Development of Co–Ni–Al–V–Ta–Cr-based superalloys with high-temperature strength and excellent oxidation resistance

Abstract

In this study, the effects of V on the microstructure, lattice misfit, solvus temperatures, and oxidation behaviors of the Co–Ni–Al–V–Ta-based superalloys are investigated. The results show that all these alloys exhibit the γ’/γ two-phase structures. More importantly, the γ’ solvus temperature increases, and the oxidation resistance is significantly improved with the reduction of V concentration. Subsequently, the Ti (2 at.%) was added into Co–40Ni–10Al–4Ta–1V–12Cr alloy to further raise the properties of the superalloy. It is found that the Co–40Ni–10Al–4Ta–1V–12Cr–2Ti alloy exhibits a higher solvus temperature reaching 1200 °C of the γ′ phase, a low density of 8.48 g/cm3, a low lattice misfit of only +0.37 %, as well as exceptional oxidation resistance and mechanical properties.

Keywords

• Cobalt-based superalloys
• Strength
• γ′ solvus temperature
• γ′ phase stability
• Oxidation resistance