Mechanical properties of homogeneous and nitrogen graded TiN thin films

Coating of metallic industrial parts with titanium nitride (TiN) is widely used with the aim to improve the mechanical and tribological properties of these parts. In the present work, TiN films were deposited via grid-assisted magnetron sputtering on aluminium substrates. The films were grown under different substrate bias voltage (-40, -75 or -100 V) and two different modes of nitrogen supply during deposition (constant and variable), resulting in homogeneous and N-graded films. The results of tension fractures observed in situ were correlated with the film microstructure and residual stress levels obtained through grazing incidence X-ray diffraction measurements. Elastic properties of the films were analysed via nanoindentation and adhesive properties were investigated by nanoscratching tests. Results show that the delamination load of the graded films is higher than in the homogeneous counterparts, suggesting the graded film have improved tribological properties.