Orenburg State University, Orenburg, Russia

S. I. Bogodukhov, Professor, Department of Materials Science and Materials Technology, Doctor of Technical Sciences, e-mail: ogu@mailgate.ru
E. S. Kozik, Associate Professor, Department of Materials Science and Materials Technology, Candidate of Technical Sciences, e-mail: ele57670823@yandex.ru
E. V. Svidenko, Associate Professor, Department of Materials Science and Materials Technology, Candidate of Technical Sciences, e-mail: tzvetkova.katia2016@yandex.ru

The article presents the study on influence of technical characteristics of continuous laser machining on the structure formation of hard alloy VK8. The essence of laser machining is that laser hardening entails diffusion processes, such as breakdown of oversaturated solid solution WС into Со and precipitation of dispersed secondary carbides. Laser impact on specimens of hard alloy inserts results in changes in the percentage composition of WC (tungsten carbide) and Со (cobalt): the percentage composition changes depending on modes and entails a decreased content of main phases of hard alloy VK8. Disadvantages of laser hardening of hard alloy VK8 are machining of a material, a metal cutting tool at limited depth, low laser efficiency, high cost of a laser machine and relevant equipment. A particular feature of laser machining is local impact. In the course of laser machining, a continuous emission of a defocused beam with emission power P and focus beam diameter D uniformly moves along the metal surface at machining speed v. A laser machining zone on the part surface has a shape of a band. To reach a uniform microstructure and hardness of strengthening, highspeed machining should be at high temperature gradients. To perform this task, it is recommended to uniformly distribute power density along the spot. The experiments were conducted with the specimens: cutting replaceable, indexable, triangular inserts with sizes l is 16.5 mm; m is 13.891 mm and d is 9.525 mm from hard alloy VK8. The microstructure of hard alloy VK8 was studied with microscopes JEOL JCM–6000 (Japan) and μVizo–MET–221 (Russia), magnified at ×1000. Laser hardening entails diffusion processes, breakdown of oversaturated solid solution WС into Со and precipitation of dispersed secondary carbides, decreased tungsten carbide (bright phase) and increased WC in cobalt near the quenching band in comparison with an original specimen.

1. Panov V. S., Chuvilin A. M. Technology and properties of sintered hard alloys and products from them. Moscow : MISIS, 2001. 428 p.
2. Kreimer G. S. Strength of hard alloys. Moscow : Metallurgiya, 1971. 247 p.
3. Bock H., Hoffman H., Blumenauer H. Mechanische eigenschaften von wolframkarbid-kobalt legierungen. Technik. 1976. Vol. 31, No. 1. ss. 47–51.
4. Suzuki H., Hayashi K. Strength of WC – Co cemented carbides in relation to their fracture sources. Planseeber. Pulverment. 1975. Vol. 23, No. 1. pp. 24–36.
5. Bogodukhov S. I., Kozik E. S. Materials science. Stary Oskol : TNT, 2021. 536 p.
6. Tokova L. V., Zaitsev A. A., Kurbatkina V. V., Levashov E. A. et al. Features of the influence of ZrO₂ and WC nanodispersed additives on the properties of metal matrix composite. Russian Journal of Non-Ferrous Metals. 2019. Vol. 55, No. 2. pp. 186–190.
7. Colovcan V. T. Some analytical consequences of experiment data on properties of WC – Co hard metals. International Journal of Refractory Metals and Hard Materials. 2021. Vol. 26, No. 4. pp. 301–305.
8. Zhang Li, Wang Yuan-Jie, Yu Xian-wang, Chen Shu et al. Crack propagation characteristic and toughness of functionally graded WC – Co cemented carbide. International Journal of Refractory Metals and Hard Materials. 2020. Vol. 26, No. 4. pp. 295–300.
9. Guo Zhixing, Xiong Ji, Yang Mei, Jiang Cijin. WC – TiC – Ni cemented carbide with enhanced properties. The Journal of Alloys and Compounds. 2020. Vol. 465, No. 1-2. pp. 157–162.
10. Gurland J. The fracture strength of sintered WC – Co alloys in relation to composition and particle spacing. Transactions of the Metallurgical Society of AIME. 1963. Vol. 227, No. 1. pp. 28–43.
11. Bondarenko V. A. Ensuring the quality and improving characteristics of cutting tools. Moscow : Mashinostroenie, 2000. 428 p.
12. Bogodukhov S. I., Kozik E. S., Svidenko E. V. Effect of heating VK and TK group hard alloys in various media on the surface quality. Izvestiya vuzov. Tsvetnaya metallurgiya. 2022. Vol. 28, No. 6. pp. 71–80.
13. Bogodukhov S. I., Kozik E. S., Svidenko E. V., Semagina Yu. V. Effect of continuous laser treatment on the wear resistance of hard alloy WCo8. Materials Science Forum. 2023. Vol. 1083. pp. 210–216.
14. Bogodukhov S. I., Kozik E. S., Svidenko E. V. Nitriding of hard alloys T15K6 and T14K8. Tsvetnye Metally. 2023. No. 7. pp. 76–82.
15. A. G. Sokolov. Method of hard-alloy tool machining. Patent RF, No. 2509173. Applied: 02.12.2013. Published: 10.03.2014.
16. Khindrik E. Cutting tool insert for steels turning. Patent RF, No. 2536014. Applied: 29.06.2010. Published: 20.12.2014.
17. Kim C. S., Massa T. P., Rohrer G. S. Modeling the relationship between microstructural features and the strength of WC – Co composites. International Journal of Refractory Metals and Hard Materials. 2020. Vol. 24, No. 1. pp. 89–100.
18. Yamamoto T., Ikuhara Y., Watanabe T. et al. High resolution microscopyst udy in Cr3C2-doped WC – Co. Journal of Materials Science. 2001. Vol. 36. pp. 3885–3890.
19. Bogodukhov S. I., Kozik E. S., Svidenko E. V. Hard alloys hardening method. Patent RF, No. 2693238. Applied: 18.10.2018. Published: 01.07.2019.
20. Jaensson B. O. Die Untersuchung von Verformungsersheinungen in hochfeste WC – Co Legierungen mit Hilfe eines neuen Localisierungsverfahrens fur die Abdruckelektronenmicroscopie. Practical Metallography. 1972. Vol. 9, No. 11. ss. 624–641.
21. GOST 6456–82. Abrasive paper. Specifications. Introduced: 01.01.1983.
22. GOST 9206–80. Diamond powders. Specifications. Introduced: 01.07.1981.