Microstructure and thermal conductivity of Mo-TiC cermets processed by hot isostatic pressing

In the scope of refractory material development for structural applications in the core of future nuclear reactors (gas fast reactors working between 500 degrees C and at least 800 degrees C in nominal conditions and up to 1650 degrees C in accidental scenarios), five Mo-TiC cermets, and single-phase TiC and Mo, were processed by hot isostatic pressing. Starting TiC volume contents were 0%, 12.5%, 25%, 37.5%, 50%, 75% and 100%. First, high dense specimens were characterized in terms of microstructure, composition and phase volume fractions. Cermets exhibited two phases in agreement with phase diagram previsions (Mo-TiC1-2at.% and TiC-Mo10-15at.%), and a residual non-reacted TiC-rich phase (TiC-Mo-1at.%). Second, heat capacity and thermal diffusivity were measured up to 1000 degrees C which allowed to evaluate the thermal conductivity of each cermet: this lays between TiC conductivity (12-18 W/m K) and Mo, conductivity (95-125 W/m K), thermal properties continuously decreasing with starting TiC content. An analytical approach based on the volume fraction and properties of each constituent allowed to highlight the existence of thermal resistance at the interphases at low temperature. (C) 2008 Elsevier B.V. All rights reserved.