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The effect of elevated temperature refinery service on the chemistry of M 23 C 6 carbides in 9Cr‐1Mo steel
Author(s) -
Hucińska J.
Publication year - 2000
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(200003)51:3<173::aid-maco173>3.0.co;2-3
Subject(s) - carbide , metallurgy , molybdenum , corrosion , materials science , chromium , carbon fibers , intergranular corrosion , alloy , sulfur , chemistry , nuclear chemistry , composite material , composite number
In a previous study the influence of sulphur‐bearing refinery environment on the corrosion behaviour of commercial 9Cr‐1Mo steel has been investigated [1]. It has been stated that the progress of high temperature sulphide corrosion can be followed by internal carburization of this steel due to a release of carbon from the sulphur‐attacked carbides and diffusion of carbon into the steel interior, accompanied by formation of new carbides, or growth of the existing M 23 C 6 carbides. In the study presenting this it has been revealed that at the rapid, intergranular progress of sulphide corrosion in the presence of hydrogen, the growth/formation of M 23 C 6 carbides, which is most intensive near the corrosion‐attacked surface, results in an increased chromium and molybdenum content close to this surface, and in increased Cr/Fe and Mo/Fe ratios in M 23 C 6 carbides, which was established by means of EDS analyses. Just beneath the surface, at a depth of less than about 0.2 mm, a steep depletion of the steel in the alloy elements measured by EPM technique can prove the reduced Cr/Fe and Mo/Fe ratios in the carbides.