Fraunhofer Institute for Mechanics of Materials IWM
The substitution of critical alloying elements contributes to the economic and technical sustainability of nickel-based alloys used in demanding applications, such as in the aerospace and energy sectors. Many critical alloying elements are subject to significant price fluctuations and regulatory requirements, and are only available in limited quantities.
The goal of substitution is to maintain and even improve properties despite the removal of critical elements. The materials science challenges include ensuring high-temperature strength, which is provided by intermetallic phases such as γ‘ particles. These particles impede dislocation motion in the nickel matrix and contribute to strength. The size and morphology of the γ‘ particles are decisive for the static yield strength, and changes in their microstructure at high temperatures can negatively affect strength. Furthermore, solid solution hardening and grain refinement are significant mechanisms that also influence high-temperature strength.
The solution strategy is based on microstructure-based modeling of high-temperature strength. This involves investigating the temperature and time-dependent microstructural evolution of nickel-based alloys with varying contents of critical alloying elements. Through thermodynamic-kinetic calculations using the MatCalc software, the γ‘ particle radius can be predicted and integrated into a model that describes the yield strength and creep properties of the alloys. These findings are crucial for making targeted substitutions.