Abstract
In this work, we investigated the low-cycle-fatigue (LCF) at room temperature (RT) and 750 °C of 100% revert commercial polycrystalline Ni-based superalloy (K417) blade re-melted by electron beam technology (EBT). The fatigue life of EBR-K417 reaches 2324, 6840, and 6925 cycles at 750 °C during the LCF, which is substantially improved compared with the as-prepared K417 (1050 cycles). Surface or subsurface defects became primary fatigue sources instead of inclusions inside alloy in purified revert K417, which is suggested to be the main reason for prolonging the fatigue life. In addition, the results and analysis show that the dislocation movement in K417 alloy at room temperature (RT) is mainly through strong-coupled-dislocation (SCD) shearing mechanism, and its contribution to yield stress is 203 MPa. Whereas the dislocation migration mechanism at 750 °C is mainly bypassing and cross slip, whose contribution to yield stress is 156 MPa. The theoretic critical resolved shearing stress (CRSS) for temperature at RT and 750 °C are calculated as 249 MPa and 198 MPa, which are very close numerically with the experimental CRSS values, 230.4 MPa and 204.6 MPa.
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