Application of diamond indenters for ultrasonic processing

Application of diamond indenters for ultrasonic processing

Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.co...

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Materials Today: Proceedings xxx (xxxx) xxx

Contents lists available at ScienceDirect

Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr

Application of diamond indenters for ultrasonic processing Viktor Gileta ⇑, Kharis Rakhimyanov, Anatoliy Beznedelnyy Novosibirsk State Technical University, Faculty of Mechanical Engineering and Technologies, 630073 Prospekt K. Marks 20, Novosibirsk, Russia

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Article history: Received 14 May 2019 Received in revised form 10 July 2019 Accepted 24 July 2019 Available online xxxx Keywords: Surface plastic deformation by ultrasonic instrument Indenter Synthetic diamond Hard alloy Static load Amplitude and frequency of oscillations Size of wear area

a b s t r a c t The possibility of using indenters from synthetic polycrystalline diamonds under conditions of reinforcing finishing treatment by an ultrasonic instrument is considered. The effect of amplitude, oscillation frequency of the instrument, static load, part velocity on the destruction and wear of indenters from synthetic semi-crystalline diamonds is investigated. Technological constraints have been identified that ensure normal wear of diamonds and prevent its destruction. The technological stability of synthetic diamond indenters was studied in the studied range of variation of technological processing parameters, and compared with the resistance of indenters made of VK8 hard alloy. The values of the limiting dimensions of the wear area are proposed, ensuring the stability of the quality of the surface layer of the workpiece and low costs for restoring the tool geometry. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Modern Trends in Manufacturing Technologies and Equipment 2019.

1. Introduction To improve the performance properties of machine parts are widely used methods of surface plastic deformation (PPD) [1]. A representative of these methods is a reinforcing finishing treatment by an instrument oscillating with an ultrasonic frequency. The message to the oscillator indenter allows you to significantly change the conditions of interaction of the tool with the surface to be machined and the stress-strain state in the deformation zone (contact zone) compared to static PPD methods (diamond smoothing, ball rolling) [2]. The stability of the quality of the surface layer of the part during ultrasonic hardening substantially depends on the wear of the indenter. Previous studies with high-speed steel and hard alloy indenters have shown that the greatest wear resistance under ultrasonic reinforcing finishing treatment with tool vibrations, the hard-alloy VK8 indenters have normal to the surface being treated [3]. They allow processing of parts from hardened steels at a speed of 50–80 m/min and have a durability of 80–90 min. Such performance indicators for many production tasks are low, limit process efficiency and inhibit its implementation in the industry.

⇑ Corresponding author.

To increase the efficiency of the ultrasonic treatment (UST), it is necessary to find such a material for the manufacture of indenters that would allow treatment at speeds exceeding 60–80 m/min and at the same time have a rather high wear resistance. Of all the materials currently used for the manufacture of cutting and deforming tools, diamond has the highest physicomechanical properties. It is 5–6 times harder than a hard alloy, 10 times harder than tool steels, has the highest modulus of elasticity and a low coefficient of friction on metal [4,5]. These properties of diamond provide its high wear resistance under smoothing conditions [6]. Possessing high hardness, diamond is at the same time quite fragile, therefore diamonds, both natural and synthetic, are recommended to be used only for making smoothers (indenters) operating under static loading. It is of interest to study the possibility of using diamond indenters in conditions of reinforcing finishing treatment with an ultrasonic tool. At the same time, it is necessary to take into account that under conditions of complex dynamic loading characteristic of a UST, polycrystals have advantages over single crystals. A natural diamond crystal has a pronounced anisotropy of properties; therefore, in its manufacture and operation, the correct crystallographic orientation is important [6]. The specificity of the interaction of the indenter with the surface in the UST: the presence of large dynamic normal and tangential forces makes it difficult to choose the orientation of the ‘‘solid” direction of the

E-mail address: [email protected] (V. Gileta). https://doi.org/10.1016/j.matpr.2019.07.690 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Modern Trends in Manufacturing Technologies and Equipment 2019.

Please cite this article as: V. Gileta, K. Rakhimyanov and A. Beznedelnyy, Application of diamond indenters for ultrasonic processing, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.690

