烟气轮机叶片断裂原因

Cause of Fracture on Flue Gas Turbine Blade

某石化企业烟气轮机运行过程中出现转子叶片断裂失效现象,采用宏观观察、扫描电镜分析、金相检验、能谱分析、布氏硬度测试等方法,对叶片断裂失效的原因进行了分析。结果表明:由于锻造及热处理过程中温度选择不当,合金材料出现混晶现象,强度、韧性降低;在后续投用运行过程中由于出现了超温运行现象,导致材料晶界碳化物减少并出现链状碳化物,其强化晶界作用弱化,抗裂纹萌生和扩展能力降低;高温烟气颗粒的不断冲击,使微观裂纹于叶片进气侧边缘的晶界弱化处萌生,在交变应力作用下沿晶界扩展形成宏观裂纹,宏观裂纹发展到一定尺寸时沿晶界瞬时断裂,造成叶片的断裂失效。

The rotor blade of flue gas turbine in a petrochemical enterprise fractured during operation.The causes of blade fracture failure were analyzed by means of macroscopic observation,scanning electron microscope analysis,metallographic examination,energy spectrum analysis and Brinell hardness test.The results show that due to the improper selection of temperature during forging and heat treatment,the mixed crystal phenomenon appeared and the strength and toughness of the alloy decreased.In the subsequent operation process,the phenomenon of overtemperature operation resulted in the decrease of carbides at grain boundaries and the appearance of chain carbides,which weakened the strengthening effect of grain boundaries and reduced the ability of resistance to crack initiation and propagation.The continuous impact of high temperature flue gas particles caused micro cracks to germinate at the grain boundary weakening area at the edge of the inlet side of the blade.Under the action of alternating stress,the micro cracks propagated along the grain boundaries and formed macro cracks.When the macro cracks develop to a certain size,the fracture along the grain boundaries instantaneously,which resulted in the fracture failure of the blade.