电厂的12Cr2MoWVTiB钢高温再热器管实际运行中易出现氧化失效,为了对其实施有效的监督,采用扫描电镜、电子探针和X射线衍射对高温高压水蒸气下运行5.0×10~4h形成的氧化膜形貌、结构、成分及物相进行了分析.结果表明:氧化膜蒸汽侧形貌呈丘状或蘑菇云状,氧化膜基体侧呈方解石状,氧化膜横断面呈石状;氧化膜结构明显分为3层,外层、中间层和内层氧化膜均由粗大的柱状晶构成,各柱状晶层间有大量孔洞,而内层氧化膜与基体结合处氧化膜晶粒为细小等轴晶;O元素含量从外层氧化膜到靠近基体处,存在正的浓度梯度分布,而Fe,Cr,Mo元素含量存在负的浓度梯度分布,Cr,Mo元素在紧靠基体的氧化膜侧产生富集,含量均高于钢基体中的含量;氧化膜物相为Fe_3O_4和FeCr_2O_4.
The appearance,structure,composition and phase of the oxide films of the high-temperature reheater pipe made of 12CrlMoV steel after running under high-temperature and high-pressure water vapor for 5.0×10~4 hours were analyzed by means of scanning electron microscopy,electron probe microanalysis,and X-ray diffraction.Results indicate that the oxide films have varied appearances depending on locations.Namely,buninoid-like or mushroom-like oxide films were formed at the locations in contact with water vapor,bulk oxide film was calcite-like,and the cross-section of the oxide film appeared as rock-candy fracture.At the same time,the oxide films can be divided into three classes in terms of the structure,including the outer layer,the middle layer,and the inner layer all composed of rough cylindrical grains.A large number of pores were formed between adjacent-cylindrical grain layers,while the grains in the middle and bulk oxide layers appeared as fine equiaxed grains.From the outer layer to bulk oxide films,a positive concentration gradient of oxygen was observed,while a negative concentration gradient of alloying elements Fe,Cr and Mo was observed.Moreover,elements Cr and Mo were enriched in the bulk oxide film in contact with the steel substrate,showing a higher content than in the steel substrate.And the oxide films are composed of Fe_3O_4 and FeCr_2O_4.
参考文献
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