Volgograd State Technical University, Volgograd, Russia

V. G. Shmorgun, Dr. Eng., Prof., Dept. of Materials Science and Composite Materials, e-mail: vgshmorgun@mail.ru
V. P. Kulevich, Cand. Eng., Associate Prof., Dept. of Materials Science and Composite Materials, e-mail: kulevich.vp@gmail.com; mv@vstu.ru
A. I. Bogdanov, Cand. Eng., Associate Prof., Dept. of Materials Science and Composite Materials, e-mail: bogdanov@vstu.ru

The thermal and electrical conductivity of the hot-dip aluminized Kh15Yu5 (Cr15Al5) alloy after long-term heat treatment at a temperature close to the operating temperature (1100 °C) has been studied. It is shown that the heat treatment of the aluminized alloy for 20 h leads to the formation of a coating with a thickness of ~260 μm of variable composition, which changes from the surface to the base in the following sequence: FeAl(Cr, Si) → Fe₃Al(Cr, Si) → Fe(Al, Cr, Si). An increase in the heat treatment time to 100 h is accompanied by the transformation of the coating surface phase composition to a solid solution of variable composition based on αFe. The microhardness of the coating surface decreases during heat treatment from 3.5 GPa to 2.4 GPa after 1000 h. It has been established that long-term high-temperature heating of the Cr15Al5 alloy with an aluminide coating leads to a decrease in its thermal conductivity, in comparison with a pure alloy, by 10–12 % due to the diffusion redistribution of the components that make up the coating. It is shown that the aluminide coating on the Kh15Yu5 (Cr15Al5) alloy surface increases the electrical resistivity of the sample by 0.2 Ohm·mm²/m, and high-temperature treatment contributes to an additional increase and stabilization of the resistance at a level above 1.55 Ohm·mm²/m. The high electrical resistivity of the Kh15Yu5 (Cr15Al5) alloy with an aluminide coating and the stability of properties during hightemperature heating make this material promising for use as heating elements.
The study was supported by the Russian Science Foundation grant No. 23-79-01245, https://rscf.ru/project/23-79-01245/.

1. Dong Z. H. et al. Vaporization of Ni, Al and Cr in Ni-base alloys and its influence on surface defect formation during manufacturing of single-crystal components. Metallurgical and Materials Transactions A. 2020. Vol. 51, Iss. 1. pp. 309–322.
2. He X. et al. High emissivity coatings for high temperature application: progress and prospect. Thin Solid Films. 2009. Vol. 517. No. 17. pp. 5120–5129.
3. Speiser R., Johnston H. L., Blackburn P. Vapor pressure of inorganic substances. III. Chromium between 1283 and 1561° K. Journal of the American Chemical Society. 1950. Vol. 72. No. 9. pp. 4142, 4143.
4. Shi C., Daun K. J., Wells M. A. Evolution of the spectral emissivity and phase transformations of the Al–Si coating on Usibor® 1500P steel during austenitization. Metallurgical and Materials Transactions B. 2016. Vol. 47, Iss. 6. pp. 3301–3309.
5. Pankov V. P. et al. Study of the patterns of diffusion coatings formation on modern heatresistant nickel alloys. Polzunovskiy vestnik. 2020. No. 1. pp. 124–129.
6. Reddy B. V., Deevi S. C. Thermophysical properties of FeAl (Fe–40 at.% Al). Intermetallics. 2000. Vol. 8. Iss. 12. pp. 1369–1376.
7. Deevi S. C. Powder processing of FeAl sheets by roll compaction. Intermetallics. 2000. Vol. 8, Iss. 5-6. pp. 679–685.
8. Panas A. J., Senderowski C., Fikus B. Thermophysical properties of multiphase Fe–Al intermetallic-oxide ceramic coatings deposited by gas detonation spraying. Thermochimica Acta. 2019. Vol. 676. pp. 164–171.
9. Palm M., Stein F., Dehm G. Iron aluminides. Annual Review of Materials Research. 2019. Vol. 49. pp. 297–326.
10. Krektuleva R. A. et al. Study of thermophysical processes in a contacting pair of St3–Al materials during argon arc welding with a non-consumable electrode. Fizicheskaya mezomekhanika. 2015. Vol. 18. No. 3. pp. 92–100.
11. Lilly A. C., Deevi S. C., Gibbs Z. P. Electrical properties of iron aluminides. Materials Science and Engineering: A. 1998. Vol. 258, Iss. 1-2. pp. 42–49.
12. Pazourek A., Pfeiler W., Šíma V. Dependence of electrical resistivity of Fe–Al alloys on composition. Intermetallics. 2010. Vol. 18, Iss. 7. pp. 1303–1305.
13. Kass M. et al. The formation of defects in Fe–Al alloys: electrical resistivity and specific heat measurements. Intermetallics. 2002. Vol. 10, Iss. 10. pp. 951–966.
14. Liu W. et al. The effective mass, vibration and electromagnetic properties of tetragonal iron aluminide FeAl2. Ceramics International. 2021. Vol. 47, Iss. 2. pp. 1766–1771.
15. Ejenstam J. et al. Microstructural stability of Fe–Cr–Al alloys at 450–550 C. Journal of Nuclear Materials. 2015. Vol. 457. pp. 291–297.
16. Pugacheva N. B., Ekzemplyarova E. O., Zadvorkin S. M. The influence of aluminum on the structure and physical properties of Fe–Cr–Al alloys. Metally. 2006. No. 1. pp. 68–75.
17. GOST 12766.2–90. Strip of high electrical resistance precision alloys. Specifications. Introduced: 01.01.1991.
18. GOST 1583–93. Aluminium casting alloys. Specifications. Introduced: 01.01.1997.
19. Shmorgun V. G., Kulevich V. P., Bogdanov A. I. Structure and properties of aluminized alloys of the Fe–Cr–Al system. Chernye Metally. 2022. No. 8. pp. 47–52.
20. Ruirui Wanga, Xiao Zhanga, Huaiyu Wanga, Jun Nia. Phase diagrams and elastic properties of the Fe–Cr–Al alloys: A first principles based study. Calphad. 2019. Vol. 64. pp. 55–65.
21. Zi-Kui Liu, Y. Austin Chang. Thermodynamic assessment of the Al–Fe–Si system. Metallurgical and materials transactions. 1999. Vol. 30A. pp. 1081–1095.
22. Mazin A. A., Korneev A. A., Galkin A. A. Application of heating elements for liquid crystal indicators. Radiopromyshlennost. 2018. Vol. 28. No. 2. pp. 90–93.