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.
Solid lubrication by decomposition of carbon monoxide and other gases
Abstract Extended duration high temperature (above 500°C) lubrication of silicon nitride sliding and rolling contacts was accomplished by solid carbon deposited and replenished via the decomposition of carbonaceous gas streams directed towards the tribological surfaces. Injection of carbon monoxide-hydrogen mixtures can lead to reductions in high temperature friction and wear of silicon nitride sliding contacts by factors of up to 10 × and 500 × respectively from the unlubricated case. Similar lubrication is attained by various hydrocarbon gas mixtures, while only a ten-fold reduction in wear is attained by a carbon dioxide-hydrogen mixture. Effective lubrication can be modeled as a favorable balance between carbon deposition from the gas phase and removal by wear. This model is based on the dependencies of solid lubricant deposition and removal processes on temperature, sliding speed, normal load, decomposition activation energy, gas flow rate, and tribosystem properties. The model is checked by the mapping of regions where measured friction indicates that lubrication by CO-H 2 mixtures is adequate, and the identification of a boundary representing the onset of marginally effective lubrication.
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics