HOT-PRESSING OF TIC-GRAPHITE COMPOSITE-MATERIALS

Monolithic TiC and TiC-graphite composites were hot-pressed at temperatures ranging from 1800 to 2100-degrees-C and with graphite contents up to 30 wt%. Densification behavior was compared for both monolith and composites based on results of microstructural observation and mechanical tests. Monolithic TiC was well densified at the hot-pressing temperature of 1800-degrees-C; significant grain growth and an accompanying decrease in the flexural strength occurred with an increase in hot-pressing temperature. Conversely, the 10 wt% graphite-containing TiC composite required higher temperatures (1900 to approximately 2000-degrees-C) to reach a similar degree of densification approaching that of monolithic TiC. As with densification, flexural strength of the composite increased with an increase in hot-pressing temperature. Graphite dispersions in the composites inhibited grain growth of TiC. Contrary to the equiaxed nature of the monolithic TiC grains, in the composite system, the graphite grains were flattened to thin platelets that aligned perpendicular to the hot-pressing axis. Apparent anisotropy in the microstructure was observed in the composites. At a fixed hot-pressing temperature, the relative density of the composites decreased with increasing graphite content.