Influence of substrate stiffness and of PVD parameters on the microstructure and tension fracture characteristics of TiN thin films

Titanium nitride is widely used as wear resistant coating thin films in industrial parts. Mechanically they correspond to nanometric 2D ceramic systems which are bound to a much thicker metallic substrate. Under uniaxial tension these films respond by forming a periodic array of cracks. The separation between the cracks is primarily defined by the strength and stiffness of the film. Secondary factors, as the elastic properties of the substrate, or the microstructure and/or induction of residual stresses during processing may also have and effect. In the present work PVD TiN films were deposited by triode magnetron sputtering in Brass and Aluminum substrates. The deposition characteristics of the films were varied by changing the bias potential and the nitrogen supply during deposition (constant or variable). Tension fractures were observed in situ using a traveling microscope and under nanoindentation/scratching tests. Energy Filtered TEM was used to access the nitrogen levels across film thickness. The results were correlated with the film residual stress levels obtained in the different deposition conditions. (C) 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers.