPa to 2.33 GPa when the volume fraction of the stainless steel increases up to 50 vol. %. In the case of the CuAl9Mn2/ER 321 composites exhibiting a volume fraction 25:75, the microhardness decreases to 2.16 GPa (Table 1). Assessment of the corrosion properties of the composites by means of voltamperometric methods Fig. 3 shows cyclic voltammograms (CVs) demonstrating reversible redox reactions and irrever- sible anodic processes occurring on the surface of the working electrodes. Anodic oxidation of the metals Fig. 2. Microstructure of CuAl9Mn2 (a), ER 321 (b) and composites with a ratio of CuAl9Mn2 : SS321 = 90 : 10 (c), 25 : 75 (d), 50 : 50 (e) and 25 : 75 (f)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 (Fe, Cu, Al) is observed at electric potentials that are beyond the passive state region (from E1 = -1.20 V to E2 = -0.05 V). In the positive region of the potentials (from +0.0 V to +1.2 V), all specimens, including CuAl9Mn2, exhibit a sharp increase in the current density due to the following (possible) anodic processes [18, 19]: Al → Al3+ + 3e- (1) Al3+ + 3OH- → Al(OH) 3 (2) Cu → Cu+ + e-, Cu+ → Cu2+ + e- (3) Cu + Cl- → CuCl + e-, 2CuCl + H 2O → Cu2O + 2H + + 2Cl- (4) CuCl + Cl- → CuCl 2 -→ Cu2+ + 2Cl- + e- (5) 2Cu+ + H 2O → Cu2O + 2H + (6) Ta b l e 1 Mechanical properties obtained by microhardness measuring and static uniaxial tensile tests Specimen Mechanical characteristics σ0.2, MPa σu, MPa ε, % HV, GPa CuAl9Mn2 148±25 440±101 62 1.4 ± 0.17 ER 321 300±42 610±136 35 1.63 ± 0.09 CuAl9Mn2 – 10% ER 321 296±43 640±145 28 1.46 ± 0.19 CuAl9Mn2 – 25% ER 321 321±49 635±130 25 1.75 ± 0.09 CuAl9Mn2 – 50% ER 321 610±97 813±183 12 2.33 ± 0.1 CuAl9Mn2 – 75% ER 321 370±55 652±145 33 2.16 ± 0.12 Fig. 3. Cyclic voltammograms (20 mV/s) of specimens obtained in 3.5 wt. % NaCl solution. The black arrows indicate peaks of the current density in the cathode branch corresponding to the copper reduction reaction
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fe → Fe2++ 2e-, Fe – 2e- + 2H 2O → Fe(OH)2 + 2H + (7) Fe2++2Cl- → FeCl 2 (8) In the cathodic branch of the CV curves, corresponding to the region from +0.05 V to -0.80 V, the peaks of copper reduction are seen (marked by black arrows in Fig. 3), which are shifted relative to each for the specimens having different volume fractions of the steel. In the CuAl9Mn2 specimen, the cathodic reduction of copper (Cu2+ + 2e- → Cu) occurs at the highest potential E = -0.29 V (relative to Ag/AgCl). In turn, in the CuAl9Mn2 + 50 vol. % ER 321 specimen the same reaction takes place at the lowest potential (E = -0.51 V). During reiteration of the CV measurements the same peaks of oxidation and reduction of copper are observed, which indicates the reversible nature of the reaction Cu ⇄ Cu2+ + 2e-. In addition, the following cathodic processes are expected to occur in aqueous solutions, in which the α-Cu phase will act as a reducing agent: O2 + 4е - + 2H 2O → 4OH - (9) O2 + 4H + + 4е- → 4OH- (10) 2H2O + 2е - → Н 2 + 2ОН - (11) 2H+ + 2е- → Н 2 (12) In the specimens containing from 50 to 75 vol. % of the ER 321 steel, the electrochemically active components of the composite are γ-Fe, α-Fe and α-Cu phases. It is reasonable to assume that in the 3.5 wt. % NaCl solution the reactions, associated with the formation of Fe/Cu galvanic couples, initiate. In the presence of strong oxidizing agents (Cl-), both metals (Fe, Cu) in these phases may oxidize. In this case, the electrons released in the reactions (3) and (7) would be captured by copper, which acts as a cathode in the Fe/Cu galvanic couple due to the significant difference in the standard reduction potentials (ECu(2+)/Cu = + 0.34 V, EFe(2+)/Fe = -0.44 V). Based on analysis of the CV curves it follows that the main processes on the surface of the composites (CuAl9Mn2 + ER 321) are anodic oxidation of copper and iron, formation of chlorides (FeCl2, CuCl2), discharge of the oxidizing agent (oxygen) and reduction of copper (reversible reaction). The corrosion rate of the specimens was assessed using a linear potential scan. In contrast to CV curves (Fig. 3), only irreversible anodic processes are observed in the polarization curves (Fig. 4), leading to the appearance of corrosion damage onto the surface of the working electrodes. All specimens are characterized Fig. 4. Voltammograms obtained in 3.5 wt. % NaCl solution for CuAl9Mn2 and composites exhibiting 10 vol. % (a) and 25, 50, 75 vol. % ER 321 (b)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 by the presence of a passive state region, limited by a narrower potential window: from -0.3 V to -0.1 V for the initial bronze and CuAl9Mn2 + 10 vol. % ER 321 (Fig. 4, a); from -0.4 V to -0.2 V for composites containing 25, 50 and 75 vol. % ER 321 (Fig. 4, b). A sharp increase in anodic currents is accompanied by an intense dissolution of the outer surface layer at E = -0.1 V. It is important to note that composites with a larger volume fraction of steel (≥ 25 %) demonstrate lower values of the anodic currents (Fig. 4, b), which indicates a formation of a protective oxide film with apparent dielectric properties onto the surface of the composites. Fig. 5 shows the voltammetric dependences, plotted in logarithmic coordinates, of the same specimens in 3.5 wt. % NaCl solution. Extrapolation of these curves by the Tafel function, which takes into account the slopes of the cathodic (bc) and anodic (ba) branches, allows to calculate the corrosion current densities and polarization resistance (Rp) using the SternGeary equation [20]. The corrosion parameters are given in Table 2. Two important conclusions could be made from the analysis of the Tafel curves. With an increase in steel content in the composites, the corrosion potential (Ecor, Table 2) shifts to the region of the positive potentials. This is, most likely, due to the fact that the surface of the samples is passivated not by copper oxides, but by nickel and chromium oxides. This suggestion is supported by the lower standard reduction potential of Ni and Cr (ECr(3+)/Cr = -0.744 V, ENi(2+)/Ni = -0.257 V) than that of copper (ECu(2+)/Cu = +0.34 V). The densities of corrosion currents naturally decrease from 11.010 to 0.512 μA/cm2 for the composites obtained at the ratios CuAl9Mn2 : ER 321 = 90 : 10; 25 : 75; 50 : 50 and 25 : 75, and the polarization resistance, on the contrary, increases by almost an order of magnitude (Table 2). It can be concluded that the formation of the austenitic γ-Fe phase in the surface layer of the samples with a volume fraction of steel ≥ 50 % more effectively prevents the development of corrosion processes than alloying the α-Cu phase with nickel and chromium. Thus, using the EBAM method, the composites characterized by a lower (~9.5 times) corrosion rate in the marine environment could be fabricated. EIS study of the electrochemical behavior of the specimens In order to reveal the electrochemical properties of the CuAl9Mn2/ER 321 composites, the impedance spectra were obtained relative to the open-circuit potential and plotted in Nyquist coordinates before and Fig. 5. Potentiodynamic polarization curves obtained in the same electrolyte (3.5 wt. % NaCl solution) for the CuAl9Mn2 and composites Ta b l e 2 Corrosion parameters determined from polarization curves by Tafel extrapolation of the CuAl9Mn2 and composites Sample Corrosion parameters Ecor, V Icor, μA/cm2 β а, V βc, V Rp, Ohm‧cm 2 CuAl9Mn2 -0.207 11.390 0.066 0.287 2,048 CuAl9Mn2 – 10% ER 321 -0.218 11.010 0.071 0.209 2,091 CuAl9Mn2 – 25% ER 321 -0.194 4.945 0.125 0.098 4,810 CuAl9Mn2 – 50% ER 321 -0.147 1.043 0.125 0.098 16,300 CuAl9Mn2 – 75% ER 321 -0.149 0.512 0.039 0.061 20,100
