Effect of rejuvenation heat treatment on re-service aging stability of γ′phase in directionally solidified superalloy

High temperature aging treatment was first conducted on the rejuvenated directionally solidified superalloy to simulate the re-service aging damage of turbine blades and the virgin directionally solidified superalloy respectively. Then re-service aging stability of γ′ phase in the virgin and rejuvenated directionally solidified superalloy was compared and analyzed, and the effect of different rejuvenation parameters on γ′ phase microstructure of the rejuvenated directionally solidified superalloy after the same re-service aging time was studied. The results show that although rejuvenation heat treatment can effectively restore creep microstructure to a nearly ‘‘as-new’’ condition, the re-service aging stability of γ′ phase in the rejuvenated directionally solidified superalloy is worse than that of the virgin directionally solidified superalloy, which is attributed to the decomposition of MC carbide. The rejuvenation heat treatment parameters have a great influence on re-service aging stability of the rejuvenated directionally solidified superalloy. The re-service aging rate of γ′ phase in the rejuvenated directionally solidified superalloy becomes higher, the higher the solution temperature, the shorter the holding time and the greater the cooling rate after solution higher. However, the increased primary aging temperature and holding time cause the decrease of the re-service aging rate of γ′ phase in the rejuvenated directionally solidified superalloy. The second aging condition has no obvious effect on the re-service aging stability of γ′ phase