Repulsive Nature for Hydrogen Incorporation to Fe3C up to 14 GPa

We have performed in situ X-ray diffraction measurements under high pressure and high temperature to study hydrogen solubility in Fe3C carbide. Hydrogen solubility can be estimated from a volume expansion associated with hydrogen incorporation into metal. The lattice volumes and phase relations of Fe3C–H system and Fe3C were measured up to 14 GPa and 1973 K. The lattice volumes of Fe3C measured in this study are well fitted using the 3rd order Birch–Murnaghan equation of state with the reported elastic parameters of Fe3C. Obtained lattice volumes of Fe3C–H are quite consistent with those of Fe3C. No difference between the melting temperatures of Fe3C–H and Fe3C was observed. These results demonstrate that hydrogen incorporation into Fe3C does not occur and hydrogen is unlikely to coexist with carbon in iron-alloy up to 14 GPa.