Thermomechanical Performance of Si–Ti–C–O and Sintered SiC Fiber-Bonded Ceramics at High Temperatures

Authors


  • This work was financially sponsored under DOE WFO Project No. NFE-08-01754 under contract DE-AC05-00OR22725 with UT-Battelle, LLC.

  • *matsunagat@ornl.gov

Abstract

The stress–temperature-lifetime response of Si–Ti–C–O fiber-bonded ceramic (Tyrannohex) and sintered SiC fiber-bonded ceramic (SA-Tyrannohex) materials as investigated in air from 500 to 1150°C and 500 to 1400°C, respectively. The apparent threshold stress in bending of Si–Ti–C–O fiber-bonded ceramic with a lifetime of more than 1000 h was about 175 MPa in the 500–1150°C temperature range. In the case of sintered SiC fiber-bonded ceramic, when the applied stress was below an apparent threshold stress in bending (e.g., ∼225 MPa) for tests conducted ≤1150°C, no failures were observed for lifetimes up to≥1000 h. While, at the temperature of ≥1300°C, the apparent threshold stress in bending decreased to 175 MPa. The decrease in strength was caused by grain growth, which was confirmed from scanning electron microscopic fractography. Both fiber-bonded ceramics exhibited much higher durability than a commercial SiC/SiC composite at temperatures above 500°C. In addition, results suggested that the sintered SiC fiber-bonded ceramic (SA-Tyrannohex) exhibited better mechanical performance than a Hi-Nicalon/MI SiC composite with BN/SiC fiber coating at temperatures above 1300°C.

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