Investigations on the thermo-mechanical fatigue of two Ni-based single-crystal superalloys

The out-of-phase thermo-mechanical fatigue (OP TMF) of two Ni-based single-crystal (SC) superalloys, TMS-75 and TMS-82+, has been investigated. Their different compositions specifically influence TMF properties. TMS-75 showed a longer rupture life than TMS-82+ at t* (hold time) = 0, while TMS-82+ showed a longer life than TMS-75 at different hold times. The different TMF behaviors were analyzed and were attributed, in TMS-82+, to the higher tensile strength at 400 °C and higher stress relaxation resistance at 900 °C. Some differences were observed between the two alloys in slip band and the γ/γ′ structure. Transmission electron microscopy (TEM) studies on the dislocations and stacking faults (SFs) confirmed the previous TEM results concerning the generation mechanisms of dislocations and SFs. The current work indicates that TMS-82+ is appropriate for use in gas turbine engines under specific conditions.