Kursk State University, Kursk, Russia

N. A. Kostin, Cand. Eng., Associate Prof., e-mail: nikolay-kostin@yandex.ru

The features of nitro cementation of steel Kh12MF at a temperature of 580 °C (in the “soft nitriding” mode) in a highly active solid nitrogen-carbon medium based on amorphous carbon and nitrogen-containing components – carbamide and potassium ferro-sulphide have been considered. Metallographic and X-ray structural analysis of nitrocemented samples has been carried out. The microstructure of nitrocemented steel has been studied on transverse grinds using an optical microscope using a Quanta FEG-650 electron scanning microscope with an EBCD focused ion beam microanalysis system. A layer-by-layer X-ray diffraction analysis of the samples on an EMMA diffractometer in chromium radiation has been carried out. Carbonitriated samples have been tested for wear under friction conditions similar to those of stamping tools. The high efficiency of the proposed paste at this temperature has been experimentally shown. As a result of nitrocementation, modified layers with a two-phase composition are formed on the steel surface. The main phases of which are hexagonal ε-carbonitride ((Fe,Cr) 2-3 (CN)), characterized by high hardness, low coefficient of friction and high wear resistance, and a solid solution based on α-iron. Based on the results of the conducted studies, it can be concluded that the nitrocementation of stamped steel Kh12MF, carried out in a highly active nitrogen-carbon paste at a nitrocementation temperature (580 °C), promotes the formation of modified layers saturated with carbonitrides (mainly hexagonal carbonitride ε) on the surface. The modified layers are characterized by a very low coefficient of friction and very high wear resistance. Thus, it can be concluded that the use of paste ensures an ecological frequency of the process, since it requires a very low consumption of K4Fe(CN)6, and also accelerates this process so much that nitrocementation in the paste becomes comparable in speed to carbonitrization in molten cyanide salts. Nitrocementation of tool steel Kh12MF at a temperature of 580°C makes it possible to obtain in a relatively short time (3 hours) a diffusion layer enriched with nitrogen with a carbonitride crust on the surface of sufficient thickness and hardness to significantly increase wear resistance.

1. Adaskin A. M. Tool materials in mechanical engineering: textbook. Moscow : NITs Infra–М, 2024. 391 p.
2. Begatov Zh., Dzhalilova M. Effect of low-temperature nitrocarburizing modes on the structure and properties of 4KhMFS steel. Belorussko-uzbekskiy nauchno-metodicheskiy zhurnal. 2022. Vol. 1. No. 2. pp. 45–48.
3. Okolovich G. A. Stamp steels for cold deformation of metals. 2nd edition, revised and supplemented. Barnaul : Izdatelstvo AltGTU, 2010. 202 p.
4. Voroshnin L. G., Mendeleeva O. L., Smetkin V. A. Theory and technology of chemical-thermal treatment: monograph. Minsk : BITU, 2006. 198 p.
5. Gerasimov S. A., Kuksenova L. I., Lapteva V. G. Structure and wear resistance of nitrided structural steels and alloys. 2nd edition. Moscow : Izdatelstvo MGTU imeni N. E. Baumana, 2014. 520 p.
6. Metals and alloys: Handbook. Edited by Yu. P. Solntsev. Saint-Petersburg : ANO NPO Professional, 2003. 1066 p.
7. Belashova I. S., Petrova L. G. Regulation of the phase composition of the nitrided layer in iron during chemical-thermal treatment under thermal cycling conditions. Vestnik Moskovskogo aviatsionnogo instituta. 2022. No. 2. pp. 237–245.
8. Gadalov V. N. et al. On the issue of application of methods of surface hardening of structural and tool materials in modern conditions. Materials and hardening technologies-2004: Collection of papers of the XI anniversary Russian scientific and technical conference. Kursk: Kursk State Technical University, 2004. pp. 8–12.
9. Kostin N. A., Kolmykov V. I., Kostin N. N. et. al. Method of carbonitriding parts made from structural and tool steels. Patent RF, No. 2592339. Applied: 26.03.2015. Published: 20.07.2016. Bulletin No. 20.
10. Kostin N. A., Kolmykov V. I., Kostin N. N. et. al. Method of carbonitriding parts made from structural and tool steels. Patent RF, No. 2600612. Applied: 05.05.2015. Published: 27.10.2016. Bulletin No. 30.
11. Kostin N. A. Pack cyaniding of steel 6KH4M2FS in order to increase heavily-loaded die durability. Metal Science and Heat Treatment. 2020. Vol. 62. Nos. 5-6. pp. 331–335.
12. Kostin N. A. Features of hardening of die steels 5KhGS and 5Kh3GS, carburized to hypereutectoid concentrations. Chernye Metally. 2020. No. 5. pp. 31–36.
13. GOST 20799–88. Industrial oils. Specifications. Introduced: 01.01.1990.
14. GOST 2999–75. Metals and alloys. Vickers hardness test by diamond pyramid. Introduced: 07.07.1976.
15. GOST 9450–76. Measurement of microhardness by diamond instruments indentation. Introduced: 01.01.1977.
16. Kostin N. A. Improvement of operational properties of 5Kh2GF stamp steel by creating carbonitride layers using chemical-thermal treatment. Metallovedenie i termicheskaya obrabotka metallov. 2016. No. 8. pp. 19–22.
17. Mosecker L., Pierce D. T., Schwedt A., Beighmohamadi M. et al. Temperature effect on deformation mechanisms and mechanical properties of a high manganese C+N alloyed austenitic stainless steel. Materials Science and Engineering: A. 2015.Vol. 642. pp. 71–83.
18. Bracke L., de Cooman B., Liebeherr M., Akdur N. Phase transformations in high strength austenitic FeMnCr steels, solid-solid phase transformations in inorganic materials. 2005. Vol. 1. 905 p.
19. Dyakov I. G. Theory and practice of anodic electrolyte-plasma saturation of steel and titanium alloys with nitrogen and carbon: Dissertation ... of Doctor of Engineering Sciences. Moscow, 2021. 403 p.
20. Ivanov A. S., Bogdanova M. V. Optimization of technology of carburization and heat treatment of low-carbon martensitic steels. Metallovedenie i termicheskaya obrabotka metallov. 2016. No. 2. pp. 59–62.
21. Gu C., Lou B., Jing X., Shen. F. Mechanical properties of the carburized Cr–Ni–Mo steels with added case nitrogen. Journal Heat Treating. 1989. Vol. 7. pp. 87–94.
22. Teldekov V. A., Gurevich L. M. Research of low-temperature nitrocarburizing technology for complex strengthening of machine parts. Izvestiya Volgogradskogo gosudarstvennogo tekhnicheskogo universiteta. 2021. No. 10 (257). pp. 64–68.
23. Popova N. A., Nikonenko E. L., Nikonenko A. V. et al. Effect of electrolytic plasma nitrocarburizing on the structural-phase state of ferrite-pearlite steels. Izvestiya vuzov. Chernaya metallurgiya. 2019. No. 10. pp. 782–789.