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

Abstract

Solid lubricant coatings with co-sputtered metal and MoS 2 have shown favorable macrotribological properties at a wide range of contact stresses and humidity levels. These materials are also candidates for use in microcontacts and micro-electromechanical systems (MEMS), but their performance at this scale is poorly understood. For this study, microtribological properties of Au-MoS 2 and Ti-MoS 2 coatings, with varying metal additives of less than 15 at%, were examined using a nanoindentation instrument. Titanium and gold were chosen for this study as metal additives due to their different influence on the mechanical properties of the coating. The hardness and reduced modulus of the coatings increased with the addition of metal, when compared to pure MoS 2 . Reciprocating microscratch tests were performed with two spherical diamond tips (50 and 10 lm radii) in dry air. A range of normal loads were used between 0.2 and 5.0 mN. Friction and wear measurements were analyzed with respect to the variation in the contact pressure and compared to literature studies performed at the macroscale. Correlations were found between the coating mechanical properties, tip-coating adhesion, interfacial shear strength, and the formation of transfer films and tribofilms.

Transition Metal–MoS2 Reactions: Review and Thermodynamic Predictions

“…1,2 Researchers in areas as varied as electronics, [3][4][5][6] optoelectronics including photovoltaics, [7][8][9] tribology (lubrication), [10][11][12] catalysis, [13][14][15] and others are interested in MoS 2 . Reduced dimensionality results in a number of unusual properties.…”

“…[3][4][5]26 Tribology researchers are investigating a wide variety of nanoscale MoS 2 -transition metal systems for coatings and solid-state lubricants to be used in different environments (high temperature, corro-sive, etc.). 10,12,27,28 The large direct bandgap of single-layer MoS 2 is ideal for the hydrogen evolution reaction, 29 so researchers want to combine various transition metals and nanoscale MoS 2 to create an optimized, high-surface-area catalyst. 13,30,31 Catalysis researchers are also looking at two-dimensional (2D) versions of existing hydrodesulfurization materials (MoS 2 with metals such as Ni and Co).…”

Micro-scale sliding contacts on Au and Au-MoS2 coatings

“…The actual area function of the tip was used to obtain a contact pressure at any given depth and normal load. This procedure is described in more detail elsewhere [20] and is very similar to the one described by Bushby and Jennett [19].…”

An investigation of material and tribological properties of Sb2O3/Au-doped MoS2 solid lubricant films under sliding and rolling contact in different environments

“…Anisotropy in the MoS 2 structure results in easy shearing of stacked basal planes and provides a low-friction interface. The tribological performance of MoS 2 depends upon conditions that include film morphology, temperature, presence of contaminants, environment and contact pressure [1,6,[15][16][17][18][19][20][21][22]. It is well known that humidity alters the tribological performance of MoS 2 , and it is believed that adsorption of moisture inhibits the ease of basal plane shearing and elevates friction [9].…”