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 after potentiodynamic polarization tests (Fig. 6). The dots in the diagrams indicate the experimental values of the impedance (real and imaginary parts), and the solid lines indicate the approximation by the model – an equivalent electrical circuit (Fig. 6, f). It is important to note that in a corrosive media (3.5 wt. % NaCl) the electrochemical activity of the composites, promoting anodic reactions, is regulated by the ratio CuAl9Mn2 : ER 321. Indeed, the impedance of the initial bronze specimens (Fig. 6, a) before corrosion tests is described by a relatively simple equivalent circuit, including a constant phase element (Q1), solution resistance (Rs) and charge transfer (Rct) and Warburg element (W). The fitted EIS data are given in Table 3. From the Table 3 it follows that the CuAl9Mn2 specimen shows high electrochemical activity because of the low charge transfer resistance (Fig. 3, a; Table 3). The presence of a Warburg element indicates the diffusion of charges (e-, Cu+, Cu2+, Fe2+) through the electrical double layer into the solution. It is interesting to emphasize that after corrosion tests the Rct value decreases by ~4.3 times. This observation can be explained by the fact that anodic processes (oxidation of copper to Cu2+) initiate the dissolution of the natural oxide film and repassivation of the surface, which leads to a change in the kinetics of a charge transfer in the electric double layer (Fig. 6, a; Table 3). For the composite fabricated at the ratio CuAl9Mn2 : ER 321 = 90 : 10 (Fig. 6, b), the equivalent circuit remains the same, and the Rct value decreases by ~3 times (Table 3) due to repassivation of the surface Fig. 6. Nyquist plots of CuAl9Mn2 (a) and composites with a ratio of CuAl9Mn2 : ER 321 = 90 : 10 (b); 25 : 75 (c); 50 : 50 (d); 25 : 75 (e) and equivalent electrical circuits (f)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Ta b l e 3 Parameters of equivalent electrical circuits for CuAl9Mn2 and CuAl9Mn2/ER 321 composites before and after potentiodynamic polarization Before corrosion Element of the electrical circuit CuAl9Mn2 CuAl9Mn2 : ER 321 90 : 10 75 : 25 50 : 50 25 : 75 Solution resistance, Ohm‧cm 2 5 5 70 4 67 Charge transfer resistance, Ohm‧cm 2 1,385 1,158 7,269 21,630 177,000 Warburg element, kOhm/с–0.5 0.21 0.26 – 15.75 – After corrosion Solution resistance, Ohm‧cm 2 5 4.9 69 43 71 Charge transfer resistance, Ohm‧cm 2 324 396 13,210 25,510 154,200 Warburg element, kOhm/с–0.5 1.05 0.64 – 16.50 – layer. With an increase in the share of steel in the composite up to 25 vol. % the Nyquist diagram is a semicircle without a linear part in the low frequency region, therefore the equivalent circuit does not include the Warburg element responsible for the charge diffusion. The Rct value increases from 7,269 to 13,210 Ohm‧cm2 (Fig. 6, c, Table 3) after a potentiodynamic polarization test, which indicates a higher passivation ability of this composite in comparison with the sample having 10 vol. % of the ER 321 steel. A composite with the ratio CuAl9Mn2 : ER 321 = 50 : 50 has a quite high charge transfer resistance before and after corrosion tests (Table 3). The presence of a semicircle in the Nyquist diagram (Fig. 6, d) and a linear dependence, when both real and imaginary parts > 10,000 Ohm‧cm2, indicate oxidation of the material and the release (diffusion) of the charged particles into solution. In the impedance spectra of the composite with the ratio CuAl9Mn2 : ER 321 = 25 : 75, only a part of the semicircle is present (Fig. 6, e), which indicates a significant charge transfer resistance Rct (~177,000 Ohm‧cm2). At the same time, an electrical discharge of the double layer does not occur and diffusion of charges into the solution is not occurred (Fig. 6, c, Table 3). As can be seen from Table 3, the charge transfer resistance of this specimen decreases slightly after corrosion. In this case, the anodic oxidation of iron and copper will be hindered if a repassivation of the surface layer takes place after appearance of the corrosion damage. We conclude that the least electrochemically active specimen is the composite with the ratio CuAl9Mn2 : ER 321 = 25 : 75, since it is