Vol. 27 No. 2 2025 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. 27 No. 2 2025 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. 27 No. 2 2025 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sundukov S.K., Nigmetzyanov R.I., Prikhodko V.M., Fatyukhin D.S., Koldyushov V.K. Comparison of ultrasonic surface treatment methods applied to additively manufactured Ti-6Al-4V alloy................................................................ 6 Kate N., Kulkarni A.P., Dama Y.B. A comparative evaluation of friction and wear in alternative materials for brake friction composites............................................................................................................................................................... 29 Naumov S.V., Panov D.O., Sokolovsky V.S., Chernichenko R.S., Salishchev G.A., Belinin D.S., Lukianov V.V. Microstructure and mechanical properties of Ti2AlNb-based alloy weld joints as a function of gas tungsten arc welding parameters............................................................................................................................................................................. 43 Jatti V.S., Singarajan V., SaiyathibrahimA., Jatti V.S., KrishnanM.R., Jatti S.V. Enhancement of EDM performance for NiTi, NiCu, and BeCu alloys using a multi-criteria approach based on utility function................................................ 57 Stelmakov V.A., Gimadeev M.R., Nikitenko A.V. Ensuring hole shape accuracy in fi nish machining using boring...... 89 EQUIPMENT. INSTRUMENTS Patil N., Agarwal S., Kulkarni A.P., Saraf A., Rane M., Dama Y.B. Experimental investigation of graphene oxide-based nano cutting fl uid in drilling of aluminum matrix composite reinforced with SiC particles under nano-MQL conditions............................................................................................................................................................................. 103 Gimadeev M.R., Stelmakov V.A., Nikitenko A.V., Uliskov M.V. Prediction of surface roughness in milling with a ball end tool using an artifi cial neural network................................................................................................................. 126 Osipovich K.O., Sidorov E.A., Chumaevskii A.V., Nikonov S.N., Kolubaev E.A. Manufacturing conditions of bimetallic samples based on iron and copper alloys by wire-feed electron beam additive manufacturing......................... 142 Babaev A.S., Savchenko N.L., Kozlov V.N., Semenov A.R., Grigoriev M.V. Performance of Y-TZP-Al2O3 composite ceramics in dry high-speed turning of thermally hardened steel 0.4 C-Cr (AISI 5135)...................................................... 159 MATERIAL SCIENCE Sokolov R.A., Muratov K.R., Mamadaliev R.A. Morphological changes of deformed structural steel surface in corrosive environment......................................................................................................................................................... 174 Chernichenko R.S., Panov D.O., Naumov S.V., Kudryavtsev E.A., Salishchev G.A., Pertsev A.S. Eff ect of heterogeneous structure on mechanical behavior of austenitic stainless steel subjected to novel thermomechanical processing............................................................................................................................................................................. 189 Panov D.O., Chernichenko R.S., Naumov S.V., Kudryavtsev E.A., Salishchev G.A., Pertsev A.S. Eff ect of cold radial forging on structure, texture and mechanical properties of lightweight austenitic steel................................................ 206 Deshpande A., Kulkarni A.P., Anerao P., Deshpande L., Somatkar A. Integrated numerical and experimental investigation of tribological performance of PTFE based composite material.................................................................... 219 Vorontsov A.V., Panfi lov A.O., Nikolaeva A.V., Cheremnov A.V., Knyazhev E.O. Eff ect of impact processing on the structure and properties of nickel alloy ZhS6U produced by casting and electron beam additive manufacturing........ 238 Misochenko A.A. Martensitic transformations in TiNi-based alloys during rolling with pulsed current........................... 255 EDITORIALMATERIALS 270 FOUNDERS MATERIALS 279 CONTENTS
