High-throughput exploration of alloying effects on the microstructural stability and properties of multi-component CoNi-base superalloys

The effects of substituting W with gamma ' formers (Al, Ti, Ta, Mo and Nb) on the microstructural stability of a base model superalloy Co-20Ni-7Al-8W-1Ta-4Ti were studied using a high-throughput diffusion-multiple approach. A substantial amount of composition-microstructure data was obtained from a single sample, enabling deeper understanding of the alloying effects. It was found that alloy 15Al0W still contains stable gamma ' phase at 1000 degrees C for 1000 h even with a W content of zero. However, the gamma ' volume fraction of this alloy was far lower than other W-containing alloys, indicating that W plays an important role on retaining the stability of the gamma ' phase. Except for Ti, substituting W with other gamma ' forming elements promotes the precipitation of detrimental phases, with a potency of Nb > Ta asymptotic to Al > Mo > Ti. The Nb content should be carefully controlled due to its strong effect on inducing the precipitation of the chi phase. The literature data for W-free alloy systems were discussed in comparison to the current W-containing alloy system in order to analyze the role of W in stabilizing the gamma ' phase at high temperatures. Furthermore, the gamma ' strength and density of more than 300 alloys from the investigated diffusion multiple were analyzed using classic models established for Ni-base superalloys, to guide the alloy design aiming to achieve higher strength to weight ratio. The substitution of W with Ti or Al could significantly reduce the alloy density, but would also decrease the gamma ' strength to some extents. These negative effects could be counterbalanced by moderate additions of Ta and Nb. This study will be helpful for the accelerated design of multi-component CoNi-base superalloys to achieve light weight and high strength. (c) 2021 Published by Elsevier B.V.