Development of Mo-TiC cermets for future nuclear systems

Mo-TiC cermets are considered to form the structure pieces of some future nuclear systems. Five composites whose TiC amounts range between 12.5% and 75% in volume have been densified by hot isostatic compression. Microstructural observations, images analyses and thermal diffusivity measurements have been carried out. The samples contain three phases: a metallic phase (mainly Mo), a composite carbide interphase (Mo, Ti)C and a residual TiC phase. Annealings of 20 h at 1000 C, 1600 C and 1800 C lead to a progressive suppression of the TiC phase and a decrease of the quantity of the metallic phase in agreement with the formation of the composite carbide (Mo, Ti)C. The thermal diffusivity measurements reveal the sudden decrease of the conduction properties of the material with the amount of TiC until a stabilization from 50% of TiC. The annealing at 1800 C leads to a supplementary decrease of the diffusivity due to the weaker quantity of metallic phase and to the appearance of porosities. (O.M.)