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Relationship between coking and metal dusting
Author(s) -
Chun C.M.,
Ramanarayanan T.A.,
Mumford J.D.
Publication year - 1999
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/(sici)1521-4176(199911)50:11<634::aid-maco634>3.0.co;2-f
Subject(s) - corrosion , carbide , materials science , metal , metallurgy , carbon fibers , supersaturation , nickel , amorphous carbon , amorphous solid , chemistry , composite material , crystallography , organic chemistry , composite number
Metal dusting is a severe form of corrosive degradation that Fe, Co and Ni base high temperature alloys undergo when subjected to environments supersaturated with carbon (a c > 1). This corrosion process leads to the break‐up of bulk metal into metal powder. The present study focuses on the fundamental understanding of the corrosion of Fe and Ni in carbon‐supersaturated environments over the temperature range, 350–1050 °C. Building on earlier research, the role of deposited carbon in triggering corrosion is further clarified. For Fe, the corrosion rate peaked at ∼ 575 °C with a sharp decrease in rate on either side of the maximum. High‐resolution electron microscopy revealed, in addition to metal particles, a mixture of graphitic carbon, amorphous carbon and filamentous carbon in the corrosion product. While the presence of a surface layer of Fe 3 C was characteristic of corrosion up to 850 °C, such a layer was absent at the higher temperatures. The corrosion rate maximum that typified the metal dusting of Fe was absent in the case of Ni where no surface carbide occurs until temperatures well below 350 °C. The mechanistic differences between iron corrosion and nickel corrosion are compared and contrasted.