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A kinetic and morphological study of the coking of some heat-resistant steels

Journal Article


Abstract


  • The coking behaviour of a range of austenitic, heat-resistant steels has been examined in the temperature range 700-1000��C. At and below 800��C, catalytic coke in the form of bundles of filaments formed at localized defect sites in the carbide scales. A wide range in weight-gain kinetics resulted from the differing efficacy of the non-catalytic carbide scales in excluding carbon from the catalytically active substrate. At and above 900��C, catalytic coke formation gave way to pyrolytic coke formation and internal carburization became significant. Parabolic kinetics resulted from the fact that internal carburization was rate-determining. Carburizing alloys gained weight an order of magnitude faster than did alloys protected by oxide films. This was a consequence of dissolution of carbon into the alloy directly from the gas stream being much faster than the rate of coke formation on the alloy surface. Oxide-protected alloys all gained weight at a similar rate, the rate being that of coke deposition on coke. Oxide films containing aluminium were more effective in excluding carbon from the alloy than chromium-containing oxides. However, under reducing conditions, preformed oxide films were not beneficial in limiting carburization in the longer term, because they were prone to spalling, cracking and conversion to non-protective carbide. �� 1994 Chapman & Hall.

Publication Date


  • 1994

Citation


  • Mitchell, D. R. G., & Young, D. J. (1994). A kinetic and morphological study of the coking of some heat-resistant steels. Journal of Materials Science, 29(16), 4357-4370. doi:10.1007/BF00414223

Scopus Eid


  • 2-s2.0-0028482721

Start Page


  • 4357

End Page


  • 4370

Volume


  • 29

Issue


  • 16

Place Of Publication


Abstract


  • The coking behaviour of a range of austenitic, heat-resistant steels has been examined in the temperature range 700-1000��C. At and below 800��C, catalytic coke in the form of bundles of filaments formed at localized defect sites in the carbide scales. A wide range in weight-gain kinetics resulted from the differing efficacy of the non-catalytic carbide scales in excluding carbon from the catalytically active substrate. At and above 900��C, catalytic coke formation gave way to pyrolytic coke formation and internal carburization became significant. Parabolic kinetics resulted from the fact that internal carburization was rate-determining. Carburizing alloys gained weight an order of magnitude faster than did alloys protected by oxide films. This was a consequence of dissolution of carbon into the alloy directly from the gas stream being much faster than the rate of coke formation on the alloy surface. Oxide-protected alloys all gained weight at a similar rate, the rate being that of coke deposition on coke. Oxide films containing aluminium were more effective in excluding carbon from the alloy than chromium-containing oxides. However, under reducing conditions, preformed oxide films were not beneficial in limiting carburization in the longer term, because they were prone to spalling, cracking and conversion to non-protective carbide. �� 1994 Chapman & Hall.

Publication Date


  • 1994

Citation


  • Mitchell, D. R. G., & Young, D. J. (1994). A kinetic and morphological study of the coking of some heat-resistant steels. Journal of Materials Science, 29(16), 4357-4370. doi:10.1007/BF00414223

Scopus Eid


  • 2-s2.0-0028482721

Start Page


  • 4357

End Page


  • 4370

Volume


  • 29

Issue


  • 16

Place Of Publication