OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 2 2023 2. It is noted that the surface layer of the coating of the first and second specimens after plasma-jet hardfacing has a heterogeneous structure, consisting of rows of different zones. The first zone has a hypereutectic structure, which consists of primary borides FeB and Fe2B, located in the eutectic, consisting of Fe2B and α-Fe. The second zone above the boundary with the base metal is represented by eutectic colonies of Fe2B and α-Fe. The third specimen is characterized by the hypoeutectic structure of the boride eutectic and primary dendrites of the α-solid solution of boron in iron. 3. The maximum microhardness of the alloyed layer is fixed at a current strength of 120 A and is 1,575 HV. The depth of the hardened layer increases with increasing current, however, the hardness value and the boron content decreases. The slight hardness gradient observed over the depth of the coating, as well as the gradual decrease in hardness due to the presence of the transition zone, are considered favorable for good adhesion of the boride layer to the surface of the base material. References 1. Voroshnin L.G., Mendeleeva O.L., Smetkin V.A. Teoriya i tekhnologiya khimiko-termicheskoi obrabotki [Theory and technology of chemical and heat treatment]. Moscow, Novoe znanie Publ., 2010. 304 p. ISBN 978-5- 94735-149-1. 2. Shin V.I., Moskvin P.V., Vorobyev M.S., Devyatkov V.N., Doroshkevich S.Yu., Koval’ N.N. Povyshenie elektricheskoi prochnosti uskoryayushchego zazora v istochnike elektronov s plazmennym katodom [Increasing the electrical strengthof theacceleratinggap inanelectronsourcewithaplasmacathode]. Pribory i tekhnikaeksperimenta = Instruments and Experimental Techniques, 2021, no. 2, pp. 69–75. DOI: 10.31857/S0032816221020191. 3. Koval’ N.N., Ivanov Yu.F., eds. Evolyutsiya struktury poverkhnostnogo sloya stali, podvergnutoi elektronnoionno-plazmennym metodam obrabotki [Evolution of the structure of the surface layer of steel subjected to electronion-plasma processing methods]. Tomsk, NTL Publ., 2016. 298 p. ISBN 978-5-89503-577-1. 4. Gulyashinov P.A., Mishigdorzhiyn U.L., Ulakhanov N.S. Vliyanie mekhanoaktivatsii poroshkovoi smesi na strukturu i svoistva boroalitirovannykh malouglerodistykh stalei [Effect of mechanical activation of the powder mixture on the structure and properties of boro-aluminized low-carbon steels]. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2020, vol. 22, no. 4, pp. 151–162. DOI: 10.17212/1994-6309-2020-22.4-151-162. 5. Yan P.X., Su Y.C. Metal surface modification by B-C-nitriding in a two-temperature-stage process. Materials Chemistry and Physics, 1995, vol. 39, iss. 4, pp. 304–308. DOI: 10.1016/0254-0584(94)01444-L. 6. Meléndez E., Campos I., Rocha E., Barrón M.A. Structural and strength characterization of steels subjected to bonding thermochemical process. Materials Science and Engineering: A, 1997, vol. 234–236, pp. 900–903. DOI: 10.1016/S0921-5093(97)00389-4. 7. Bindal C., Üçisik A.H. Characterization of borides formed on impurity-controlled chromium-based low alloy steels. Surface and Coatings Technology, 1999, vol. 122, iss. 2–3, pp. 208–213. DOI: 10.1016/S0257-8972(99)00294-7. 8. Voroshnin L.G. Borirovanie promyshlennykh stalei i chugunov [Borating of industrial steels and cast irons]. Minsk, Belarus’ Publ., 1981. 205 p. 9. Lin L., Han K. Optimization of surface properties by flame spray coating and boriding. Surface and Coatings Technology, 1998, vol. 106, iss. 2–3, pp. 100–105. DOI: 10.1016/S0257-8972(98)00501-5. 10. Kim H.-J., Grossi S., Kweon Y.-G. Wear performance of metamorphic alloy coatings. Wear, 1999, vol. 232, iss. 1, pp. 51–60. DOI: 10.1016/S0043-1648(99)00160-X. 11. Eroglu M. Boride coatings on steel using shielded metal arc welding electrode: Microstructure and hardness. Surface and Coatings Technology, 2009, vol. 203, iss. 16, pp. 2229–2235. DOI: 10.1016/j.surfcoat.2009.02.010. 12. Bourithis L., Papadimitriou G. Boriding a plain carbon steel with the plasma transferred arc process using boron and chromium diboride powders: microstructure and wear properties. Materials Letters, 2003, vol. 57, iss. 12, pp. 1835–1839. DOI: 10.1016/S0167-577X(02)01077-7. 13. Sizov I.G., Smirnyagina N.N., Semenov A.P. The structure and properties of boride layers obtained as a result of electron-beam chemical-thermal treatment. Metal Science and Heat Treatment, 2001, vol. 11, pp. 45–46. 14. Balanovskiy A.E., Nguyen Van Trieu, Nguyen Van Vinh, Astafieva N.A. Characteristics and abrasive wear resistance of plasma alloyed layers based on tin bronze and chromium carbide. Tribology in Industry, 2022, vol. 44 (3), pp. 518–527. DOI: 10.24874/ti.1274.03.22.06. 15. Kulka M., Pertek A. Microstructure and properties of borocarburized 15CrNi6 steel after laser surface modification. Applied Surface Science, 2004, vol. 236, iss. 1–4, pp. 98–105. DOI: 10.1016/j.apsusc.2004.04.005.
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