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Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatmentsOxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.
Document ID
19760033254
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Young, C. T.
(Bendix Research Laboratories Southfield, Mich., United States)
Tenney, D. R.
(NASA Langley Research Center Hampton, Va., United States)
Herring, H. W.
(NASA Marshall Space Flight Center Huntsville, Ala., United States)
Date Acquired
August 8, 2013
Publication Date
December 1, 1975
Publication Information
Publication: Metallurgical Transactions A - Physical Metallurgy and Materials Science
Volume: 6A
Subject Category
Metallic Materials
Accession Number
76A16220
Distribution Limits
Public
Copyright
Other

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