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Comparison of ultrasonic surface treatment methods applied to additively manufactured ti-6al-4v alloy Sergey Sundukov a, *, Ravil Nigmetzyanov b, Vyacheslav Prikhodko c, Dmitry Fatyukhin d, Vladimir Koldyushov e Moscow Automobile and Road Construction State Technical University (MADI), 64 Leningradsky prospect, Moscow, 125319, Russian Federation a https://orcid.org/0000-0003-4393-4471, sergey-lefmo@yandex.ru; b https://orcid.org/0009-0008-1443-7584, lefmo@yandex.ru; c https://orcid.org/0000-0001-8261-0424, prikhodko@madi.ru; d https://orcid.org/0000-0002-5914-3415, mitriy2@yandex.ru; e https://orcid.org/0009-0005-6711-6256, v.koldyushov@list.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. 2025 vol. 27 no. 2 pp. 6–28 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2025-27.2-6-28 ART I CLE I NFO Article history: Received: 30 January 2025 Revised: 17 February 2025 Accepted: 17 March 2025 Available online: 15 June 2025 Keywords: Ultrasonic treatment Cavitation Abrasive Surface deformation Selective laser melting Surface roughness Spherical defects Funding This research was funded by the Russian Science Foundation, grant number No. 21-79-00185, https://rscf.ru/project/ 24-19-00463/ ABSTRACT Introduction. Selective Laser Melting (SLM) of metal powders enables the fabrication of parts with arbitrary geometries, which is unattainable through conventional manufacturing technologies. The main disadvantages of the method include high surface roughness, resulting from metal spattering, spheroidization, partial melting and powder adhesion, as well as difficulties with finishing complex surface areas. One effective approach for processing such parts is the application of ultrasonic liquid technologies, where cavitation bubbles act as working bodies, penetrating and performing work on any area of the surface. The purpose of this study is to determine the influence of different types of ultrasonic treatment on the surface properties obtained by selective laser melting through comparative testing. Materials and methods. Samples made from Ti-6Al-4V titanium alloy, manufactured using selective laser melting on an EOS M280 machine, were investigated. For ultrasonic treatment, a rod-shaped magnetostrictive vibratory system was used, with the end of the emitter positioned 20 mm from the side surface of the sample. A etching solution (3% HF + 5% HNO3 + H2O) was used as a liquid medium to remove the oxide film that hinders the effect of cavitation. Cavitation-erosion (CET) treatment, cavitation-abrasive (CAT) treatment, and additionally, ultrasonic surface plastic deformation (USPD) were performed. After treatment, the surface condition, roughness, and sub-microgeometry were assessed for all samples. The microstructure of the USPD-treated samples was also investigated. Results and discussion. A high-speed imaging method was used to compare the main mechanisms of interaction with the surface during CET and CAT. During CET, collapsing and pulsating cavitation clusters are observed, located at the points of highest peaks and valleys on the surface. During CAT, the micro-cutting action of abrasive particles is added. These particles receive shock waves generated by collapsing bubbles, hit the surface, and undergo oscillatory, rotational, and longitudinal movements. Comparison of the surface condition dynamics revealed that CET enables complete removal of surface defects down to the melt tracks. CAT removes some surface defects while deforming the remaining ones. During USPD, spherical defects are crushed, forming large flat areas. All types of ultrasonic treatment reduce surface roughness: Ra is reduced by 33% during CET, by 43% during CAT, and by 52% during USPD. However, Rmax is lowest with CAT. The microstructure after USPD is characterized by a hardened layer with a depth of approximately 100 µm and an increase in microhardness up to 35%. However, after USPD, defects in the form of cracks, partially deformed spheres, and the presence of untreated deep surface depressions are formed in the surface layer, which significantly reduces performance characteristics. Therefore, it is advisable to perform CET or CAT before USPD to remove surface defects. For citation: Sundukov S.K., Nigmetzyanov R.I., Prikhodko V.M., Fatyukhin D.S., Koldyushov V.K. Comparison of ultrasonic surface treatment methods applied to additively manufactured Ti-6Al-4V alloy. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2025, vol. 27, no. 2, pp. 6–28. DOI: 10.17212/1994-6309-2025-27.2-6-28. (In Russian). ______ * Corresponding author Sundukov Sergey K.., Ph.D. (Engineering), Associate Professor Moscow Automobile and Road Construction State Technical University (MADI), 64 Leningradsky prospect, 125319, Moscow, Russian Federation Tel.: +7 926 369-19-70, e-mail: sergey-lefmo@yandex.ru Introduction Layer-by-layer synthesis enables the fabrication of parts with nearly any shape, which reduces the metal consumption and weight of structures and replaces critical assembly processes by manufacturing them entirely in a single operation [1–3].
