超临界机组低压末三级叶片开裂原因分析  

Cause Analysis of Crack on the Last Three Stage Low-pressure Blade of Supercritical Unit

作　　者：邓辉 DENG Hui(Central South Electric Power Test Research Institute,China Datang Corporation Science and Technology Research Institute,Zhengzhou 450000,China)

机构地区：[1]中国大唐集团科学技术研究院有限公司中南电力试验研究院,郑州450000

出　　处：《汽轮机技术》2023年第4期301-305,共5页Turbine Technology

摘　　要：某超临界机组低压转子末三级叶片发生开裂,取样进行了宏观检验、化学成分分析、显微硬度试验、力学性能试验、显微组织及能谱分析。结果表明:叶片热处理工艺控制不当,导致在出汽侧边缘形成宽约20mm的硬化层和不均匀马氏体组织,材料耐蚀性下降;机组运行时汽水品质不佳,存在Cl、S等腐蚀元素,叶片形成腐蚀点坑;在叶片离心力产生的拉应力和残余应力的共同作用下,在应力集中的出汽侧边缘点坑处萌生微裂纹,继而发生应力腐蚀开裂。The last three stage blades of low pressure rotor of a supercritical unit cracked.The samples were intercepted and macroscopic test,chemical composition analysis,microhardness test,mechanical properties test,microstructure and energy spectrum analysis were carried out.The results show that improper process control during blade heat treatment leads to that a 20 mm wide hardened layer and inhomogeneous martensite structure are formed at the edge of the steam outlet side.The corrosion resistance of the material decreases.The steam water quality of the unit is poor during operation.There are Cl,S and other corrosive elements.Corrosion pits are formed on the blades.Under the combined action of tensile stress and residual stress caused by blade centrifugal force,microcracks sprout at the edge pit of steam outlet side where the stress is concentrated.Then stress corrosion cracking occurs.

关 键 词：叶片 裂纹 腐蚀点坑 残余应力 应力腐蚀 

分 类 号：TM621[电气工程—电力系统及自动化]