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Fiedler M.,Hamburg University of Applied Sciences | Kuhn E.,Hamburg University of Applied Sciences | Franco J.M.,University of Huelva | Litters T.,Fuchs Europe Schmierstoffe GmbH
Tribology Letters | Year: 2011

Friction and wear tests were performed with a number of greases based on biogenic esters and thickened with two metal soaps and a highly dispersed silica acid gel. The series of experiments was performed on a Nonotribometer in material combination of sapphire ball on steel disks with a range of normal loads from 1 up to 500 mN. Results directly show influences of the bulk grease components on frictional and wear behavior. Comparison of frictional and wear results makes manifest that, while in most combinations of base oil and thickener, the highest influence is found in the thickening agent, some combinations are mainly influenced by the base oil. All frictional results along with wear widths and depths as well as micrographs of the prevailing wear mechanisms are presented and discussed. © 2011 Springer Science+Business Media, LLC. Source


Gili F.,Fiat Group | Igartua A.,Fundacion TEKNIKER | Luther R.,Fuchs Europe Schmierstoffe GmbH | Woydt M.,BAM Federal Institute of Materials Research and Testing
Lubrication Science | Year: 2011

The dilution of biogenic fuels into lubricating engine oils often leads to a shortening of the recommended oil drains (between 30% and 60%) and an increase in wear. The large number of overlapping and influencing factors, of which dilution and polymerization of fuel components in the engine oil are emphasised, makes it difficult to find a uniform solution to prevent failures in the various applications. Insofar single solutions for the different types of biofuels are needed. The contribution of base oil chemistry and additives as well as triboactive materials is featured to deal with the adverse effects of biofuels. In the frame of the European Commission (EC)-funded project 'cleanengine', tentative engine oils based on esters with a content of renewables and polyglycols are formulated to increase the lubricant's tolerance in engines fuelled with biofuel-based blends, with the aim of ensuring required lubricating and wear protection performance while keeping oil drain intervals unchanged. The present paper focuses on four-stroke diesel applications, fuelled by biodiesel (fatty acid methyl ester â FAME) as well as by rapeseed oil and Jatropha oil (pure vegetable oils, triglycerides), together with relevant blends of those biofuels and conventional diesel fuel. This paper screens the functional profile (in particular rheological, toxicological, bio-compatibility, tribological and biofuels affinity) of lube families with respect to biofuel contamination. Moreover, this is followed by the contributions of piston ring and liner materials as well as thin film coatings. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd. Source


Braun J.,Fuchs Europe Schmierstoffe GmbH
Sealing Technology | Year: 2011

This feature article looks at the new ISO methods for elastomer testing and specifying standard reference elastomers. Current methods are compared with those specified by previous DIN standards, the differences are pointed out and their effects on the test results are discussed. © 2011 Elsevier Ltd. Source


Wolfrath T.,Fuchs Europe Schmierstoffe GmbH | Lubben T.,IWT - Foundation Institute of Materials Engineering | Frerichs F.,IWT - Foundation Institute of Materials Engineering
HTM - Journal of Heat Treatment and Materials | Year: 2014

Immersion quenching is a widely used technique in heat treatment workshops, because these techniques provide higher heat transfer coefficients than gas and liquid salt quenching techniques. The disadvantage of immersion quenching in evaporating fuids can be the complex heat transfer mechanism which consists of the three stages of quenching film boiling, nucleate boiling, and convection. Especially the transition from film to nucleate boiling - the rewetting of the sample surface - is a complex process which leads to a strong position dependence of the heat transfer coefficient of the cooled work pieces. In order to minimize the risk of distortion mostly high performance quenching oils can be used, because these kinds of oils offer a shortened film boiling phase. However, by application of those oils the effect of deformation can be reduced but not completely eliminated. Maybe an improvement of the distortion behavior can be achieved by using water-polymer-solution, because the rewetting occurs in such media very fast, almost explosively over the entire work piece surface. To verify this assumption in a more detailed manner, the distortion behavior of SAE52100 thin walled bearing rings was investigated by quenching the rings in polymer-water-solution, in high performance quenching oil, and with nitrogen in a gas nozzle field. Further the influences of different batch structures and bath temperature of the polymer solution were investigated. On the basis of quenching experiments with distortion sensitive bearing rings it could be shown that using polyvinyl pyrrolidone (PVP) based polymer-water-solution result in some cases to comparable, if not even better results than those obtained by using high performance quenching oil. Source


Koskinen J.,University of Helsinki | Tapper U.,VTT Technical Research Center of Finland | Andersson P.,VTT Technical Research Center of Finland | Varjus S.,VTT Technical Research Center of Finland | And 3 more authors.
Surface and Coatings Technology | Year: 2010

It has been demonstrated that tetrahedral amorphous carbon (ta-C) films provide excellent wear and friction properties in dry sliding. Recently the applications of ta-C coatings in lubricated conditions have become more important. The use of carbon coatings aims at reducing the wear and coefficient of friction under minimum lubrication and without hazardous lubricant additives. For optimum tribological performance, a modification of the ta-C coated surfaces is required. The present paper describes an innovative method of coated surface texturing, by which nanometer and micrometer size pores are processed by various methods. Particle masking was used for processing micrometer size pores and for controlling the coating growth conditions in order to produce nanometer size pores in the ta-C surface. The masking by particles yielded a pore geometry which varied from complex shaped channels to small individual pores. The texturing was performed by distributing metallic powder particles on the surface or by direct chemical deposition of metal particles on the substrate in prior to pulsed vacuum arc deposition. The tribological characterization was carried out by applying reciprocating friction tests with controlled lubricant replenishment, in order to simulate metal forming processes. The friction reducing effect, which was observed in the tribological tests, indicated a microlubrication effect of the textured coating surfaces. © 2010 Elsevier B.V. Source

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