Joining Silicon Carbide Plates by Titanium Disilicide-Based Compound

International audienceThe present work describes the methodology and the results for joining SiC substrates in the solid state by reactive and non reactive metallic silicides in order to use these materials as container for the Gas Fast Reactor. The operation temperatures are in the range of 1000°C but short time incursions at 1600 or 2000°C have to be anticipated. As joining material, we have chosen to study four titanium and niobium silicides : TiSi 2 , NbSi 2 (non reactive with SiC), Ti 5 Si 3 and Nb 5 Si 3 (reactive with SiC) in order to modify the joint/substrate bonding. The joining between these silicides and the silicon carbide substrate was prepared by Spark Plasma Sintering in order to limit the contact time during the sintering. Post thermal treatments in the solid state performed under a controled atmosphere have been carried out in order to study the thermal stability of the assembly. Polished cross sections were prepared to study the interface composition, the cracking path in the vicinity of the joint/substrate interface. In order to decrease the residual stresses within the joint, SiC particles were mixed with the silicides powders. In the case of the non reactive silicides, the SiC particles effectively reduce the cracks whereas for the reactive silicides, the SiC particles react with the joint leading to a thermally stable composition and an improved bonding to the substrate. In order to prepare the joining technology, few trials of local heating have been investigated with a CO 2 laser beam. The advantage of local heating is the possibility to heat at high temperature (around 1800°C) for short time without damaging the composite structure. Thermal measurements have been done from one side to the other of the silicon carbide plate