Influence of an O2 Type Oxidizing Environment on SiCf/SiC Composites: Properties/Microstructure Relationship

International audienceCeramic matrix composites have been identified as a potential material of core structure for the IV th generation of fission nuclear reactors. Regarding its excellent mechanical behavior in very harsh conditions (high temperature and high irradiation flux), the CVI-SiC f /SiC composites with pyrocarbon interlayer are of prime interest for the fuel cladding in the Gas-cooled Fast Reactor (GFR). Although the working atmosphere is helium in these advanced reactors, presence of oxidizing impurities could have a significant role on the mechanical behavior of materials for a long time exposure. Within this framework, this study is intended to investigate the influence of oxidation on the SiC f /SiC composites mechanical properties. Different pre-damage states were intentionally operated by mechanical tensile tests on plate specimens before performing an oxidation treatment of 1000 hours at 1000°C under helium with 10 ppm of O 2. The degradation of the composite was determined from the mechanical behavior of post-exposure specimens. Results were correlated both with microstructural observations of the damaged tows and with characterizations of the generated oxides at the surface of the composites. The most severe decline of mechanical properties occurs for the higher predamaged loadings. A degradation mechanism, depending on the damage state, is proposed to explain the mechanical behavior change in accordance to the different examinations