Effects of substrate bias on structure and mechanical properties of (TiVCrZrHf)N coatings

(TiVCrZrHf)N coatings were deposited via reactive radio-frequency (RF) magnetron sputtering at different substrate biases (0 to 200 V). The chemical composition, microstructure, and mechanical properties of the coatings were investigated. As the substrate bias increased, the preferred orientation of the (TiVCrZrHf)N coatings changed from (111) to (200). Reduced grain size and surface roughness were also observed. The microstructure obviously changed, from a V-shaped columnar structure with clearly faceted surface features to a highly dense structure with a very smooth surface. Moreover, a continuous variation in the microstructure, from randomly oriented nanograins to columns with a face-centered cubic (FCC) phase, was evident. The hardness of the coatings deposited at 100 V or higher was around 32–33 GPa. The structural evolution and strengthening mechanism of the coatings were also discussed.