Analysis on Fracture Reasons of Turbine Blades in a Heat-power Plant

The last stage moving blades of a generators turbine in a heat-power plant were found cracking on extrados at the end of the steam admission side during maintenance downtime. The cracking reasons of the turbine blades were analyzed by macroscopic observation, chemical composition analysis, hardness testing, metallographic examination, fracture scanning and energy spectrum analysis. The results show that: the origin of the cracks was located in the water-eroded pits on the extrados surface of steam admission side of the last stage turbine blades; the intergranular stress corrosion cracking was caused by tensile stress of moving blades and the working environment of chloride ion corrosion.