A novel type of Co-Ti-Cr-base γ/γ′ superalloys with low mass density

A γ′ strengthened Co-Ti-Cr superalloy is presented with a mass density ∼14 % below that of typical Co-Al-W-based alloys. The lattice misfit is sufficiently low to form coherent cuboidal γ′ precipitates. Atom probe tomography shows that Cr partitions to the γ phase, but increases the γ′ volume fraction compared to a binary Co-Ti alloy to more than 60 %. The solubility of Cr in the γ′ phase is significantly higher than expected from previously published values. The γ′ solvus temperature is above 1100 °C. The yield strength shows a distinct increase above 600 °C surpassing that of Co-9Al-8W (at.%) and conventional Co-base superalloys, even more so when it is normalized by the mass density.

433