Analysis on the Causes of Cracking at the Last Stage Blade of the Low-pressure Rotor in thermal power plant

Abstract

Transverse cracking occurred in the blade body of the last stage of the low pressure rotor of a 200MW unit in a thermal power plant. The causes of blade cracking were analyzed by means of macro morphology, SEM, microstructure, mechanical properties, chemical composition and energy spectrum analysis. The results show that the corrosive Cl- accumulates on leaves, and then combined action of tensile stress is formed with the static load and dynamic load during the blade operation, and the stress corrosion microcracks had been conceived in the Cl- corrosion region. Under the long period cyclic excitation stress of the blade during the rotor rotation at high speed, the crack source extends in fatigue mode, finally resulting in cracking.