The effect of temperature on the adsorption of benzene on the nascent surface of steel was examined. Cutting tests were carried out under high vacuum condition. The components adsorbed onto or desorbed from the nascent surfaces formed by cutting were monitored by a quadrupole mass spectrometer. The adsorption rate of benzene decreased with increasing temperature whereas desorption rate of hydrogen and adsorption rate of water increased. It appeared that water from residual gas preferentially adsorbed onto the nascent surface to disturb benzene adsorption as the temperature increased where the water was decomposed to form hydrogen. In this study, it was found that the reaction of adsorption on mechanically formed nascent surfaces is affected by temperature. Adsorption activity of mechanically formed nascent surfaces was calculated.

View full abstract

In a tribological experiment, one relies on the ability to measure accurately the wear scar in the contact. Usually, in a point contact, the wear scar diameter (WSD) is measured, and measurements of this kind may be compared for several different oils, for example. This type of experiment might be carried out on a ball-on-disk tribometer with a point contact, where the disk measurement might be considered of secondary importance. In a recent study, it was advantageous to measure the wear scar width (WSW) of the disk wear scar, which led to the question of whether the relative rankings provided by the WSWs would correspond to the more tedious profilometry that is often carried out in various tribological investigations. In this study of modern passenger car oils, we make that comparison and show that there is a 1-to-1 correspondence between the WSW determinations by optical microscope (OM) and the profilometry studies. These studies were carried out using the versatile and modified MTM^TM tribometer.

View full abstract

The UV irradiation of Z-Tetraol films on amorphous nitrogenated carbon surfaces was investigated. COF₂ evolution, captured in the gas phase, decreased with increasing number of OH end groups in the order: Z > Zdol > Z-Tetraol after UV irradiation. Both UV irradiation and annealing on 11 Å Z-Tetraol films produced virtually identical interfacial properties - surface energy as a function of bonded fraction. The UV-irradiated 11 Å Z-Tetraol films also demonstrated equilibrium behavior exhibiting bonding or debonding to the asymptotic 80% bonded level under ambient conditions. UV-irradiated thick films of Z-Tetraol (∼ 20-40 Å) exhibited film properties that differed from the non-irradiated films. The oscillations in the polar component of the surface energy, normally observed in Z-Tetraol films and attributed to amphiphilic structuring, disappeared. Terraced flow exhibited a rapidly moving front below ∼ 10 Å compared to the remainder of the irradiated film. Both observations were tentatively attributed to loss of OH functionality. The latter was verified by chemical extraction and subsequent analyses by NMR and TGA.

View full abstract

Indentation experiments and friction measurements were performed at three low index faces of fluorite (CaF₂) crystal. Deformation patterns were analyzed by observing step structures with atomic force microscopy (AFM). Upon indentation at (0 0 1) surface, {1 0 0}<0 1 1> slip steps were formed at limited parts of the surface near the compressed area, where horizontal shear stress is added to vertical one. Upon indentation at (1 1 1) surface, the surface was split into 6 sectors separated by {1 1 1} cleavage lines. Steps formed on each sector were also explained by the {1 0 0}<0 1 1> slip. The signs of steps suggest that the steps in three alternate sectors were formed by vertical compression, and the steps in the other sectors were formed mainly by horizontal compression. The slip mechanism was explained by a simple mechanical model. Upon scratching the (0 0 1) surface in [1 0 0] direction, only steps in [1 0 0] direction, not in [0 1 0] direction, were formed outside the wear track. Scratch on (1 1 1) surface activated the slip in three possible directions selectively, depending upon the scan directions of the stylus. Slip did not occur easily at (1 1 0) surface, where slip can occur in five directions close to each other. Frictional anisotropy was discussed in relation to the slip system.

View full abstract

Friction and wear are the most commonly encountered industrial problems leading to the replacement of components and assemblies in engineering. There have been great advances in the development of aerospace technology because of the use of titanium alloys. Titanium alloys have wide range of applications for which they have received considerable interest recently because they show an astonishing range of mechanical properties. The present investigation covers the study of dry sliding friction and wear of the Ti6Al4V alloy, which alone covers about 50% of the total world production of titanium alloys. The main objective of this study is to investigate the dry sliding friction and wear behaviour of titanium alloy (Ti-6Al-4V) sliding against EN31 steel. The results show that the wear rate of the Ti6Al4V alloy decreases with increasing sliding velocity and decreasing normal load with few exceptions thus showing typical transition characteristics. The average coefficient of friction decreases as the normal load increases with few exceptions. Also the average coefficient of friction increases as the sliding distance increases for all loads and sliding velocities. The average length of biggest, medium and smallest wear debris was found to be 1.026 μm, 0.711 μm and 0.401 μm respectively.

View full abstract