Development of novel Ni-based alloys reinforced by carbides produced by casting and additive manufacturing for high temperature applications

• Applicant: Dr.-Ing. Ulrike Hecht
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545501618

The aim of the DENICAM project is to develop a Ni-Co-Cr-Hf-C alloy reinforced with hafnium carbides (HfC) and containing small amounts of refractory elements, specifically W and Re, for solid solution strengthening. Hafnium carbides form in-situ from the melt following a terminal eutectic reaction and display a unique thermodynamic stability over the entire temperature range down to room temperature. In cast Ni-Cr based alloys HfC is known to provide good creep and oxidation resistance at temperatures as high as 1100°C. However, the carbide distribution is rather coarse, being confined to the interdendritic network. Preliminary investigations showed, that laser powder bed fusion (LPBF) is capable of achieving a novel and unique degree of HfC dispersion, with nano-size carbide particles densely spaced inside the matrix grains and at grain boundaries. This is achieved thanks to the fast directional solidification of the primary solid solution phase inside the travelling melt pool which provides a “magic” length scale for dispersing secondary phases. The DENICAM applicants propose to follow both process technologies, conventional casting and LPBF to produce very distinct microstructures and assess their impact on creep, oxidation in air and corrosion in lime glass melts. Furthermore, LPBF offers means for tailoring the grain size and texture of the face centered cubic matrix phase by controlling grain selection across neighboring melt pools. DENICAM proposes to take this opportunity and investigate the possibility to obtain even single crystalline materials. This necessarily means to question the stability against recrystallization. The dispersed HfC particles are possibly effective in this regard due to Zener pinning. To meet all project goals the proposal combines computational and experimental alloy design, advanced manufacturing, microstructure tailoring as well as a broad range of materials characterization tools. Microstructure-property relationships will be discussed and assessed on the background of established theoretical models.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Professor Dr. Patrice Berthod