Columnar growth of TiN coatings on HSS substrates

The TiN film widely applied as a wear resistant coating can grow with various preferred orientations and morphology of columnar grains. It has been shown that, when grown on HSS substrate, the TiN polycrystalline coating has columnar structure in a wide range of magnetron sputter ion plating deposition process parameters. The size and shape of columns as well as the column´s boundary are strongly dependent on the flux and energy of bombarding particles, but in all cases the mean radius of circular columns increases during the film growth. This effect is more pronounced without any bias or additional source for intensifying gas discharge around the substrate. The theory based on the minim film surface energy as the driving force for the columns evolution can describe the mean column radius increase but not the existence of preferred film orientation different than (111) in the case of f.c.c. crystal structure. The theoretical predictions of the increase of the mean column radius were verified for the case of the TiN grown onto HSS substrate.