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A novel tribometer has been designed using commercially available components for sliding motion at 40kHz with amplitude between 2.5 and 5µm. The tribometer is equipped with means to measure amplitude, frequency, power required to keep the sample in motion and load applied. The effective motion between the two contacting bodies is monitored. These data are used to evaluate the coefficient of friction. The wear rate was determined after the tests. The set-up was tested using novel, non-commercial substrates such as AlFeCrTi-alloys and tungsten carbide-based coatings as well as Magnéli-type coatings (Tin-2Cr2O2n-1 and TinO2n-1). This paper presents the principle of the ultra-high frequency tribometer and first tribological quantities of materials and coatings tested.
The use of alternative base oils, like esters or polyglycols, with more intrinsic properties for the lubrication of automobile engines has a potential for ecological and technical advantages. Being in competition with hydrocarbon-based formulations, detailed knowledge of several thermophysical and viscometric properties as well as tribological properties over a large temperature range are required (mapping). The tested polymer-free polyglycols and ester-based formulations displayed no visible tribological weaknesses regarding wear resistance and EP-behavior as well as offering significant advantages in order to meet metal- and ash-free and bio-no-tox criteria. Especially the formulated polyglycols without friction modifiers also showed an intrinsic retention of low coefficients of friction and a hydrodynamic film forming behavior comparable to hydrocarbon-based factory-fill oils. The wear resistance and EP-behavior of low-additivated polyglycols, but also of esters, can be enhanced by means of triboactive materials. Lubricious oxides or triboactive materials and polar base oils, or a combination thereof, may substitute the EP and AW properties realized by the additives, thus enabling long drains and responding to eco-tox or bio-no-tox requirements as well as restrictions from the chemical box.
Testing friction and wear of the tribosystem piston ring and cylinder liner outside of engines
(2008)
An OEM-driven working group started in January 2004 to elaborate the philosophies, concepts and test procedures for testing piston ring and cylinder liner materials as well as engine oils outside of engines using the SRV (abbreviation for German: Schwingung, Reibung, Verschleiß; in English: Oscillation, Friction, Wear) test equipment. The different SRV test philosophies in use by OEMs are compiled. The working group focuses on (i) ASTM fuel economy sequence by ageing oils; (ii) friction and wear in the top-dead-centre region under mixed/boundary lubrication; (iii) extreme pressure load under mixed/boundary lubrication; and (iv) hydrodynamic friction. Tribological test results and precision data are presented.
The research institution TEKNIKER has coordinated the EUROPEAN Project EREBIO, were different biodegradable lubricants have been formulated by FUCHS and BAM for heavy duty engines (GUASCOR), and passenger cars (RENAULT). In the frame of this article, it has been summarised the results obtained when developing biodegradable passenger car lubricants in combination with triboreactive materials.
Replacing hydrocarbon-based oils with biodegradable products is one of the ways to reduce adverse effects on the ecosystem caused by the use of lubricants. The application of low or no sulphur, ash and phosphorous (lowSAP) ester- or polyglycol-based oils, intended for passenger car engine lubricants as substitutes for hydrocarbon-based oils, required the preparation of a composition of lubricants with comparable tribological and functional properties.
The study is focussed on passenger car motor oils (PCMO) with reduced metal-organic additives. This is necessary in order to reduce the ash build-up in the after treatment system and therefore improve its efficiency and lifetime. High fuel efficiency and long drain intervals are requested, as well. To follow a line in a consequent way, these oils have to be biodegradable and non-toxic to the aqueous environment according to the directive EC/1999/45, coherent with other international standard. In a modern diesel or gasoline engine, the engine oils has to fulfil quite a number of different functions, such as lubricating and cooling the system, wear protection, soot and particle handling with less deposit tendency and so on.
In the paper a study of the biodegradability, toxicity and the tribological properties has been carried out for new developed prototype engine bio-oils. Also, some different plasma sprayed triboreactive coatings have been deposited on cast iron piston rings, being studied also their tribological properties. Finally, the behaviour of the new bio-oils selected and plasma sprayed triboreactive coatings on piston rings have been screened in a real engine.