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Engineering plastics
Testing EP oils
Sputtered films Sputtering has immense potential for applying thin films of solid lubricants. It enables virtually any solid lubricant to be applied in a single operation to any bearing component, regardless of its geometry, and it is becoming increasingly possible to produce coatings with tailor-made properties. Sputtered films, particularly of MoS2, are finding a growing number of industrial applications but their performance depends strongly on proper selection of the sputtering parameters and substrate condition. A programme of work at NASA's Lewis Research Center has been directed to improving understanding of the factors which affect the lubricating performance of sputtered thin films. The main emphasis has been on the characterization and evaluation of MoS2 with electron microscopy and other sensitive analytical techniques being used to investigate the interrelationships of film adherence, chemical composition, film thickness, substrate temperature, etc. Some work is also reported on the use of sputtered films of tungsten disulphide, polytetrafluoroethylene (ptfe) and soft metals in tribological applications. Among the main findings for MoS2 films are: Film structure and frictional properties depend greatly on substrate temperature; negative potential (bias) on the substrate during sputtering depletes the sulphur in the film and can destroy its lubricating properties; in reduced atmospheric pressure conditions the friction coefficient falls from 0.15 at 50 kPa (half normal pressure) to 0.04 at 13 kPa where it stabilizes (dry air, nitrogen and argon will give a friction coefficient of 0.04); that poor adherence of the films to copper, silver and bronze surfaces result from chemical reaction and can be avoided by oxidizing the surface; that film thicknesses above 2/am greatly increase the size of defects; that a duplex sputtered film (steel bearings sputter coated with Cr3 Si2
150
underlayer and then by MoS2) gave much better endurance than an MoS2 film. It has also been established that tungsten disulphide films are suitable for vacuum applications and that though soft metals such as gold, silver and lead can be sputtered, ion plating is a more suitable technique. The strong adherence and low friction coefficients (0.08 to 0.2) of ptfe films hold out great promise and they have already found one unique medical application. Further information is contained in an 18-page report 'Sputtering technology in solid film lubrication' by T. Spalvins, reference N78-26214 available as microfiche £1.19 (inc vat) or reproduced paper-copy £1.50 from Te chAlert*
Specifications based on a 'Timken test' on the EP properties of lubricating oils have been used for about 30 years. The test was first adopted as a standard method by ASTM in 1969 and a revised method recently developed. In the November 1978 issue of NLGI Spokesman, Roberton describes the revised test procedure, reviews factors which might affect the accuracy of results, and gives the results of a cooper. ative program to establish the precision limits of the method using test pieces produced by an improved process. The cooperative test results show a significant improvement over previously published data. NLGI Spokesman, Volume 42, Number 8 is published by NLGI, 4635 Wyanchotte St., Kansas City, Me 64112, USA
Engineering maintenance
Engineering plastics
Based on experience of over 500 assignments in the last 5 years, Idhammar Konsult AB have produced a 160 page manual on engineering maintenance. This course in basic maintenance is aimed at supervisors and operators.
Ciba--Geigy's Plastics Division have produced a 24 page booklet for design engineers on Crastine, one of their thermoplastic polyester moulding compounds which is marketed in the UK under the trade name Tenatine.
The manual covers general principles, economics, aspects associated with design, purchasing and installation, condition monitoring, maintenance work and maintenance systems. One valuable aspect of the book is that it relates maintenance to specific components, such as bearings, gearboxes, couplings etc, rather than making general comments.
The bulk of the booklet is devoted to assembly methods, followed by short sections on machining and finishing. The final three pages give information on bearings and gears.
