Abstract
Tribological coatings made of MoS2 and WSe2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30–40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSex film (specific wear rate of 2 × 10−8 mm3 N–1m–1 and a friction coefficient of 0.03–0.05) was compared with that of the well-established MoS2 lubricant material.
Highlights
The interaction between surfaces in mechanical contacts significantly affects energy loss, machinery performance and endurance
The chemical composition of the films was determined by electron probe microanalysis (EPMA)
The morphology and thickness of the coatings were investigated by cross-sectioning the specimens and subsequent observation by scanning electron microscopy (SEM) in a high resolution field emission gun microscope, Hitachi-4800 (Tokyo, Japan), equipped with an energy-dispersive X-ray (EDX) detector (Bruker, XFlash4100, Billerrica, MA, USA)
Summary
The interaction between surfaces in mechanical contacts significantly affects energy loss, machinery performance and endurance. MoS2 has been the most commonly employed intrinsic solid lubricant over the past 40 years [4,5,6] and still is the object of exhaustive studies for determining its functionality for space applications [7,8,9]. These coatings are soft, have poor adhesion and load-bearing capacity, and degrade in humid air [10], not as significantly as graphite.
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