Tensile, Low Cycle Fatigue, and Very High Cycle Fatigue Characterizations of Advanced Single Crystal Nickel-Based Superalloys

Abstract

Tensile and fatigue life variabilities are investigated for new-generation single crystal Ni-based superalloys: the 3rd generation CMSX-4 Plus, the 6th generation TMS-238, and a newer Ni-based superalloy, TROPEA containing Pt. Consistently from the results of previous research, very high cycle fatigue (VHCF) properties at the chosen condition of T = 1000 °C/Rε = −1/f = 20 kHz are mainly influenced by the solidification/homogenization pore size and position. TROPEA alloy has the best low cycle fatigue (LCF) life among all tested alloys at 650 °C and Rσ = 0.05/f = 0.5 Hz. To better understand the influence of chemical composition on the LCF endurance, tensile properties were investigated using nine different single crystalline alloys at 650 °C with the strain rate of 5 × 10−4 s−1. The yield stress is directly affected by the chemical composition of the Ni-based superalloys, and alloys with high contents of Ti and Ta have a higher yield stress, due to an increased shearing resistance of γ′ precipitates. Hence, the yield stress is the main control parameter of LCF at the selected condition. No influence of chemical composition on VHCF life durability has been observed, in good agreement with previous studies.