【摘要】 针对某火电机组调峰服役10年的660MW汽轮机17-4PH末级叶片，采用显微分析及力学性能测试等方法揭示其进汽、出汽侧水蚀的不同特征，探究水蚀机理，并基于缺口敏感性评价水蚀对末级叶片运行可靠性的影响。结果表明，调峰运行汽轮机末级叶片进汽、出汽侧均明显存在水蚀，且不同部位的水蚀程度不同，呈现孕育期、加速期和稳定期3个阶段的特征。二次水滴冲击叶片表面导致塑性变形，形成水蚀坑；水蚀坑底部局部应力集中诱发微裂纹萌生与扩展，导致材料剥落，水蚀坑越来越深。出汽侧水蚀主要取决于调峰过程，相比于进汽侧，其水蚀坑数量少、尺寸大、深度低，水蚀程度较小。服役态17-4PH末级叶片缺口试样的拉伸力学性能较无缺口试样有所下降，具有一定的缺口敏感性，严重水蚀降低其服役可靠性。更多还原

【Abstract】 Aiming at the 17-4PH last stage blade ofa 660MW turbine unit after operating for 10 years undertaking peak regulation, microstructure analyses and mechanical property tests were executed to reveal the different characteristics of water erosions at steam inlet/outlet sides of the last stage blade, to explore the water erosion mechanism, and to evaluate the influence of water erosion on the operational reliability of the last stage blade via the notch sensitivity measurement. The results show that there is apparent water erosion at steam inlet/outlet sides of the turbine last stage blade, but of distinct water erosion degrees in different areas of the same side, presenting three stage characteristics, i.e., the incubation period, the acceleration period and the stable period.Impact of the secondary water droplets causes plastic deformation of the blade surface to form thewater erosion pits; and then the stress concentration induces generation and propagation of the microcracks in local areas at the bottom of the pits, resulting in materials exfoliation. Therefore, the erosion pits turn to be deeper and deeper. The water erosion at the steam outlet side mainly depends onthe peak regulation process. Compared with the steam inlet side, the water erosion pits at the steam outlet side are less in amount, larger in size, but smaller in depth, corresponding to lower water erosion degree. The tensile mechanical properties of the notched specimens of the ex-service 17-4PH last stage blade are all lower than those of the unnotched specimens, indicating that the ex-service blade has a certain notch sensitivity. Severe water erosion should decrease the service reliability of the last stage blade.更多还原