Lubrication of Mo, W, and their Alloys with H2S gas admixtures to room temperature air
Abstract The in situ lubrication of molybdenum and tungsten using admixtures of hydrogen sulfide to room temperature and pressure air was achieved. Raman spectroscopy confirmed the presence of molybdenum disulfide and tungsten disulfide solid lubricants on elemental molybdenum and tungsten specimens, respectively. Pin-on-disk experiments were conducted with elemental molybdenum, elemental tungsten, and alloys of molybdenum and tungsten in atmospheres containing hydrogen sulfide. Friction coefficients were continuously recorded and comparisons between the sliding friction coefficient in air and in the hydrogen sulfide atmospheres were evaluated. In general, hydrogen sulfide admixtures reduced the friction coefficient for all materials containing molybdenum or tungsten. Friction coefficients for self-mated elemental molybdenum and self-mated elemental tungsten were reduced to μ =0.15 with hydrogen sulfide admixtures to air of 5% and 15%, respectively. In some cases friction coefficients as low as μ =0.08 were recorded.
22 Solid Lubricants and Self-Lubricating Films *
22.
Friction studies in ultrahigh vacuum of Fe surfaces with thin films from exposure to perfluorodiethylether
The coefficient of friction for both clean and oxidized contacting polycrystalline Fe surfaces following exposure to a perfluorodiethylether (PFDE), (CF3CF2)2O, was measured in ultrahigh vacuum (UHV) using a pin‐on‐flat device (0.05–0.30 N loads). This system was chosen to examine the influence of thin films on friction using a molecule having functionalities that are present in perfluoropolyether lubricants. The friction coefficient measured for the clean (∼0.2–1.0 A oxide) surfaces in UHV was ∼3.0. The friction was measured for both oxidized and clean Fe surfaces in PFDE atmospheres (3–150 Pa). During this exposure the friction for the oxidized Fe surfaces dropped to 0.7–0.9 compared to 1.2–1.5 obtained in O2 environments. The friction for clean Fe surfaces measured in UHV following similar PFDE exposures showed two distinct friction ranges, 0.1–0.8 and 1.2–1.8. The Fe surfaces were examined in situ in the same UHV chamber using x‐ray photoelectron spectroscopy and showed the formation of a Fe fluoride ...