Microstructure, mechanical and tribological properties of multilayer Ti-DLC thick films on Al alloys by filtered cathodic vacuum arc technology

Abstract Low hardness and poor wear resistance are major limitations of Al alloys, which hinder their application in several applications, especially automotive moving parts. DLC can effectively improve hardness and wear resistance of Al alloy, but high residual stress and poor adhesion limit the film thickness. Multilayer thick films (~10 μm) composed of alternating Ti and Ti-DLC layers were successfully deposited on Al alloys. The influence of the Ti content on the microstructure, mechanical and tribological properties of the films were emphasized. As the Ti content decreases from 10.42 to 1.35 at.%, the microstructure evolved from polycrystalline composite film to nanocrystalline composite film, and then to amorphous film. The mechanical and tribological properties of the films depend on the microstructure. The amorphous composite films (Ti > 6.06 at.%) exhibited more excellent wear resistance than polycrystalline composite films (Ti  0.1) than. H3/E⁎2 (>0.2) and elastic recovery (>60%). When the doped Ti content was 6.06 at.%, the nanocrystalline composite multilayer film showed superior comprehensive performance of high hardness (~23 GPa), high elastic recovery (~69%), low friction coefficient (~0.13) and low wear rate (1.0 × 10−7 mm3/Nm).