1000 MW超超临界机组小汽轮机22Cr12NiWMoV叶片失效分析

Fracture Failure Analysis of 22Cr12NiWMoV Blade of Small Turbine in a 1000 MW USC unit

通过宏观观察、金相分析、力学性能分析、拉伸/冲击断口扫描电镜分析,对1000 MW超超临界机组给水泵汽轮机(简称小汽轮机)22Cr12NiWMoV断裂叶片进行分析。结果表明:叶片显微组织晶粒粗大,呈现明显的过热特征,宏观硬度明显高于标准要求,叶片冲击韧性降低,材料呈现明显的硬脆特征,分析叶片开裂原因为工艺不佳引起过热脆性,以致在应力集中部位产生断裂失效。

The fracture failure analysis of 22Cr12NiWMoV blade of feed pump turbine(small turbine)of 1000 MW USC steam turbine was carried out by means of macroscopic observation,metallographic analysis,mechanical property testing and tensile/impact fracture surface analysis in a scanning electron microscope(SEM).The results show that the microstructure of the blade is coarse and the grain size is obviously over-heated.The macro hardness is higher than the standard value.Decrease of the impact toughness shows that the blade material is hard and brittle.It is considered that the cause of blade cracking is that the overheat brittleness caused by poor production process,and the fracture failure occurred at the stress concentration area.