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Metallology and Metallography
ArticleName Fe – 100% C diagram. Part 1. Basic contradictions of the Fe–Fe3C diagram
DOI 10.17580/chm.2023.02.10
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:


For more than 90 years, the classical view of the diagram Fe-Fe3C has not undergone significant changes, becoming a kind of standard, replicated in the educational and scientific educational space. The fundamental contradiction of the Fe-Fe3C diagram is the combination of two phase equilibrium systems - stable graphite equilibrium and metastable cementite equilibrium on the field of the diagram, which contradicts the basic provisions of the theory of alloy state diagrams and causes the main doubt about the correctness of this combination. The presence of stable (graphite) and metastable (cementite) equilibria in the same diagrammatic field reflects an incomplete, superficial understanding of structure formation processes in the Fe-Fe3C system and, as a consequence, a violation of diagramming rules. Some directions of theoretical calculations of the Fe-Fe3C diagram based on the thermodynamics of iron-carbon alloys and the construction of the diagram of the "iron – diamond" system are analyzed. It is shown that the alloys with a carbon content of more than 6.67 % C are not currently investigated and in fact the Fe-Fe3C diagram is a huge area terra incognita because of the impossibility of obtaining these alloys by existing melting methods under normal conditions. A number of modern alternative diagrams Fe-Fe3C constructed without due regard for the basic laws of the theory of state diagrams of alloys and physical materials science.

keywords Diagram of the Fe-Fe3C system alloys, stable graphite equilibrium, metastable cementite equilibrium, alternative Fe-Fe3C diagrams

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