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.
Friction Behavior and Wear Analysis of SiC Sliding Against Mo in SO2, O2 and H2S at Gas Pressures Between 4 and 40 Pa
Friction tests were performed in an ultrahigh vacuum chamber with an SiC pin sliding against an Mo flat during and after exposure to gases at pressures between 4 and 40 Pa. Wear tracks, scars and debris were, analyzed ex situ with scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). Steady-stale friction coefficients were between 0.10 and 0.15 in SO2 and O2 gases and less than 0.01 in H2S gas; in contrast, tests performed at <10−5 Pa after H2S exposure gave friction coefficients of about 1. SEM/EDX of wear features formed in SO2 and O2 tests showed that tracks on Mo and scars on SiC were covered and surrounded by small (1–5 μm), flakelike Mo particles. In contrast, tracks formed in H2S had long stretches, of a smoothly burnished surface with very little debris. TEM of wear debris collected from both pin and flat also found only metallic Mo particles. The lubricant afforded by the gases is discussed in terms of the third-body products formed...
Heat Transfer Characteristic for a New Plate Metal Hydride Reactor
The property of major metal hydride reactors in the world was analyzed and a new plate metal hydride reactor was designed.An experimental facility to test the metal hydride reactor was also designed correspondingly.The effective thermal conductivity of the plate metal hydride reactor was measured by varying the initial metal hydride packing fraction,the kind of filled gas and the pressure of the filled gas,cycle numbers.The test results show that the effective thermal conductivity of the reactor,has exceeded(7.5) W/(m·K) before activation,which is increased greatly.After alloy activation,the effective thermal conductivity of the reactor has a linear change trend with the hydrogen pressure during the interval 0.1~3.5 MPa.The effective thermal conductivity of the reactor just only decreases quickly at the beginning,but becomes stable after several cycles.