Adhesion and fatigue properties of Ti/TiB2/MoS2 graded-composite coatings deposited by closed-field unbalanced magnetron sputtering

In this study, Ti/TiB2/MoS2 graded-composite coatings were deposited by the closed-field unbalanced magnetron sputtering (CFUBMS) technique. The structural properties of the Ti/TiB2/MoS2 graded-composite coatings were analyzed by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the hardness of the coatings was measured using a microhardness tester. The adhesion and fatigue properties of the coatings were evaluated via a scratch test in two modes. A sliding-fatigue multimode operation was used that involved multi-pass scratching in the same track at different fractions of the critical load (unidirectional sliding), and a standard mode with progressive loading was also utilized. Failure mechanisms are discussed according to microscopic image examinations of the scratch tracks. The Ti/TiB2/MoS2 graded-composite coatings have a dense and non-columnar structure. The X-ray diffraction patterns of coatings exhibited predominantly MoS2 (002) and TiB2 (100) reflections. The target currents significantly affected the thickness and hardness values of coatings. The adhesion and fatigue resistance of coatings improved with increases in hardness and thickness and with decreased Ti/Mo and S/Mo ratios.