Precipitation behavior of phases in a novel low-cobalt nickel-based superalloy

The phase precipitation behavior of a low-cobalt nickel-based superalloy was investigated using JMatPro simulations and differential scanning calorimetry . Microstructural and compositional analyses of the experimental ingot were compared with those of a control sample. The cast structure primarily consisted of γ (matrix), γ', σ, μ phases, carbides (MC, M6C, M23C6), and a γ+ γ' eutectic structure, which accounted for approximately 13.9 % of the volume. During solidification. tantalum and hafnium exhibited positive segregation. The initial melting point, final melting point, and the remelting temperature of the γ-phase were determined to be 1300.1°C, 1349.6°C, and 1272.1°C, respectively. The theoretical calculations were in close agreement with the experimental findings. Thermodynamic analysis suggested that increasing the aluminum and tungsten content could enhance the precipitation amount and resolution temperature of γ' and M6C carbides, respectively. Furthermore, hafnium and tantalum were found to promote the liquid-phase evolution of MC carbides. The low-cobalt alloy demonstrated superior expected durability compared to existing commercial nickel-based polycrystalline cast superalloys.