Influence of gradient interlayer thickness on corrosion and tribological behavior of Ti-containing multilayer graphite-like carbon films

Abstract

Structural design is a crucial strategy to improve the service performance of amorphous carbon films in aggressive environments. In this study multilayered graphite-like carbon (GLC) films with adhesive layer/gradient interlayer/doping layer architectures with varied gradient interlayer thickness were deposited on 316L stainless steel substrates by closed field unbalanced magnetron sputtering. The effect of gradient interlayer thickness on microstructure, mechanical, tribological and corrosion behavior of the GLC films was investigated. The results show that the mechanical properties and bonding strength decrease with increasing gradient interlayer thickness due to the increased sp2 content, surface roughness and decreased film integrity. The friction coefficient curves in ambient air and 3.5% NaCl solution show similar three-stage feature with distinctive wear mechanism in stage III. The decreased mechanical properties and loose microstructure of GLC films with thicker gradient interlayer thickness caused the decreased wear resistance in both ambient air and NaCl solution. In comparison with the uncoated substrate, the GLC films show improved corrosion resistance in NaCl solution, which also decreases with the increased gradient interlayer thickness due to the low film compactness and high electrical conductivity.