characterized by the maximum value of Rct, which, in turn, is inversely proportional to the density of corrosion current. Summarizing the data of electrochemical experiments (EIS, CV, linear polarization), we conclude that the composite with 75 vol. % of the steel could be considered to be the most corrosion resistant one. The lowest corrosion resistance was found for the CuAl9Mn2 and the composite with 10 vol. % of the ER 321 steel. Based on electrochemical reactions (1)–(12) and literature data on the corrosion properties of Fe-Cu alloys [21] and bronze [22, 23], we can expect that the possible corrosion products of the studied CuAl9Mn2/ER 321 composites are insoluble or poorly soluble compounds – copper and iron oxides. In the X-ray diffraction patterns of the CuAl9Mn2 (Fig. 7, a) and the composite CuAl9Mn2 – 10 vol. % ER 321 (Fig. 7, b), subjected to corrosion tests in the cyclic potential sweep mode, the main diffraction lines from the matrix phases are recorded (α-Cu, β′, α-(Fe,Cr), Cu3Al), found earlier in [13]. In this case, additional reflections belonging to the Cu2O and FeCl2 phases are detected (Fig. 7, a, b). These phases (Cu2O, FeCl2) can be formed as a result of microgalvanic corrosion occurring primarily at the grain boundaries between α-(Fe,Cr) ferrite particles and the α-Cu matrix in chloride-containing electrolytes. Analysis of the corrosion damage (Fig. 7, c, d) on the composite’s surface has shown that the mechanisms of localized corrosion are realized in the CuAl9Mn2 alloy, leading to the appearance of shallow pits
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 and selective dissolution of copper phases. The dissolution of copper according to reactions (3)–(6) is limited by a protective oxide film, which impedes the spread of corrosion pits over the entire surface. Therefore, the morphology of the CuAl9Mn2 alloy after CV measurements is characterized by protrusions (“flakes”) and neighboring areas free of corrosion pits (Fig. 7, c). On the contrary, in the specimen CuAl9Mn2 – 10 vol. % ER 312 an intensive corrosion damage (Fig. 7, d) of a pitting nature is observed. Numerous and deeper pits predominate, forming a network of porous structures. In our opinion, the nature of corrosion damage in the CuAl9Mn2/ER 312 composites is associated with contact and crevice corrosion. When the α-Cu and α-(Fe,Cr) phases come into contact, the Fe/Cu galvanic couples are formed, which change the kinetics of the redox reactions due to the movement of charges between dissimilar metals (Fe, Cu) with different electrochemical potentials. As a result of contact corrosion, the primary sites for pitting initiation are the α-Cu/α-(Fe,Cr) interphase boundaries due to the formation of corrosion couples (Fig. 7, e). In this case, the working surface of the CuAl9Mn2 – 10 vol. % ER 321 composite is divided into cathodic (matrix grains α-Cu) and anodic (particles α-(Fe,Cr)) areas. It is important to note that due to a spontaneous passivation of the ferrite phase (presumably by nickel and chromium oxides), its dissolution in 3.5 wt. % NaCl solution is limited, while Cu-containing phases are Fig. 7. XRD patterns and SEM images of the surface after corrosion tests of CuAl9Mn2 (а, c) and composite CuAl9Mn2 – 10% ER 321 (b, d); e – scheme of the formation of pitting damage on the composite surface due to galvanic corrosion
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 subject to continuous anodic oxidation accompanied by the formation of Cu+ and Cu2+ ions. Additionally, cathodic processes described by reactions (9), (10) are possible on the surface of copper phases, partially impeding its ionization. Thus, in the presence of strong oxidizing agents (Cl-) the formation of corrosion pits in the composites based on aluminum bronze and stainless steel will be accelerated if the formation of Fe/Cr microgalvanic couples is not prevented (Fig. 7, e). In order to increase the corrosion properties of these composites, it