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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]

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]

Abstract: Hydrogenated amorphous carbon films containing Si and Al (a-C:H/(Si, Al)) were deposited on Si(100) substrates at different negative bias voltages, by radio frequency (RF, 13.56MHz) magnetron sputtering. The chemical composition and structure were detected by means of X-ray photoelectron spectroscopy (XPS) and Raman spectra, respectively. It was found from the results of Raman spectra that the film deposited at zero negative bias voltage was highly hydrogenated, but significant graphitization happened to the films when high bias voltages were applied. The results of atomic force microscope (AFM) showed that the films deposited at moderate negative bias voltage had ultra-smooth surface. The mechanical and tribological properties of the films were measured by nano-indentation test and tribo-meter in ball-on-disk mode, respectively. It was revealed that the negative bias voltage had great impacts on the mechanical properties of the films. The tribological properties of the films were significantly improved when bias voltages were applied on substrates. Particularly, the film deposited at −200V performed a super-low friction behavior (0.0085) and long wear life (>105 revolutions) in ambient air under high Hertz contact stress (as high as 1.6GPa) though it showed a relatively low hardness. [Copyright &y& Elsevier]

Abstract: A Ni3Al–Ag–Mo–BaF2/CaF2 self-lubricating composite coating was fabricated by a powder metallurgical process. The tribological properties of the coating against Si3N4 were investigated over a wide temperature range (25–1000°C). The results showed that the coating had a low friction coefficient (0.24–0.38) in the entire temperature range. Lubricating mechanism analysis results indicated that Ag took effect at low temperature (below 400°C); BaF2/CaF2 began to work as a solid lubricant as the temperature raised; and the molybdates, which formed by the fluorides oxidation, act as lubricants at higher temperatures (above 800°C). As a result, the coating expressed a low friction coefficient from 25°C to 1000°C. [Copyright &y& Elsevier]

Abstract: Ti–Al–C films were deposited on silicon (100) substrates using magnetron sputtering TiAl target and graphite target in argon atmosphere at various substrate negative bias voltages. The composition, surface morphology, hardness and friction coefficient of the resulting films were characterized using x-ray photoelectron spectroscope, energy dispersive spectrometry, atomic force microscopy, nanoindentation and tribological tester. Results show that the structure and properties of the deposited films strongly depend on the applied substrate negative bias voltage. The Ti–Al–C films deposited at high substrate negative bias voltage show high surface roughness, low hardness and short wear life. In contrast, the Ti–Al–C films deposited without negative bias voltage exhibit uniform and smooth surface, a high hardness of approximately 37 GPa and low friction coefficient and long wear life. Excellent friction and wear behaviors of the Ti–Al–C films deposited without negative bias may be attributed to the dense structure and high hardness. [Copyright &y& Elsevier]