Creep Fracture Characteristics of Nickel-Based Single Crystal Superalloy at Different Temperatures

Creep tests were carried out on DD407 single crystal superalloy under different conditions (760℃/750 MPa, 850℃/500 MPa, 980℃/260 MPa, 1 050℃/140 MPa). The creep fracture morphology and the microstructure and dislocations after creep fracture were observed. The mechanism of creep fracture was analyzed. The results show that at 760℃, the test alloy fractured in slip shear modes, and the strengthening phase γ' was slightly deformed, but no obvious rafting structures were found; creep dislocations were mainly distributed at the γ/γ' phase interface, and only a small number of dislocations entered the γ' phase. At 850℃, the alloy still mainly fractured in slip shear modes, and the γ' phase began to show rafting structures. At 980℃ and 1 050℃, the alloy had ductile fracture, and the rafting of the γ' phase became more serious with the creep temperature. Under the condition of 1 050℃/140 MPa, a large number of dislocations were packed in the γ matrix channel, and a large number of dislocations cut into the γ' phase in the form of long straight dislocation lines.