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 These advantages make additive technologies one of the fastest-growing industries, as demonstrated by the annual increase in the proportion of additively manufactured parts used relative to those produced using traditional technologies [4, 5]. For mechanical engineering, the technologies that enable the production of metal products from powder are of the greatest interest, including selective laser sintering (SLS) and selective laser melting (SLM). Production using these methods has a number of significant disadvantages [6–8]: – low productivity; – high requirements for the granulometric composition of metal powders; – the need to print supporting structures, which then have to be removed; – the need to remove non-melting powder, which prevents manufacturing hollow parts with a closed circuit; – formation of pores inside the part; – differences in the mechanical properties of the part in parallel and perpendicular directions relative to the layers of the part; – high roughness of the resulting surfaces, which, if non-compliant with the specified requirements, requires additional treatment that may not be available for areas with complex geometry. Since the quality of the surface layer largely determines the operational properties of the product as a whole, high roughness is the main factor preventing the wider use of additive technologies [9]. Regardless of the chemical composition of the metal being fused during selective laser melting, surface roughness is formed as a result of the following factors [10–15]: – metal splashing from the melt pool; – spheroidization of liquid metal under the action of surface tension forces when the laser beam is removed from the melting zone; – incompletely melted powder particles with different adhesion to the surface; – non-molten powder particles stuck to the surface; – boundaries between individual layers caused by varying degrees of melting of powder particles located along the boundaries of each layer. Another significant problem with additive manufacturing is the high probability of pores appearing inside the product, which significantly reduces the strength properties of the product, especially if the pores are close to the surface. The treatment issues of such products are relevant and are reflected in many scientific papers that propose methods such as laser surface infusion [16], isostatic pressing, which is primarily used to densify the material [17, 18], various types of chemical action [19, 20], coating [21] and surface plastic deformation (SPD) [22]. The disadvantage of these methods is that they do not provide for the treatment of complex surfaces. For this purpose, one of the most effective methods is ultrasonic liquid treatment [23–24]. In this case, the working bodies are cavitation bubbles that can penetrate into any surface areas and modify them [25-26]. In modern research on this topic, two types of ultrasonic liquid treatment are considered [27-37]: cavitation-erosion (CET) and cavitation-abrasive (CAT). The results in all studies showed a decrease in various roughness parameters and a change in the morphology of the treated surface, manifested as a decrease in the number of defects on the surface. At the same time, the results vary greatly and are achieved with different treatment parameters: time from several minutes [27, 28, 31] to several hours [30, 37], and the amplitudes of ultrasonic vibrations from 5 µm [29] to 80 µm [33–34]. The best results are achieved with CAT at a distance of 1–2 mm between the end of the radiator and the treated surface, which is, in fact, dimensional processing and cannot be used for treatment of complex parts, or with CAT and CET combined with electrochemical polishing at high oscillation amplitudes of 60–80 µm [33–34], which leads to significant heating of the electrolyte, which, in turn, accelerates chemical reactions and makes it difficult to assess the contribution of ultrasound to the resulting effect.
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Anumber of works are devoted to ultrasonic SPD [38–47], which leads to a significant reduction in surface roughness, surface hardening and promotes the closure of pores in the subsurface layer. The disadvantage of this method is the difficulties and limitations in the treatment of complex surfaces associated with the inability to bring the indenter of the ultrasonic oscillatory system to hard-to-reach places. Thus, additional research is required to study in more detail the effect of various types of ultrasonic treatment on the properties of surfaces obtained by additive technologies and to optimize the conditions for the treatment of complex products. Based on the above, the purpose of this work is to determine the effect of various types of ultrasonic treatment on the properties of the surface obtained by selective laser melting through comparative tests. To achieve this purpose, the following research objectives are set: – analysis of the main mechanisms of action in ultrasonic treatment methods (CET, CAT, SPD); – studying the dynamics of surface changes using these methods; – studying the micro- and submicrogeometry of the treated surface; – studying the microstructure of the transverse microsection after ultrasonic SPD. Research method Material and sample production The samples for experimental studies were cubes of 10×10×10 mm, made by selective laser melting of Ti-6Al-4V titanium alloy powder with the chemical composition shown in Table 1. Ta b l e 1 Chemical composition of Ti-6Al 4V powder Element Ti Al V Fe Zr Bal. Content, % 89.72 5.3 3.7 0.17 0.04 ≈ 1 This material was chosen for research because it is widely