An investigation of the failure of low pressure steam turbine blades

An analysis of the failure of low pressure turbine blades has been presented in this paper. Cracks with different lengths were found in the quenching region of final stage low pressure blades after about in service for 13,200 hours. The failure analysis of blades was performed in terms of chemical analysis, microstructure, fractography and mechanical tests etc. It was found that the chemical composition, metallographic microstructure and mechanical properties of the root region of blades did not show any degradation compared to the corresponding standard. As far as the quenching region is concerned, the elongation percentage, contraction of cross sectional area and impact toughness were lower than the corresponding standard though the hardness was reasonable. From the analysis of the crack micrograph, the fractography and the composition analysis of fractured surface, it was found that the fracture was caused by fatigue and accelerated slightly by corrosion. The formation of cracks related with the stress concentration in the position corresponding to the salient on the configuration of blades.