Microstructural and physical properties of titanium nitride coatings produced by CVD process

The effects of CVD deposition variables such as temperature, H2, N2 and TiCl4 concentrations on deposition rate, lattice parameter, grain size, surface morphology, surface roughness, hardness and adherence of TiN coatings on tungsten carbide substrates were investigated. The results indicated that the kinetics of chemical reaction on the surface was the controlling mechanism for the deposition process. By decreasing nitrogen and increasing hydrogen concentrations the deposition rate increased. The deposition rate increased by increasing TiCl4 up to about 2.1%. By raising the amount of hydrogen and lowering the amount of TiCl4 in the system, the film became more uniform, denser and harder. TiN lattice parameter decreased by increasing temperature. In general, increasing nitrogen and decreasing hydrogen caused an increase in the lattice parameter. TiN grain size decreased by increasing temperature and nitrogen concentration. The surface morphology was found to be sensitive to the deposition parameters and the growth feature changed from equiaxed grains to columnar structure to powdery and flaky-type deposit. The coating roughness, adherence and hardness were closely related to the microstructural properties of the surface influenced by the deposition conditions.