Iron-carbon interactions at high temperatures and pressures

We have performed experiments in the Fe - C system at 2200 - 3400 K and 25 - 70 GPa 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. (C) 2008 American Institute of Physics.