used in aerospace engineering, where the production of complex-shaped parts is particularly promising. Furthermore, after selective laser melting, it exhibits pronounced surface defects, as described previously. The samples were produced at the STANKIN Institute, Department of High-Efficiency Treatment Technologies, using an EOS M280 machine. The powder had a diameter of 40 µm, and the SLM process used a laser beam power of 200 W and a scanning speed of 1,100 mm/s. A total of 25 samples were produced: 5 control samples (without treatment) and 5 samples for each type of treatment under consideration. The treatment schemes are shown in Fig. 2 and Fig. 4. The lateral surface was selected as the surface for study, as it forms complex elements. Fig. 1, a shows a photograph of the surface condition after production, Fig. 1, b shows a transverse microsection illustrating defects. The surface relief is characterized by a sequence of spheres of various diameters. Some of these spheres are the result of spheroidization, while others are partially molten powder or particles of non-molten powder adhering to the surface during the crystallization of the outermost melt tracks. From the perspective of reducing roughness through further treatment, the spheroidization defects are the most challenging. These spheres are formed from molten tracks of liquid metal and, after crystallization, become almost an integral part of the surface. Ultrasonic treatment schemes and equipment Ultrasonic cavitation-erosion treatment (CET), cavitation-abrasive treatment (CAT), and surface plastic deformation (SPD) were used to modify the surface condition. Preliminary experiments on liquid-based CET and CAT of Ti-6Al-4V samples showed that the alloy’s strong surface oxide film results in high cavitation resistance. Consequently, even with prolonged ultrasonic
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 a b Fig. 1. Images showing the condition of the samples side surface: a – top view; b – cross-sectional micrographic image treatment (1 hour), only a small number of loosely adhered powder particles were removed from the surface, with a negligible effect on the overall surface condition. Therefore, the surface was pre-treated in an etching solution consisting of hydrofluoric and nitric acids, as well as distilled water (3% HF + 5% HNO3 + H2O), according to the schemes shown in Fig. 2. To assess the effectiveness of ultrasound exposure, chemical treatment (CT) was performed in an etching solution without ultrasonic vibrations (Fig. 2, a). CT was performed by immersing the sample in the etching solution for 30 minutes. Every 10 minutes, the sample was removed, rinsed under running water for 1 minute, dried, and wiped with ethyl alcohol. The side surface was then photographed using a microscope. Fig. 2. Schematic diagrams of treatment The combined processes of CET + CT and CAT + CT were carried out by introducing an emitter of the ultrasonic rod oscillatory system PMS 2.0/22, consisting of a magnetostrictive transducer, which is a package of O-shaped plates made of permendur, and a titanium alloy waveguide soldered to it. The radiator made from VT-3 has a radiating surface diameter of 30 mm. The distance between the end of the radiator and the treated surface of the sample was 20 mm. The oscillatory system was powered by a UZG 2.0/22 ultrasonic generator. The resonant oscillation frequency was f = 19,750 Hz, the oscillation amplitude ξm = 20 µm. Under these treatment conditions, the power consumption of the generator was approximately 600 W. The oscillation amplitude of 20 µm corresponds to high-amplitude treatment conditions, where, in addition to cavitation bubbles, large-scale acoustic currents directed from the end of the radiator to the sample surface make a significant contribution to the treatment. Under the selected experimental conditions, the flow force of the formed streams exceeds the abrasive particles’ gravitational force, ensuring
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Fig. 3. Boron carbide particles their continuous circulation within that volume and return to the cavitation treatment zone. Boron carbide powder B4C was used as an abrasive (Fig. 3), chosen for its high hardness and resistance to chemical attack. The abrasive powder was added to a level above the treated surface, with a volume concentration of 20%. After the ultrasound was activated, the abrasive was distributed throughout the volume by the acoustic streaming. To minimize the thermal effects during ultrasonic treatment, a glass container holding an etching solution was placed in a large container with water at room temperature of 20 °C. The treatment was interrupted at intervals of 1 to 3 minutes to photograph surface changes. Ultrasonic SPD was performed by pressing the end of the oscillatory system against the sample under its own weight P =70 N (Fig. 4). The treatment was carried out for 10 seconds while photographing the surface every 2 seconds. Comparison of surface treatment mechanisms in CET and CAT To compare the impact mechanisms on the surface during CET and CAT, high-speed photography of the metal plate treatment in water was performed. The metal plate was also positioned at a distance of 20 mm from the end of the radiator. The photography was performed using a Fastec Hispec camera, capable of recording video clips at frame rate ranging from 500 to 112,000 fps. To analyze the movement patterns of cavitation bubbles and abrasive particles over the treated surface, video clips were recorded at 5,339 fps, with a field of view of 3.40×3.3 mm. Subsequently, frame-by-frame processing of the recorded video clips was performed using specialized