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Abstract: The effects of substrate temperature on the structure and tribological properties of Ag films deposited at low temperatures (LT, 130–217K) by arc ion plating (AIP) have been studied. The structure and morphology of the Ag films were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). The results showed that there exist (111) and (200) preferred orientation transitions for decreasing temperature at different bias voltages. The tribological properties were evaluated by a ball-on-disk tribometer and wear tracks were analyzed by means of scanning electron microscopy (SEM). The results show that substrate deposition temperature significantly affected the wear of LT Ag films. For each bias voltage studied, the film showing the highest wear rate was deposited at the lowest temperature and the film with the lowest wear rate, (significantly lower than room temperature (RT) deposited Ag films), was deposited at a temperature between the highest and the lowest temperatures examined. The wear mechanism was discussed in terms of lubrication effect of film material transferred to the counterpart and its dependence on the microstructure of the original deposited film. [Copyright &y& Elsevier]

Abstract: Pure WS2 and WS2/Cu multilayer films were deposited by radio frequency sputtering method and the erosion behavior caused by moisture was studied. For the pure WS2 film, the morphology, microstructure, composition and also the tribological properties experienced substantial change upon storage in humid air environments. Depth XPS and Raman analysis showed that the pure WS2 film suffered deep oxidation due to the open structure, but the compact WS2/Cu multilayer film resisted oxidation very well. For the multilayer film, the oxidation was restricted on the surface layer owing to the protective effect of the reactive product cladding layer of W and Cu oxidation and the compact microstructure. The open lamella structure of pure WS2 film allowed moisture to diffuse into the film interior, and so the deep oxidation, evolution of structure and Fe substrate corrosion contributed to the deterioration of tribological properties. The WS2/Cu multilayer film exhibited better deep oxidation resistance even after storage for long durations in humid air environments, and accordingly still showed low and stable friction coefficient and long wear life. [Copyright &y& Elsevier]

Abstract: The Ag film, and double layer films of Ag/Si and Ag/SiN x were deposited by magnetron sputtering technique. The atomic oxygen (AO) irradiation tests were conducted using a ground AO simulation facility. The microstructure and composition of these films before and after AO irradiation tests were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), respectively, atomic force microscope (AFM) and scanning electron microscopy (SEM), respectively. Then the protective effects of nanoscaled amorphous Si and SiN x layers on the atomic oxygen resistant property of Ag film were investigated. The results show that nanoscaled Si or SiN x protective layer can provide better protection to Ag film against oxidation caused by AO irradiation. The silica layer formed on the surface of amorphous protective layers during AO exposure process plays the key role in protecting Ag film from oxidation. On the other hand, the tribological performance of Ag film and the multilayer films was comparatively studied using a ball-on-disc tribometer in vacuum condition. The tribotest results indicate that Ag/Si and Ag/SiN x films show the better lubricating performance before and after AO irradiation than pure Ag film. [Copyright &y& Elsevier]

Abstract The WS 2 /CrN bilayered films with different interface morphologies between WS 2 and CrN layer were prepared by physical vapor deposition. By controlling the deposition parameters, the surface of CrN interlayer exhibited compact granular structure when deposited under low partial pressure of Ar while a cone array-like surface appeared under high Ar partial pressure. The surface texture of the CrN interlayer had a great effect on the tribological performance of the WS 2 /CrN film. The compact CrN textured WS 2 film exhibited a wear life about 2.6 × 105 cycles while the optimal cone array-like CrN textured WS 2 film showed a much longer wear life reaching to 6.8 × 105 cycles, which was more than 2.6 times of that for compact CrN textured WS 2 film and 3.5 times of that for WS 2 film without the CrN interlayer. The improved tribological property of the optimal cone array-like CrN textured WS 2 film was attributed to the high adhesion between the WS 2 layer and the CrN interlayer. Meanwhile, the reservoir and replenishment of the WS 2 lubricant by the CrN nanocones during the friction made a significant contribution for the long wear life. Highlights • Compact and cone array-like CrN interlayers were deposited under different Ar partial pressure. • Different tribological performances would be resulted by tailoring the interface of WS 2 /CrN bilayered film. • The reservoir and replenishment of the WS 2 lubricates by CrN nanocone array contribute to the tribological performances. [ABSTRACT FROM AUTHOR]

