Compositional design considerations for microsegregation in single crystal superalloy systems

Solute Redistribution during Planar and Dendritic Growth of Directionally Solidified Ni-Base Superalloy CMSX-10

“…Of all solute elements that were presented in Table II, Ti and heavy refractory elements such as Re, Ta, and W exhibited particularly strong segregation tendency. This segregation tendency was found to be comparable with those reported for dendritically solidified commercial single crystal superalloys [3,4,7,11] and model single crystal superalloys [6,23]. (Table II).…”

“…This can be deduced from analyzing the segregation pattern of Cr during the γ/γ′ eutectic growth with planar S/L interface ( Figure 9) and the local distribution of Cr in the interdendritic region of dendritically solidified sample (Figure 11(f)). The EPMA profile of Cr shown in Figure 9 revealed that Cr enriches in liquid during the growth of γ/γ′ eutectic because of its very low solubility in γ′ phase [23,24]. As a result, the compositions of Cr in γ/γ′ eutectic were lower than those in the entire preceding primary γ.…”

“…Considering that γ/γ′ eutectic is composed of γ and γ′ phases, and a higher volume fraction of γ′ phase in γ/γ′ eutectic, this result indicates that the solubility of these elements in γ′ phase is higher than in γ phase. Conversely, the other solute elements such as Co, Cr, Mo, Re, and W exhibited that the C values are lower than C , which implies that the solubility of these elements in γ′ phase is lower than that in γ phase [23,24].…”

Diffusion and γ′ Phase Coarsening Kinetics in Ruthenium Containing Nickel Based Alloys

“…Unfortunately, the amount of the refractory elements in Ni based superalloys is limited by the formation of TCP (topologically close packed) phases during high temperature exposure due to the microsegregation of these elements. 4,[9][10][11] Recently, an increase in microstructural stability of the nickel based superalloys upon TCP phases formation has been achieved by the addition of Ru, resulting in the enhancement of the creep strength. 12,13) Intensive researches are being conducted concerning the role of Ru as a new potent alloying element in the next generation of the single crystal nickel based superalloys.…”

Studies on the Solidification Path of Single Crystal Superalloys

“…[34,35] The actual values of the partition coefficients however do depend on the overall alloy composition as shown by Hobbs et al [26] and attempts have been made to minimize microsegregation through additions of for example Ru. [36] The weak partitioning of Cr during the early stages of solidification has led to some surprising findings however. During a study on CMSX-4 it was found that Cr showed a partition coefficient greater than one, contrary to what was expected from thermodynamics calculations and simulations.…”