Sandwich Structure to Enhance the Mechanical and Electrochemical Performance of TaN/(Ta/Ti)/TiN Multilayer Films Prepared by Multi-Arc Ion Plating

TaN/(Ta/Ti)/TiN multilayer films at various target to substrate distances (dts), composed of hexagonal TaN, (t-Ta/fcc-Ti) and fcc-TiN with a sandwich structure, were prepared via multi-arc ion plating. With increasing dts, the deposition rate of the films first increased and then decreased, and the average grain size increased from 11.9 to 13.9 nm and then decreased to 10.4 nm. The TaN/(Ta/Ti)/TiN multilayer films have a high ratio of hardness to elastic modulus (H/E*) and H3/E*2 ratios, displaying an outstanding level of both hardness and toughness compared with Ta-related films. The nano-multilayer TaTi interlayers inhibited the columnar structure and prolonged the corrosion diffusion path by increasing stable interfaces. The TaN/(Ta/Ti)/TiN multilayer film at dts = 220 mm exhibited comprehensive properties, including a high hardness of 25 GPa, strong adhesion strength of 68 N, low coefficient of friction of 0.41, low wear rate of 2.7 × 10−6 mm3(mN)−1 and great corrosion resistance in 3.5 wt% NaCl solution, showing promising application as a protective coating.