On the nature of cementite

Thermal expansion of cementite in hypereutectoid iron-carbon alloy

“…However, the diffractograms do not exhibit even the most intense reflections ofct-Fe (I 10). In accordance with [2,3] cementite should hardly be treated as a chemical compound. Even if the impurity encloses cementite particles, the thickness of such an adsorbed film is insufficient to change the coefficient of thermal expansion of cementite.…”

“…It should be noted that cementite is treated by some authors [2,3] as a solid solution, because it does not obey the valence rule and its composition may vary. The heat of cementite formation is very low, which is typical for solid solutions and is virtually never observed in the formation of chemical compounds.…”