Bryansk State Technical University, Bryansk, Russia:

S. V. Davydov, Dr. Eng., Prof., Dept. of Tribotechnical Materials Science and Technology of Materials, e-mail: fulleren_grafen@mail.ru

This paper considers three groups of problems in the study of the right side of the "Fe₃C–100 % C" diagram. The first group of problems includes the absence in the diagram of a sufficiently large line of iron carbides: FeC, Fe₂C, (except Fe₃C), Fe₃C₂, Fe₄C, Fe₅C₂, Fe₆C, Fe₇C₃, Fe₈C, Fe₂₀C₉, Fe₂₃C₆. From this group of carbides, except cementite Θ-Fe₃C, only three significant types of carbides are objectively identified: ε-carbide Fe₂C, Hegg carbide χ-Fe₅C₂ and Extrem-Adcock carbide æ-Fe₇C₃, which are located on the right side of cementite line and not shown on the diagram of state "Fe₃C–100% C" as complete phases or diagram components, which are considered to be metastable, transitional phases by default. The second group of problems is that the liquid-vapor phase equilibrium region of the "Fe–100 % C" diagram is currently not scientifically convincing, has not been studied, and no attempt has been made to investigate it. The third group of problems is that carbon as the main component of the "Fe–100 % C" diagram alloys is currently considered as a pure graphite chemical substance with a "crystalline hexagonal layered lattice" in general. It is also shown that when describing graphite crystallization, the iron melt should be considered as a single-phase system in the form of a carbon-iron polymer whose structural basic elements are fullerenes and carbon nanoparticles based on them. The application of carbon allotropes to explain the problems of graphite structure formation is considered. It is proposed that the existing line of graphite in the diagram "Fe₃C–100 % C" be designated as the line of atomic carbon – Сatom.

1. Davydov S. V. Fe – 100 % С diagram. Part 1. Basic contradictions of the Fe – Fe₃С diagram. Chernye Metally. 2023. No. 2. pp. 66–73.
2. Kosolapova Т. Ya. Carbides. Moscow: Metallurgiya, 1968. 300 p.
3. Kulikov I. S. Thermodynamics of carbides and nitrides. Reference edition. Chelyabinsk: Metallurgiya. Chelyabinskoe otdelenie, 1988. 320 p.
4. High temperature carbides. Edited by G. V. Samsonov. Kiev: Naukova Dumka, 1975. 192 p.
5. Samsonov G. V., Kosolapova Т. Ya., Gnesin G. G. et al. Carbides and alloys based on them. Kiev: Naukova Dumka, 1976. 267 p.
6. Toth L. E. Transition metal carbides and nitrides. Moscow: Mir, 1974. 296 p.
7. Cementite in carbon steels. Edited by V. М. Schastlivtsev. Ekaterinburg: Izdatelstvo UMTs UPI, 2017. 380 p.
8. Okamoto Hiroyuki. The C-Fe (carbon-iron) system. Journal of Phase Equilibria. 1992. Vol. 13. No. 5. pp. 543–565.
9. Kundu S., Bhadeshia H. K. D. H. Crystallographic texture and intervening transformations. Scripta Materialia. 2007. Vol. 57. pp. 869–872.
10. Jack D. H., Jack K. H. Invited review: Carbides and nitrides in steel. Mater. Sci. Engin. 1973. Vol.11. pp.1–27.
11. Wood I. G., Vocadlo L., Knight K. S. et al. Thermal expansion and crystal structure of cementite, Fe3C, between 4 and 600 K determined by time-of-flight neutron powder diffraction. J. Appl. Cryst. 2004. Vol. 37. pp. 82–90.
12. Wicks C. Е., Block F. Е. Thermodynamic properties of 65 elements, their oxides, halides, carbides and nitrides. Moscow: Metallurgiya, 1965. 240 p.
13. Hester Esna Du Plessis. The Crystal Structures of the Iron Carbides. University of Johannesburg. 2006. 185 p.
14. Bhadeshia H. K. D. H. Cementite. International Materials Reviews. 2020. Vol. 65, Iss. 1. pp. 1–27.
15. Silman G. I. Refinement of the Fe-C diagram based on the results of thermodynamic analysis and generalization of data on the Fe-C and Fe-C-Cr systems. Metallovedenie i termicheskaya obrabotka metallov. 1997. No. 11. pp. 2–7.
16. Zhukov А. А., Snezhnoy R. L. On the shape of the liquidus curve in the melting region of cementite on the iron-diamond phase diagram. Izvestiya AN SSSR. Metally. 1976. No. 3. pp. 192–199.
