ORIGINAL PAPER Increasing the Upper Temperature Oxidation Limit of Alumina Forming Austenitic Stainless Steels in Air with Water Vapor M. P. Brady • K. A. Unocic • M. J. Lance • M. L. Santella • Y. Yamamoto • L. R. Walker Received: 2 December 2010 / Revised: 25 January 2011 / Published online: 13 February 2011 Ó Springer Science+Business Media, LLC 2011 Abstract A family of alumina-forming austenitic (AFA) stainless steels is under development for use in aggressive oxidizing conditions from *600–900 °C. These alloys exhibit promising mechanical properties but oxidation resistance in air with water vapor environments is currently limited to *800 °C due to a transition from external protective alumina scale formation to internal oxidation of aluminum with increasing temperature. The oxidation behavior of a series of AFA alloys was systematically studied as a function of Cr, Si, Al, C, and B additions in an effort to provide a basis to increase the upper-temperature oxidation limit. Oxidation exposures were conducted in air with 10% water vapor environments from 800–1000 °C, with post oxidation characterization of the 900 °C exposed samples by electron probe microanalysis (EPMA), scanning and transmission electron microscopy, and photo-stimulated luminescence spectroscopy (PSLS). Increased levels of Al, C, and B additions were found to increase the upper-temperature oxidation limit in air with water vapor to between 950 and 1000 °C. These findings are discussed in terms of alloy microstructure and possible gettering of hydrogen from water vapor at second phase carbide and boride precipitates. Keywords Stainless steel Á Third-element effect Á Multi-phase alloy oxidation Á Water vapor Á Alumina Á Internal oxidation Notice: This submission was sponsored by a contractor of the United States Government under contract DE-AC05-00OR22725 with the United States Department of Energy. The United States Government retains, and the publisher, by accepting this submission for publication, acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this submission, or allow others to do so, for United States Government purposes. M. P. Brady (&) Á K. A. Unocic Á M. J. Lance Á M. L. Santella Á Y. Yamamoto Á L. R. Walker Division of Materials Science and Technology, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6115, USA e-mail: bradymp@ornl.gov 123 Oxid Met (2011) 75:337–357 DOI 10.1007/s11085-011-9237-7