烟气轮机转子叶片开裂原因分析

Analysis on Crack of Flue Gas Turbine Blade

利用光学显微镜、扫描电子显微镜和化学分析手段对断裂的烟气轮机转子叶片进行微观组织、断口形貌、化学成分等观察与分析。结果表明,叶片的化学成分除碳含量偏高外其余元素基本符合K213合金锭标准。叶片的物相组成为奥氏体+γ'+碳化物,γ'与碳化物的分布不均匀,特别是碳化物沿晶界分布弱化了晶界强度。高温工况下长时间运行的叶片在交变热应力作用下力学性能降低,再加上内部缺陷和沿晶分布的脆性相是导致其断裂的主要原因。

The chemical composition, microstructure and fracture appearance was investigated through optical microscope, SEM and chemical analysis method. The results show that the chemical composition of the blade meets the standard of K213 except the slightly higher carbon content. The main phases of the blade are austenite, γ＇ and carbide. The distribution of γ＇ and carbides are not uniform, especially the carbides locate at the grain boundary to weaken the interface strength. The main reasons for the fracture are internal defects, the intergranular brittle phases and the action of alternating thermal stress at high temperature and long times.