Work

A novel low-density Co-Ni-Al-Nb-based multicomponent superalloy with superior medium-to-high temperature mechanical properties and oxidation resistance

Year: 2025

Type: article

Abstract: Chromium (Cr) is widely used in superalloys to improve oxidation resistance and creep strength. Still, excessive additions can promote the formation of detrimental topologically close-packed (TCP) phases, compromising microstructural stability. Therefore, controlling the Cr content to achieve excellent overall performance is a critical aspect in the design of superalloys. By employing the CALPHAD approach and the Co-based superalloy thermodynamic database developed by our research team, in conjunction with investigations into the γ/γ′ microstructure, phase transformation temperatures, and lattice misfit, this study optimized a Co-40Ni-14.5Al-4Nb alloy. Based on this alloy, the Cr content was systematically incorporated and controlled through CALPHAD calculations combined with experimental characterization. This led to the development of an optimized Co-40Ni-14.5Al-4Nb-12Cr alloy, featuring a high γ′ solvus temperature (1172 °C), a well-aligned γ/γ′ microstructure, and a reduced lattice misfit. Moreover, this alloy exhibited a compressive yield strength of 745 MPa at 800 °C, a low density of 7.73 g/cm³ , and excellent specific yield strength. Notably, the alloy maintained a high compressive yield strength with minimal variation over the 500–800 °C temperature range, owing to the interaction between lattice misfit and dislocation behavior. After 200 h of oxidtion, a protective oxide layer composed of Al₂O₃, Nb₂O₅, and (Al,Cr)₂O₃ formed, markedly enhancing oxidation resistance. These findings highlight the effectiveness of Cr content optimization in achieving a balanced enhancement of mechanical and oxidation performance, offering valuable insights for next-generation superalloy design.

Source: Journal of Alloys and Compounds

DOI: 10.1016/j.jallcom.2025.183495