High hardness is an very important features of TiN films, and high hardness will correspond to good wear resistance. The arc source current has a great influence on the hardness of the film. Figure 1 shows the hardness variation rule of TiN films at different arc source currents. It can be seen that the hardness of the TiN film increases with the increasing of arc source current. The hardness of the TiN film prepared at an arc source current of more than 80 A exceeds HV2000.
Fig. 1 Relationship between hardness of the TiN film and arc source current
The temperature of the substrate affects the growth structure of the film and thus affects its performance. When the temperature is low, the structure of the thin film is a relatively large columnar crystal structure. This structure is rather rough with low density and lots of the hole defects, so the hardness of the film is low. With the increasing of the arc source current, the temperature of the substrate also increases, and the diffusion of atoms that deposited on the substrate is accelerated, so the film structure transforms from a looser and coarser columnar structure to a denser and smaller columnar crystal structure. At the same time, the grains become finer and the grain boundary strengthens the film, so the hardness of the film increases.