Silicide–carbide composites obtained from alloyed melt infiltration

The development of a Cf/(Mo, Ti)Si2–SiC composite using melt infiltration technique was investigated. C/C preforms and also Cf-felts were infiltrated with an alloyed melt of Si, Ti and MoSi2. The amount of each element was selected so that the melting point of the alloy was lower than 1600 C. It was then possible to prevent the melt from reacting heavily with the carbon fibers and preserve their reinforcing effect in case of the C/C preforms. After infiltration no residual silicon could be detected in the matrix of the infiltrated C/C composites. The infiltrated C/C samples reached a maximum bending strength of 210 MPa at room temperature. At 1600 C there is even an increase in their bending strength to 250 MPa. Infiltrated felts showed monolithic and brittle characteristics. Their bending strength at room temperature was not higher than 150 MPa. Because of softening of the residual silicon, the strength of the infiltrated felts was reduced at high temperatures. The felt samples which were infiltrated with an alloyed melt showed higher mechanical strength than pure silicon infiltrated felts both at room temperature and at 1600 C.