Investigation of the Effect of Complex Treatment on the Wear Resistance of Titanium Alloys

Investigation of the Effect of Complex Treatment on the Wear Resistance of Titanium Alloys

Available online at www.sciencedirect.com ScienceDirect Materials Today: Proceedings 11 (2019) 359–362 www.materialstoday.com/proceedings ICMTMTE_2...

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Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 11 (2019) 359–362

www.materialstoday.com/proceedings

ICMTMTE_2018

Investigation of the Effect of Complex Treatment on the Wear Resistance of Titanium Alloys Victor Ovchinnikov*, Elena Lukyanenko, Svetlana Yakutina Moscow Polytechnic University, B. Semenovskaya st., 38 Moscow, 107023, Russian Federation

Abstract The article considers the possibility of using complex treatment of VT6 alloy including ion implantation with subsequent laser surface treatment in order to improve the operational properties. The results of comparative studies of surface microhardness and wear resistance after various treatments are presented. It is shown that the use of complex treatment leads to a decrease in the VT6 alloy weight wear. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Modern Trends in Manufacturing Technologies and Equipment 2018: Materials Science. Keywords: ion implantation; laser hardening; titanium alloy; microhardness; wear resistance.

1. Main text The influence of various treatment types on the VT6 alloy surface property is discussed. The perspective direction of complex treatment application is considered. Modern conditions make constantly increasing demands on the operational properties of various equipment types. Given that many performance characteristics are determined by the material surface structure and properties, it is very important to develop methods for their purposeful modification. Among modern construction materials, an important place is occupied by titanium alloys due to an advantageous combination of properties.



The work is performed within the framework of state assignment No 11.3560.2017/ПЧ.

* Corresponding author. Tel.: +7-495-223-05-23. E-mail address: viko[email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Modern Trends in Manufacturing Technologies and Equipment 2018: Materials Science.

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V. Ovchinnikov, E. Lukyanenko, S. Yakutina / Materials Today: Proceedings 11 (2019) 359–362

Currently, high-energy beam technologies based on concentrated energy flows for modifying the surface of titanium alloys are successfully used: electron ion quantum technologies (EIQT), ion-quantum technologies (IQT) and radiation beam technologies (RBT). Unlike the traditional thermal and mechanical, thermal and chemical treatment of titanium alloys, radiation beam technologies show a higher efficiency of modifying near-surface layers. Restructuring processes developing during such treatment occur under conditions that are far from thermodynamic equilibrium, and make it possible to obtain surface layers with a unique complex of physical and mechanical properties [1]. During ion treatment, in particular—ion implantation, the material surface properties undergo changes as a result of the high-energy ions introduction causing a change in the elemental composition (alloying addition) and the structural-phase state. On the other hand, a very promising direction of laser technology from the point of view of modifying the material properties is surface laser hardening, in which the structural-phase state of the near-surface layers changes directionally by pulse thermal treatment. The promising nature of this technology is due to the possibility of creating new various surface structures with improved physical, chemical and mechanical properties in sufficiently thick layers using relatively simple equipment [2]. Analysis of various technology processes has shown that the efficiency of laser treatment methods can be significantly increased by creating combined methods based on combining laser sources with ion sources of energy impact on materials. The purpose of this study is to investigate the possibility of using combined treatment methods for titanium alloys: ion implantation followed by laser hardening. As a material for the study, we used plates of VT6 alloy with a thickness of 5 mm with dimensions 100x100 mm. Ion implantation of VT6 alloy samples was carried out using the ion implantation plant equipped with two independent ion sources: metal ion source and gas ion source (the so-called two-beam device). During the operation, the metal ion source provides a wide aperture beam of circular cross section with a diameter of 150 mm at a beam current of 0.1-1A. The accelerating voltage is 40 kV. In this source, the arc pulses with a frequency of 50 Hz and a pulse duration is ~ 300 μs [3]. The implantation dose of the test samples was 5×1017 ion/cm2. The cathode material was a Fe-Cu powder alloy with the content of components 1:1. Ion implantation using the Kvant-18 devise is followed by the laser thermal hardening of VT6 titanium alloy samples. We used universal digital hardness meter Affri 251 VRSD (Italy) to study the effect of treatment types on the VT6 titanium alloy surface microhardness. The results of VT6 titanium alloy surface microhardness measuring after various treatment methods are presented in Fig. 1.

