Effect of a Ti interlayer on TiN thin films grown on glass substrates as surrogates for PVD-coated natural rocks

Physical-Vapor-Deposition-Coating of a cutting tool with TiN can improve the tool's overall performance during operation. For a prolonged tool life, the coating's adhesion is essential, which depends on chemical, physical, and mechanical interactions. The general feasibility of coating natural rocks with TiN has already been shown. However, the adhesion solely relies on mechanical interlocking. To investigate the effect of differently deposited Ti interlayers on the chemical interaction, glass substrates with a comparable chemical composition but extremely low surface roughness, which prevents mechanical interlocking, were chosen as a surrogate. The Ti interlayers are deposited with a constant dc-bias voltage and a pulsed dc-bias voltage with varying frequencies. Here, the thin films and their structural and mechanical properties are analyzed and discussed in depth. The microstructural analysis reveals strong textured Ti interlayer with a growth direction in {001} and {101} and a strong {111} texture in TiN top layer. The residual stress states in the thin film system correlates with the thermal expansion of the substrate material and the Ti interlayer. Ti-TiN thin film systems achieve the highest hardness on quartz glass with 20 GPa, whereas the coating on borosilicate glass is slightly lower. The Ti interlayer has a positive effect on adhesion, although pulsed variants do not adhere to window glass. • Extremely low hardness of 6 GPa of TiN with constant bias voltage on window glass • Highest TiN hardness on quartz glass achieved with pulsed bias voltage of 10–40 kHz • Compressive stresses on window, tensile stresses on quartz and borosilicate glass • Positive effect on adhesion of Ti interlayer on quartz and borosilicate glass • Ti-TiN thin films deposited with pulsed bias voltage delaminates on window glass