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α‐Fe layer formation during metal dusting of iron in CO‐H 2 ‐H 2 O gas mixtures
Author(s) -
Zhang J.,
Schneider A.,
Inden G.
Publication year - 2003
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200303740
Subject(s) - cementite , graphite , coke , materials science , carbon fibers , layer (electronics) , metallurgy , metal , chemical engineering , particle (ecology) , analytical chemistry (journal) , chemistry , nanotechnology , composite material , microstructure , organic chemistry , austenite , oceanography , geology , composite number , engineering
The formation of an α‐Fe layer between cementite and graphite was observed and investigated during metal dusting of iron in CO‐H 2 ‐H 2 O gas mixtures at both 600°C and 700°C. The condition to form this phenomenon is determined by the gas composition which depends on temperature. The iron layer formation was observed for CO content less than 1 % at 600°C and less than 5 % at 700°C. With increasing CO contents, no α‐Fe layer was detected at the cementite/graphite interface by optical microscopy. In this case cementite directly contacts with the coke layer. The morphologies of the coke formed in the gas mixtures with low CO contents were also analysed. Three morphologies of graphite have been identified with 1 % CO at 600°C: filamentous carbon, bulk dense graphite with columnar structure, and graphite particle clusters with many fine iron containing particles embedded inside. At 700°C with 5 % CO the coke mainly consists of graphite particle clusters with some filamentous carbon at the early stage of reaction. Coke analysis by X‐ray diffraction shows that both α‐Fe and Fe 3 C are present in the coke. The mechanism of α‐Fe accumulation between cementite and graphite is discussed in this paper.