The investigations of rejuvenation heat treatment on the microstructure and mechanical properties of a serviced gas turbine blade

Directionally solidified gas turbine blades are wildly used in land-based industrial gas turbines for power generation. During long-term service, the harsh service environment causes microstructural and mechanical deterioration of the blades. In order to increase usage and save costs, this study analyzed the microstructure damage in different sections of the blade. Meanwhile, this investigation discussed the optimum rejuvenation heat treatment parameter and applied it to the serviced blade for the lifetime extension. The microstructural analysis indicated that the appropriate solution temperature for the serviced blade is 1205 °C. Furthermore, the microstructure of the degraded blade was effectively recovered including the γ′ dissolution and reprecipitation with the cubic shape, tertiary γ′ reprecipitation in γ matrix, part of film-like M23C6 redissolution and dislocation networks were eliminated after rejuvenation heat treatment. In addition, the stress rupture lifetime and the tensile and yield strength were effectively improved by rejuvenation heat treatment.