The promotion of Ru on topologically close-packed phase precipitation in the high Cr-containing (∼9wt.%) nickel-base single crystal superalloy

The partitioning behaviors of alloying elements Cr, Co, Al, Ta, etc. on the γ and γ′ phases of high Cr-containing (∼9wt.%) nickel-base single crystal superalloys have been investigated with and without the addition of 3wt.% Ru. The "reverse partitioning effect" occurs, which means that the addition of Ru causes the partition of Cr and Co into γ′ phase, while Al an Ta concentrate into γ matrix. However, Ru promotes the precipitation of topologically close-packed (TCP) phases, since the diffusion coefficient between the TCP phase and the matrix interface increases with the diffusion behaviors of refractory elements. For the coarsening and slightly rafting of γ′ phases, the increase of elemental diffusion plays much more important role in its kinetic process than the decrease of lattice misfit. - Highlights: • The high Cr-containing (∼9wt.%) superalloys are chosen in this study. • The "reverse partitioning" behavior occurs with the addition of 3wt.% Ru. • Ru promotes the precipitation of topologically close-packed (TCP) phases. • Ru accelerates the diffusion process of alloying elements. • Increase of elemental diffusion plays important role in coarsening of γʹ phases