Effects of the target-to-substrate distance on the microstructure and properties of TiN coatings fabricated by pulse-enhanced vacuum arc evaporation

Pulse-enhanced vacuum arc evaporation (PEVAE) is promising in surface engineering and produces coatings with better structure and properties. In PEVAE, the target-to-substrate distance (Dt-s) affects the substrate ion current and ion bombardment energy which is closely related to the structure and properties of the coatings. In this work, TiN coatings are deposited on high-speed steel (HSS) and silicon plates by the traditional DC mode and PEVAE mode at various Dt-s and the substrate current, microstructure, morphology, mechanical properties, and corrosion resistance are evaluated. The results show significant improvements of 42.8%, 33%, and 51.6% for the average substrate current (IAve.), ion bombardment energy (Ebi), and deposition rate (ad) in the PEVAE mode and as Dt-s is increased, IAve., ad and Ebi decrease less substantially compared to the DC mode indicating that TiN coatings are still bombarded by more ions despite a larger Dt-s. The hardness and wear rate (WR) in the PEVAE mode increase by 41.4 and 56.1%, respectively, and the corrosion resistance and adhesion strength are improved as well. When Dt-s is increased, the hardness and corrosion resistance decrease and WR increases in both modes but the effects are less significant in the PEVAE mode.