17. Zhukov А. А. On the state diagram of alloys of the Fe-C system. Metallovedenie i termicheskaya obrabotka metallov. 1988. No. 4. pp. 2–9.
18. Zhukov А. А., Shterenberg L. Е., Shalashov V. А., Tomas V. К., Berezovskaya N. А. Pseudohexagonal iron carbide Fe7C3 and eutectic Fe3C-Fe7C3 in the Fe-C system. Izvestiya AN SSSR. Metally. 1973. No. 1. pp. 181–184.
19. Bannykh О. А., Buddberg P. B., Alisova S. P. et al. State diagrams of binary and multicomponent systems based on iron. Moscow: Metallurgiya, 1986. 440 p.
20. Vertman А. А., Samarin А. М. Properties of iron melts. Moscow: Nauka, 1969. 279 p.
21. State diagrams of binary metallic systems: Handbook: in 3 Volumes. Vol. 1. Edited by N. P. Lyakishev. Moscow: Mashinostroenie, 1996. 992 p.
22. Lakhtin Yu. М. Materials science and heat treatment of metals: textbook for universities; 3rd edition revised and additional. Moscow: Metallurgiya, 1983. 360 p.
23. Doru M. Stefanescu, Gorka Alonso, Ramon Suarez. Recent developments in understanding nucleation and crystallization of spheroidal graphite in iron-carbon-silicon alloys. Metals. 2020. Vol. 10, Iss. 2. pp. 221–260.
24. Alonso G., Doru M. Stefanescu, Larranaga Pello. Graphite nucleation in compacted graphite cast iron. International Journal of Metalcasting. 2020. Vol. 14, Iss. 2. pp. 1162–1171.
25. Theuwissen K. J., Lacaze L. Structure of graphite precipitates in cast iron. Carbon. 2016. Vol. 96. pp. 1120–1128.
26. Radzikowska J. M. Metallography and microstructures of cast iron. Metallography and Microstructures. 2004. Vol. 9. pp. 565–587.
27. Binder C., Bendo T., Hammes G. O. Structure and properties of situ-generated twodimensional turbostratic graphite nodules. Carbon. 2017. Vol. 124. pp. 685–692.
28. McSwain R. N., Bates C. E. Graphite growth in cast iron. AFS International cast metal journal. 1976. No. 3. pp. 53–57.
29. Bunin К. P., Malinochka Ya. N., Taran Yu. N. Fundamentals of cast iron metallography. Moscow: Metallurgiya, 1969. 416 p.
30. Zhukov А. А., Snezhnoy R. L., Davydov S. V. On forming of compact graphite in cast iron. Metallovedenie i termicheskaya obrabotka metallov. 1981. No. 9. pp. 21–25.
31. Zhukov А. А., Davydov S. V., Ivanenko S. М. Radial structural component in graphite globules of ductile iron. Metallovedenie i termicheskaya obrabotka metallov. 1985. No. 10. pp. 44–45.
32. Davydov S. V. Crystallization of nodular graphite in ductile iron melt. Zagotovitelnye proizvodstva v mashinostroenii. 2008. No. 3. pp. 3–8.
33. Kasperek J., Tellier J.-C., Ortiz M. Aspects de la germination du graphite dans des fontes synthetiques еlaborees sous vide. Fonderie fоndeur d`aujourd`hui. 1991. Iss. 101. pp. 29–37.
34. Stefanescu D. M., Crisan A., Alonso G. Growth of spheroidal graphite on nitride nuclei: disregistry and crystallinity during early growth. Metallurgical and Materials Transactions A. 2019. Vol. 50A, Iss. 4. p. 1763–1772.
35. Itofuji H. Magnesium map of the spheroidal graphite structure in ductile cast irons. Cast metals. 1992. Vol. 5, Iss. 1. pp. 6–19.
36. Cast iron: reference edition. Edited by A. D. Sherman and A. A. Zhukov. Moscow: Metallurgiya, 1991. 576 p.
37. Zhukov А. А., Snezhnoy R. L., Girshovich N. G., Davydov S. V. On the submicroheterogeneous structure of liquid iron. Liteynoe proizvodstvo. 1980. No. 6. pp. 3, 4.
38. Zhukov А. А., Snezhnoy R. L., Davydov S. V. On the role of "metal-carbon" sandwich complexes in mass transfer in the graphitization of cast irons and the synthesis of diamonds. Liteynoe proizvodstvo. 1983. No. 1. pp. 5, 6.
