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Abstract The turbine of a 350MW thermal power unit’s feedwater pump in the Mengxi region experienced blade fracture and failure during operation. To identify the cause of blade fracture, comprehensive testing and analysis were conducted on the fractured blade using experimental methods such as macroscopic analysis, chemical make-up analysis, mechanical property testing, microstructure testing, and SEM micro area analysis of the fracture surface. The results indicate that the inner shoulder of the first tooth of the blade root is at a 90° right angle and belongs to the weak part of stress concentration. The steam of this unit contains Cl - , which poses a significant risk to blade materials. Corrosive Cl - accumulates at the inner arc shoulder of the blade root long and forms tensile stress together with the static and dynamic loads during blade operation, leading to the initiation of SCC microcracks in this area. Under the long-term cyclic excitation stress generated by the high-speed rotation of the rotor, the source of stress corrosion cracks propagates in a fatigued manner, resulting in severe fracture of the blade.
Gao et al. (Mon,) studied this question.