汽动给水泵汽轮机叶片失效分析

Analysis on Failure of Turbine Blade of Steam-driven Feedwater Pump

长204 mm、材料为2Cr12MoV钢的汽动给水泵汽轮机末级叶片在使用中断裂。为了揭示叶片断裂的原因,对断裂的叶片进行了宏观检查、化学成分分析、硬度检测、显微组织检验、断口分析和能谱分析。检验结果表明,叶片的化学成分和硬度符合标准要求;叶片出汽侧存在含有易形成可溶性盐的0. 32%～4. 6%K、0. 4%～1. 45%Ca、0. 51%～1. 63%Na和1. 55%～2. 67%Cl等元素的污垢,机组停运期间可溶性盐溶解使叶片电化学腐蚀,并在叶片的出汽侧形成点蚀坑,机组运行时,在激振力作用下在点蚀坑处萌生微裂纹,最终导致叶片疲劳断裂。

The last stage blades of turbine for steam-driven feedwater pump,204 mm long and made of 2Cr12MoV steel,fractured in service.The fractured blade was subjected to macroscopic examination,chemical composition analysis,hardness measurements,microstructure survey,fracture test,and energy spectrum analysis for the purpose of discovering the reason why the blade fractured.The results were described below:chemical composition and hardness of the blade conformed with the standard;a dirt containing 0.32%-4.6%K,0.4%-1.45%Ca,0.51%-1.63%Na,1.55%-2.67%Cl that would form soluble salt was present in the outlet side of blade;dissolution of the soluble salt caused the blade to suffer electrochemical corrosion,and consequently pitting pits developed on the outlet side of the blade during outage of the unit;fine cracks formed by the action of an exciting force on the pitting pit during operating of the unit,finally leading to the fatigue fracture of the blade.