| Summary: | Multi-scale morphology observations and fatigue performance tests were carried out to study the damage evolution mechanism and fatigue performance attenuation behavior of K403 turbine blades in service. During service in field, the dendrite separation and breakage, γ' phase polymerization and rafting, MC carbide decomposition, harmful phase precipitation and grain boundary weakening are having adverse effects on the fatigue performance of turbine blades. Meanwhile, the loss of alloying elements in matrix causes the alloy matrix to soften. In addition, a large number of pores and microcracks formed in the process of service further deteriorate the service performance of turbine blades. Therefore, after long-term operations, the solid solution strengthening, precipitation strengthening, dispersion strengthening and grain boundary strengthening effects of K403 turbine blades are all weakened, which led to serious degradation of the fatigue performance of these turbine blades with the fatigue life reduced. Besides, the crack initiation source of turbine blade is gradually transformed from subsurface metallic pore initiation to carbide initiation.
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