Cr-Si-Alloys for High Temperature Applications beyond 1000 °C
Wall Forum
- Datum: 13.01.2025
- Uhrzeit: 13:00 - 14:00
- Vortragende: Jun. Prof. Dr.-Ing. Anke Silvia Ulrich
- Lehrstuhl Metallische Werkstoffe, Universität Bayreuth
- Ort: D3 Seminar room / Zoom room 1
- Gastgeber: IPP
Promising candidates for high-temperature applications are refractory metal based systems such as Cr-rich Cr-Si-based alloys. These alloys consist of an A2 Cr solid solution matrix and strengthening A15-phase precipitates. Compared to Ni-bases superalloys, they allow an increase of efficiencies due to their higher melting point, thus a potential increase in working temperature by 100 – 200 °C. Compared to Ni-based superalloys and other refractory metal based alloys (e.g. Mo, Nb, Ta, W) they have lower densities and higher worldwide resources of Cr and Si. However, some challenges must be overcome before using Cr-based alloys at temperatures higher than 1000 °C as structural materials: (i) Depending on the surrounding atmosphere, Cr-based systems have a low oxidation and nitridation resistance (e.g. Cr2N layer formation). (ii) The ductile to brittle transition temperature is in the range of 400 – 900 °C. (iii) Production of large parts with low impurity concentrations.
Ge, Mo, and Pt were found to be promising alloying elements that maintain the two-phase microstructure. Ge stabilizes A15-phase formation and improves oxide scale adhesion, and Pt binds nitrogen by forming an antiperovskite phase instead of a brittle Cr2N layer. Mo improves creep properties and nitridation resistance of the A2 matrix phase. The alloying elements can be combined in such a way that their advantages are combined by maintaining the two-phase microstructure.
Ge, Mo, and Pt were found to be promising alloying elements that maintain the two-phase microstructure. Ge stabilizes A15-phase formation and improves oxide scale adhesion, and Pt binds nitrogen by forming an antiperovskite phase instead of a brittle Cr2N layer. Mo improves creep properties and nitridation resistance of the A2 matrix phase. The alloying elements can be combined in such a way that their advantages are combined by maintaining the two-phase microstructure.