%0 journal article
%@ 1438-1656
%A Bauer, A., Neumeier, S., Pyczak, F., Goeken, M.

%D 2015
%J Advanced Engineering Materials
%N 6
%P 748-754 
%R doi:10.1002/adem.201400266
%T Influence of Iridium on the Properties of Gamma′-Strengthened Co-Base Superalloys
%U https://doi.org/10.1002/adem.201400266
6 
%X The influence of iridium on the phase stability, oxidation behavior, and high temperature creep strength of γ′-hardened Co-base superalloys is discussed. Ir increases the γ′-solvus temperature and γ′-volume fraction since it partitions slightly to the γ′-phase. However, Ir leads also to a discontinuous precipitation transformation of the metastable γ/γ′-microstructure into a lamellar microstructure of Co3W, CoAl, and a Co-rich fcc phase for the W-rich alloys. A reduction of W in presence of Ir leads to a higher phase stability. The constrained lattice misfit between the γ and γ′ phase in the Ir and high W containing alloy is +0.5%. The alloying element Ir strongly increases the creep strength at 850 °C as long as the γ/γ′-microstructure is not discontinuously transformed. Furthermore, the oxidation resistance is improved by the addition of iridium.