过热器受热面蒸汽氧化层形成机理研究

Steam-side Oxide Scale Growth on High Temperature Heat-absorbing Surface for Superheater

针对电厂锅炉屏式过热器TP304H钢管内壁蒸汽氧化现象,采用光学显微镜、扫描电镜、能谱和X射线衍射等测试技术,对其氧化层表面形貌,管内壁截面的Fe、Cr、Ni元素分布以及氧化层的物相进行了分析。研究结果表明:TP304H奥氏体不锈钢氧化层为双层结构,其内层为铁铬尖晶石结构FeCr2O4,外层为Fe3O4和Fe2O3氧化物结构,而Fe3O4多孔疏松结构和多层氧化物热膨胀系数差异是导致长期运行后氧化层的剥落重要原因。

The oxidation behavior of TP304H for the superheater exposed in supercritical water was investigated. The rust scale morphography of the inner wall for boiler pipe was observed by the optical microscope and scanning electron microscope, the phase structure of the oxide layer was also analyzed by X-ray diffraction. The results showed that the oxide scale of austenitic stainless steel was two-layers structure, and the inner oxide layer of steel tube was the layer of FeCr2O4, the outer layer was Fe3O4 and Fe2O3. The steam-side oxide layer was easily to peel off because of the porous structure of Fe3O4 and the difference in thermal expansion coefficients between the metal and oxide.