Irradiation creep of advanced silicon carbide fibers

The bend stress relaxation (BSR) method was applied to study irradiation enhanced creep (IEC) of small diameter silicon carbide (SiC) fibers after 10 MeV proton irradiation. A first series of tests was conducted on Sylramic™ fibers irradiated at 600°C with average bending stresses of 400 and 667 MPa and for irradiation doses smaller than 0.04 dpa. The BSR results are compared to previously obtained torsional creep test results for the Textron SCS-6™ type SiC fibers by calculating the tensile equivalents for both testing methods. For the Sylramic fibers, the creep constant κ=4.7×10−6 Mpa−1 dpa−1, was a factor of 6 smaller than the κ-value determined for SCS-6 fibers at 600°C. In contrast, for T<900°C the κ-value determined by R.J. Price [Nucl. Technol. 35 (1977) 320] for high purity monolithic β-Si after 7.7 dpa neutron irradiation was only 0.4×10−6 MPa−1 dpa−1.