Synthesis of a (MoSi2, Mo5Si3)/SiC composite using an in situ solid-state displacement reaction between Mo2C and Si

The intermetallic compound, MoSi2, has great potential as an elevated-tempe rature structural material but it exhibits some undesirable properties such as low fracture toughness and low strength at elevated temperatures. Impro vement of these properties can be achieved by reinforcing MoSi2 with the ad dition of SIC particles or whiskers, or by alloying it with Mo5Si3. The pre paration of MoSi2 composites from powders gives rise to an oxidation proble m since SiO2 covers the raw powder. To avoid this problem, the material mus t be prepared in situ, In this work, multiphase composites based on the Mo- Si-C system have been prepared using a solid-state displacement reaction be tween Mo2C and Si. Samples were prepared from a mixture, containing differe nt proportions of Si and Mo2C powders, which was pelletized under vacuum at 40 MPa and heat-treated in argon, The pieces obtained exhibit different pr oportions of SiC, MoSi2 and Mo5Si3 The microhardness obtained ranges from 1 2 to 14 GPa, and K-c is over 8 MPa.m(1/2), which is higher than that of pie ces made of MoSi2 only.