Microhardness of non-stoichiometric TiC x, plates prepared by chemical vapour deposition

Abstract

The relationship between Vickers' microhardness and non-stoichiometric composition of titanium carbide (TiC x ) plates was investigated. TiC x plates having a composition range from x = 0.57 to 1.0 were prepared by chemical vapour deposition using TiCl 4, CCl 4 and H 2 as source gases at total gas pressures ( P tot) of 4 and 40 kPa and deposition temperatures ( T dep) of 1573 to 1873 K. The microhardness increased from about 2000 to 3000 kg mm −2 with increasing x independent of T dep , but this change depended on P tot. The TiC x plates prepared at P tot = 4 kPa showed slightly higher hardness values than those prepared at P tot = 40 kPa. The relationship between P tot and microhardness was explained by the difference in grain sizes. The grain sizes of deposits prepared at P tot = 4kPa were about half the size of those prepared at P tot = 40 kPa.