Oxidation behaviour of a MoSi2-based composite in different atmospheres in the low temperature range (400–550 °C)

Artikel i vetenskaplig tidskrift, 2004

The oxidation characteristics of a MoSi2-based composite within the temperature range of 400–550 °C were investigated. The effects of temperature and water vapour on oxidation were examined. The oxidation kinetics were studied using a thermobalance, while the morphology and composition of the oxides were examined using XRD, ESEM/EDX, and SEM/EDX. The peak oxidation rates in dry O2 and View the MathML source were found to occur at temperatures of approximately 510 and 470 °C, respectively. Within the temperature range of accelerated oxidation (400–500 °C), the oxidation rate in View the MathML source was substantially higher than that in dry O2. At higher temperatures, the oxidation rate decreased, and the magnitude of the decrease was steeper and occurred at a lower temperature for View the MathML source (510 °C) than for O2 (550 °C). Furthermore, the rate of depletion of molybdenum (Mo) from the oxide scales during oxidation increased with increasing temperature and water vapour content. It appears that Mo loss is a key process influencing the protective properties of the oxide layer on the MoSi2 composite. A potential mechanism for the different oxidation behaviours in O2 and View the MathML source is proposed.