Effect of Modulation Periods on the Mechanical and Tribological Performance of MoS2–TiL/MoS2–TiH Multilayer Coatings

Ping Zhang,Tao Yang,Tianle Wang,Changhong Lin,Yihang Fang,Jianbo Wu,Vladimir Levchenko,Puyou Ying,Min Huang

doi:10.3390/coatings11101230

Abstract

MoS2–Ti coating is a widely used solid lubricant owing to its low friction coefficient. The mechanical and tribological performance of the coating can be further improved via introducing a multilayer structure, which is closely related to the modulation period and significantly affects the properties of the coating. Herein, the effect of two different modulation periods on the mechanical and tribological performance of the MoS2–TiL/MoS2–TiH multilayer coatings (where L and H represent low and high-powered sputtering of the titanium target) was studied. The performance of the coatings was found to depend on modulation periods of single layer thickness and thickness ratio, respectively. When the thickness ratio of MoS2–TiL layer to MoS2–TiH layer was fixed with different number of layers, the adverse effects of the interface outweighed the beneficial effect; thus, the mechanical and tribological performance of the multilayer coatings were improved with an increase in the single layer thickness. When the effect of the multilayer interfaces on the studied coatings was similar with the same number of layers, the MoS2–TiH layer had more impact on the hardness of the MoS2–TiL/MoS2–TiH multilayer coatings, whereas the MoS2–TiL layer substantially affected the adhesion properties, friction behavior and wear resistance. This study can provide a way to regulate coatings with different performance requirements via building different multilayer microstructures.

Highlights

Under certain operating conditions, for wear reduction purposes, solid lubricants are sometimes more suitable than liquid lubricants [1]
Surface and cross-sectional morphologies of the MoS2–TiL/MoS2–TiH multilayer coatings with different single layer thicknesses are presented in Figures 2 and 3
The adverse effects of the multilayer interface outweigh the benefits, evidencing that the adhesion properties, mechanical properties, friction behavior and wear resistance of the MoS2–TiL/MoS2–TiH multilayer coatings improve with an increase in single layer thickness

Summary

Introduction

For wear reduction purposes, solid lubricants are sometimes more suitable than liquid lubricants [1]. Pure MoS2 coating exhibits low hardness, poor oxidation, moisture and wear resistance, which is related to its porous microstructure. This attribute limits its application [1,4]. The doped additives can be classified into four main categories: metals (Ti [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], Au [22], Pb [16,20,21,23], Sn [24], Ta [25], W [26], Zr [27], Ni [28] and Cu [29]), compounds (Sb2O3 [28], PbO [30], WS2 [31], NbN [32] and TiN [33]), non-metallic elements (B [34], C [35] and N [36]) and composite additives (Mo–S–Ti–C [37], Mo–S–Ti–Pb [38] and Ti/TiB2/MoS2 [39])

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Discussion

Conclusion