Kinetics of liquid metal infiltration in TiC-SiC or SiC porous compacts

Abstract

TiSi2/SiC composites are promising materials for high temperature applications. The synthesis of these composites by metal infiltration is an interesting method that is not still mastered. This study aims at identifying the thermodynamic and kinetic processes involved during the synthesis of TiSi2/SiC composites by capillary infiltration of liquid silicon or Si-Ti molten alloys in porous compacts. Three cases were examined to produce dense TiSi2/SiC materials: 1) the infiltration of molten TiSi2 in pure SiC compacts at 1550 °C, 2) the reactive infiltration of the molten eutectic Ti0.16Si0.84 alloy in SiC + TiC compacts at 1380 °C, and 3) the reactive infiltration of pure liquid silicon in SiC + TiC compacts at 1450 °C. The effect of a TiC excess was considered for each reactive case. The infiltration kinetics and the filling percentage were measured from the monitoring of the weight gain increase. The decisive role played by thermodynamics on the infiltration progress is confirmed. It induces the dissolution and diffusion of Ti atoms from TiC which results in the presence of free silicon in the infiltrated areas. Excess content of TiC is not found favorable to the infiltration. This original study based on thermodynamic calculations and kinetic measurements at high temperatures provides decisive results for a complete understanding and improvements of the examined processes.