Structural reorientation and compaction of porous MoS2 coatings during wear testing

High-Sensitivity Low-Energy Ion Spectroscopy with Sub-Nanometer Depth Resolution Reveals Oxidation Resistance of MoS2 Increases with Film Density and Shear-Induced Nanostructural Modifications of the Surface

“…Sliding on low-density coatings has two major roles, (1) it reorients the surface microstructure to be basally oriented (Figure b,c), thereby reducing potential edge sites for oxygen to bond, and (2) sliding densifies the coating by removing voids through compaction, eliminating pathways for oxygen to penetrate the coating (Figure c). Though we have not verified that sliding removes surface and subsurface voids in our coatings, Krauβ et al observed that highly porous pure MoS 2 coatings undergo compaction during sliding, the degree to which depends on sliding cycles and contact pressure. In the case of the high-density coatings, we posit that shear modification only reorients the film and does not densify it (Figure d); thus, the benefits of shear modification in mild oxidation conditions are not observed.…”

“…Benefits of basally oriented coating microstructures are highlighted by Curry et al using nitrogen-impinged coatings consisting of large, basally oriented crystallites capable of achieving steady-state coefficients of friction within fewer sliding cycles than sputter-deposited coatings. Often, sputter-deposited pure MoS 2 coatings are composed of either nanometer-sized crystallites with a vertical orientation (i.e., columnar) or are amorphous, − making them susceptible to oxidation. , When mechanical shear is applied through sliding, surface crystallites reorient to a ∼5–20 nanometer-thick basal orientation , and coalesce, forming a low-shear-strength interface. The oriented surface layer composed of larger, basally oriented crystallites has been shown to improve the environmental resilience from water and oxygen over the as-deposited coating microstructure and minimize unwanted increases in the initial coefficient of friction and prolonged run-in imparted by aging.…”

Tribological Behavior of SINTER30 Steel Subjected to Duplex Treatment

“…[2][3][4][5][6][7][8][9] Several surface treatment techniques can enhance metallic materials with properties such as wear resistance, corrosion resistance, and increased toughness, among others. [10][11][12][13][14][15][16][17][18][19] Plasma nitriding by cage cathodic has been studied in the past decade as a technique that can be used both in the nitriding process and in the deposition of thin films. [5,[20][21][22][23][24][25][26][27] Recently, some researchers have highlighted the potential of this technique for the deposition of duplex films, with the effect of nitriding parts followed by the deposition of a film on the substrate, with this process being performed continuously without the need for reactor replacement.…”

Compaction of Hydrophobic Molybdenum Disulfide Coatings for Promoting Tribological Behaviors on Engineering Steel

“…The sliding contact under a high load induces MoS 2 to rearrange parallel to the sliding direction, thus reducing the COF of the coating. However, the disadvantages of magnetron sputtering are the harsh deposition conditions of high vacuum and high pressure, the strict requirements for experimental targets, expensive instruments, etc. ,,− In addition, exposure of MoS 2 to a moist environment can lead to chemical deterioration and reduced lubrication performance. − Therefore, exploring the convenient technology to realize the long service life of MoS 2 coatings in an atmospheric environment is a key problem to be solved urgently in industrial applications.…”