High-Temperature Pre-deformation and Rejuvenation Treatment on the Microstructure and Creep Properties of Ni-Based Single-Crystal Superalloys

Unintentional plastic deformation during production of turbine blades made from Ni-based single-crystal superalloy has a huge risk on its durability. In the present study, a plastic deformation was applied at various temperatures to AM1 alloy and its effect on the alloy’s microstructure and creep properties were analyzed. Microstructure evolution during aging treatment was different for plastic deformation at lower temperature (≤750 °C) and higher temperature (950 °C) because of different deformation mechanisms. AM1 with mild γ′ directional coarsening after plastic deformation at 950 °C and following aging treatments performed well in creep test at 1050 °C/140 MPa, but poorly at 850 °C/500 MPa. Rhenium containing CMSX-4 Plus was tested similarly to AM1. Pre-deformation has huge impact on creep durability of CMSX-4 Plus at 1150 °C/110 MPa; however, the creep life debit at 1050 °C/200 MPa was minor. In order to restore properties of pre-deformed single-crystal superalloys, rejuvenation heat treatment process was added after pre-deformation. Rejuvenation treatment successfully restored microstructure after room-temperature plastic deformation, and creep properties of rejuvenated specimens are equivalent to that of original AM1 and CMSX-4 Plus.