Structure evolution of vacancy-hydrogen complexes in a nickel-based single-crystal superalloy

ABSTRACT The structural stability of vacancy-hydrogen complexes at the interface in nickel-based single-crystal superalloy is accessed mainly by calculating the activation energies associated with the evolution of their structures. It is found that the structure evolution and subsequent decomposition of the complex needs little time to be thermally activated at the service temperature of an aeroengine, and misfit dislocations at the interface significantly reduces the energy barrier for decomposition. Therefore, during the creep process, which is more severe at high temperatures, vacancies around misfit dislocations are not expected to enhance hydrogen interfacial segregation, although vacancy-hydrogen complexes are quite stable at room temperature.