Bias–induced energy engineering of Ta– and Y– doped TiAlN coatings: linking densification, residual stresses and tribological performance

Controlling the energetic conditions during PVD growth is critical for tailoring the structure–stress–property relationships of advanced TiAlN–based coatings intended for severe tribological and machining environments. The influence of substrate bias voltage (−60, −90 and –135 V) on the microstructural evolution, residual stress development and tribo–mechanical response of TiAlTaN and TiAlYN coatings deposited by reactive DC sputtering was investigated. Increasing negative bias enhanced ion bombardment and atomic peening, promoting grain refinement, coating densification and smoother morphologies. Simultaneously, compressive residual stress increased between 2.88 and 4.32 GPa for TiAlTaN and between 2.12 and 3.17 GPa for TiAlYN due to intensified energetic growth conditions. The results demonstrated that residual stress alone does not govern coating performance. TiAlTaN coatings developed higher compressive stresses but limited hardness improvement, whereas TiAlYN coatings showed superior structure–property synergy and resistance to plastic deformation. The TiAlYN coating deposited at –135 V showed the best overall mechanical and tribological performance. The Y-containing coating architecture promoted a more efficient conversion of ion-bombardment-induced energy into enhanced mechanical and tribological performance. The combined analysis of microstructure, residual stress and tribological behavior established a bias–driven structure–property framework, highlighting distinct strengthening and stress accommodation mechanisms in TiAlN–derived coatings for advanced wear–resistant applications.