Direct visualization of sliding-induced tribofilm on Au/MoS2 nanocomposite coatings by c-AFM

Abstract

The nanoscale lubrication mechanism of nanocomposite Au/MoS 2 solid lubricant coatings has been studied by conductive atomic force microscopy (c-AFM). A direct visualization of the lubricating process suggests tribomechanical formation of a MoS 2 tribofilm to be a key mechanism. The sliding-induced tribofilm formation was visualized by a reduction in local friction and conductivity in nanoscale AFM images. The tribofilm was found to possess considerable crystallinity and orientation, which was not observed in the as-deposited coatings. The observed mechanism is broadly applicable to a range of nanocomposite metal/MoS 2 coatings.

Microtribological Performance of Au–MoS2 and Ti–MoS2 Coatings with Varying Contact Pressure

“…It has been previously shown with macro-and nanotribology [8,21], that a crystalline tribofilm is formed on the worn surface of the MoS 2 film, which contributes to a low shear stress and therefore a low coefficient of friction. This typically occurs in the run-in stage, where the basal planes become oriented in a parallel direction to the sliding path and transfer occurs to the counterface.…”

“…For a little more than a decade, the testing of nano-and micro-scale sliding contacts has been an important research area that seeks to improve the tribological performance of nano/micro-devices and to have a better understanding of a material's behavior during single and multi-asperity contacts [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Due to their applications in hard drives, diamond-like carbon (DLC) coatings have been well studied for their tribological behavior at these small length scales [12][13][14][15][16][17][18].…”

“…The demonstration of atomic-layer deposition of chalcogenides [19,20], such as WS 2 , has provided the opportunity to include these materials, as solid lubricants, in micro-electromechanical system (MEMS). Additionally, there has been interest in using high-metal additions to MoS 2 [8,10] for the possible use of these coatings in micromotors, switches or actuators.…”

“…However, their microtribological performance is not nearly as well studied. Previous research has been performed using an atomic force microscope (AFM) [8] and a nanoindentation instrument [32,33] to investigate the influence of the gold content on the microtribological properties of MoS 2 . It has been shown that higher gold content (i.e.…”

Tribofilms in Solid Lubricants

“…In fact, many instrumental techniques of material characterization and surface analysis have been used in tribofilm characterisation, as shown in Table 1. Readers interested in this issue can read more in literatures [11,[12][13][14][15][16] .…”