Paper Title:
On the Loss of Protective Scale Formation in Creep-Resistant, Alumina-Forming Austenitic Stainless Steels at 900°C in Air
  Abstract

A family of creep-resistant, Al2O3-forming austenitic (AFA) stainless steels was recently developed. The alloys exhibit excellent oxidation resistance up to ∼800°C, but are susceptible to internal attack of Al at higher temperatures. In the present work, higher levels of Ni, Cr, Al, and Nb additions were found to correlate with improved oxidation behavior at 900°C in air. The alloys generally appeared to be initially capable of external Al2O3 scale formation, with a subsequent transition to internal attack of Al (internal oxidation and internal nitridation) that is dependent on alloy composition. Compositional profiles at the alloy/scale interface suggest that the transition to internal oxidation is preceded by subsurface depletion of Al in the lower-Al compositions. In higher Al-containing compositions, NiAl second-phase precipitates act as an Al reservoir, and Al depletion may not be a key factor. Alloy design directions to increase the upper-temperature limit of protective Al2O3 scale formation in these alloys are discussed.

  Info
Periodical
Materials Science Forum (Volumes 595-598)
Edited by
Pierre Steinmetz, Ian G. Wright, Alain Galerie, Daniel Monceau and Stéphane Mathieu
Pages
725-732
DOI
10.4028/www.scientific.net/MSF.595-598.725
Citation
M.P. Brady, Y. Yamamoto, B. A. Pint, M.L. Santella, P.J. Maziasz, L.R. Walker, "On the Loss of Protective Scale Formation in Creep-Resistant, Alumina-Forming Austenitic Stainless Steels at 900°C in Air", Materials Science Forum, Vols. 595-598, pp. 725-732, 2008
Online since
September 2008
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$32.00
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