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Oxidation of Metals

, Volume 9, Issue 5, pp 427–440 | Cite as

The high-temperature oxidation resistance of Co-Al alloys

  • G. N. Irving
  • J. Stringer
  • D. P. Whittle
Article

Abstract

Most Ni and Co-base alloys used for high-temperature service rely on the production of a compact, stable Cr2O3 scale for their oxidation resistance. However, as operating temperatures have risen above 900–950° C, the loss of Cr2O3 as the volatile CrO3 has led to an inadequate life span of these alloys, particularly in rapidly flowing, turbulent gas streams. As a result of this, it has been necessary to examine the possibility of using Al2O3 as the protective scale. Al2O3 has a lower growth rate than Cr2O3, it is nonvolatile, and, unlike Cr-containing systems, it is less likely to form compound oxides such as spinels. In this study, the amount of Al which must be present in the Co-Al system to form a continuous layer of Al2O3 in the temperature range 800–1000° C has been determined. The quantity was found to rise from about 7–10 wt. % at 800° C to 10–13 wt. % at 900° C and 13 wt. % at 1000° C. Notice has also been taken of the abilities of the alumina-forming alloys to re-form a protective oxide in the event of spalling, blistering, or any other disruptions of the scale, and some “cyclic-oxidation” checks have been conducted on the Co13Al alloy at 900 and 1000° C.

Key words

cobalt cobalt-aluminum alloys oxidation thermal cycling 

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Copyright information

© Plenum Publishing Corporation 1975

Authors and Affiliations

  • G. N. Irving
    • 1
  • J. Stringer
    • 1
  • D. P. Whittle
    • 1
  1. 1.Department of Metallurgy and Materials ScienceUniversity of LiverpoolLiverpoolEngland

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