The mechanical behavior of the SiC layer in nuclear TRISO fuel particles

• EBSD and in-situ SEM nanoindentation are used to study deformation in TRISO SiC. • CVD 3C-SiC shows fine grains with high-angle boundaries and ∼ 37% Σ3 CSL boundary. • Lower loading rates produce measurable plasticity and higher misorientation fields. • MD simulations reveal a transition from dislocation slip to glide-limited plasticity. • Crack-free nanoindentation tests provided hardness and modulus. This study investigates the room-temperature deformation behavior of cubic silicon carbide (3C-SiC) crystals, a critical structural layer in tri-structural isotropic (TRISO) nuclear fuel particles. A combined experimental and computational approach is used. Electron backscatter diffraction is used to quantify initial microstructure, guide in-situ nanoindentation experiments conducted in a scanning electron microscope and determine the effects of nanoindentation on local orientation variations enabling direct correlation with the underlying deformation mechanisms. It is observed that the SiC layers are fine-grained and weakly textured, with a high fraction of high-angle grain boundaries. Nanoindentation experiments show high hardness of 47.36 ± 1.16 GPa, elastic modulus of 477.67 ± 13.05 GPa, and fracture toughness of 2.71 ± 0.13 MPa·m 0.5 . It is shown that the deformation response was rate-dependent, with non-negligible plasticity observed at slow loading rates and suppressed plasticity at high rates. Molecular dynamics simulations uncovered the mechanistic transition from dislocation-mediated slip and prismatic loop formation at low rates to glide-limited plasticity and local amorphization at high rates, depicting the rate dependent plasticity. By combining crack–free, rate–dependent nanoindentation with grain–resolved EBSD analysis and atomistic simulations, this study provides a unified framework linking the microstructure, local deformation mechanisms, and macroscopic mechanical response of the 3C-SiC layer.