Yhe~uthors' attempt to cover such a broad subject in a relatively limited space inevitably opens them to the criticism of some superficiality. For example, they show graphically the savings from condition based maintenance, but give no guidelines on how much to spend on establishing a condition monitoring system. Also, one can only agree with the authors' comment that the chapter on inspection instruments and aids "does not claim to be complete". Copies of 'Reliability and Maintenance 1' are available, price S.Kr. 160, from Idhammar Konsult AB, Box 30, 14700 Tumba, Sweden
TRIBOLOGY international June 1979
Ciba-Geigy Plastics and Additives Company, Plastics Division, Duxford, Cambridge CB2 4QA, UK
Graphite powders According to Lonza, the effectiveness of graphite in lubricants is governed by purity, crystalline structure, texture and particle size distribution. They have just published a brochure which aims "to set new accents in graphite powder characterisation and to create a better understanding with the industries using the material". The brochure outlines the properties of graphite powder, gives technical data on Lonza products, and indicates some applications. Copies are available from Lonza Ltd., Inorganic Chemicals Division, P.O. Box, CH-4002, Basle, Switzerland
Sputtered films Sputtering has immense potential for applying thin films of solid lubricants. It enables virtually any solid lubricant to be applied in a single operation to any bearing component, regardless of its geometry, and it is becoming increasingly possible to produce coatings with tailor-made properties. Sputtered films, particularly of MoS2, are finding a growing number of industrial applications but their performance depends strongly on proper selection of the sputtering parameters and substrate condition. A programme of work at NASA's Lewis Research Center has been directed to improving understanding of the factors which affect the lubricating performance of sputtered thin films. The main emphasis has been on the characterization and evaluation of MoS2 with electron microscopy and other sensitive analytical techniques being used to investigate the interrelationships of film adherence, chemical composition, film thickness, substrate temperature, etc. Some work is also reported on the use of sputtered films of tungsten disulphide, polytetrafluoroethylene (ptfe) and soft metals in tribological applications. Among the main findings for MoS2 films are: Film structure and frictional properties depend greatly on substrate temperature; negative potential (bias) on the substrate during sputtering depletes the sulphur in the film and can destroy its lubricating properties; in reduced atmospheric pressure conditions the friction coefficient falls from 0.15 at 50 kPa (half normal pressure) to 0.04 at 13 kPa where it stabilizes (dry air, nitrogen and argon will give a friction coefficient of 0.04); that poor adherence of the films to copper, silver and bronze surfaces result from chemical reaction and can be avoided by oxidizing the surface; that film thicknesses above 2/am greatly increase the size of defects; that a duplex sputtered film (steel bearings sputter coated with Cr3 Si2
150
underlayer and then by MoS2) gave much better endurance than an MoS2 film. It has also been established that tungsten disulphide films are suitable for vacuum applications and that though soft metals such as gold, silver and lead can be sputtered, ion plating is a more suitable technique. The strong adherence and low friction coefficients (0.08 to 0.2) of ptfe films hold out great promise and they have already found one unique medical application. Further information is contained in an 18-page report 'Sputtering technology in solid film lubrication' by T. Spalvins, reference N78-26214 available as microfiche £1.19 (inc vat) or reproduced paper-copy £1.50 from Te chAlert*
Specifications based on a 'Timken test' on the EP properties of lubricating oils have been used for about 30 years. The test was first adopted as a standard method by ASTM in 1969 and a revised method recently developed. In the November 1978 issue of NLGI Spokesman, Roberton describes the revised test procedure, reviews factors which might affect the accuracy of results, and gives the results of a cooper. ative program to establish the precision limits of the method using test pieces produced by an improved process. The cooperative test results show a significant improvement over previously published data. NLGI Spokesman, Volume 42, Number 8 is published by NLGI, 4635 Wyanchotte St., Kansas City, Me 64112, USA
Engineering maintenance
Engineering plastics
Based on experience of over 500 assignments in the last 5 years, Idhammar Konsult AB have produced a 160 page manual on engineering maintenance. This course in basic maintenance is aimed at supervisors and operators.
Ciba--Geigy's Plastics Division have produced a 24 page booklet for design engineers on Crastine, one of their thermoplastic polyester moulding compounds which is marketed in the UK under the trade name Tenatine.
The manual covers general principles, economics, aspects associated with design, purchasing and installation, condition monitoring, maintenance work and maintenance systems. One valuable aspect of the book is that it relates maintenance to specific components, such as bearings, gearboxes, couplings etc, rather than making general comments.
The bulk of the booklet is devoted to assembly methods, followed by short sections on machining and finishing. The final three pages give information on bearings and gears.
Yhe~uthors' attempt to cover such a broad subject in a relatively limited space inevitably opens them to the criticism of some superficiality. For example, they show graphically the savings from condition based maintenance, but give no guidelines on how much to spend on establishing a condition monitoring system. Also, one can only agree with the authors' comment that the chapter on inspection instruments and aids "does not claim to be complete". Copies of 'Reliability and Maintenance 1' are available, price S.Kr. 160, from Idhammar Konsult AB, Box 30, 14700 Tumba, Sweden
TRIBOLOGY international June 1979
Ciba-Geigy Plastics and Additives Company, Plastics Division, Duxford, Cambridge CB2 4QA, UK
Graphite powders According to Lonza, the effectiveness of graphite in lubricants is governed by purity, crystalline structure, texture and particle size distribution. They have just published a brochure which aims "to set new accents in graphite powder characterisation and to create a better understanding with the industries using the material". The brochure outlines the properties of graphite powder, gives technical data on Lonza products, and indicates some applications. Copies are available from Lonza Ltd., Inorganic Chemicals Division, P.O. Box, CH-4002, Basle, Switzerland