Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Mechanical Properties III
MM 15.1: Vortrag
Montag, 26. März 2012, 15:45–16:00, H 0106
Microstructure and mechanical properties of γ′ hardened Cobalt-base superalloys — •Steffen Neumeier, Alexander Bauer, and Mathias Göken — Institute I: General Materials Properties, University of Erlangen-Nürnberg, Germany
The material of choice for components in gas turbines like turbine blades and discs are Nickel-base superalloys. Due to their excellent mechanical properties, corrosion and oxidation resistance, they can bear high loads in harsh environments at high temperatures. The reason for the extraordinary mechanical strength at temperatures up to 80% of the melting temperature is the two-phase microstructure with a high volume fraction of the intermetallic γ′ phase Ni3Al (L12 crystal structure) coherently embedded in the γ phase, a face centered cubic Ni solid solution. Conventional solid solution and carbide hardened Cobalt-based alloys possess even a superior corrosion resistance, but they can be used only for low-loaded parts. In contrast to Nickel-base superalloys a similar γ/γ′ microstructure, stable at high temperatures, could not be obtained in Cobalt alloys until the recent discovery of Sato et al. They found a stable γ′ phase (Co3(Al,W) with L12 crystal structure) in the ternary Co-Al-W system which has led to a new class of γ′ hardened Co-base superalloys. In this paper the microstructure of several γ/γ′ Co-base superalloys will be presented along with the mechanical properties at high temperatures. Creep experiments have shown that the creep strength is by far higher than that of conventional Cobalt based alloys and comparable to Nickel-base superalloys.