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Metallology and Metallography
ArticleName Fe-100% C diagram. Part 2. Development problems and incompleteness of the diagram Fe3C – 100 % C
DOI 10.17580/chm.2023.04.11
ArticleAuthor S. V. Davydov

Bryansk State Technical University, Bryansk, Russia:

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


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.

keywords Alloy diagram of the system "Fe3C–100 % C", iron carbides, phase equilibrium "liquid– vapor", fullerenes, allotropes of carbon, lamellar graphite, globular graphite

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