脱硫装置循环泵叶轮断裂失效分析

Fracture Failure Analysis of Circulating Pump Impeller in Desulfurization Unit

某电厂吸收塔浆液循环泵发生故障,经检查发现叶轮片断裂。现对断口进行扫描电镜微观形貌观察、材质成分、金相组织、物相检测、硬度测量和电子探针微区成分分析等。从试验结果上判断造成叶片断裂的原因是叶片内部既存在集中态疏松孔洞,又普遍存在微小铸造孔洞,严重削弱钢基体强度和增加脆性及加速受腐蚀破坏的速度。同时叶轮在实际运行中其工作环境的氯离子含量及pH值超过设计极限,这就进一步加剧本来材质欠佳的叶轮失效速度。

The fracture of circulating pump impeller in desulfurization unit was found during inspection. The experiment were carried out with SEM micro-morphology analysis, component analysis, metallurgical structure, phase analysis, hardness measurement and EPM etc. The result shows the root cause is there are both some concentrated loose holes and plenty of micro casting holes in the impeller, which seriously weakened the strength of steel matrix and increased the corrosion speed. Meanwhile, the concentration of chloride ion and pH values in working circumstance is over the design limit that further aggravated the corrosion speed of the impeller.