Thermogravimetric study of the effect of the vapour concentration in wet air on the oxidation start at heating and on the oxide spallation at cooling of a nickel-chromium alloy exposed at high temperature
The high temperature oxidation behaviour of alloys in air may be influenced by the presence of water vapour. In this work this is more precisely the effect of the water concentration which was investigated. Four thermogravimetry runs were performed for a nickel-chromiumalloy, at temperature ranging from 1000 to 1300°C, in air especially enriched in water vapour by comparison with previous studies. The heating parts and the cooling parts of the mass gain curves were characterized with comparison with previous results obtained in dry air and in moderately humidified air. The supplementary addition of water vapour to air already wet led to another reduction in oxidation rate during heating and in total mass gain achieved before the isothermal stage. This new vapour concentration also improves the adherence of the oxide scale during cooling by comparison with dry air, but not so efficiently as the moremoderate water concentration earlier tested.