Degradation effects of the rafts and dislocation network on creep property of single crystal superalloy at medium temperature

Generally, raft structure and interfacial dislocation networks enhance the creep resistance at elevated temperatures above 1000 °C and low stresses in Ni-based single crystal superalloys. However, the formation of raft structure and dislocation networks by raising the Mo content increased the creep rate at 900 °C and 392 MPa, accelerating the final failure. The formation of rafts was closely related to the creep rate acceleration, promoting dislocations piling up at the γ′/γ interface and the shearing events in the γ′ phase. Moreover, the dislocation networks formed at 900 °C and 392 MPa did not differentiate significantly with different Mo content, which could not enhance the creep resistance as expected. This work revealed the microstructural evolution at medium temperature and provided a new perspective for understanding the creep mechanisms and alloy design.