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V. Gileta et al. / Materials Today: Proceedings xxx (xxxx) xxx

diamond mesh. Synthetic diamonds have physicomechanical properties close to natural. The structure of polycrystalline diamonds provides isotropy of physicomechanical properties and makes it possible to work with variable loads. Aim of the work was to establish the possibility of using synthetic polycrystalline diamonds as indenters of ultrasonic tools for reinforcing finishing treatment and identifying the range of technological parameters that ensure their high tool durability. 2. Materials, equipment and methods of experimental research The working part of the instruments (indenters) in the experiments was spherical tips with a sphere radius of 3–4 mm from synthetic polycrystalline diamonds (ASPK) made according to TU 2037-100-78. The wear resistance of indentors from ASPK was studied when processing samples of cylindrical shape with diameters of 10– 50 mm on a 1 K62 lathe. The machine was equipped with a special device for fastening magnetostrictive transducers, which were powered from ultrasonic generators UZG2-4 and UZG3-0,4. The static force of pressing the tool to the part was created by calibrated weights. The amplitude of oscillations of the indenter was determined by the optical method. Processing modes: tool oscillation frequencies f = 18; 14; 66 kHz; oscillation amplitude A = 3–25 lm, static load Pst = 20– 300 N; I tool feed S = 0.08–0.3 mm/rev; detail speed V = 50– 300 m/min; coolant - Industrial 45 oil. The wear of the indenters was evaluated with ultrasonic hardening of ground samples (Ra = 0.78 lm) from steel 45 (Hl = 500∙107 Pa) and 50 XFA (Hl = 380107 Pa). The microhardness of the treated surface was determined using a PMT-3 microhardness tester, and the surface roughness was determined with a profile profilograph mod. 252. The size of the wear area formed on the sphere was measured with a prefix with a target price of 0.01 mm, made on the basis of the optical system of the PMT-3 microhardness tester and installed directly on the machine. The morphological state of the wear area was studied using a Carl Zeiss Axio A1m optical microscope. The performance of polycrystalline diamonds in UST conditions was estimated from the change in the size of the wear area and its morphology depending on the friction path (Fig. 1). 3. Results and discussion The impact of the tool on the surface to be treated with UST is significantly different from the static methods of PPD and has a pulsed high-frequency impact character. The value of the shock

Fig. 1. Wear area (run-in area) at the friction path L = 3500 m.

Fig. 2. The dependence of the size of the wear area on the time of work at different amplitudes of tool oscillations: Pst = 120 N, f = 18 kHz, V = 50 m/min, S = 0,1 mm/ rev, 1 – A = 25 lm; 2 – A = 11 lm; 3 – A = 6 lm.

pulse is mainly determined by the amplitude of the tool oscillations. Experiments have shown (Fig. 2) that with amplitudes up to 12–14 lm, normal wear of ASPK indenters with the presence of a running-in area is observed in the entire range of the UST modes under study. An increase in amplitude above 12–14 lm leads to an intense destruction of the diamond, and in some cases to the precipitation of the diamond insert from the metal holder. Such behavior of diamonds is due to their low strength properties of impact. To ensure normal wear of indentors from ASPK and to exclude their destruction during ultrasonic reinforcing finishing treatment, it is necessary to limit the magnitude of the amplitudes used to 12–14 lm. Studies have established that the wear rate at the running-in areas and normal wear depends on the UST modes. Increasing the oscillation frequency from 18 kHz to 44 kHz, 66 kHz reduces the wear of the indenters (Fig. 3). This influence of the oscillation frequency can be explained by the following factors: an increase in frequency leads to a decrease in the force of the dynamic effect of the tool on the part due to a significant change in the waveguide mass and the time of interaction of the tool with the surface. Reducing the exposure time under pulsed loading conditions obviously leads to a decrease in the average temperature occurring at the wear site. That is, an increase in frequency leads to a decrease in temperature and power parameters in the focus

Fig. 3. The dependence of the size of the wear area on the friction path for different tool oscillation frequencies: Pst = 120 N, V = 115 m/min, A = 8 lm, S = 0,1 mm/rev.1 – f = 18 kHz; 2 – f = 44 kHz; 3 – f = 66 kHz.

Please cite this article as: V. Gileta, K. Rakhimyanov and A. Beznedelnyy, Application of diamond indenters for ultrasonic processing, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.690

