ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The oxidation behaviour of binary Fe-Cr alloys containing 10 and 20 mass % Cr,respectively, was studied in Ar-20%O2, Ar-7%H2O and in Ar-4%H2-7%H2O at temperaturesbetween 800 and 1050°C. Thermogravimetric analyses in combination with analytical studies usingSEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is thesource of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar-O2gas. Contrary to previous studies which showed the presence of water vapor to affect transportprocesses in the surface oxide scale, the present results reveal that the presence of water vapor alsoaffects the transport processes in the alloy. The enhanced internal oxidation, which is likely theresult of water vapor increasing the solubility and/or the diffusivity of oxygen in the alloy, explainsthe frequently observed effect that Fe(Ni)Cr alloys with intermediate Cr contents (e.g. 10-20%,depending on temperature) exhibit protective oxidation in dry gases but breakaway type oxidationin steam. The temperature dependence of the change from protective to non-protective behaviour inAr-H2O differs quantitatively, but not qualitatively from that in Ar-O2
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.595-598.699.pdf
Permalink
