Athermogravimetric andmetallographic study of the high temperature oxidation of a binary nickel-chromium alloy in humidified air. Part II: Scale spallation at cooling

摘要

A Ni-25Cr binary alloy was subjected to oxidation at four high temperatures, comprised between 1000 and 1300°C during 48 hours in dry air and in air enriched in water vapour, with recording of the mass gain. The cooling parts of the obtained thermogravimetry curves were exploited to observe the occurrence or not of scale spallation and the temperatures of spallation start if this happens. The oxides formed were observed after test by electronic and optical microscopy, and characterized by X-Ray Diffraction and image analysis. By comparison with dry air, the water concentration tried in this work induced a finer structure of the oxides scales formed during the isothermal stage, and a better resistance of these oxides against spallation when temperature decreases.