Failure analysis of gas turbine blades in a thermal power plant

A case study of failure analysis of a 40 MW gas turbine blade made of Udimet 500 is presented. The cause of failure is found to be intergranular cracks which started during exposure to high temperature. The cracks initiated from the grain boundaries and propagated to the critical length to result in catastrophic fracture. In many locations M6C type secondary carbides were found agglomerated on grain boundaries. Also micro-cavities were found on fracture surfaces which served as an origin of creeping failure mechanism.