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Effect of sulfur removal on Al2O3 scale adhesionThe effect of removing sulfur impurity on the adhesion of Al2O3 scale to NiCrAl was investigated in four experiments. It was found that removing sulfur to concentration less than 1 ppm per weight is sufficient to produce a very significant degree of alpha-Al2O3 scale adhesion to undoped NiCrAl alloys. Results of experiments show that repeated oxidation, and polishing after each oxidation cycle, of pure NiCrAl alloy lowered sulfur content from 10 to 2 ppm by weight (presumably by removing the segregated interfacial layer after each cycle); thinner samples became adherent after fewer oxidation-polishing cycles because of more limited supply of sulfur. It was found that spalling in subsequent cyclic oxidation tests was a direct function of the initial sulfur content. The transition between the adherent and nonadherent behavior was modeled in terms of sulfur flux, sulfur content, and sulfur segregation.
Document ID
19910043317
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Smialek, James L.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 14, 2013
Publication Date
March 1, 1991
Publication Information
Publication: Metallurgical Transactions A - Physical Metallurgy and Materials Science
Volume: 22A
ISSN: 0360-2133
Subject Category
Metallic Materials
Accession Number
91A27940
Distribution Limits
Public
Copyright
Other

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