Fig. 1. Microhardness of VT6 alloy samples in the initial state (Initial) and after various treatments: II—ion implantation; LH—laser hardening.

V. Ovchinnikov, E. Lukyanenko, S. Yakutina/ Materials Today: Proceedings 11 (2019) 359–362

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Analysis of the results shows an increase in the microhardness of VT6 alloy sample surface both after ion implantation and laser hardening. A sharp increase in the VT6 alloy microhardness under combined action of ion implantation followed by laser hardening (II+LH) can be explained by: – Influence of radiation defects formed by embedded ions; – Formation of quenching structures under laser thermal hardening; – Change in the surface microstructure (in particular, an increase in the dispersion). We used transmission electron microscope JEOL JEM-2100 (Japan) to determine the microstructure nature and distribution of dislocations in the surface layer of the treated sample. Performed metallographic analysis showed that the microstructure of the investigated alloy is represented by αphase with face-centered close-packed lattice and β phase with body-centered cubic lattice with a last-order volume ratio of 10%. And α-phase is represented by two structural components—globular particles and plates. In the process of studying electron microscopic images of the VT6 titanium alloy near-surface layer obtained by scanning the electron beam with thin films of 100 nm in thickness at a scale of 500-50 nm, we can conclude that the complex treatment technology makes it possible to obtain a nanostructure on the metal surface, see Fig. 2.

Fig. 2. Nanostructure of the VT6 alloy near-surface layer before and after complex treatment.

The dislocation density ρD in the near-surface layer was calculated by the cross-section method. At the initial dislocation density ρDini ≈ 5×1011 (cm-2), the dislocation density increased by more than 19 times reaching the value of 9.8×1012 (cm-2) as a result of complex treatment. In the framework of this study, we investigated the wear resistance of the VT6 alloy in the initial state, after ion implantation, after laser treatment, and after complex treatment involving implanting samples with Fe-Cu alloy ions followed by laser treatment. Wear resistance tests of VT6 titanium alloy samples after various surface treatments were carried out using a friction machine with the sample pressing force against the coupled element of 250 N and rotation speed of 250 min– 1 . The friction path was 60 m for all samples. Material wear was measured by a weighting method using analytical balance VLR-200. Fig. 3 shows a histogram of the relative weight wear of the test samples. The use of complex treatment based on ion implantation followed by laser treatment of the target surface makes it possible to reduce the relative wear to 15% of the VT6 alloy weight wear in the initial state. Thus, the use of complex treatment makes it possible to achieve a synergistic effect of reducing the VT6 alloy weight wear. Further research is required to reveal the mechanism lying in it basis.

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Fig. 3. VT6 alloy relative weight wear after various surface treatment options: Initial—initial state; II—ion implantation; LH—laser hardening; II+LH—ion implantation + laser hardening.

References [1] S.N. Bratushka, L.V. Malikov. Questions of atomic science and technology. Series: Vacuum, pure materials, superconductors, 6 (2011) 126– 140. [2] N.V. Uchevatkina, V.V. Ovchinnikov, O.A. Zhdanovich, A.G. Sbitnev, Strengthening technologies and coatings, 6 (2016) 15-22. [3] N.V. Uchevatkina, V.V. Ovchinnikov, V.V. Istomin-Kastrovskiy, O.A. Zhdanovich, E.V. Lukyanenko, Procurement industries in mechanical engineering, 12 (2014) 8–12.