High-Temperature Creep Properties of SiC Fibers with Different Compositions

Abstract

Silicon carbide (SiC) fiber–reinforced SiC matrix (SiC/SiC) composites have been widely investigated for potential fusion reactor applications. In this present investigation, the high-temperature creep performance of five types of SiC fibers is evaluated and microstructural analysis is performed. The creep behavior of the fibers was assessed by the bend stress relaxation method at various applied strains at 1500°C and 1700°C. The fibers tested include developmental-grade fibers with different residual silicon amounts (~0%, 2% to 3%, and 5% to 6%) fabricated by laser chemical vapor deposition at Free Form Fibers. Generally, the creep behavior of the Free Form (FF) fibers was similar to Hi-Nicalon Type S and/Tyranno-SA SiC fibers currently used for fabrication of SiC/SiC composites for fusion applications. However, all FF fibers exhibited the formation of pores after the creep tests at 1700°C regardless of residual silicon amount, which can be improved by further development via optimization of the composition and microstructure.

Keywords:

• SiC fiber
• bend stress relaxation creep
• structural material

Acknowledgments

This manuscript has been co-authored by UT-Battelle, LLC under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. Government retains and the publisher, by accepting the paper for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This study was also supported by the DOE Office of Fusion Energy Sciences under contact DE-AC05-00OR22725 with Oak Ridge National Laboratory (ORNL) managed by UT Battelle, LLC. This work was also supported by the Nuclear Engineering Science Laboratory Synthesis (NESLS) program at ORNL. Shay Harrison at Free Form Fibers provided the SiC fibers.