39. Zhukov А. А. On the forms of existence of carbon in cast irons. Metallovedenie i termicheskaya obrabotka metallov. 1992. No. 11. pp. 34, 35.
40. Davydov S. V. Different mechanisms for compacting the graphite phase in cast iron and graphitized steel. Liteynoe proizvodstvo. 1998. No. 12. pp. 8, 9.
41. Davydov S. V. Crystallization of nodular graphite in ductile iron melt. Zagotovitelnye proizvodstva v mashinostroenii. 2008. No. 3. pp. 3–8.
42. Davydov S. V. New ideas about the crystallization of nodular graphite. Chernaya metallurgiya. Byulleten nauchno-tekhnicheskoy i ekonomicheskoy informatsii. 2018. No. 6. pp. 67–75.
43. Zhukov А. А. Geometric thermodynamics of iron alloys: 2^nd edition revised. Moscow: Metallurgiya, 1979. 232 p.
44. Zhukov А. А. Fullerenes and graphite spheroidization in iron alloys. Metallovedenie i termicheskaya obrabotka metallov. 2000. No. 7. pp. 3–6.
45. Kuzeev I. R., Zakirnichnaya М. М., Samigullin G. Kh. et al. Fullerene model of high-carbon iron-based alloys. Izvestiya AN SSSR. Metally. 1999. No. 1. pp. 74–79.
46. Zakirnichnaya М. М., Kuzeev I. R., Tkachenko О. I. Formation of fullerenes during the diffusion of carbon into the steel structure. Neft i gaz. 2012. No. 2. pp. 112–119.
47. Zakirnichnaya М. М. Formation of fullerenes in carbon steels and cast irons during crystallization and thermal effects: thesis of inauguration of Dissertation … of Doctor of Engineering Sciences. Ufa: UGNTU, 2001. 48 p.
48. Zakirnichnaya М. М. Influence of cast iron cooling conditions on the formation of fullerenes. Liteynoe proizvodstvo. 2001. No. 8. pp. 8, 9.
49. Zakirnichnaya М. М. Method for identification of fullerenes isolated from iron-carbon alloys. Zavodskaya laboratoriya. 2001. No. 6. pp. 39–49.
50. Domrachev G. А., Lazarev А. I., Kaverin B. S. et al. The Role of carbon and metal in the self-organization of the iron-carbon system at different contents of components. Fizika tverdogo tela. 2004. Vol. 46, Iss. 10. pp. 1901–1915.
51. Bunina N. V., Petrakovskaya E. А., Marachevskiy А. V. et al. Synthesis and study of ironfullerene clusters. Fizika tverdogo tela. 2006. Vol. 48, Iss. 5. pp. 952–954.
52. Zhukov А. А. On the state diagram of alloys of the Fe–C system. Metallovedenie i termicheskaya obrabotka metallov. 1988. No. 4. pp. 2–9.
53. Bataleva Yu. V., Palyanov Yu. N., Borzdov Yu. М., Bayukov О. А., Sobolev N. V. Conditions for the formation of graphite and diamond from iron carbide at P,T-parameters of the lithospheric mantle. Geologiya i geofizika. 2016. Vol. 57. No. 1. pp. 225–240.
54. Palyanov Y. N., Bataleva Yu. V., Sokol A. G. et al. Mantle-slab interaction and redox mechanism of diamond formation. Proceedings of the National Academy of Sciences. 2013. Vol. 110. No. 51. pp. 20409–20413.
55. Nikolis G., Prigozhin I. Self-organization in nonequilibrium systems. Moscow: Mir, 1979. 308 p.
56. Haken H. Advanced synergetics: instability hierarchies of instabilities in self-organizing systems and devices. Translated from English. Moscow: Mir, 1985. 432 p.
57. Prigozhin I. The end of certainty. Time. Chaos and the new laws of nature. Translated from English by Yu. A. Danilov. Izhevsk: NITs "Regulyarnaya i khaoticheskaya dinamika", 2001. 208 p.
58. Davydov S. V. A new approach to the classification of modification methods. Metallurgiya mashinostroeniya. 2006. No. 5. pp. 5–9.
59. Davydov S. V. New technologies for modifying cast irons. Metallurgiya mashinostroeniya. 2010. No. 3. pp. 8–13.
60. Davydov S. V. State diagram of alloys of the "iron-carbide ε-Fe₂C" system: monograph. Moscow; Vologda: Infra-Inzheneriya, 2021. 280 p.