Kuban State Technical University (Krasnodar, Russia)

E. E. Bobylev, Cand. Eng., Associate Prof., ebobylev@mail.ru

Armavir Institute of Mechanical Engineering and Technology, (branch) of Kuban State Technical University (Armavir, Russia)
I. D. Storozhenko, Senior Lecturer, Dept. of Mechanical Engineering, storojenko_armv@mail.ru

This paper investigates the effect of diffusion layers formed by diffusion alloying from low-melting liquid metal solutions (DALMMS) and combined thermochemical treatment on the heat resistance of structural steels St3, 40Kh, and 40Kh13. Saturation was carried out at 1050 °C in Pb-Li melts with Ni, Cu, and Cr additions. Combined processes included carburizing (950 °C, propane-butane) and nitriding (80 % NH3) in various cycles. Heat resistance was evaluated by weight loss at 650 °C for 100 hours according to GOST 6130-70. It was found that the maximum increase in heat resistance is achieved by forming diffusion layers based on chromium carbides and carbonitrides. The best results were shown by the «carburizing → Cr DALMMS → carburizing» cycle, which reduced the specific weight loss of St3 steel from 621 to 1.4 g/m², corresponding to a 443.5-fold increase in heat resistance. For 40Kh steel, heat resistance increased 175-fold, and for 40Kh13 steel, 3-fold. The high protective ability is attributed to the thermodynamic stability of carbides, low oxygen diffusion through the dense layer, and the formation of a protective chromium oxide film on the surface. The oxidation kinetics for carbide layers are parabolic. Diffusion layers based on Ni-Cu and Ni-Cr showed lower efficiency due to linear oxidation kinetics and an inability to form a dense oxide barrier.

1. GOST 6130-70. Metals and method for determining their heat resistance. Introduced: 01.01.1972.
2. Sokolova I. S., Oborin A. V., Porozova S. E. Modification of the surface of steels used in valve engineering. Izvestiya vuzov. Poroshkovaya metallurgiya i funktsionalnye pokrytiya. 2024. No. 18 (4). pp. 83–90. DOI: 10.17073/1997-308X-2024-4-83-90
3. Krasikov A. V., Merkulova M. V., Mikhailov M. S., Petrov S. N. Nanostructure of galvanic Ni–W coatings annealed at different temperatures. Voprosy materialovedeniya. 2024. No. 2 (118). pp. 46–54. DOI: 10.22349/1994-6716-2024-118-2-46-54
4. Kolubaev A. V., Sizova O. V. Structure and properties of coatings obtained by thermal spraying. Izvestiya vysshikh uchebnykh zavedeniy. Chernaya metallurgiya. 2024. No. 67 (6). pp. 710–715. DOI: 10.17073/0368-0797-2024-6-710-715
5. Jing Liang, Ye Liu, Sheng Yang, Xiuyuan Yin, Suiyuan Chen, Changsheng Liu. Microstructure and wear resistance of laser cladding Ti-Al-Ni-Si composite coatings. Surface and Coatings Technology. 2022. Vol. 445. pp. 128727. DOI: 10.1016/j.surfcoat.2022.128727
6. Kang Yang, Cheng Chen, Guozheng Xu, Zitao Jiang, Shihong Zhang, Xia Liu. HVOF sprayed Ni–Mo coatings improved by annealing treatment: microstructure characterization, corrosion resistance to HCl and corrosion mechanisms. Journal of Materials Research and Technology. 2022. Vol. 19. pp. 1906–1921. DOI: 10.1016/j.jmrt.2022.05.181
7. Bathini Lavakumar, Prasad M. J. N. V., Wasekar Nitin P. Development of continuous compositional gradient Ni-W coatings utilizing electrodeposition for superior wear resistance under sliding contact. Surface and Coatings Technology. 2022. Vol. 445. p. 128728. DOI: 10.1016/j.surfcoat.2022.128728
8. Yuling Yang, Yingxin Xin, Hongnan Chen, Zhenyu Liu, Bo Wang, Hongchao Qiao, Erlin Zhang. Improving wear and corrosion resistance of U71Mn rail steel subjected to laser in-situ fabrication of Fe based Cr–V coatings. Wear. 2024. Vol. 546–547. DOI: 10.1016/j.wear.2024.205312
9. Zheng Q., Guryev M. A., Ivanov S. G., Mey Sh., Guryev A. M. Effect of boron-chromium-lanthanum diffusion coating on heat and wear resistance of 4Kh5MF1S steel. Vestnik Sibirskogo gosudarstvennogo industrialnogo universiteta. 2024. No. 3 (49). pp. 22–29. DOI: 10.57070/2304-4497-2024-3(49)-22-29
10. Xingzhi Su, Sufang Zhao, Juan Hou, Guojun Yu, Yanjun Chen, Hua Sun, Peng Zhang, Leidong Xie. Formation of chromium carbide coatings on HT250 steel by thermal diffusion processes in fluoride molten salt bath. Vacuum. 2018. Vol. 155. pp. 219–223. DOI: 10.1016/j.vacuum.2018.06.015
11. Medvedovski E., Leal Mendoza G., Rzad E., Solecka M., Dudziak T. P. Influence of multi–layered thermal diffusion coatings on high–temperature sulfidation resistance of steels. Surface and Coatings Technology. 2020. Vol. 403. 126430. DOI: 10.1016/j.surfcoat.2020.126430
12. Çömez N., Yurddaskal M., Gül V., Durmuş H., Albayrak S. Fe-Cr-C-V hardfacing coatings with molybdenum addition: Wear, corrosion, and cavitation performances. Surface and Coatings Technology. 2024. Vol. 482. p. 130715. DOI: 10.1016/j.surfcoat.2024.130715
13. Pryakhin E. I., Mikhailov A. V., Sivenkov A. V. Technological features of surface alloying of metal products with Cr-Ni complexes in the medium of low-melting metal melts. Chernye Metally. 2023. No. 2. pp. 58–66.
14. Bobylev E. E., Storozhenko I. D., Popov R. A. Kinetics of formation of carbide-chromium diffusion layers on structural steels obtained by complex chemical-thermal treatment. Voprosy materialovedeniya. 2025. No. 3 (123). pp. 21–30. DOI: 10.22349/1994-6716-2025-123-3-21-30
15. Bobylev E. E., Storozhenko I. D., Marchenko V. D., Matorin A. A. Development and implementation of diffusion alloying technology in low-melting liquid metal solutions. Advanced research in Kuban. Transactions of the Annual Reporting Conference of Grant Holders of the Kuban Science Foundation. Krasnodar: Kuban Science Foundation, 2023. pp. 82–90.
16. Sokolov A. G., Bobylev E. E., Storozhenko I. D., Popov R. A. Device for diffusion metallization in medium of low-melting liquid metal solutions. Patent RF, No. 2767108. Applied: 20.05.2021. Published: 16.03.2022.