is necessary to carry out surface treatments leading to the formation of continuous and dielectric oxide films on the surface of α-Cu, α-(Fe,Cr) and γ-(Fe,Ni,Cr) phases, preventing a direct electrochemical contact of Fe/Cr at interphase boundaries. Conclusions The paper presents experimental results of the electrochemical behavior of the CuAl9Mn2/ER 321 composites obtained by the additive electron beam method. With an increase in the volume fraction of steel in aluminum bronze, the microhardness, yield strength and strength of the composites change in a nonmonotonic manner and reach the highest values in the specimen containing 50 vol. % of the steel. Corrosion resistance of the specimens in 3.5 wt. % NaCl solution was estimated using the Tafel extrapolation method. It has been found that the densities of corrosion currents monotonically decrease for the composites obtained at the ratios CuAl9Mn2 : ER 321 = 90 : 10, 75 : 25, 50 : 50 and 25 : 75, and the polarization resistance, that is inversely proportional to the corrosion rate, increases by an order of magnitude. A comprehensive assessment of the electrochemical properties of the specimens using impedance spectroscopy and cyclic voltammetry has shown that the most corrosion resistant is a composite with 75 vol. % of the ER 321 steel, and the lowest corrosion resistance is demonstrated by the CuAl9Mn2 alloy and a composite with 10 vol. % of the ER 321 steel. It has been observed that the main processes on the surface of composites are anodic oxidation of Cu and Fe, leading to the formation of corrosion products – Cu2O and FeCl2. It is assumed that the main mechanism of the corrosion damage in the CuAl9Mn2/ER 321 composites is a galvanic corrosion caused by the formation of galvanic Fe/Cr pairs at the interphase boundaries between ferrite particles α-(Fe,Cr) and the α-Cu matrix. References 1. Wang L., Tieu A.K., Lu S., Jamali S., Hai G., Zhu Q., Nguyen H.H., Cui S. Sliding wear behavior and electrochemical properties of binder jet additively manufactured 316SS /bronze composites in marine environment. Tribology International, 2021, vol. 156, p. 106810. DOI: 10.1016/j.triboint.2020.106810. 2. Ateya B.G., Ashour E.A., Sayed S.M. Corrosion of α-Al bronze in saline water. Journal of the Electrochemical Society, 1994, vol. 141 (1), p. 71. DOI: 10.1149/1.2054712. 3. Davis J.R., ed. Copper and copper alloys. Materials Park, OH, ASM International, 2001. 869 p. 4. Blau P.J. Investigation of the nature of micro-indentation hardness gradients below sliding contacts in five copper alloys worn against 52100 steel. Journal of Materials Science, 1984, vol. 19, pp. 1957–1968. DOI: 10.1007/ BF00550266. 5. Shi Z., Sun Y., Bloyce A., Bell T. Unlubricated rolling-sliding wear mechanisms of complex aluminium bronze against steel. Wear, 1996, vol. 193 (2), pp. 235–241. DOI: 10.1016/0043-1648(95)06773-6. 6. Kwarciak J., Bojarski Z., Morawiec H. Phase transformation in martensite of Cu-12.4% Al. Journal of Materials Science, 1986, vol. 21, pp. 788–792. DOI: 10.1007/BF01117355. 7. Adorno A.T., Guerreiro M.R., Benedetti A.V. Isothermal aging kinetics in the Cu–19 at.%Al alloy. Journal of Alloys and Compounds, 2001, vol. 315 (1–2), pp. 150–157. DOI: 10.1016/S0925-8388(00)01268-8. 8. Zykova A.P., Panfilov A.O., Chumaevskii A.V., Vorontsov A.V., Nikonov S.Yu., Moskvichev E.N., Gurianov D.A., Savchenko N.L., Tarasov S.Yu., Kolubaev E.A. Formation of microstructure and mechanical characteristics in electron beam additive manufacturing of aluminum bronze with an in-situ adjustment of the heat input. Russian Physics Journal, 2022, vol. 65, pp. 811–817. DOI: 10.1007/s11182-022-02701-6. 9. Li W.S., Wang Z.P., Lu Y., Gao Y., Xu J.L. Preparation, mechanical properties and wear behaviours of novel aluminum bronze for dies. Transactions of Nonferrous Metals Society of China, 2006, vol. 16 (3), pp. 607–612. DOI: 10.1016/S1003-6326(06)60107-6.
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