software provided by the high-speed camera manufacturer. The results are presented as a sequence of frames starting from the moment the ultrasound was activated. The time indicated in the upper right corner of each frame was calculated as the ratio of the frame number N (starting from the moment the ultrasound was activated) to the frame rate (t = N/5,339). Surface structure and roughness studies During all the above-mentioned types of treatment, the lateral surface of the samples was photographed using a METAM-RV-22 metallographic microscope. After ultrasonic SPD, a transverse microsection made from the sample was additionally examined to analyze changes in the microstructure resulting from the surface deformation. After reaching the treatment time beyond which no significant surface changes were observed, the roughness parameters were measured using a Model 130 profilometer to obtain surface profiles in the form of profilograms. The results were based on the average values from five measurements of the height roughness parameters Ra, Rz, Rmax. Changes in the sub-microgeometry of surfaces after treatment were evaluated by atomic forcemicroscopy (AFM) using a SMM-2000 scanning multimicroscope with an MSCT cantilever having a beam stiffness of 0.1 N/m. Microhardness was measured using the Vickers hardness test method on a PMT-3 device by indenting the surface with a diamond pyramid under a load of 50 g for 10 seconds. The results were based on the average values from five measurements taken in different locations of the sample. Fig. 4. Scheme of ultrasonic surface plastic deformation
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 Results and discussion Comparison of CET and CAT surface mechanisms Fig. 5 shows a film diagram of the CET process. Fig. 5. CET process cinematography (frame rate: 5,339 fps) At the moment ultrasound is activated, the liquid is subjected to varying compressive and tensile forces corresponding to the oscillation phases of the radiator end. As a result of breaks in liquid continuity, cavitation bubbles are formed. These bubbles oscillate, collapse, combine, and move within the treated volume under the influence of acoustic streams. The most favorable locations for bubble formation and accumulation are various surface irregularities, such as protrusions and depressions of the microrelief. The first frame shows the formation of cavitation bubbles on the treated surface. This process begins even before the bubbles formed under the radiator are transferred to the surface by the acoustic stream. Over time, the number of bubbles increases, and they combine near the largest surface irregularity, forming a cavitation cluster. Similarly, other clusters form on the surface at different times. The frames illustrate the formation and a portion of the life cycle of two cavitation clusters, which pulsate, absorb cavitation bubbles carried by the acoustic stream, collapse and reform. The frame corresponding to 168 ms of the treatment process shows the collapse of cluster 2. In the next frame (187 ms), it begins to reform in the same location and reaches its maximum size by 261.8 ms. At 280.5 ms, the two clusters begin to merge. The combined cluster then partially collapses, and the remaining part of the bubbles splits into two (317.9 ms), which return to their previous locations and begin to grow again (336.6–355.3 ms).
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology As a result, the main mechanism of CET is the collapse and pulsation of cavitation bubbles in locations of maximum surface irregularity. From the perspective of treating additive products, this mechanism, on the one hand, helps to remove surface defects; on the other hand, it leads to an increased depth of microrelief depressions. In CAT (Fig. 6), cavitation clusters also form on the surface covered with an abrasive layer at the time when ultrasound is activated. The pulsation of these clusters leads to the separation of abrasive particles (0-18.7 ms). As the clusters grow, the process intensifies, and most abrasive particles are separated from the surface (56.1–112.2 ms). By this time, the acoustic stream and the cavitation bubbles carried by it from the radiator reach the treatment area (130.9 ms), drag the abrasive particles with them, and transfer them back to the surface. This results in a shock effect, which is determined by the speed of movement of the abrasive. This speed can be equal to the stream velocity or significantly increase when a bubble collapses next to an abrasive particle, imparting a pulse via the resulting shock wave (frames after 149.6 ms). After impacting the surface, a significant number of particles enter the field of action of the clusters, where they oscillate with them, rotate (187 ms), impact the surface during the cluster collapse, and move along the surface (243.1–261.8 ms). In all cases, the surface is subjected to a micro-cutting effect from abrasive particles, which changes the microrelief. When the power of the acoustic stream escaping to the sides exceeds the forces acting on the abrasive particle, the particle is carried away. Subsequently, the acoustic stream returns under the end of the radiator, from where it is transferred to the surface, where it performs micro-cutting. At frames 336.6–355.3 ms, the combined effect of cavitation clusters and abrasive particles is more pronounced. Fig. 6. CAT process cinematography (frame rate: 5,339 fps)
