Microstructure evolution and mechanism of IC10 alloy under over-temperature and stress condition

The microstructure evolution under over-temperature (1070-1250 degrees C) and tensile/compressive stress (30-90 MPa) conditions of IC10 alloy was analyzed to simulate the alloy deterioration process during over-temperature operation of gas turbine blades. The results show that the degeneration of secondary gamma' phase in IC10 alloy during thermal exposure without stress includes spheroidizing, coarsening, and redissolution. As thermal exposure temperature and time increase, the shape of secondary gamma' phase transforms from flower-like to rounded cubic and spherical, driven by the decrease of gamma/gamma' phase interface energy. The area fraction of secondary gamma' phase decreases with the increase in temperature and the prolonging of time. The secondary gamma' phase is completely redissolved after thermal exposure at 1225-1250 degrees C for more than 50 h. The size of secondary gamma' phase increases with the increase in temperature and time. The coarsening of gamma' phase conforms to the Lifshitz-Slozov-Wagner theory controlled by diffusion. Under the overtemperature and stress condition, the rafting of gamma' phase gradually intensifies with the increase of temperature. The tensile stress promotes the N-type rafting of gamma' phase perpendicular to the stress axis, while the compressive stress promotes the P-type rafting of gamma' phase parallel to the stress axis. The gamma' phase rafting process is faster under the tensile stress state than under the compressive stress. The microstructure of IC10 alloy under over-temperature and stress conditions can be used to evaluate the service conditions of the blade after service.