Experimental investigation on creep-fatigue behaviours of as-received and service-exposed turbine blades: Mechanism and life evaluation

In the present study, both the as-received and the 600-h-serviced turbine blades were tested under the creep-fatigue loading. The results showed that the service-exposed blades exhibited a longer creep-fatigue life than the as-received ones due to the refinement of grain size and the increasing of hardness during the service process. Micro structural characterization revealed that there was no directional coarsening or rafting of γ′ precipitate after 600 h of service. Moreover, the as-received blades exhibited initial cyclic hardening followed by saturation and softening, whereas the 600-h-serviced blades only exhibited continuous softening until fracture. A conservative service life prediction approach was proposed considering the experienced mission profile. This service life estimation method provides a new way to assess the durability of turbine blade.