Effect of Ru addition on γ/γ′ microstructural stability in a low-density CoNi based superalloy

The present work explores the effect of ruthenium (Ru) addition to the gamma/gamma' strengthened Co-30Ni-10Al-5Mo-2Nb superalloy. A 2 at.% Ru increases the gamma/gamma' microstructural stability at 900 degrees C. XRD and APT revealed a reduction of gamma/gamma' lattice misfit by 26% and segregation of Ru at gamma/gamma' interface, respectively that contribute to the decrease of gamma/gamma' interfacial energy. The temporal evolution of gamma' precipitates at 900 degrees C shows the classical matrix diffusion controlled LSW mechanism with a coarsening rate constant (K-r) similar to 6.03 nm(3)/s similar to the values for Co-Al-W based superalloys. Furthermore, Ru addition increases the degree of anomalous strengthening with a peak 0.2% proof stress (PS) value of similar to 630 MPa at 770 degrees C. The results show Ru as a promising alloying addition to increase the gamma/gamma' microstructural stability at high temperatures for the low-density class of CoNi-based superalloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The addition of Ru enhances the microstructural stability of γ/γ' phase in Co-30Ni-10Al-5Mo-2Nb superalloy, reduces the interfacial energy of γ/γ', and increases the degree of anomalous strengthening.