A novel Co-Ni-Ti-V-based superalloy exhibiting low density and high strength

Abstract

This paper presents an innovative investigation on γ/γ'-strengthened multi-component Co-Ni-Ti-V-based superalloys, which has led to the successful development of high-strength Co-Ni-Ti-based superalloys. This research holds immense importance for the advancement of Co-Ti-based superalloys, offering valuable insights and support for their future progress. We present a design process that utilizes CALPHAD to develop the Co-Ni-Ti-V-Al quinary alloy from Co-Ni-Ti-V quaternary superalloy in this paper. The optimized composition of Co-20Ni-10Ti-4V was determined in the Co-Ni-Ti-V quaternary system, which exhibited high γ' solvus temperature, low coarsening rate of γ' precipitates, and high yield strength (after 60 h of annealing at 750 °C, the maximum value at room temperature can reach 1718 MPa and the maximum value at 900 °C reaches 600 MPa). The addition of Al as a microalloying element in Co-20Ni-10Ti-4V reduces lattice mismatch and density, and improves the thermal stability of the γ' phase, thereby further enhancing the alloy's high-temperature performance. The study also revealed that the distribution behavior of Al shifted with an increase in its content, which may be attributed to the complex interactions among Al, Ti, and V atoms. Moreover, the developed Co-20Ni-10Ti-4V-1Al alloy demonstrated excellent performance with high γ' solvus temperature, low mass density, low γ/γ' lattice mismatch, and exceptional γ' phase thermal stability. This alloy also exhibited superior specific yield strengths compared to W and Ta-free Co-Ti-based lightweight superalloys, thus positioning it as a promising contender for high-temperature applications.