Fatigue fracture failure analysis of 12Cr12Mo steam turbine blade

Turbine blade is one of the key components in thermal power plant, and its premature failure is a common accident. The fourth blade of the low-pressure turbine unit in a power plant broke, resulting in the unplanned shutdown of the turbine unit. Through different analysis methods, the failure cause of the steam turbine blade was determined. The macro morphology of the fracture was observed by optical light microscope (OLM), and the micro characteristics of the fracture were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The mechanical properties of the failed blade were analyzed by room temperature tensile test and Charpy impact test. The results indicated that the root cause of blade fracture was the decrease of fatigue strength and rupture strength caused by high 8-ferrite content. Consistency between crack propagation direction and banded 8-ferrite direction further promotes crack initiation and prolongation. Eventually leading to fatigue fracture of the blade. According to the test and analysis results, some recommendations to prevent the early failure of steam turbine blades are put forward.

Automated summary

Turbine blade, a crucial component in thermal power plants, often experiences premature failure. A broken blade in a power plant's low-pressure turbine unit caused an unplanned shutdown. Through various analysis methods, the failure cause of the steam turbine blade was identified. Macro morphology of the fracture was observed using optical light microscope (OLM), while micro characteristics were observed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Mechanical properties were analyzed through room temperature tensile test and Charpy impact test. Results showed that the root cause of the blade fracture was a decrease in fatigue and rupture strength caused by high 8-ferrite content. Consistency between crack propagation direction and banded 8-ferrite direction further promoted crack initiation and prolongation, leading to fatigue fracture. Based on the test and analysis results, recommendations to prevent early failure of steam turbine blades are proposed.