J. Phys. IV France 02 (1991) C2-649-C2-655
FABRICATION AND EVALUATION OF SiC/C FUNCTIONALLY GRADIENT MATERIALM. SASAKI and T. HIRAI
Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980, Japan
A plate-like deposit having a compositional gradient from carbon (C) to silicon carbide (SiC) (SiC/C FGM) was obtained on a graphite substrate with chemical vapour deposition (CVD) by changing the Si/C molar ratio in input gas during deposition. Cracking due to heat flux was investigated using a CO2 laser setup. Heat flux which resulted in cracking in SiC-coated graphite (SiC NFGM) was 5.8 MWm-2 at a surface temperature (Ts) of 1300 K and a reverse surface temperature (Tb of 1220 K. In the case of SiC/C FGM, heat flux occurred cracking was 7.4 MWm-2 at a Ts of 1650 K and a Tb of 1080 K. The temperature difference between Ts and Tb was 570 K in FGM and 80 K in NFGM. Thermal stress calculation showed that in cracking caused by hoop stress, the stress was close to the fracture strength of SiC. It was clear that SiC/C FGM has effective thermal shock resistance and thermal barrier characteristics.
© EDP Sciences 1991