Recrystallization and fatigue fracture of single crystal turbine blades

Fatigue Fracture Mechanism of a Nickel-Based Single Crystal Superalloy with Partially Recrystallized Grains at 550 °C by In Situ SEM Studies

“…For NBSC superalloys, since the grain boundaries have been removed, grain boundary strengthening elements, such as Hafnium, and Boron, etc. have been removed or greatly reduced to increase the melting temperature of the superalloy [2,3]. Hence, it makes single crystal superalloy susceptible to transverse grain boundaries, for instance recrystallization (RX) [2,3].…”

“…have been removed or greatly reduced to increase the melting temperature of the superalloy [2,3]. Hence, it makes single crystal superalloy susceptible to transverse grain boundaries, for instance recrystallization (RX) [2,3]. Generally, recrystallization is formed in nickel-based single crystal superalloy due to plastic deformation and subsequent exposure to high temperature [2,3].…”

“…Hence, it makes single crystal superalloy susceptible to transverse grain boundaries, for instance recrystallization (RX) [2,3]. Generally, recrystallization is formed in nickel-based single crystal superalloy due to plastic deformation and subsequent exposure to high temperature [2,3]. In the turbine industry, there have been some reports on recrystallization-induced turbine blade accidents in China and other countries [4][5][6][7].…”

Effect of Local Recrystallized Grains on the Low Cycle Fatigue Behavior of a Nickel-Based Single Crystal Superalloy

“…Due to its excellent mechanical properties under elevated temperatures, single crystal (SX) and directionally solidified (DS) superalloys, with the elimination of transverse grain boundaries, have been widely used as the primary materials for turbine blades [1]. However, single crystal superalloys usually have removed grain boundary (GB) strengthening elements, making them sensitive to any transverse boundaries or defects, e.g., recrystallization [1,2]. With increasing attention on the safety of turbine engines in recent decades, there have been more and more studies on the recrystallization issue of turbine alloys, i.e., SX and DS superalloys [3][4][5][6].…”

“…With increasing attention on the safety of turbine engines in recent decades, there have been more and more studies on the recrystallization issue of turbine alloys, i.e., SX and DS superalloys [3][4][5][6]. It has been reported that recrystallization (RX) grains can act as the preferred fatigue crack initiation sites of turbine blades [1,7]. So far, little research has been done regarding the effect of RX on the fatigue behavior of SX superalloys [8], aside from the limited studies on directionally solidified (DS) alloys [9][10][11].…”