Oxidation behaviour of a (Mo, W)Si2-based composite in dry and wet oxygen atmospheres in the temperature range 350–950◦C
Artikel i vetenskaplig tidskrift, 2009

The oxidation of a (Mo, W)Si2-based composite was investigated in the temperature range (350–950 °C). The influence of temperature and water vapour on the oxidation was examined. The kinetics was studied using a thermobalance whereas the morphology and composition of the oxides were examined using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray (EDX). Focused ion beam (FIB) milling was performed on some of the oxide scales which allowed us to look at a non-mechanically disturbed scale/oxide in cross-section. Rapid oxidation was found to occur in the 550–750 °C temperature range. The mass gains were significantly larger in O2 than in O2 + 10%H2O. The different mass changes in the two exposure atmospheres were attributed to the higher vapour pressure of the volatile MoO2(OH)2 and WO2(OH)2 species in O2 + 10%H2O than that of (MoO3)3 and (WO3)3 in dry O2. The peak mass gain was found to occur at a temperature of about 750 °C in O2 and 650 °C in O2 + 10%H2O. At temperatures above 850 °C, especially when water vapour is present, the removal of Mo and W from the oxide scales is rapid enough to allow partial healing of the silica, causing the oxidation rate to drop. At 950 °C in O2 + 10%H2O, a protective SiO2 scale could be re-established quickly and maintained, causing the oxidation to essentially cease.









Kristina M Hellström

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Jun Eu Tang

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Torbjörn Jonsson

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Mats Halvarsson

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Robert Pompe

Swerea IVF AB

Mats Sundberg

Kanthal AB

Jan-Erik Svensson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Journal of the European Ceramic Society

0955-2219 (ISSN)

Vol. 29 10 2105-2118


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