Influence of Ru addition on microstructure and stress-rupture property of Ni-based single crystal superalloys

The effects of Ru on the microstructure and stress-rupture property were investigated in two experimental Ni-based single crystal superalloys with and without Ru addition (5.1%, mass fraction). The results indicate that the morphology of γ′ precipitates in the dendrite core and interdendritic region are intermediate and nearly spherical, respectively, in the Ru-free alloy after being aged at 1 100 °C for 8 h. The Re partitioning ratio increases due to Ru addition and Ru partitioned preferentially to the γ phase in both dendrite core and interdendritic region of the Ru-containing alloy, which results in more negative lattice misfit and more cuboidal γ′ precipitates. Meanwhile, the γ′ volume fraction increases while the precipitate size and γ channel width decreases due to Ru addition in both dendrite core and interdendritic region. Ru addition improves the stress-rupture life at 1 100 °C/140 MPa significantly due to higher γ′ volume fraction, more negative lattice misfit and a well rafting structure as well as less γ channel width.