Abstract:The degradation behavior of the microstructure and mechanical properties of a long time serviced GTD111 DS superalloy turbine blade was investigated. Rejuvenation heat treatment was subsequently applied by using a treatment of hot isostatic pressing (HIP) followed by solution and double-aging treatments. The results demonstrated that during service: pore density increased significantly from blade tip to root; MC carbides degenerated into M??C? carbides and η phase; secondary γ′ precipitates underwent severe spheroidization and rafting, accompanied by the dissolution of tertiary γ′ precipitates. The overall microstructural degradation pattern along the blade longitudinal axis follows the order: tip > central region > root > tenon, and along the transverse axis follows the order: trailing edge > leading edge > suction side > pressure side. The microstructure degradation directly led to a progressive reduction in Ultimate tensile strength at both room temperature and 980 °C and stress rupture life at 980 °C/220 MPa from the tenon to the blade tip. After rejuvenation heat treatment, the microstructure and mechanical properties were markedly improved: the area fraction of microporosity at the blade tip was reduced, MC carbides were partially restored, and the sizes of secondary and tertiary γ′ precipitates decreased to approximately 0.5 μm and 59 nm, respectively. Ultimate tensile strength of the blade tip increased from 810 MPa to 1122 MPa at room temperature and from 388 MPa to 468 MPa at 980 °C; and the stress rupture life (980 °C/220 MPa) increased from 1.95 h to 11.31 h. After rejuvenation, all mechanical properties at the blade tip exceeded those of the tenon region.