MECHANISM OF SIEAM OXIDATION OF IRON-CHROM ALLLYS FOR POWER TENERATION ULTRA-SUPERCRITICAL CONDITION AND SUPPERESION OF

铁铬合金作为发电锅炉管的材料，在使用条件下对许多数据进行了修正。然而，蒸汽氧化的机理尚不清楚，需要抑制氧化保护层的剥落。超超临界水操作是提高能源效率的关键问题，本项目的目的是澄清蒸汽氧化机理和抑制剥落。透射电镜观察了氧化垢早期的形成过程。少量硅的加入对内氧化区（IOZ）有很大影响。IOZ的生长和消失有助于氧化鳞的保护作用。氧化鳞片中存在许多孔洞，这些孔洞可能控制着氧化鳞片的脱落。结果表明，通过计算尺度上的化学势分布和质量守恒，可以定量地解释空洞的形成。结果表明，溶蚀在氧化垢中的质子可能影响孔隙的形成。关于质子通过尺度渗透的研究仍在进行中。

Iron-chromium alloys have been used as materials for boiler tubes in power generation and many data were corrected in service conditions. However, the mechanism of steam oxidation has not been clarified yet and the suppression of exfoliation of protective oxide scales is required. The operation with ultra-supercritical water is a key issue to improve energy efficiency and the objects of this project area clarification of the steam oxidation mechanism and suppression of the exfoliation.The development of the oxide scale at the early stage was observed by transmission electron microscopy. The internal oxidation zone (IOZ) was strongly affected by small amount of added silicon. The growth and disappearance of IOZ contributed to the protectiveness of oxide scales. Many voids, which may govern the exfoliation, existed in the oxide scales. It was revealed that the formation of voids was quantitatively explained by calculation of chemical potential distribution in the scale and of mass conservation. It was suggested that the proton dissolved in the oxide scale might affect the void formation. The study on the permeation of proton through the scale is still in progress.