Functionally graded TiC-based cermets

A well-known approach for manufacturing ceramic-metal composites is based on infiltration of a ceramic preform by a molten metal. The particular properties of the TiC_x-M system (M is an infiltrating metal) allow to follow two different strategies in order to generate functionally graded structures. According to the first approach a graded distribution of porosity is generated in the carbide preform by taking advantage of the dependence of the sinterability on the carbon content (x). Liquid metal infiltration generates a varying ceramic-to-metal ratio and a concurrent property profile. According to the second approach, a pre-designed spatial carbon variation in a TiC_x preform generates a corresponding affinity variation towards an infiltrating carbon containing molten alloy, e.g. a carbon steel. By appropriate heat treatments and as a function of the carbon content, one can induce significant variations and produce pre-designed property profiles in the metallic component and, thence, in the ceramic-metal composite. Examples will be put forward in order to illustrate the two approaches.