Recrystallization and fatigue failure of blades made of a directionally solidified alloy

The crack and fracture of blades made of a directionally solidified superalloy were analyzed. The failure mode and cause were studied in virtue of fracture observation and metallographic structure analysis. The results show that the crack and fracture on the superalloy blades have the same fatigue failure mode resulting from surface recrystallization. Owing to the plastic deformation at the blade surface, recrystallization is formed during the solid solution heat treatment. Before the blade application, the recrystallization zones already exist on its two sides.