Irradiation creep of high purity CVD silicon carbide as estimated by the bend stress relaxation method

The bend stress relaxation technique was applied for an irradiation creep study of high purity, chemically vapor-deposited beta-phase silicon carbide (CVD SiC) ceramic. A constant bend strain was applied to thin strip samples during neutron irradiation to fluences 0.2-4.2 dpa at various temperatures in the range ∼400 to ∼1080 °C. Irradiation creep strain at <0.7 dpa exhibited only a weak dependence on irradiation temperature. However, the creep strain dependence on fluence was non-linear due to the early domination of the initial transient creep, and a transition in creep behavior was found between ∼950 and ∼1080 °C. Steady-state irradiation creep compliances of polycrystalline CVD SiC at doses >0.7 dpa were estimated to be 2.7(±2.6) × 10^-7 and 1.5(±0.8) × 10^-6 (MPa dpa)^-1 at ∼600 to ∼950 °C and ∼1080 °C, respectively, whereas linear-averaged creep compliances of 1-2 × 10^-6 (MPa dpa)^-1 were obtained for doses of 0.6-0.7 dpa at all temperatures. Monocrystalline 3C SiC samples exhibited significantly smaller transient creep strain and greater subsequent deformation when loaded along 〈0 1 1〉 direction.