In order to improve the tribological performance of MoS 2 based films under vacuum conditions, the lubricating properties of WS 2 /MoS 2 -Ag film with different ionic liquids (IL1 and IL2) were evaluated. A good synergy effect was present for the composite lubricating systems. They exhibited longer wear durability, lower wear rates than pure solid film. For both the ionic liquids related, IL2 exhibited better tribological performance than IL1, which were due to their different friction mechanisms. IL1 could interact with friction pairs to form tribo-chemical films during the friction process, which ensured effectively the lubricating properties. By contrast, IL2 with longer alkyl chain groups would prefer to adsorb with the basal crystal plane to improve the tribological performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pure WS2 and WS2-Al composite films with different structures were prepared. [•] The compactness of WS2 film was significantly improved due to incorporation of Al. [•] Different mechanisms of atomic oxygen resistance of both the films were discussed. [•] Films before and after AO irradiation kept the unchanged tribological properties. [•] The composite films showed much better wear resistance than pure WS2 film. [Copyright &y& Elsevier]

The WS2–Ag composite films were prepared by radio frequency co-sputtering method. The effects of alloying Ag content on composition, microstructure, mechanical properties and friction behaviors have been analyzed by X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscope (HRTEM), scratch tester, nano-indentation tester and ball-on-disk tribo-tester. The Ag addition was in present of nanocrystalline phase in the boundary of the crystalline WS2 matrix and induced morphology change, but could not completely prevent the columnar platelets. The columnar platelet was composed of a great deal of nanocrystalline and a small amount of amorphous WS2 phase. There were no substantial variations in the hardness of the composite films when the Ag content was in the range of 0–20.3at.%. The suitable amount of Ag content was benefited for improving the film adhesive strength and wear resistance both in vacuum and humid air environment. Particularly, the composite film with 9.0at.% Ag exhibited the longest wear life (about 7.6×105 cycles in vacuum, 6.7×105 cycles in humid air) under high Hertzian contact pressure (as high as 1.0GPa). The wear mechanism was discussed in terms of the rearrangement of wear track and formation of transfer film. [ABSTRACT FROM AUTHOR]

MoS 2 -Cr 3 O 4 composite films were prepared by the combination method of PVD and liquid phase synthesis. The microstructure and tribological properties of films have been investigated. The results indicate that the size of Cr 3 O 4 varied from 5 nm to 500 nm and the shape of Cr 3 O 4 changed from nanospheres to nanorods by adjusting concentration of CrCl 3. The MoS 2 -Cr 3 O 4 composite films developed excellent wear resistance and much lower friction coefficient than sputtered MoS 2 both in vacuum and 45%RH air. During friction, the Cr 3 O 4 @MoS 2 core-shell structure with Cr 3 O 4 core of high hardness and soft MoS 2 shells were formed and played the role of nano-bearing, which reduced the friction and wear of the composite film. Besides, better oxidation resistance and tribological property of the MoS 2 -Cr 3 O 4 composite films in humid air were attributed to the Cr 3 O 4 nanoparticles, which occupied the most of dangling bond sites. Unlabelled Image • Cr 3 O 4 nano-particles are connected to dangling bonds of the sputtered MoS 2 film. • Occupied dangling bonds by Cr 3 O 4 can much improved the antioxidant of MoS 2 film. • The Cr 3 O 4 @MoS 2 core-shell structure formed and played a role of nano-bearing. • The Cr 3 O 4 greatly improves tribological properties of films both in air and vacuum. [ABSTRACT FROM AUTHOR]