Influence of Water Vapor on Oxide Scale Morphology of lncoloy800HT at 850℃

摘要

This paper aims to report the influence of water vapor on thermal oxide scale grown on incoloy800HT at 850℃. Alloy was prepared in coupons with a surface finishing up to 1200 SiC abrasive paper. Oxidization was performed in tubular furnace at 850℃ during 50 hours. The oxidizing gases were varied as a dry oxygen gas and a wet oxygen gas. Thermal oxide morphology was characterized by scanning electron microscopy (SEM). Oxide phases were identified by X-ray diffraction (XRD) and Raman spectroscopy techniques. The oxide multilayers were revealed in all the oxidized samples. Oxide spallation was obviously detected on the samples oxidized under a dry oxygen gas, whereas, the spallation was not detected on the samples oxidized under a wet oxygen gas. Moreover, by water vapor mixing gas, the alloy surface presented a finer oxide. XRD and Raman spectroscopy provided the coincident oxide identification results. The corundum oxide of (Fe,Cr)_2O_3 and the spinel oxide of (Fe,Cr)_3O_4 were identified as a typical thermal oxide, however, the oxides were different in stoichiometry. The existence of water vapor promoted a Cr_2O_3 corundum oxide, whereas, a Fe_3O_4 spinel oxide was hindered from the outer oxide layer. Hence, water vapor not only clearly influenced on oxide scale morphology but also affected on stoichiometry of (Fe,Cr)_2O_3 and (Fe,Cr)_3O_4 solid solution.