Effect of ruthenium on high-temperature creep rupture life of a single crystal nickel-based superalloy

The addition of 3 wt% ruthenium (Ru) has been found to improve the creep rupture lives of a single crystal Ni-based superalloy under both conditions of 1100 °C/150 MPa and 1000 °C/310 MPa. Creep curve analysis indicates that the creep mechanisms are different from each condition. The improvement of creep rupture lives by 3 wt% Ru addition is discussed not only from the view of dislocation movement but also the γ′ phase evolution. The change of γ/γ′ lattice misfit in the initial microstructure is believed to be the key role of Ru on the high-temperature creep deformation. The larger negative lattice misfit caused by an addition of 3 wt% Ru induces smaller and more regular γ′ particles in the initial state, as well as denser dislocation networks at the γ/γ′ interface during creep. These two aspects are crucial to the high-temperature creep rupture life. In addition, a little topologically close-packed (TCP) phases are observed after creep rupture in the two experimental alloys.