C. Garcia-Rosales, A. Muniategui, University of Navarra, San Sebastian (Spain); I. López Galilea (Sp),
CEIT & TECNVN (University of Navarra), San Sebastian (Spain)
Carbon-based materials are attractive materials for aerospace applications due to their light weight, thermal
stability and excellent thermomechanical properties. However, their application is limited by oxidation, if no
protective surface coating is applied when exposed to oxidizing atmospheres at high temperatures. The addition
of B4C and SiC is known to supply an effective self-passivating barrier against carbon oxidation at high
temperatures due to the formation of a glassy coating consisting of B2O3, SiO2 and B2O3-SiO2. The ratio
SiC/B4C and the amount of SiO2 and B2O3 formed during the oxidation process are the most important factors
affecting the inhibition of carbon oxidation, since the volume of oxides generated must be enough to cover
completely the surface. This protection would make feasible the use of carbon-based materials for aerospace
applications.
The aim of this work is to improve the oxidation and thermal-shock resistance of fine-grained isotropic graphite
by adding finely dispersed B4C and SiC particles to two different carbon precursors. Particle size and amount of
carbides were varied to study their effect on oxidation resistance and final thermomechanical properties.
The oxidation behavior was analyzed by TG/DTA at temperatures up to 1400ºC and the resulting composition and
microstructure of the protective coating was characterized by XRD and SEM analysis. In addition, the thermal and
mechanical properties were measured. First results let assume that SiC-B4C/C composites with a self-passivating
effect against oxidation are promising materials for operation under oxidizing atmospheres and high
temperatures, as are present in aerospace applications.