GH901高温合金CV阀阀杆断裂原因分析

Fracture Analysis on Control Valve Stem of Superalloy GH901

某电站300MW机组汽轮机的多个GH901高温合金材质的高压调节阀阀杆相继发生断裂。为查找断裂原因,采用宏观形貌观察、化学分析、显微组织观察、力学性能试验以及析出相能谱分析等方法,对断裂阀杆进行研究。结果表明:由于阀杆材料热处理不当,组织异常,导致材料塑性差、脆性大、缺口敏感性差。在长期运行过程中,由于阀门调节频繁,阀芯处摆动大,引起下部阀杆圆弧过渡区受到较大的弯曲应力,造成阀杆在薄弱处被掰断。

Several high pressure control valve stems with superalloy GH901 fractured successively in 300MW steam turbine of a power plant. For analyzing the reason of failure, the macro-appearance observation, the chemical composition analysis, microstructure observation, mechanical properties examination and EDS analysis of precipitated phase were used to study GH901 control valve stems. The results show that the improper heat treatment of control valve stem materials leads to abnormal microstructure, which can cause the poor ductility, great brittleness and low notch sensitivity. During operation for long time, because of the valve frequent adjustment, the swinging of the valve core becomes larger, which can cause the lower stem bears larger bending stress in the circular arc transitional region. Then, the stein snaps off in the weak place.