A physically based model for correlating the microstructural degradation and residual creep lifetime of a polycrystalline Ni-based superalloy

The microstructure evolution and creep property degradation of the Ni-based superalloy K417 were studied at different high-temperature thermal exposure conditions. The results showed that the equivalent radius of γ′ precipitates increased with the exposure time at all the temperatures and displayed spherical morphologies. Moreover, small blocky-type Cr-rich M₂₃C₆ carbides were observed due to the decomposition of the primary MC after exposure to 950 °C for 200 h and 50 h both at 1000 °C and 1050 °C. The creep-rupture lifetimes deteriorated with increased exposure time and temperature due to γ′ precipitates coarsening and the decomposition of the primary carbides. Furthermore, a physically based analytical model was developed to describe the influence of the microstructural evolution of the γ′ precipitates on the residual creep lifetime.