Institute of Materials, Khabarovsk Science Centre, Far Eastern Branch of the Russian Academy of Sciences, Khabarovsk, Russia:

А. А. Burkov, Senior Researcher, e-mail: burkovalex@mail.ru
М. А. Kulik, Junior Researcher

Kosygin Institute of Tectonics and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, Khabarovsk, Russia:
V. O. Krutikova, Junior Researcher

Ti – Si coatings were obtained by the electrospark treatment of titanium alloy Ti6Al4V in a mixture of titanium granules with crystalline silicon powder. Three mixtures of granules with a silicon content of 1.2; 2.3 and 3.8 wt.% were prepared. The deposition of the coatings was carried out for 10 minutes pulses with energy of 0.33 J and a frequency of 1 kHz. According to X-ray analysis, it was found that titanium silicide Ti₅Si₃ is observed in the composition of all coatings. Silicide was formed as a result of the exothermic interaction of molten titanium with silicon under the influence of multiple electrical discharges. Titanium silicide Ti₅Si₃ prevailed in the composition of coatings when using a mixture of granules with silicon content above 2.3 wt. %, which is confirmed by the data of energy dispersive X-ray microanalysis. The thickness of the coating with the highest silicon content reached 50 μm. In the microstructure of this coating, the titanium silicide crystals surrounded by titanium interlayers were observed. Metallography of the cross section of the coatings showed that there are no longitudinal cracks in the coatings and there is no clear boundary between the deposited Ti – Si layer and the substrate. The hardness of Ti –Si coatings increased with an increase in the concentration of silicon in the mixture of granules from 4.9 to 12 GPa, which is 2–4 times higher than that of the Ti6Al4V alloy. The coefficient of friction of the coatings was in the range of 0.65–0.9. Tests for wear at the dry sliding mode showed that Ti – Si coatings had a wear rate ranging from 2.1 to 26.9·10^–6 mm³/Nm. Thus, Ti – Si coatings can increase the wear resistance of the Ti6Al4V alloy up to 23 times. The wear rate of the samples at a load of 70 N was higher as compared to 25 N. Testing samples with Ti – Si coatings for resistance to high-temperature corrosion at a temperature of 900 ^oC for 56 hours showed that the technology of electrospark treatment in a mixture of Ti granules and Si powder can improve the oxidation resistance of the Ti6Al4V alloy up to 18 times.

1. Liu Y., Liu W., Ma Y., Liang C., Liu C., Zhang C., Cai Q. Microstructure and wear resistance of compositionally graded Ti – Al intermetallic coating on Ti6Al4V alloy fabricated by laser powder deposition. Surface and Coatings Technology. 2018. Vol. 353. pp. 32–40.
2. Jakobsen S. S., Lidén C., Søballe K., Johansen J. D., Menné T., Lundgren L., Bregnbak D., Møller P., Jellesen M. S., Thyssen J. P. Failure of total hip implants: Metals and metal release in 52 cases. Contact Dermatitis. 2014. Vol. 71. pp. 319–325.
3. Dai J., Li S., Zhang H., Yu H., Chen C., Li Y. Microstructure and hightemperature oxidation resistance of Ti – Al – Nb coatings on a Ti – 6Al – 4V alloy fabricated by laser surface alloying. Surface and Coatings Technology. 2018. Vol. 344. pp. 479–488.
4. epicka M., Gradzka-Dahlke M. Surface modification of Ti6Al4V titanium alloy for biomedical applications and its effect on tribological performance — A review. Reviews on Advanced Materials Science. 2016. Vol. 46. pp. 86–103.
5. Hao Y. J., Liu J. X., Li J. C., Li S. K., Zou Q. H., Chen X. W. Rapid preparation of TiC reinforced Ti6Al4V based composites by carburizing method through spark plasma sintering technique. Materials and Design. 2015. Vol. 65. pp. 94–97.
6. Peretti V., Ferraris S., Gautier G., Hellmich C., Lahayne O., Stella B., Yamaguchi S., Spriano S. Surface treatments for boriding of Ti6Al4V alloy in view of applications as a biomaterial. Tribology International. 2018. Vol. 126. pp. 21–28.
7. Liu X.-B., Wang H.-M. Microstructure, wear and high-temperature oxidation resistance of laser clad Ti5Si3/γ/TiSi composite coatings on γ-TiAl intermetallic alloy. Surface and Coatings Technology. 2006. Vol. 200. pp. 4462– 4470.
8. Zhou Z.-Y., Liu X.-B., Zhuang S.-G., Wang M., Luo Y.-S., Tu R., Zhou S.-F. Laser in-situ synthesizing Ti5Si3/Al3Ni2 reinforced Al₃Ti/NiTi compo site coatings: Microstructure, mechanical characteristics and oxidation behavior. Optics and Laser Technology. 2019. Vol. 109. pp. 99–109.
9. Anand A., Das M., Kundu B., Balla V. K., Bodhak S., Gangadharan S. Plasma-Sprayed Ti6Al4V Alloy Composite Coatings Reinforced with In Situ Formed TiB – TiN. Journal of Thermal Spray Technology. 2017. Vol. 26. pp. 2013–2019.
10. Kovâcik J., Baksa P., Emmer Š. Electro spark deposition of TIB2 layers on Ti6Al4V alloy. Acta Metallurgica Slovaca. 2016. Vol. 22 (1). pp. 52–59.
11. Nikolenko S. V., Syuy N. A., Burkov A. A. Investigation of microstructure and properties of coatings on the steel 45, applied by TiC – Ni – Mo based electric discharge deposition. Tsvetnye Metally. 2017. No. 4. pp. 69–75.
12. Burkov A. A., Pyachin S. A. Formation of WC – Co coating by a novel technique of electrospark granules deposition. Materials and Design. 2015. Vol. 80. pp. 109–115.
13. Burkov A. A., Chigrin P. G. Effect of tungsten, molybdenum, nickel and cobalt on the corrosion and wear performance of Fe-based metallic glass coatings. Surface and Coatings Technology. 2018. Vol. 351. pp. 68–77.
14. Kuzmichev E. N., Nikolenko S. V., Babenko E. G. Minerals-containing electrode materials for electrophysical machining of steels and alloys. Khabarovsk : Izdatelstvo DVGUPS, 2018. 255 p.
15. ASTM G99 – 04a. Standard Test Method for Wear Testing with a Pin-on-Disk Apparatus.
16. Burkov A. A., Pyachin S. A., Vlasova N. M., Astapov I. A., Kulik M. A. Enhancement of anticorrosion and trybological properties of the Ti6Al4V alloy through deposition of the electric-spark Ti – Al – Si – C coatings. Obrabotka Metallov. 2018. Vol. 20, No. 3. pp. 85–96.
17. Matsushita J.-I., Satsukawa T., Iwamoto N., Wang X., Yang J., Goto T., Sekino T., Wu X., Yin S., Sato T. Oxidation of Pentatitanium Trisilicide (Ti5Si3) Powder at High Temperature. Materials Science Forum. 2016. Vol. 868. pp. 38–42.