Microstructure and tribological properties of MoS2+Zr composite coatings in high humidity environment

Abstract

MoS2+Zr composite coatings with different Zr contents and their pure MoS2 counterparts were deposited on silicon wafers and steel substrates by closed field unbalanced magnetron sputtering system. The microstructure, mechanical and tribological properties of as-prepared coatings were systematically investigated using a number of analytical techniques and the effect of different Zr contents on tribological behaviors in humidity conditions of these as-deposited composite coatings was discussed. It is clearly uncovered from the present results that the MoS2+Zr composite coatings were amorphous nature embedding some nanocrystallites. Doping of MoS2 coatings with Zr can remarkably improve the mechanical and tribological properties of pure MoS2 coating in high humidity (68% RH) environment, rendering the coefficient of friction (COF) decreases with increasing Zr content. Additionally, MoS2+Zr composite coatings exhibit much more stable and lower friction coefficients with increasing applied load. The lowest friction coefficient of as-deposited MoS2+Zr composite coating was about 0.04 with an applied load of 20N (at 68% RH), where the friction coefficient of pure MoS2 coating was around 0.7. The improved tribological property of the MoS2+Zr composite coatings in high humidity environment was discussed in terms of the obtained lower friction coefficient, higher hardness and better adhesion of the composite coatings combined with inhibition of MoS2 oxidation.