还原性气氛下水冷壁材料15CrMoG的高温腐蚀特性

针对多数电厂在低氮燃烧还原性气氛下水冷壁高温腐蚀严重的现状，在高温管式炉中进行水冷壁材料15CrMoG的高温腐蚀试验.试验中以配制好的标气模拟锅炉水冷壁贴壁处的2种还原性气氛，试片表面涂积灰模拟灰腐蚀影响.通过腐蚀增重曲线分析不同气氛和积灰对于腐蚀的影响，采用扫描电子显微镜（SEM）和能量色能谱（EDS）观测材料试片的腐蚀微观形貌和元素成分，研究高温腐蚀机理.结果表明，CO+H2S+O2+N2气氛比H2S+O2+N2气氛的腐蚀能力更强，CO使得腐蚀能够持续进行，有积灰试片的腐蚀程度略高于无积灰试片；致密氧化层以及Cr元素向金属基体富集的特性能够减缓H2S渗透腐蚀，CO的存在削弱氧化层和Cr的保护作用；积灰中的碱金属能够向金属基体迁移，碱金属盐类能够破坏氧化层并且侵蚀金属基体，但是在还原性气氛下积灰腐蚀受到一定抑制.
Abstract: The experiment around high-temperature properties of water wall material 15CrMoG was conducted, aiming at the situation that severe high-temperature corrosion occurred in most power plant under low-nitrogen combustion reducing atmosphere. Two reducing atmospheres were simulated by preparing standard gases, and specimens were coated with ash deposit to simulate the corrosivity of ash. The effects of different atmospheres and ash deposit were analyzed by mass gain curves, and scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were utilized to observe the micro-morphology, measure the elements distribution, and analyze the mechanism of high-temperature corrosion. Results showed that the CO+H2S+O2+N2 atmosphere was more corrosive than the H2S+O2+N2 atmosphere, and the corrosion process was sustained by CO. The corrosion degree of deposit-coated specimens was higher than deposit-free specimens. The corrosion process of H2S can be slowed down by compact oxide layer and enrichment of Cr, but CO can fade the protective effect. Alkali metal in the ash deposit could migrate to matrix and alkali metal salt could destruct the oxide layer and corrode the metal matrix, but the corrosion of alkali metal salt was slightly inhibited under reducing atmosphere.