某燃机电厂凝结水泵轴在机组运行过程中发生断裂，通过断口宏、微观形貌分析、化学成分分析、金相检验和力学性能测试等方法对泵轴的断裂原因进行了分析。结果表明：由于热处理工艺不当，导致泵轴显微组织中存在魏氏组织和明显的带状偏析，使其抗疲劳性能下降；加之泵轴在运行过程中受到持续的交变应力，从而导致泵轴于应力集中的键槽位置过早地发生疲劳断裂。

The condensate pump shaft in a gas turbine plant fractured during runtime. The fracture reasons of the pump shaft were analyzed by means of macro and micro morphology analysis of fracture, chemical compositions analysis, metallographic test, mechanical property test and so on. The results show that improper heat treatment led to the existence of Widmanstatten structure and obvious zonal segregation in the microstructure of the pump shaft, which made its fatigue resistance decline. In addition, the pump shaft was subjected to continuous alternating stress during runtime, which led to premature fatigue fracture of the pump shaft in the stress concentration keyway position.