Advanced Ni-based superalloys, Low Re-Containing, Diffusion couple, Synergic effects of Co and Ta, Elemental partitioning behavior, Mining engineering. Metallurgy, TN1-997

Reducing Re content is a trend in the development of advanced Ni-based single crystal (SX) superalloys. In this research, the synergic effects of Co and Ta additions on the microstructural stability and γ/γ' elemental partitioning behaviors in low Re-containing Ni-based superalloys were investigated, utilizing a high-throughput diffusion multiple method after aging at 1100 °C for 1000h, in combination with electron microscopy image analysis, quantitative EPMA, and nanoindentation. The results indicated that the microstructure remained stable γ/γ' phases across a relatively broad range of Co and Ta contents. The synergic effect of Co and Ta on the γ' volume fraction was different on the different concentration levels, and higher Co addition would counteract the positive effect of Ta addition. Moreover, the increase of Co and Ta contents altered the partitioning behavior of elements within the γ/γ' phases. The partitioning of Re into γ phase was enhanced with appropriate Co and Ta contents, resulting in a peak of hardness of γ phase. While, the hardness of γ' phase continuously increased with Ta additions. Therefore, moderate Co and Ta additions may be more suitable for optimizing the composition of the investigated low Re-containing Ni-based SX superalloy, considering both the microstructural stability and the strength of γ/γ' phases. This study will be helpful for the accelerated development of low Re-containing Ni-based SX superalloys by adjusting the contents of other alloying elements to maximize the benefits of Re.