Lubrication of metal surfaces by oxide films

Lubrication of metal surfaces by oxide films

PEEEEN, H. Lubricants and lubrication. Erdijl und Kohle, Vol 21, No 1 (January 1968) p8 Lubrication was an important topic in the programme of t...

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PEEEEN,

H.

Lubricants

and lubrication.

Erdijl

und Kohle, Vol 21,

No 1 (January 1968) p8 Lubrication was an important topic in the programme of the 7th World Petroleum Congress in Mexico City. Essentially, it was dealt with in the Panel Discussions NOS 28 and 31 in interesting lectures on fuels as well as lubricants. In this article, a survey is given of the requirements which modern lubricants must meet, and the ways and means which can be used to obtain satisfying results by the choice of production process, the selection of suitable additives, or by constructive measures. (Tribology 1968, abstract 81)

RABINOWICZ, E. Lubrication of metal surfaces by oxide films. Transactions of the American Society of Lubrication Engineers, Vol 10, No 4 (October-December 1967) ~409 Experimental data obtained with sixteen metals suggest that hexagonal structured metals have low friction, whilst other metals have high friction unless a lubricating oxide layer is formed. In order for an oxide to lubricate, it must not be much thicker than the substrate, and the oxide thickness must be adequate. For pin-on-desk tests at loads of about lkg, the critical oxide thickness if IO-ecm, and the metals must be heated until this thickness is reached. Other solid lubricant films appear to obey the same criteria of ‘not too hard, not too thin’. (Tribology 1968, abstract 82)

ROBERTS, A. D. and TABOR, D. Fluid film lubrication of rubber--an interferometrtc study. Wear, Vol 11,No 2 (February 1968) ~163 During the past few years studies have been made of the extrusion of liquid films between rubber and a hard transparent solid such as glass or quartz. Earlier work showed that conventional rubber surfaces are rough, and poorly reflecting, 50 that interferometric observations were unsatisfactory. The difficulty was solved by Blok by covering the rubber surface with a thin sheet of smooth plastic aluminized on its outer face. In preliminary studies good interference patterns could be obtained by gilding the rubber surface itself. Recently, with guidance from NRPRA and with the assistance of the Avon Rubber Company, it has been possible to prepare rubber surfaces of spherical, cylindrical and flat form which are optically smooth, and without gilding, give excellent interference patterns against glass even when very large elastic deformations occur. (Tribology 1968, abstract 83)

SCHULZ, H. H. and ENAPPWOST, A. Die Festirperreibung des Eises als Relaxationseffekt. Wear, Vol 11, No 1 (January 1968) p3 The frictional properties of ice on stainless steel have been determined in the temperature range -170°C to 0°C. The coefficient of friction shows an unusual behaviour and predictions based on the well-known equations of external friction fail. On varying temperature, the friction exhibits maxima which shift in a characteristic way with variation in speed of sliding. Comparison of this phenomenon with a known mechanical relaxation effect in ice shows that identical rate processes must take place in sliding friction as well as in mechanical damping experiments. A simple relaxation process is described with the aid of a mechanical relaxation model and a consistent equation for the coefficient of friction is established. (Tribology 1968, abstract 84)

SHARMA, C. S., RICE, W. B. and SALMON, R. Cutting fluid research. Lubrication Engineering, Vol 23, No 12 (December 1967) ~481 The mechanism of chip formation is discussed, theories of cutting action are reviewed, and cutting fluid research in progress is described. (Tribology 1968, abstract 85)

STRINGER, L. S. oil bath lubricatton. Industrial Lubrication, Vol 20, No 2 (February 1968) p44 The ever-pressing demand for increased output from a given size of equipment causes progressively more arduous requirements from lubrication arrangements. The situation creates the need for improvements to arrangements which have in the past been satisfactory, but now are not capable of meeting present day demands. This article gives details of experimental work carried out during the development of an improved self-contained oil lubrication arrangement for rolling bearings with horizontal rotating shaft. This arrangement has been given the trade mark CIRCON and has been used successfully for light series bearings operating at speed factors up to 42O,OOOmm/min. It is based on the oil bath arrangement which, owing to its simplicity, has been adopted for a variety of application5 over many years. In spite of this, little information is available on its performance and on its limitations. It was therefore necessary to study the operation of the basic oil bath arrangements in order to judge what improvements could be made. (Tribology 1968, abstract 86)

TABOR, D. and WILLIS, R. F. Thin film lubrication with substituted silicones: the role of physical and chemical factors. Wear, Vol 11, No 2 (February 1968) ~145 A preliminary study of the lubricating properties of silicone fluids, and the way in which they may be influenced by ‘tailoring’ the molecular structure, is described. Experiments with methyl alkyl silicones show that they have poor boundary lubricating properties in the classical sense. They can, however, provide partial elastohydrodynamic lubrication between heavily loaded steel surfaces. Such lubrication is improved by increasing the size of the substituent alkyl group. This appears to be due to a favourable change in the viscous properties of the fluids. A complicating factor,particularly at high temperatures, is the degradation of the compounds to form a thin polymeric film at the interface. The protective nature of this film, together with the load-bearing capacity of the superincumbent fluid itself, lead to a marked enhancement of lubricating properties. These observations may explain some of the apparent anomalies which have appeared in recent literature regarding the mechanism by which these fluids are able to lubricate sliding surfaces at high temperatures. (Tribology 1968, abstract 87)

TALLZAN, T. E. On compettxig fatlure modes in roller contact. Transactions of the American Society of Lubrication Engineers, Vol lO.No 4 (October-December 1967) ~418. Railer contact failures are classified according to their failure mode as (a) wear, (b) plastic flow, (c) fatigue, and (d) bulk failures, with the last class arising outside the immediate contact area. The wear failures are subdivided into mild wear by loose particle removal, and smearing involving metal transfer. Plastic failure5 may arise from overload or temperature imbalance. Fatigue is of the spalling or the surface distress type. An analysis of the stress conditions in a rolling contact is sketched; the refinements of the contact model are considered step by step, starting from Hertz theory, and including progressively surface traction, plasticity, elastohydrodynamic lubricant films, surface microtopography, and the inhomogeneities of real metals. Each failure mode is associated with the relevant severity parameters of the contact stress condition, and a description of its mode of formation is given. Guidelines are provided for the identification of that failure mode which, among competing modes, is most likely to render a rolling contact inoperative in a given operating environment. (Tribology 1968, abstract 88) TRIBOLOGY

March

1968

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