Influence of Withdrawing Rates on Elements Segregation and Creep Properties of A Single Crystal Nickel-Based Superalloy

The single crystal nickel-based superalloys with different dendrite spacings were prepared by using various withdrawing rates, and the influence of withdrawing rates on elements segregation and creep properties of them is investigated through creep property measurements and microstructure observation. Results show that relatively bigger withdrawing rate leads to the smaller dendrite spacing and lower segregation extent of elements between the dendrite/interdendrite regions, which further causes the better creep resistance of the alloy. Dislocations climbing over the rafted gamma' phase is deemed as the deformation mechanism of the superalloys during steady state creep. In the later stage of creep, significant amount of dislocations shear into the rafted gamma' phase, which may promote the alternative slipping of dislocations to twist the rafted gamma' phase. At the further latter stage of creep, the initiation and propagation of the cracks occuring up to creep fracture is the fracture mechanism of the superalloy.