Deformation microstructures after low-cycle fatigue in a fourth-generation Ni-base SC superalloy TMS-138

The deformation microstructures of a fourth-generation single-crystal (SC) Ni-base superalloy TMS-138 after low-cycle fatigue (LCF) have been studied. For comparison, a typical third-generation (TMS-75), and a second-generation (CMSX-4) Ni-base SC superalloy were also examined. The TMS-138 exhibited an excellent LCF behavior under a condition of R ratio of 0 at temperatures of 1073 K and 1173 K. The addition of refractory elements resulted in a remarkable improvement of LCF properties due to the different microstructure developed in TMS-138 as compared to the reference superalloys. The formation of a large number of stacking faults (SFs) in the matrix at 1073 K and the more completed rafts and smaller interfacial dislocation spacing at 1373 K were observed and discussed in relation to the performance of TMS-138 under a specific condition of R = 0. This work suggests that a fourth-generation SC superalloy TMS-138 is a promising candidate for applications in aeroengines.