Abstract
Thermodynamic properties of carbides present in 2.25Cr-lMo steel were determined at 985 K by a gas flowing method with fixed CH4/H2 gas mixtures and by a silica capsule method with reference alloys. The carbon activity range was from 0.06 to 0.5. Total carbon content, carbide species, and Cr and Mo partitionings between the matrix and carbides were measured as a function of the carbon activity. Both M6C and M23C6 carbides were present after 1000 to 3000 hours at the test temperature and in the carbon activity range studied. The amount of M6C was greater in the low carbon activity range, while M23C6 carbide became the major carbide with increasing carbon activity. The M6C carbide contained Mo as a major element and Cr and Si as minor elements; approximately 13 pct of the metal constituent was (Cr + Si). The stability of M6C carbide in this steel is significantly higher than M6C formed in the Fe-Mo-C system. The M23C6 carbide contained Cr as a major metal component and Mo as a minor. The M23C6 carbide is more stable in an extended range of the carbon activity in 2.25Cr-lMo steel than in the Fe-Cr-C system. The presence of Si is apparently low in M23C6. Thermodynamic parameters were computed for M6C and M23C6 carbides using a regular solution model of component carbides, FeCx, CrCx, and MoCx.
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Wada, H. Thermodynamic properties of carbides in 2.25Cr-1Mo steel at 985 K. Metall Trans A 17, 1585–1592 (1986). https://doi.org/10.1007/BF02650095
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DOI: https://doi.org/10.1007/BF02650095