STUDY OF THE STRUCTURAL-PHASE STATE AND MECHANICAL-TRIBOLOGICAL PROPERTIES OF STRUCTURAL STEELS AFTER PLASMA ELECTROLYTIC CARBURIZING

The paper presents a study of the influence of plasma electrolytic carburizing (PEC) regimes on the structural, phase, microhardness, and tribological characteristics of structural steels. Plasma electrolytic carburizing was carried out in an aqueous solution containing 10% soda ash (Na₂CO₃) and 20% urea (CO(NH₂)₂), at a temperature of about 950°C and a voltage of 300V. Two cooling regimes were implemented after PEC for steel 20: natural cooling in the electrolyte and active nozzle cooling with electrolyte supply to the treatment zone, and for 30CrMnSiA steel only natural cooling in the electrolyte. The morphology of the structure and phase composition were studied using X-ray diffraction analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and optical microscopy. The results showed that the microstructure of steels after PEC morphologically has a zonal structure with a main martensitic phase with Fe₃C and Fe₇C₃ carbide inclusions. The microhardness profile was determined from the cross-section of the modified layer using a FISCHERSCOPE HM2000 device. Tribological tests were performed using the ball on disc method on a TRB3 machine under dry friction conditions at a normal load of 10 N and a sliding speed of 0.05 m/s. It was found that active cooling promotes the formation of a harder martensitic structure with maximum microhardness values of up to 430 HV for steel 20 and up to 720 HV for 30CrMnSiA steel, while their initial microhardness values were 170 HV and ~250 HV, respectively. It was also found that the coefficient of friction for these steels decreases by an average of 25–30% compared to the initial samples. The results confirm the effectiveness of PEC in forming hardened layers with increased microhardness and improved tribological parameters and demonstrate the potential of the method for use in the production of parts operating under high mechanical and frictional loads.

1. Study of the current state and technological capabilities of the method of electrolytic-plasma chemical-thermal treatment of steels / L.G. Sulyubaeva et al // Bulletin of the NNC RK. – 2023. – Vol. 3. – P. 182-191. https://doi.org/10.52676/1729-7885-2023-3-182-191.

2. Pogrebnyak A.D. Electrolytic-plasma technology for coating and processing metals and alloys / A.D. Pogrebnyak, A.Sh. Kaverina, M.K. Kylyshkanov // Surface physical chemistry and protection of materials. – 2014. – Vol. 50, № 1. – P. 72-88.

3. Modification of the surface of 30KhGSA steel using electrolyte-plasma thermal cyclic hardening / B.K. Rakhadilov et al // NEW MATERIALS AND TECHNOLOGIES: POWDER METALLURGY, COMPOSITE MATERIALS, PROTECTIVE COATINGS, WELDING. – 2022. – P. 610-616.

4. Kulikov I., Vaschenko S., Kamenev A. Electrolyte-plasma treatment of materials. – Litres, 2022.

5. Analysis of thermal phenomena during jet focused electrolytic-plasma treatment / A.I. Popov et al // Global Energy. – 2016. – № 4(254). – P. 141-150.

6. Anodic electrolytic-plasma saturation of low-carbon steel with carbon, nitrogen, boron and sulfur / S.A. Kusmanov et al // Letters on materials. – 2015. – Vol. 5, № 1. – P. 35-38.

7. Belkin P.N. Plasma electrolytic saturation of steels with nitrogen and carbon / P.N. Belkin, A. Yerokhin, S.A. Kusmanov //Surface and Coatings Technology. – 2016. – Vol. 307. – P. 1194-1218.

8. Surface modification of chromium–nickel steel by electrolytic plasma nitriding method / Z. Satbayeva et al // Crystals. – 2024. – Vol. 14(9). – P. 759. https://doi.org/10.3390/cryst14090759.

9. Increasing the wear resistance of high-speed steels by electrolytic-plasma nitriding / М. Skakov et al // Bulletin of the Kazakh National University. Physical series. – 2014. – № 1. – P. 44-52.

10. Effect of electrolyte composition on the surface properties of titanium alloy VT6 during anodic electrolytic-plasma carburizing / M.R. Komissarova et al // Bulletin of higher educational institutions. Series «Chemistry and chemical technology». – 2016. – Vol. 59, № 11. – P. 100-105.

11. Modification of steel surface by cathodic cementation and anodic polishing under electrolysis plasma conditions / S.A. Kusmanov et al // Electronic processing of materials. – 2020. – Vol. 56(2). – P. 1-8.

12. Kulka M. Laser Surface Modification of Carburized and Borocarburized 15CrNi6 Steel. Mater / M. Kulka, A. Pertek // Charact. – 2007. – № 58. – Р. 461-470.

13. Belkin P.N. Electrolyte-plasma cementation of metals and alloys / P.N. Belkin, S.A. Kusmanov // Kostroma State University. – 2020. – № 56(5). – P. 40-74. https://doi.org/ 10.5281/zenodo.

14. Materials Science / F.K. Malygin et al. – 2015. – P. 110-114.

15. Burov S.V. Effect of temperature of anodic electrolyte-plasma carburizing on the complex of properties of steel 20 / S.V. Burov, L.V. Tabachnikova // Best research article 2020. – 2020. – P. 275-287.

16. Investigation on the effect of technological parameters of electrolyte-plasma cementation method on phase structure and mechanical properties of structural steel 20X / В. Rakhadilov et al // AIMS Materials Science. – 2023. – Vol. 10(5). – P. 934-947.