Evaluation of service-induced microstructural damage for directionally solidified turbine blade of aircraft engine

Turbine blades of gas turbine engines usually suffer from severe operational conditions characterized by high temperature and stress. Severe operational conditions during service cause microstructural changes in turbine blades and degrade their mechanical properties. In this study, service-induced microstructural damages in serviced turbine blades manufactured from a directionally solidified superalloy were evaluated. The observed microstructural damage of the turbine blade mainly involves the coarsening and rafting of γ′ precipitates. The leading edge of 60% height of the turbine blades undergone most severe microstructural damage with significant microstructural evolution at this area. Microstructural damage affects the mechanical properties such as Vickers hardness, that is, Vickers hardness decreases as the equivalent diameter decreases. Microstructural damage shows great position-dependent feature as service temperature and radial stress on blade changes. With the aid of energy-dispersive spectrometer (EDS) analysis on carbide, the transformation of carbide does not exist. In addition, no topological closed-packed phase exists in the turbine blade.