Mechanical behaviour of polycrystalline TiC

Abstract

The mechanical behaviour of hot-pressed TiC was studied. Compacts were fabricated from commercially available TiC powders, which were found to contain impurities including iron, cobalt, silicon and free carbon. Those impurities segregated to the grain boundaries and formed low melting-point phases which degraded the high-temperature strength. Differences in the temperature at which strength began to fall sharply were correlated with differences in the impurity chemistry of the TiC starting powders. It was found that a high-temperature vacuum heat treatment of the as-hot-pressed TiC significantly reduced the levels of impurities at the grain boundaries. This, in turn, caused a dramatic improvement in high-temperature strength. The TiC, so treated, possessed a grain size of approximately 25μm and exhibited a D-B transition in bending at about 1425° C.