Achieving High Tensile Strength of Heat-Resistant Ni-Fe-Based Alloy by Controlling Microstructure Stability for Power Plant Application

A new, wrought Ni-Fe-based alloy with excellent creep rupture life has been developed for 700 degrees C-class advanced ultra-supercritical (A-USC) steam turbine rotor application. In this study, its tensile deformation behaviors and related microstructure evolution were investigated. Tensile tests were carried out at room temperature, 700 degrees C, and 750 degrees C. The results show that the Ni-Fe-based alloy has excellent yield strength at 700 degrees C, which is higher than that of some other Ni-based/Ni-Fe-based alloys. The fracture surface characteristics indicate trans-granular and intergranular fracture modes at room temperature, 700 degrees C, and 750 degrees C. However, the intergranular fraction mode became dominant above 700 degrees C. Dynamic recrystallization occurred at 700 degrees C and 750 degrees C with increasing average misorientation angles. The volume fraction of the gamma ' precipitate was around 20%, and the average size of the gamma ' precipitates was around 30 mu m, which had no noticeable change after the tensile tests. The predominant deformation mechanisms were planar slip at room temperature, bypassing of the gamma ' precipitates by the Orowan mechanism, and dislocation shearing at 700 degrees C and 750 degrees C. The tensile properties, fracture characteristics, and deformation mechanisms have been well-correlated. The results are helpful in providing experimental evidence for the development and optimization of high-temperature alloys for 700 degrees C-class A-USC applications.

Automated summary

A new Ni-Fe-based alloy has been developed for 700 degrees C-class A-USC steam turbine rotor application, exhibiting excellent creep rupture life. The alloy has high yield strength at 700 degrees C and shows different fracture modes at various temperatures. Dynamic recrystallization occurred during tensile tests and influenced the deformation mechanisms. These findings provide valuable experimental evidence for the development and optimization of high-temperature alloys for 700 degrees C-class A-USC applications.