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The oxidation behaviour of oxide dispersion strengthened (ODS) alloys of the Cr5Fe type with different yttria contents prepared by two different manufacturing techniques was studied in Ar/H(2)/H(2)O at 950 C and 1000 C during isothermal exposure. Transmission electron microscopy (TEM) studies of alloy microstructure after oxidation revealed that the oxidation rate of the Cr-based ODS materials does depend on the yttria content, but even more so on yttria distribution. Transport of Y from the alloy to the scale occurs through dispersions which become embedded in the inwardly growing scale and/or by transport of Y along structural defects in the alloy. Because of the low rate of Y-incorporation into the scale, the alloys exhibit high initial oxidation rates and only after long times very low Kp values are observed. Sputtered neutral mass spectrometry (SNMS) and secondary ion mass spectrometry (SIMS)-analyses revealed that the scale growth mechanism differs from that observed for NiCr-based ODS alloys: the scale growth does not occur by exclusive inward oxygen grain boundary diffusion.

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Authors: QUADAKKERS W J ET AL, Forschungszentrum Jülich GmbH (DE);NORTON J F, JRC Petten (NL);GIL A, University of Mining and Metallurgy, Krakow (PL)
Bibliographic Reference: Paper presented: 3rd International Conference on Microscopy of Oxidation, Cambridge (GB), September 16-18, 1996
Availability: Available from (1) as Paper EN 40867 ORA
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