Analysis on Fracture Reasons of Steam Turbine Blades

The quality problems of early fracture of last stage blades were found during the expansion and overhaul of the steam turbine unit in a thermal power plant. Methods of fracture analysis, metallographic examination, chemical composition analysis, technology analysis of hardened surface layer were used to analyze the fracture reasons of turbine blades. The results show that:the failure mechanism of steam turbine blades was fatigue fracture; defects of cracks, porosity, non-hardened part and so on existed in hardened layer of the blade surface and reduced the resistant ability of erosion, which was the main reason for the early fatigue fracture of blades.