针对发电厂锅炉水冷壁管内表面腐蚀坑的成因进行了失效分析.通过微观形貌观察、扫描电镜及能谱仪分析和X射线衍射等手段确定腐蚀产物为Fe3O4;对水冷壁管各典型部位的化学成分(包括残余元素量)、显微组织、晶粒度、非金属夹杂物、脱碳层进行分析,排除引起腐蚀失效的内部因素;通过锅炉水质的碱度、pH值等检测记录,综合分析表明:炉水碱度偏高导致水冷壁内表面发生碱腐蚀反应,即碱腐蚀失效.
Failure analysis was carried out to find out the causes of corrosion pits on the inner surface of boiler water?cooled wall tubes of power station. The corrosion product Fe3O4 was confirmed by microstructural observation,SEM and EDS and X?ray diffraction;the typical parts of water?cooled wall tube were analyzed,including chemical composition(the amount of residual elements),microstructure,grain size,nonmetallic inclusions,decarburized layer. According to the results,it is excluded that internal factors may cause corrosion failure. By analyzing testing records of alkalinity and pH value of boiler water,it is found that the high alkalinity of boiler water results in alkali corrosion reaction.
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