TiB2 coatings deposited via High Power Impulse Magnetron Sputtering

Titanium diboride (TiB2) is a versatile high potential material for thin film applications due to its high strength, melting point and conductivity. It crystallizes in the hexagonal AlB2 type structure, where close-packed Ti layers are interleaved by B atoms, which are arranged in a honeycomb pattern. The crystal orientation of TiB2 coatings is essential for the film properties, including hardness. Indeed, the highest hardness values (H > 40 GPa) are reported for (001)-textured films and therefore such orientation is highly desired. There are several studies of magnetron sputtered TiB2 coatings in the literature. Depositions are generally performed using TiB2 compound targets and often result in overstoichiometric coatings, i.e. B/Ti > 2. Coating microstructure and hence properties are heavily influenced by the sputtering parameters. This study is devoted to deposit stoichiometric boride layers and to investigate the influence of HiPIMS frequency, substrate temperature and bias on the resulting microstructure and mechanical properties.