Notes:
Numerous carbides are reported in the literature but only two of them have been investigated under normal pressure and metastable equilibrium conditions: firstly cementite, which is usually assigned the formula fe3C and crystallizes in an orthorhombic structure and secondly between room temperature and 230 C Fe22C, generally called the Hagg carbide.Fe7C3 and carbon in the form of diamond appear only at high pressure and carbon concentration exceeding 30-35 at.%. Zhukov and Snezhnoy suggest a hypothetical metastable Fe-C(diamond) phase diagram for normal pressure. to
