Development of a low-density Co-Ni-Al-Ta-Cr superalloy with high mechanical performance and superior oxidation resistance

Abstract

In this study, a Co-30Ni-10Al-6Ta-10Cr alloy was designed based on CALPHAD (Calculation of Phase Diagrams) method targeting high γ′ phase fraction and solvus, and optimal thermal processing window. Experimental results concurred with the calculations and validated Cr as a γ phase-forming element in Co-Ni-Al-Ta-based alloys. The incorporation of Cr in the alloy helps mitigate lattice misfit, coarsening rate, and alloy density, while enhancing microstructural stability. A certain amount of Cr led to the development of a superalloy with both high mechanical performance γ′ solvus and low density. Moreover, the oxidation resistance of the Co-Ni-Al-Ta-based high-temperature alloy can be substantially elevated by the introduction of Cr. At 1000 °C, the Co-30Ni-10Al-6Ta-10Cr alloy displayed comparatively low oxidation weight gain, which signifies its excellent oxidation resistance. This is mainly attributed to the formation of continuous (Co,Ni)(Al,Cr)2O4 spinel oxide layers during prolonged oxidation.