Structural and mechanical properties of IBAD deposited nanocomposite Ti–Ni–N coatings

TiN–Ni films (∼ 0.5 μm thick) were deposited on (100) Si wafer and 304L stainless steel, using an ultrahigh vacuum dual ion beam sputtering technique, in order to obtain nanocomposite films with nanograins of TiN surrounded by an intergranular Ni/NiTi metallic/intermetallic phase. A composite Ti–Ni target was sputtered with 1.2 keV Ar+ ions and the growing film was bombarded with a mixture of 50 eV Ar+–N2+–N+ ions during deposition. The Ni content and temperature were varied from 0 to 22 at.% and 25 to 400 °C, respectively, to get optimum structural and mechanical properties. Coating composition was obtained from RBS analysis. Phases, grain size, and texture of the coatings were determined by XRD in the θ–2θ and GIXRD geometries; TiN was the only crystalline phase observed. The grain size, which was calculated using the Scherrer equation from the (200) peaks, decreases from 16 to 4 nm as the Ni content varies from 0 to 22 at.%. A texture evolution of TiN crystallites from (111) to (200) was observed when increasing the temperature and the Ni concentration. Nanoindentation tests indicate that the hardness of the coatings is around 40 GPa. The hardness slightly increases with the Ni concentration and the maximum value roughly corresponds to an intergranular distance of 0.5 nm.