Microstructure, adhesion, mechanical and corrosion properties of TiN coatings deposited by high energy pulse-enhanced vacuum arc evaporation

Abstract

Pulse-enhanced vacuum arc evaporation (PEVAE) which combines pulsed and direct current operation of the arc source is a new method in cathodic arc evaporation technology. One advantage is to emit large amount of electrons which leading to more ionization of gas and metal. In this work, microstructure, adhesion and properties of TiN coatings related to substrate ion current and deposition energy Ebi at different nitrogen pressure were investigated. The experimental results revealed that compared to DC mode the substrate current and energy Ebi during PEVAE process were increased by 111 and 40.0% at most inducing denser morphology, a little bigger crystal size and much higher compressive stress which was related to the enhancement effect of the high pulse current on electron emission. Hardness values of TiN coatings were increased up to about 36–38 GPa. Adhesion of the coating was substantially improved with critical load 100 N and adhesion class HF 1 in scratch test and indentation test, respectively. This is due to denser morphology, higher H/E and H3/E2 ratios and less defects caused by higher substrate ion current and Ebi. The resistance to electrochemical corrosion and high-temperature oxidation and wear performance were also substantially improved because of the denser structure and higher H3/E2 ratio. In spite of changes in the nitrogen pressure, less changes had taken place in the microstructure and properties of the TiN thin coatings deposited by PEVAE than those prepared with the DC mode.