Degradation of TiB2/TiC Composites in Liquid Nd and Molten NdF3–LiF–Nd2O3 System

Abstract

The degradation of titanium diboride (TiB2)/titanium carbide (TiC) composites in the liquid Nd and molten NdF3–Nd2O3–LiF salts is investigated at 1,060 °C, respectively. The penetration of TiB2/TiC composites by liquid Nd mainly depended on the grain boundaries and residual pores, even if the coherent interface is formed between TiB2 and TiC. The oxidation of TiB2 led to further interfacial chemistry reactions, which speeded up the degradation of TiB2/TiC composites at the initial stage in NdF3 –LiF–Nd2O3 system. After that, the degradation was slowed because of the formation of diffusion boundary layer, and then chemical penetration was replaced gradually by the physical penetration. The dissolved Ti in liquid Nd and NdF3–LiF–Nd2O3 melts are used to evaluate the corrosion rate of TiB2/TiC composites, and the calculated values were about 0.56 and 7.8 mm/year, respectively. After the penetration by liquid Nd and NdF3–LiF–Nd2O3 melts, the bending strengths of TiB2/TiC composites decreased and the fracture mode changed from transgranular to intergranular due to the decreased grain boundary force.

Keywords

• tib2/tic composites
• grain boundary
• penetration
• fracture mode
• corrosion rate