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Abstract : |
Turbine blades in a power station exposed to a temperature of about 800 degrees C were refurbished after 40,000 h of operation. However, after only 900 h of service at the same temperature, a number of refurbished blades were fractured. Various electron microscopy techniques as well as computational modeling were used to develop a one-to-one correspondence between microstructure and temperature distribution. Fracture was found to occur by a ductile intergranular mode. Although there was no evidence for overheating during service, the results showed that the blades initially contained gamma' precipitate-free zones alongside grain boundaries, which could accelerate intergranular failure consistent with the observed fracture mode. It was concluded that the blades were damaged by improper heat treatment during refurbishing. (C) 2008 Elsevier Ltd. All rights reserved., |
