某燃机余热锅炉给水泵05Cr17Ni4Cu4Nb马氏体不锈钢泵轴在使用过程中发生开裂。采用宏观观察、化学成分分析、断口分析、金相检验、力学性能测试和硬度测试等方法,对泵轴开裂的原因进行了分析。结果表明:泵轴开裂性质为镀铬层次表面加工缺陷诱发的多源启动疲劳扩展开裂,泵轴的显微组织中含有大量高温δ铁素体,局部区域δ铁素体的含量可达50%,导致材料冲击韧性明显降低,削弱了泵轴的承载能力,加速了应力集中部位裂纹的形成和扩展,最终导致泵轴发生开裂。

The 05Cr17Ni4Cu4Nb martensitic stainless steel pump shaft of a gas turbine waste heat boiler feed pump cracked during use. The causes of pump shaft cracking were analyzed by means of macro observation, chemical composition analysis, fracture analysis, metallographic examination, mechanical property test and hardness test. The results show that the cracking nature of the pump shaft was a multi-source start-up fatigue propagation crack induced by the surface processing defects of the chromium plating layer, and the microstructure of the pump shaft contained a large amount of high temperature δ ferrite, with the content of δ ferrite up to 50% in local areas, led to a significant decrease in the impact toughness of the material, weakened the bearing capacity of the pump shaft, accelerated the formation and propagation of cracks at the stress concentration part, and finally led to the cracking of the pump shaft.