ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00414223
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