V. Gileta et al. / Materials Today: Proceedings xxx (xxxx) xxx

of interaction of the indenter with the part, which causes a decrease in the intensity of wear of the indenters. An increase in the static load from 20 N to 300 N in the studied frequency range of the tool oscillations intensifies the wear of indenters (Fig. 4). This can be explained by the fact that with increasing static load, the depth of the indenter penetration into the surface layer of the part increases and the friction force between the contacting bodies in the treatment zone increases, causing an increase in diamond wear [7]. At the same time, the use of ultrasonic vibrations in case of surface plastic deformation allows one to achieve the quality parameters of the layer of parts obtained by diamond smoothing at twice lower values of the static load. This allows ultrasonic reinforcing finishing treatment of parts of lesser rigidity and processing surfaces of high hardness (HRC 60 and above) with indenters of radius R = 3–4 mm with low static loads. For diamond smoothing of such materials, tools with a radius of R = 1–3 mm are recommended [6]. The use of indenters with large radius for UST compared to diamond smoothing allows to increase the processing capacity (UST) by increasing the feed rate. Studies of the effect of speed on the wear of indenters found that with its increase, an increase in the size of the wear area is observed (Fig. 5). Technological parameter V affects both the running-in time and the intensity of steady-state wear. As the speed increases, the running-in time decreases, but at the same time the size of the wear area, at which the transition to steady wear is observed, remains almost constant (Fig. 6). More substantial wear is observed at speeds in excess of 220 m/min, while indenters from ASPK remain operational up to a speed of 300 m/ min. This property gives them a significant advantage over carbide indenters and allows to increase the performance of the UST and expand the technological capabilities of this method. Studies have shown that the allowable wear of the indenter is advisable to establish taking into account two factors: first, the requirements for the stability of the quality parameters of the surface layer of the workpiece; the second is the cost-effectiveness of restoring worn-out indenters and the number of possible refills. Taking into account the second factor, the allowable size of the wear area is (0.2–0.3) R, that is, for indenters with a radius of the working part R = 3–4 mm, this value is 0.6–0.9 mm and 0.8– 1.2 mm, respectively. Upon reaching such dimensions of the wear area, the height of asperities of the machined surface increases by 15–20%, and the microhardness decreases by 5–8%, that is, the stability of the quality parameters is ensured. With the observance of the identified technological limitations, the resistance of ASPK

Fig. 4. The dependence of the size of the wear area on the friction path under various static loads: A = 8 mm, f = 44 kHz, S = 0,1 mm/rev. 1 – Pst = 300 N; 2 – Pst = 140 N; 3 – P = 50 N.

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Fig. 5. The dependence of the size of the wear area of the indenter on the speed of the part: L = 60,000 m, Pst = 220 N, A = 8 mm, f = 44 kHz, S = 0,1 mm/rev.

Fig. 6. The dependence of the wear of the deformer on the time at different processing speeds: Pst = 120 N, A = 8 mm, f = 44 kHz, S = 0,1 mm/rev.1 – V = 288 m/ min; 2 – V = 226 m/min; 3 – V = 115 m/min; 4 – V = 50 m/min, f = 18 kHz; 5 – V = 50 m/min.

indenters with ultrasonic reinforcing finishing treatment is 70103 80103 m of the friction path or 5–28 h of machine time. This is commensurate with the durability of these tools under the conditions of diamond smoothing [6] and is 10–15 times higher than the resistance of indenters made of hard alloy VK8.

4. Conclusions 1. When limiting the amplitudes of tool oscillations to a size of 12–14 lm, synthetic semi-crystalline diamonds can be used as the material of the indenters for ultrasonic reinforcing finishing. 2. The stability of indenters from synthetic semi-crystalline diamonds in the studied range of technological parameters is 70103–80103 m of the friction path or 5–28 h of machine time, which is commensurate with their resistance under conditions of diamond smoothing and 10–15 times higher than the hardness of carbide tools. 3. It is advisable to limit the allowable size of the wear area to a value equal to (0.2–0.3) of the sphere radius of the working part of the indenter. This ensures the stability of the formed quality of the surface layer of the part and low costs for the restoration of indenters. 4. The use of indenters from synthetic semi-crystalline diamonds makes it possible to process hardened steels with a tool with a radius of 3–4 mm at speeds up to 300 m/min, which 3–3.6 times increases the productivity of the process compared to treatment with indenters from hard alloy VK8.

Please cite this article as: V. Gileta, K. Rakhimyanov and A. Beznedelnyy, Application of diamond indenters for ultrasonic processing, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.690

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References [1] L.G. Odintsov, Hardening and Finishing Details by Surface Plastic Deformation: Reference Book, Mechanical Engineering, Moscow, 1987. [2] I.I. Mukhanov, Impulse Reinforcing-Finishing Treatment of Machine Parts with an Ultrasonic Tool, M. Mashinostroenie, 1978. [3] V.P. Gileta, A.I. Beznedelnyy, V.B. Asanov, Selection of deformer for strengthening finish machining by ultrasonic tools, Actual Prob. Mach. Build. (2015) 163–168, No. 2.

[4] L.A. Vasiliev, Z.P. Belykh, Diamonds, Their Properties and Applications, M., Nedra, 1983. [5] N.V. Novikov, The Physical Properties of Diamond, Naukova Dumka, Kiev, 1987. [6] L.G. Odintsov, Finishing Treatment of Parts with Diamond Smoothing, M., Mashinostroenie, 1981. [7] N.M. Mikhin, External Friction of Solid Bodies, M., Nauka, 1977.

Please cite this article as: V. Gileta, K. Rakhimyanov and A. Beznedelnyy, Application of diamond indenters for ultrasonic processing, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.690