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Thermodynamics of Hägg carbide (Fe 5 C 2 ) formation
Author(s) -
Schneider André,
Inden Gerhard
Publication year - 2001
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.200100158
Subject(s) - carbide , thermodynamics , materials science , chemistry , metallurgy , physics
Gas carburisation experiments on iron samples were conducted in CO‐H 2 ‐H 2 O‐H 2 S atmospheres with different carbon activities at 500 °C. Carbon activities well above a C = 1 (equilibrium iron/graphite) were used in order to form iron carbides such as cementite (Fe 3 C) and Hägg carbide (Fe 5 C 2 ). The Gibbs energy of formation ΔG for Fe 5 C 2 was determined at 500 °C. This result combined with thermodynamic properties at other temperatures taken from literature strongly supports the existence of the three phase equilibrium α‐Fe+Fe 3 C+Fe 5 C 2 at about 350°C in the binary Fe‐C system.