Oxidation of Metals

, Volume 38, Issue 5–6, pp 407–424 | Cite as

The hot-corrosion behavior of novel CO-deposited chromium-modified aluminide coatings

  • B. Gleeson
  • W. H. Cheung
  • W. Da Costa
  • D. J. Young
Article
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Abstract

This paper reports the successful co-deposition of inclusion-free chromiummodified aluminide coatings using a pack-cementation process. The substrate used was the nickel-base superalloy, René 80H. The coatings were of the outward-diffusion type; however, unlike the usual outward-diffusion coatings, the present coatings were relatively free of pack inclusions. The coatings consisted of α-Cr precipitates in a matrix of β-NiAl. The morphology and distribution of the α-Cr precipitates could be adjusted to the extent that two types of coating structures could be obtained. The Type I coating structure contained lamellar α-Cr precipitates situated in the surface region of the coating, whereas the Type II coating structure contained small, spheroidal α-Cr precipitates distributed throughout the outer of a two-layered coating. Both coating types exhibited significantly improved hot-corrosion resistance in a 0.1% SO2-O2 environment at 900°C compared to a commercial aluminide coalting. A study of the corrosion behavior of Type I coatings containing pack inclusions showed that the inclusions were deleterious to the corrosion resistance of the coatings. The corrosion behavior of chromium-aluminide coatings was dependent on both the distribution and amount of α-Cr precipitates in the coating.

Key words

chromium-modified aluminide coatings hot corrosion pack inclusions 
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Copyright information

© Plenum Publishing Corporation 1992

Authors and Affiliations

  • B. Gleeson
    • 1
  • W. H. Cheung
    • 1
  • W. Da Costa
    • 1
  • D. J. Young
    • 1
  1. 1.School of Materials Science & EngineeringUniversity of New South WalesKensingtonAustralia

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