ISSN:
1573-4889
Keywords:
oxidation kinetics
;
extruded honeycomb structures
;
Si
;
Fe−Cr−Al alloys
;
weight gain
;
growth stresses and elongation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The oxidation behavior of Fe−20Cr−5Al−(0.5–5)Si and Fe−(12–20)Cr−(5–7)Al−(1–2)Si alloys extruded into honeycomb structures has been investigated at 1150°C in air for up to 500 hr. The oxidation weight gains decrease with increasing Si and Cr contents in the 5-Al alloys. Si additions are more efficient than Cr additions to reduce the weight gain. Increasing Si content in the 5-Al alloys suppresses the formation of an iron-chromium complex oxide, forming mullite and vitreous silica in the scale, although the location is not clearly indicated. The 5-Si alloy shows anisotropy in elongation of the honeycomb specimen during oxidation in the Fe−20Cr−5Al−xSi alloys, whereas alloying with Si and Cr does not improve the oxidation resistance of the 7-Al alloys significantly. These results are explained by Wagner's theory of a secondary getter. However, we point out additionally that the difference between Si and Cr in the Pilling-Bedworth ratio and the solubility of their oxides in the Al2O3 scale may contribute to the significant effect of Si additions. Finally, this paper demonstrates that the selected Fe−Cr−Al−Si honeycombs having walls 200 μm thick show excellent oxidation resistance over 500 hr at 1150°C in air. The time to catastrophic oxidation is roughly proportional to the wall thickness in extruded honeycombs.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01050798
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