Iron-carbon interactions at high temperatures and pressures

We have performed experiments in the Fe–C system at 2200–3400K and 25–70GPa using a multianvil press and laser-heated diamond anvil cell in order to constrain the stability of Fe3C. Iron carbide was observed experimentally as a stable phase using both experimental methods and independently confirmed by thermodynamic calculations. Our results imply that pure iron and carbon cannot coexist in a stable equilibrium at high pressure and high temperature. The high reactivity between metallic iron and the diamond requires a careful design of diamond anvil cell experiments in order to avoid carbon transport to the sample.