Effects of rhenium on the microstructure and creep properties of novel nickle-based single crystal superalloys

Two novel single crystal superalloys were designed to obtain affordable third generation single crystal superalloys. Creep tests and long-term thermal exposure were utilized to evaluate the microstructure and creep properties of the experimental alloys. Moreover, the role of Re in the microstructure and creep performance was investigated. Interestingly, the results showed that the two experimental alloys with different addition of Re demonstrated similar creep properties under the condition of 1120 °C/137 MPa. The alloy with 1 wt% Re owned much better microstructural stability for the rare presence of the TCP phase. However, With higher volume fraction of the γ′ phase and denser γ/γ′ interfacial dislocation networks, the alloy with 2 wt% Re addition is believed to be provided with better precipitation strengthening and interfacial strengthening effects, which strongly guarantee the mechanical properties and hinder superdislocations shearing into the γ′ phase. Affected by the synergistic effects of their strengthening and weakening factors, the two experimental alloys exhibited few difference in creep rupture life under elevated-temperature and low stress condition. Important guidance for the further designs of single crystal alloys could be summarized from the present study.