Thermodynamics of the Fe-Mo-C system at 985 K

Abstract

The solubility of carbon and the composition of carbides in the ferritic Fe-Mo-C system were measured at 985 K by a gas flowing method and a sealing method. The composition of alloys ranged from 0.24 pct to 2.93 pct Mo. An iron-carbon binary alloy was included in the equilibration as a reference material. The molybdenum-carbon interaction in the α-phase was analyzed by the central atoms model. The Wagner interaction coefficient was determined as ε ^Mo_c = •100 ± 2, which is a higher negative value than that in the Fe-Cr-C system at the same temperature. The carbide phase was analyzed as a regular solution of two component carbides, FeC _x and MoC _x . M₆C carbide was in equilibrium with α in the carbon activity range from 0.045 to 0.156, and M₂C carbide was in equilibrium at the carbon activity 0.51. M₆C and M₂C carbides were present at the carbon activity 0.45. Molybdenum partitioning between α- and carbide phases was measured. The standard free energies of formation of two component carbides and the interaction energy parameters were determined for M₆C and M₂C carbides.