A Comparative Study of Thermo-Mechanical Fatigue of Two Ni-Based Single Crystal Superalloys

Abstract

The properties of thermo-mechanical fatigue (TMF) of two Ni-base single-crystal (SC) superalloys developed at NIMS were studied. The superalloys with different Re amounts of 5% (TMS-75) and 2.4% (TMS-82+) showed different TMF behaviors. The cycles to failure for both alloys decreased drastically with the increase of hold time (tH). The TMS-75 showed a longer life than that of the TMS-82+ at tH= 0. While, the TMS-82+ showed a longer life than that of the TMS-75 at tH�. 0, which would be attributed to the higher tensile strength at 400 oC and higher stress relaxation resistance at 900 oC in the TMS-82+. From microstructural studies, some differences were observed between the two alloys in slip bands, and a little rafted J/J' structure parallel to the loading stress axis was observed in the TMS-82+ for TMF with a hold time. Transmission electron microscopy (TEM) studies on the stacking faults confirmed the previous results. This work indicates that the TMS-82+ could be used satisfactorily in gas turbine engines under some specific condition.