On the effect of gamma prime phase particle morphology on the high temperature strength of Ni-base superalloys for large later stage blades in land based gas turbines. (T08*)

• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 190389738

The present project aims at exploring the role of gamma prime phase particle morphology on the high temperature strength of Ni-base superalloys. In SFB/Transregio 103, techniques were established, which allow to explore the associated elementary processes. So far, materials were considered, which consist of cuboidal γ’-particles which are separated by thin γ-channels. These microstructures are found in small blades (for aero engines and for the first stage blades of land-based gas turbines). The present project focusses on a superalloy, which is used to make larger scale later stage blades for land-based gas turbines (tip to root distance: 1m). Their high thermal mass results in slow cooling rates during solidification. The alloy composition is optimized to ensure good castability (utmost importance) and low density (to minimize high centrifugal forces exerted on the rotor during operation). The industrial partner has succeeded in successfully casting a large blade with a lightweight superalloy with a γ’-volume fraction of 50%. In this alloy non-cuboidal types of γ’-morphologies are observed: γ’-doublets, octoads and large γ’-particles with dendritic features. These morphologies have been documented before and have been sporadically discussed in the literature. How they affect elementary high temperature deformation processes is unknown. This hampers the development of better alloys and heat treatments and makes mechanical design and lifetime analysis difficult. The objective of the present work is to identify the elementary mechanisms which govern the formation of these morphologies and to explore how they affect high temperature strength, focusing on creep and on thermo mechanical fatigue. The advanced processing methods and microstructural and mechanical characterization techniques developed and validated in SFB/TR 103 for cuboidal/ high volume fraction microstructures are ideally suited to provide this information which is needed to support the development of new superalloys for land-based gas turbines in a competitive environment.

• DFG Programme: CRC/Transregios (Transfer Project)
• Subproject of: TRR 103: From Atoms to Turbine Blades - A Scientific Approach for Developing the Next Generation of Single Crystal Superalloys
• Applicant Institution: Ruhr-Universität Bochum
• Business and Industry: Siemens Energy Global GmbH & Co. KG
• Project Head: Professor Dr.-Ing. Gunther Eggeler