Joining of C/C-SiC ceramic matrix composites to high-entropy alloys using cobalt-based fillers for in-space applications
- Paper number
IAC-24,C2,5,10,x90884
- Author
Mrs. Ebrar Ekiz, ARCEON B.V., The Netherlands
- Year
2024
- Abstract
Carbon fiber reinforced SiC (C/C-SiC) ceramic matrix composites (CMCs) offer ideal properties for high-temperature aerospace applications like combustion chambers and nozzle extensions for rockets. However, challenges with the integration of CMCs into metal structures, despite extensive manufacturing knowledge, limited their use in aerospace. Improving joining techniques with metals is becoming increasingly important. In addition, research on different materials that replace metal components due to their undesirable properties has increased greatly in recent years. One attractive candidate for this is high-entropy alloys (HEAs). This relatively novel group of materials is promising to dethrone superalloys due to their potential for high specific strength and impressive resistance to oxidation at elevated temperatures. The brazing method has been investigated for the integration of C-C/SiC CMC combustion chambers onto metal injector plates to create hybrid in-space thrusters. For this purpose, CMC plates manufactured by the melt infiltration (MI) method were brazed with arc-melted HEA (TaNbVTi-Cr) buttons using BCo-1 (CoNiCrSiWB) conventional filler materials under a vacuum atmosphere at 1250 $^{\circ}$C. The selected cobalt-based, chrome-containing filler material allowed the CMC surface to be wetted without the need for any surface metallization process, by altering the high surface tension. The joining area was analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX), where it was found that the Cr$_{23}$C$_{6}$ compound detected at the interface between CMC and filler played a major role in creating a sound joint with this filler metal. Additionally, the effects of surface grinding, increased holding time at brazing temperature, and HEAs with different Cr content on the interface were examined. It was found that while smooth CMC surfaces with increased holding times at brazing temperature enabled the creation of more sound joints compared to other trials, HEAs with increased Cr content did not have a major effect on joint quality. With this study, it has been proven that the use of active filler metals, which bring low service temperature limitations, is not mandatory when joining C/C-SiC CMCs with dissimilar materials. It has been shown that a sound joint between these two dissimilar material groups is possible by preventing the formation of brittle intermetallics at the joint interface. This research is a major step in the adoption of CMC materials for space propulsion, providing new options for integrating these materials with metal structures.- Abstract document
- Manuscript document
IAC-24,C2,5,10,x90884.pdf (🔒 authorized access only).
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