Solid lubricant behavior of MoS₂ and WSe₂-based nanocomposite coatings

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.

Reactive Pulsed Laser Deposition of Clustered-Type MoSx (x ~ 2, 3, and 4) Films and Their Solid Lubricant Properties at Low Temperature

“…The intensive and narrow peak at 2~ 44.5° was due to reflection from the steel substrate. The diffractograms of the MoS2 coatings were similar in many respects to those measured for transition metal-dichalcogenide-based coatings obtained through ion sputtering or PLD at room temperature [19,21,22,38]. The XRD patterns of these coatings showed an intense and broad peak near 2~ 13° and a pronounced peak at 2~ 33°, followed by a broad peak at 2~ 43°.…”

“…The most common structural state of deposited coatings is "amorphous", which is generally assumed to form from nanoclusters with a lamellar structure typical of the 2H-MoS 2 phase [19][20][21][22]. Friction sliding is associated with the tribo-induced crystallization of such coatings.…”

“…Friction sliding is associated with the tribo-induced crystallization of such coatings. During this process, a tribo-layer with enhanced lamellar structure ordering forms on the coating surface in the friction zone [22]. Most studies that have obtained Mo/W/S x /Se x coatings have done so with a chalcogen-to-metal ratio within~1 < x ≤ 2, and have tested these coatings for tribological properties.…”

Effect of Humidity on Friction and Wear—A Critical Review

“…This phenomenon is also suggestive that the edge sites play an important role in the humidity dependence. Moreover, it was reported that the friction and wear of MoSe 2 and WSe 2 are hardly influenced by ambient humidity [123,124]. The chemistry of disulfide and diselenide materials in humid environments appear to be drastically different.…”

Nanotribological Properties of the h-BN/Au(111) Interface: A DFT Study

“…Charge density difference at a distance of z = 2.8 Å (left panels) and z = 3.1 Å (right panels) at the point (x, y) = (0, 1.45) Å as defined inFigure 1. Countour plots at three heights (BN sheet (1), topmost Au layer(3), and the midplane between the two materials (2)) are also shown together with the plane-averaged charge density difference. On the plane-averaged Δρ plots the three planes are marked with vertical lines.…”