Intrinsic stress and preferred orientation in TiN coatings deposited on Al using plasma immersion ion implantation assisted deposition

TiN coatings were deposited on Al substrates using the plasma immersion ion implantation and deposition (PIIIAD) technique, employing a filtered Ti cathodic arc in a nitrogen atmosphere. Negative pulsed bias voltages between 0 to −4.0 kV were applied with varying duty cycles, at a constant time-averaged bias. Stress measurements using X-ray diffraction reveal an increase and then a decrease in the intrinsic compressive stress at increasing on-time bias. A bias-dependent preferred orientation of TiN is observed, i.e. {111}, {200} and {220} at low bias and predominantly {200} at higher bias. The hardness reduces from 29 GPa at lower bias to 20 GPa at higher bias. Thus, the time averaged energy of ion bombardment does not uniquely determine the properties of the growing coating, which can be adjusted by the on-time substrate bias applied for very short durations. A simplified subplantation model of stress development is formulated for the case of pulsed bias, the predictions of which are in reasonable agreement with the experimental data.