While formation of deposits in machinery used under high temperature conditions is inevitable, it needs to be minimized as much as possible. Desorption of deposits, though rarely reported, also needs to be addressed, as it could cause secondary damage. There have been a number of reports on the formation of high-temperature deposits and the effects of additives, none of which, however, addresses the desorption phenomenon as part of the deposit formation mechanism. Paying attention to the polar properties of lubricating oils and evaluating the formation, dissolution, and desorption of deposits by lubricating oils, the formation mechanism of high-temperature deposits was considered. Taking notice also of the changes in polar characteristics of oils with the progress of oxidative degradation of oil, we examined the influence of oxidative degradation of oils on the tendency to form high-temperature deposits. Furthermore, the countermeasure to prevent from deposit formation is also considered.
Micro cone-shaped projections formed on the Nip surface by laser technique are described as a new texture of rigid disks. In order to achieve the lower glide height (G/H), the projection height must be lower. Therefore, it is required that the projection spacing is short and the top shape of projection has large curvature as that real contact area between a slider and a projedion does not increase. Optimized texture pattern guaranteed 1.2 uin. G/H showed excellent CSS performances. The good tribological durability is attributed to the precise controllability of the real contact area according to the projection density, considering the wear of carbon layer.
We have electrodeposited Co into the micropores of an anodic Al2O3 coating on Al, making Co rods of about 120 Å in diameter and 0.3–1 μm in length. The Al2O3 is amorphous, while the Co is crystalline (hexagonal form) with no preferred orientation exhibiting saturation magnetization 80% of that of bulk Co. The composite Al2O3/Co film shows prominent magnetic anisotropy perpendicular to the surface due to the shape anisotropy of the Co rods, having coercive force of ∼1.2 kOe. The Kerr rotation and the reflectivity of the films at λ=0.63 μm, Θ̂k =±15′ to ±50′, and R=5 to 15% varied from sample to sample due to interference effect of light in the films. The values of θk and R change irreversibly when heated above ∼150 °C. Stripping the Al2O3-Co film from the Al substrate by dissolving the Al, we have measured the Faraday effect and light transmittance. They increase linearly with increasing rod length, giving Θ̂f(rotation) =−0.41 deg/μm, Ψ̂f(ellipticity) =1.14 deg/μm, and α̂(absorption coefficient)=1.1 μm−1. These values conform with what is expected from the effective dielectric tensor, including off-diagonal elements, which we [Jpn. J. Appl. Phys. 23, 1580 (1984)] have formulated for composite materials containing magnetic fine particles or rods.
Under severe bearing conditions, deposits form on the loaded part of bearing pads and if this happens excessively, it could lead to unacceptable rises in temperature and vibration. Deposits are mainly organic compounds, formed as oxidation by-products, which are insoluble in lubricating oil and can be the precursor to deposits. In this study, the deposit precursor in lubricating oil was investigated in detail and the deposit production mechanism was demonstrated. Furthermore, the difference of oil type effects and the dependence of conditions on deposit formation are also considered.
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