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 Fig. 7. Dynamics of surface changes during chemical treatment process Thus, when an abrasive is added to the liquid, a uniform effect is ensured over all surface areas due to the combined action of cavitation clusters and abrasive particles. Dynamics of changes in the surface layer during various types of treatment In CT, the oxide film is initially removed by the etching solution. Subsequently, the etching solution begins to interact with the alloy, dissolving the contacting surface areas at a low rate (Fig. 7). During CT, the size of the spheres decreases, and the boundaries between spheres in clusters become less distinct, leading to the formation of larger areas. As the CT time increases, these areas partially combine to form large areas. Simultaneously, depressions of the surface irregularities are etched, appearing as unfocused regions in the photographs. When ultrasonic vibrations are introduced into the solution, the dynamics of the treatment change significantly (Fig. 8). Cavitation clusters form and perform work at the locations of the greatest surface irregularity. When bubbles collapse in these clusters, shock waves and cumulative jets occur, accompanied by instantaneous pressures reaching up to 700 MPa and temperatures up to 4,000 °C [48–49]. As a result of the cumulative effect, plastic deformation of the treated surface occurs [50–51]. In the case of CET+CT, these instantaneous high temperatures further intensify the chemical reaction at the bubble collapse sites. Consequently, after 3 minutes of treatment with CET+CT, the resulting surface is similar to the surface treated with CT for 20 minutes, indicating an acceleration of the process by almost a factor of 7. The main difference between CET+CT and CT alone is that, with increasing treatment time, the number of protrusions of irregularities decreases, and the unfocused area increases in each subsequent photo, indicating the removal of surface defects. Starting from minute 7 of treatment, a portion of the surface becomes clearly visible, showing an alternation of powder melting tracks. After 15 minutes of treatment, defects such as metal splashes and spheres are completely removed from the surface. Adding abrasive particles during CAT also changes the nature of the treatment (Fig. 9).
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Fig. 8. Dynamics of surface changes during CET + Chemical treatment Fig. 9. Dynamics of surface changes during CAT + Chemical treatment
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 In this case, a significant portion of the energy generated by bubble collapse is transferred to the abrasive particles, which, upon impacting the surface, perform micro-cutting. This redistribution of energy changes the nature of the treatment towards a predominantly mechanical abrasive process. After one minute of CAT, a significant portion of the spheres is removed. The formation of sites characteristic of both CT and CET+CT is almost imperceptible. This suggests that defects with poor adhesion are preferentially removed first due to the impact of the abrasive. Further, the effect of CET+CT is that CT etches defects, reducing the strength of their adhesion to the surface, after which they are removed by the abrasive. Defects with high adhesion strength, primarily those resulting from spheroidization, deform upon impact of the abrasive, leading to a reduction in the height of the relief irregularities. As a result, after 10 minutes of treatment with CAT, the surface consists of significantly deformed spheres and melting tracks, also exhibiting traces of abrasive action. The mechanism of ultrasonic SPD involves the plastic deformation of surface irregularities (Fig. 10). Under the action of a force applied normally to the surface, the protrusions of irregularities deform. The height of the spheres decreases with the formation of a flattened area, while they simultaneously grow in width and begin to touch other spheres. Consequently, deformed areas of a sufficiently large size are formed on the surface. With continued treatment, the spheres located below begin to deform, and the area of the deformed regions increases. The largest area is achieved after approximately 10 seconds of treatment. As the treatment time increases further, no significant changes occur, likely due to the achievement of the maximum degree of deformation. Despite the significant effect of surface smoothing, treatment of microrelief depressions is not achievable with this method, as illustrated in all the photos. Despite the significant effect of surface smoothing, treatment of microrelief depressions is not available for this method, which is illustrated in all the photos. The analysis of microstructure changes is presented below. Analysis of surface roughness changes The surface changes resulting from the considered treatment methods lead to change in surface roughness. Profilometer traces, each 2.5 mm long, and height roughness parameters for all treatment types are presented in Table 2. Рис. 10. Dynamics of surface changes during ultrasonic SPD
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Ta b l e 2 Surface microgeometry Treatment Surface profile section (2.5 mm) Roughness parameters Without Treatment Ra = 28,6 Rz = 114 Chemical treatment (30 min) Ra = 23,2 Rz = 103 CET and chemical treatment (15 min) Ra = 19,3 Rz = 94,2 CAT and chemical treatment (10 min) Ra = 16,2 Rz = 80,5 USPD (10 sec) Ra = 13,6 Rz = 76,3 The profile of the micro-irregularities of the control sample consists of alternating protrusions with rounded peaks and depressions, with a predominance of protrusions. The maximum profile height is Rmax = 174 µm. Following CT, the profile exhibits a similar relief but with a reduced height of the protrusions and a slightly increased width of the depressions. The arithmetic mean deviation of the profile, Ra, decreases from 28.6 to 23.2 µm.
