Content and Dispersion of Ferroalloys in the Coating During Microarc Alloying of Steel

Introduction. The main disadvantage of traditional processes of diffusion surface hardening of steel products is its long duration. Therefore, the problem of intensification of such processes is relevant. To solve it, the use of high-energy effects on the material is proposed, which allows us to obtain a hardened surface layer from a coating composed of ferroalloy powders containing alloying elements. There is no data in the literature on the required content and dispersion of such powders in the composition of the coating. The aim of this study was to select the particle size of ferroalloys and their concentration in the coating to achieve the most effective hardening of the processed product.

Materials and Methods. For experimental studies, cylindrical samples made of steel 20 with a diameter of 12 mm and a length of 35 mm were used. On the surface of these samples, an alloying coating containing ferroalloy powders and an electrically conductive gel as a binder was applied. After that, the samples were immersed vertically for half their length into a metal container, which was then filled with carbon powder with a particle size of 0.4–0.6 mm. Then an electric current of 2.5 to 3.0 A was passed in the circuit power source — container — carbon powder — sample. The duration of the process was 2–8 minutes.

Results. The calculated estimation of the electrical conductivity of coal powder was performed, and the thermophysical parameters of microarc heating of steel were calculated. These include the power released by electric current on the surface of the steel product, the density of the heat flux, and the energy of a single microarc discharge. The expressions for calculating the particle size of ferroalloy powder were obtained, as well as the experimental dependencies of the diffusion layer thickness on the particle size of ferroalloys and their content in the coating.

Discussion and Conclusion. The results of this study have allowed us to determine the size range of ferroalloys and their content in the coating. This information is essential for optimizing the alloying process and ensuring the most efficient surface hardening treatment for steel products. The data collected will be used to develop improved technological processes for the surface hardening process, leading to improved product quality and performance.

1. Mittemeijer EJ, Somers MAJ. (eds.). Thermochemical surface engineering of steels. Woodhead Publishing; 2015. 827 p.

2. Czerwinski F. Thermochemical treatment of metals. INTECH Open Access Publisher; 2012. 418 p. http://doi.org/10.5772/51566

3. Berlin EV, Koval NN, Seidman LA. Plazmennaya khimiko-termicheskaya obrabotka stal'nykh detalei. Moscow: Tekhnosfera; 2012. 464 с. (In Russ.).

4. Kaputkin DE, Duradji VN, Kaputkina NA. Accelerated diffusion saturation of the metal surface during electro- chemical-thermal treatment. Physics and chemistry of materials treatment. 2020;(2):48–57. https://doi.org/10.30791/0015-3214-2020-2-48-57 (In Russ.).

5. Aleksandrov VA, Petrova LG, Sergeeva AS, Aleksandrov VD, Akhmetzhanova EU. Kombinirovannye plazmennye sposoby khimiko-termicheskoi obrabotki dlya sozdaniya modifitsirovannykh pokrytii na instrumente. STIN. 2019;(3):13–16. (In Russ.).

6. Liexin Wu, Li Meng, Yueyue Wang, Shuhuan Zhang, Wuxia Bai, Taoyuan Ouyang, et al. Effects of laser surface modification on the adhesion strength and fracture mechanism of electroless-plated coatings. Surface and Coatings Technology. 2022;429:127927. https://doi.org/10.1016/j.surfcoat.2021.127927

7. Suminov IV, Epelfeld AV, Lyudin VB, Borisov AM, Krit BL. Mikrodugovoe oksidirovanie (obzor). Pribory. 2001;(9):13–23. (In Russ.).

8. Belkin PN, Kusmanov SA. Plasma electrolytic carburising of metals and alloys Surface Engineering and Applied Electrochemistry. 2021;57(1):19–50. https://doi.org/10.3103/S1068375521010038

9. Stepanov MS, Dombrovskii YuM, Davidyan LV. Evaluation of the mechanical properties of diffusion layer in the process of microarc steel vanadation. Izvestiya. Ferrous Metallurgy. 2018;61(8):625–630. https://doi.org/10.17073/0368-0797-2018-8-625-630 (In Russ.).

10. Stepanov MS, Dombrovskiy YuM. Deposition of carbide-type coatings during micro-arc thermodiffusion tungstening of steel. Materialovedenie. 2018;(1):20–25. (In Russ.).

11. Gyulmaliev AM, Golovin GS, Gladun TG. Teoreticheskie osnovy khimii uglya. Monograph. Moscow: Moscow State Mining University; 2003. 550 p. (In Russ.).

12. Eremeeva ZhV, Volkogon GM, Ledovskoi DA. Sovremennye protsessy poroshkovoi metallurgii. Moscow: Infra-Inzheneriya; 2020. 207 p. (In Russ.).