超超临界机组循环泵轴的失效分析

Failure Analysis on Circulating Pump Shaft of Ultra-supercritical Unit

超超临界机组2Cr13钢循环泵轴断裂。对断裂的泵轴进行了断口分析、化学成分检验、室温力学性能检测和金相检验,以揭示其断裂的原因。结果表明:泵轴的化学成分、力学性能和显微组织均符合要求,但泵轴发生了化学腐蚀,表面形成了腐蚀坑。据此可以断定,使用中在交变应力的作用下腐蚀坑底部产生了裂纹,从而导致泵轴腐蚀疲劳断裂。

Circulating pump shaft of 2Cr13 steel broke in a ultra-supercritical unit. The broken pump shaft was subjected to fracture test, chemical composition analysis, room-temperature mechanical property measurement and metallographic examination for the purpose of discovering cause of its breaking. The results indicated that chemical composition, mechanical properties and microstructure all conformed with the requirements, however, the pump shaft surface was chemically corroded and corrosion pits formed at its surface. From this it is concluded that crack originated from the corrosion pit bottom under the action of alternating stress in service,thus leading to corrosion fatigue fracturing of the pump shaft.