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 Ultrasonic treatment methods result in significant profile changes, both in the shape of the profilogram and in the numerical values of the roughness parameters. After CET+CT, the surface profile is leveled and consists of similarly sized protrusions and depressions. This is due to the absence of spherical defects on the surface. The Ra parameter decreases to 19.3 µm. The profile after CAT+CT is characterized by fewer depressions and a larger number of protrusions deformed by the abrasive. Ra = 16.2 µm, representing a decrease of 43.5%. Additionally, the profilogram after this treatment method exhibits the lowest maximum profile height of 89 µm. The surface relief after ultrasonic SPD, due to the presence of large, flat areas, has the lowest value of Ra = 13.6 µm. However, the difference in the height of the protrusions and the depth of the depressions reaches 98 µm, which is greater than with CAT+CT. This indicates that combined cavitation and abrasive action is a more effective method for reducing surface protrusion height. Assessment of changes in the submicrostructure Three-dimensional images of the surface topography, measuring 308×308 nm (Fig. 11), were obtained by atomic force microscopy (AFM) using the Constant Height method. This method maintains a constant distance between the cantilever and the surface under study during scanning. These images allow assessment of the formation mechanisms of the studied surfaces. Fig. 11. AFM images of surfaces (308×308 nm) As a result of the flattening of spherical irregularities, the surface profile is leveled and consists of large, rectilinear sections alternating with depressions. In this case, the surface layer acquires several defects (hereafter, the defect number corresponds to the designation in Fig. 12): – discontinuity of metal at the points of contact of deformed spheres, appearing as vertical cracks; – discoloration of spheres under the influence of vibrations and shock loading; – partially deformed spheres with poor adhesion to the surface; – untreated deep depressions that increase roughness and may contain adhering powder particles. The deformed layer after ultrasonic SPD is approximately 90 to 100 µm thick. Without treatment, the sample has a lamellar microstructure typical of Ti-6Al-4V alloy, which is the same in the surface layer (Fig. 13, a) and the base metal (Fig. 13, b). After treatment, the microstructure of the material shows clearly marked traces of deformation (Fig. 13, c, d). Furthermore, the area of the surface without spheres (Fig. 13, c) is deformed to a greater extent than the area with spheres (Fig. 13, g), where the spheres themselves are deformed much more intensively than the underlying metal layer.
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Fig. 12. Surface Profile in Cross-Sectional Micrograph: 1, 2, 3, 4 – surface layer defects The submicrostructure of the control sample has a slightly rounded shape with undulating steps, which is probably a consequence of the crystallization of a spherical particle. The AFM image after CT shows a region with a boundary between a sphere (right corner of the image), which exhibits pronounced steps after etching, and a portion of the surface formed during normal crystallization of the melt track. After CET+CT, the banded submicrostructure results from directional heat dissipation during the crystallization of the melt track. The surface after CAT+CT differs from the others in its chaotic structure, formed by periodic exposure to abrasive particles. Wide steps, resembling surges, indicate the flow of metal perpendicular to the direction of deformation during ultrasonic SPD. Examination of the hardened layer after ultrasonic SPD The changes in the surface profile (Fig. 12) correspond to the surface profilometer traces presented in Table 2. The deformed layer is characterized by high microhardness (Fig. 14). The maximum hardening is achieved closer to the edge of the surface layer, reaching approximately 35 %. As the distance from the surface increases, the microhardness gradually decreases, reaching the base metal level after 100 µm. As a result, ultrasonic SPD leads to a significant reduction in surface roughness and the creation of a hardened layer. However, the resulting surface defects can significantly decrease the performance characteristics of the part. Therefore, it is advisable to perform ultrasonic SPD after removing surface defects using the aforementioned methods of CAT+CT or CET+CT. Description of the mechanisms of action during ultrasonic treatment Three-dimensional images of the sample surfaces, obtained by extended depth of field microscopy, are shown in Fig. 15. These images visualize the surface changes that occur during various types of treatment. Changes in the surface condition are determined by the type of ultrasonic treatment used and the corresponding mechanisms of action, schematically shown in Fig. 16. In the case of CET, the primary effect is exerted by cavitation clusters formed at locations of greatest surface inhomogeneity, which are spherical defects and depressions of micro-irregularities. The pressure and temperature formed during the collapse of clusters lead to plastic deformation of the surface, removal of spheres, and an increased depth of depressions. Since the depressions in the samples under consideration are mainly formed between the spheres, the roughness will decrease during treatment until all the spheres
