On the Variations of Phase Interface Microstructure and the Effects on Stress Rupture Property of Nickel-Based Single Crystal Superalloy after Thermal Exposure

Lattice constants, phase interface microstructure and stress rupture properties of nickel-based single crystal superalloy after thermal exposed for different time at 1100℃ were investigated using synchrotron radiation diffraction and transmission electron microscopy techniques. The results show that the lattice constants of γ and γ' phase at room temperature decrease and the misfit at room temperature becomes more negative after 200h exposure, and these parameters remain unchanged during subsequent exposure process up to 1000h. The releasing of misfit stress during thermal exposure is completed by coherent and semi-coherent interface changing as well as the formation of misfit dislocation. The misfit dislocation network generating in thermal exposure is mainly rectangular shape, its formation process is analyzed in detail. Additionally, it is found that the stress rupture lives decrease obviously after thermal exposure, while the morphology and size of interfacial dislocation network of thermal exposed alloys after rupture are very similar with that of unexposed alloy. The relation of γ' phase morphology and interfacial dislocation network to the stress rupture property deterioration has been discussed.