Functionally gradient materials in the SiC-Ti3SiC2 system.

Functionally Gradient Materials (FGMs) present a new form of composite laminates characterised by a continuous distribution of constituent phases without macroscopic phase boundaries. Such materials possess very promising charcteristics especially mechanical, thermal and chemical resistance. The authors present a preparation method of the new ceramic multilayered composites obtained according to the FGM concept with controlled hardness and fracture toughness. The two different ceramic materials, namely a very hard silicon carbide and a relatively soft ceramics of a high fracture toughness based on Ti3SiC2 were joined in one layered composite. The materials were prepared by a powder metallurgy procedure with the use of a hot-pressing technique. The starting sinterable powders were made separately by the Self-propagating High-temperature Synthesis. Then, after an appropriate preparation, they were hot-pressed in a graphite mould in an inert atmosphere. Microstructure investigations and indentation tests showed the FGM structure with a hardness distribution.