Nondestructive testing and analysis of SiC coating on surface of C/SiC composites after oxidation with Micro CT

The SiC coatings on the surface of C/SiC composites which were annealed in the dry and wet oxidizing environment at 1300°C for 60 h were examined nondestructively using X-ray microtomography (Micro CT). The oxidation morphology along the coating surface and depth direction was investigated by reconstructing images of different depth SiC coatings assisted with SEM, EDS and XRD. The results demonstrate that Micro CT is applicable to distinguish the oxidation products of SiO₂ in the SiC coating and the oxidation depth. Oxidation products SiO₂ along the SiC coating surface and depth direction is non-uniform distribution. With increasing depth of the coating, the oxidized area percentage of the coating decreases in the dry oxidizing environment; and first increases and then decreases in the wet oxidizing environment. The different oxidation mechanisms of SiC coatings in the dry and wet oxidizing environment are confirmed by Micro CT.