Structural and textural evolution of CVD-SiC to indentation, high temperature creep and irradiation
Résumé
The structure and microtexture of different SiC based CVD coatings have been studied by RMS, in their as-processed state and after high temperature annealing, creep, indentation and irradiation. Both annealing and creep resulted in the same degree of SiC crystal growth and decrease of stacking faults. A slight influence of stress was however observed on the structure and texture of the co-deposited free-carbon, supporting an intergranular creep mechanism. Room temperature indentation induces substantial structural disorders (dislocations, stacking faults, small grains) near the contact and more extended damages due to dislocation slip parallel to the compact Si-C planes. These structural changes were found to depend on the single crystal orientation and therefore, on the texture of polycrystalline SiC. Room temperature proton irradiation produced only small amounts of disorders. The specific alterations of the Raman features were explained using a phonon confinement model. They support very low scale defects, likely as punctual defects.