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

M.P. Brady; Yukinori Yamamoto; Bruce A. Pint; M.L. Santella; P.J. Maziasz; L.R. Walker

doi:10.4028/www.scientific.net/MSF.595-598.725

Paper Titles

Modelling the Development of Type I Hot Corrosion on Coated and Uncoated Single Crystal Superalloys
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Enhanced Internal Oxidation as Reason for Breakdown of Protective Chromia Scales on FeCr-Alloys in Water Vapour Containing Gases
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Cyclic Oxidation of Two FeCrAlRE Foils at 1100 °C - The Influence of the Concentration of Minor Alloying Elements on Scale Microstructure
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Evaluation of Al₂O₃ MOCVD Coating for Titanium Alloys Protection under Severe Conditions at High Temperature
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On the Loss of Protective Scale Formation in Creep-Resistant, Alumina-Forming Austenitic Stainless Steels at 900°C in Air
p.725

Effect of Lanthanum Sol-Gel Coating on the Oxidation Behaviour of the AISI 304 Steel at 1000°C
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High Temperature Corrosion of the Si-Mo Cast Iron in Exhaust Atmosphere
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On the Effect of Surface Treatment to Improve Oxidation Resistance and Conductivity of Metallic Interconnects for SOFC in Operating Conditions
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High Temperature Sulphidation Behavior of Fe20Cr6Al-Y,Hf Steel
p.763

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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.