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 Fig. 14. Microhardness profiles of samples Fig. 13. Microstructures: а – edge of control sample; b – bulk material; c – edge of sample after USPD; d – deformed spheres after USPD a b c d
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Fig. 15. Three-dimensional images of surfaces after various treatments are removed. The combination of CET+CT significantly speeds up the treatment process by removing the strong oxide film and intensifying chemical etching due to high temperatures. When clusters collapse during the CAT process, the resulting shock waves are transferred to abrasive particles that strike the surface, exerting a micro-cutting effect. In addition, the particles, when interacting Fig. 16. Schematic illustration of surface change dynamics during various types of ultrasonic treatment
OBRABOTKAMETALLOV technology Vol. 27 No. 2 2025 References 1. Peng X., Kong L., Fuh J.Y.H., Wang H. A review of post-processing technologies in additive manufacturing. Journal of Manufacturing and Materials Processing, 2021, vol. 5 (2), p. 38. DOI: 10.3390/jmmp5020038. 2. Sundukov S.K. Ul’trazvukovye tekhnologii v protsessakh polucheniya neraz”emnykh soedinenii [Ultrasonic technologies in the processes of obtaining permanent connections]. Moscow, Tekhpoligraftsentr Publ., 2023. 263 p. ISBN 978-5-94385-209-1. 3. Grigor’ev S.N., Tarasova T.V. Vozmozhnosti tekhnologii additivnogo proizvodstva dlya izgotovleniya slozhnoprofil’nykh detalei i polucheniya funktsional’nykh pokrytii iz metallicheskikh poroshkov [Potential of additive manufacturing technology for manufacturing complex-shaped parts and obtaining functional coatings from metal powders]. Metallovedenie i termicheskaya obrabotka metallov = Metal Science and Heat Treatment, 2015, no. 10 (724), pp. 5–10. 4. Metel A., Tarasova T., Gutsaliuk E., Khmyrov R., Egorov S., Grigoriev S. Possibilities of additive technologies for the manufacturing of tooling from corrosion-resistant steels in order to protect parts surfaces from thermochemical treatment. Metals, 2021, vol. 11 (10), p. 1551. DOI: 10.3390/met11101551. 5. Magnien J., Cosemans P., Nutal N., Kairet T. Current surface issues in additive manufacturing. Plasma Processes and Polymers, 2020, vol. 17 (1), p. 1900154. DOI: 10.1002/ppap.201900154. with the cluster, undergo oscillatory, rotational, and longitudinal movements along the surface, deforming its irregularities. In ultrasonic SPD, the main mechanism is the deformation of the protrusions of micro-irregularities and spheres under the action of a high-frequency micro-shock load. Conclusions Comparative studies of various types of ultrasonic treatment of Ti-6Al-4V titanium alloy samples obtained by selective laser melting have shown the following: – the microgeometry of the sample surface is a set of spherical defects caused by manufacturing features, resulting in high roughness; – liquid processing methods, CET and CAT, are effective in the etchant environment (3% HF + 5% HNO3 + H2O), which allows for the removal of the oxide film; – a comparison of CET and CAT using high-speed imaging showed that with CET, cavitation bubbles cluster at locations of greatest surface irregularities where work is carried out. With CAT, clusters and abrasive particles act together, which, in addition to impacting the surface, undergo oscillatory, rotational, and longitudinal movements, deforming the protrusions of micro-irregularities; – high pressures and temperatures that occur during the collapse of cavitation bubbles significantly accelerate chemical etching at the collapse sites; – CET+CT for 15 minutes leads to the complete removal of all spherical surface defects, resulting in a surface that is an alternation of melt tracks; – with CAT+CT, the resulting pressures and temperatures are largely transferred to abrasive particles, which, when accelerated, perform micro-cutting actions, resulting in the removal and/or deformation of some of the defects; – ultrasonic SPD treatment leads to the flattening of surface defects and the formation of large, flat areas on the surface; – with all the considered types of ultrasonic treatment, surface roughness decreases: Ra decreases by 33% with CET+CT, by 43% with CAT+CT, and by 52% with ultrasonic SPD. However, the greatest height of irregularities, Rmax, is the least with CAT+CT; – analysis of the microstructure after SPD reveals a hardened layer with a depth of approximately 100 µm and an increase in microhardness of up to 35%; – the primary disadvantage of SPD is the formation of defects in the surface layer, including cracks, partially deformed spheres, and the presence of untreated deep surface depressions; – prior to SPD, it is advisable to carry out CET+CT or CAT+CT to remove existing surface defects.
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