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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/12345

Title: Effect of theta-alumina formation on the growth kinetics of alumina-forming superalloys
Authors: PRASANNA, KMN
KHANNA, AS
CHANDRA, R
QUADAKKERS, WJ
Keywords: oxide scales
ods alloys
oxidation
yttrium
mechanisms
Issue Date: 1996
Publisher: SPRINGER/PLENUM PUBLISHERS
Citation: OXIDATION OF METALS, 46(5-6), 465-480
Abstract: Alumina-forming ODS superalloys are excellent oxidation-resistant materials. Their resistance relies upon the establishment of a stable, slow-growing, and adherent alpha-alumina. In the present investigation, these alloys exhibited unstable and relatively less adherent theta-alumina phase, which increased the oxidation rate in the transient stage and converted into alpha-alumina in the later part of the exposure. The oxide-growth process was found to depend upon various parameters such as temperature, time, and presence of an active element in the superalloy. Characterization carried out by XRD, SEM/EDAX, and AES on oxidized ODS and non-ODS alloys demonstrated a significant influence of the active element, Y on the transformation of theta- to alpha-alumina. SIMS analysis of two-stage oxidation at 900 degrees C for two different durations evidently showed that the change in the transport process is due to theta-to-alpha-alumina transformation. On the basis of these results, a new and consistent mechanism is proposed to explain the influence of theta-alumina and its transformation on growth kinetics and the effect of yttrium on the transformation leading to good scale adherence and oxidation resistance.
URI: http://dx.doi.org/10.1007/BF01048641
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12345
http://hdl.handle.net/10054/12345
ISSN: 0030-770X
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