Role of microstructural stability and superdislocation shearing on creep behavior of two low-cost Ni-based single crystal superalloys at 1100 °C/130 MPa

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In order to satisfy the pursuit of advanced aeroengines with low cost and high temperature capacity, the novel Re-free and Re-low single crystal superalloys were designed based on the strategy of Re-reduction. The creep lives of the two experimental alloys at 1100 °C/130 MPa both exceed that of René N5, and the Re-low alloy displays better creep performance and microstructural stability than the Re-free alloy. At the end of steady creep stage, due to the strong hindrance of interfacial dislocation networks, only a few superdislocations with Burgers vectors a<110> and a<001> enter into γ′ phase in the Re-low alloy. In the Re-free alloy, non-uniform plastic deformation leads to the severe γ/γ′ topological inversion, resulting in high-density a<110> superdislocation arrays in γ′ rafts, which can further react to form superdislocation networks. Moreover, the increasing μ phase precipitated with the prolonging creep time also promotes earlier failure of the Re-free alloy. In summary, the Re addition can improve creep resistance through reducing rafting rate of γ′ particles, stabilizing interfacial dislocation networks and increasing the APB energy of ordered γ′ phase. The above results provide favorable experimental basis for the development of low-cost single crystal superalloys.