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Eingeladener Vortrag
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Biolubrifiants
(2013)
Les huiles perdues, les fuites accidentelles et les lubrifiants perdus rejoignant les sols et les eaux (comme ce fut le cas pour le lac de Constance par exemple) sont l'un des points de departs de la mise en route des lubrifiants « neutres pour l'environnement».
Meme en prenant en compte les voies du recyclage, la combustion dans les moteurs et les fuites connues, environ 30 % (entre 20 % et 40 %, selon les etudes du votume de lubrifiants entrent dans l'environnement par des voies non maitrisees ou sont probablement mis en decharge de maniere illegale. Avec de tels chiffres publies, les arguments des lobbyistes de l'industrie petrochimique, affirmant que, dans la plupart des applications, les fluides sont enfermes dans des reservoirs dos et etanches, ne convainquent pas les politiques. C'est aussi peut-etre parce qu'en Allemagne, environ 60 % des particuliers changent leur huile eux-memes.
Dans une annee d'economie normale, environ 4,5 millions de tonnes de lubrifiants neufs sont vendues dans l'Europe des 15.
The tribological profile of alumina (99,7%) mated against binderless niobium Carbide (NbC) rotating disks under under unlubricated (dry) friction and the type of motions of unidirectional sliding (0.1 m/s to 7.5 m/s; 22°C and 400°C) and oscillation (f= 20 Hz, Ax= 200 mm, 2/50/98% rel. humidity, n= 105/106 cycles) was determined including the microstructure and mechanical properties. The obtained tribological data were benchmarked with different ceramics, cermets and thermally sprayed coatings. The established tribological profile revealed a strong position of NbC under tribological considerations and for closed tribosystems against traditional references, like WC, Ci‘3C2, (Ti,Mo)(C,N), etc..
Environmental legislations prescribe globally more and more environmentally acceptable lubricants (EALs), based on esters and polyglycols. The compatibility of EALs with tribo-materials used in hydraulic System such sliding parts and oil seals needs to be considered. Aluminium alloys are widely used as lightweight material for sliding parts in many applications. It is necessary to provide optimized design on its surface because of the inferior wear resistance under mixed/ boundary lubrication. The AA6061 alloy (uncoated and coated by different conversion coatings) and an alternative AI-Fe-XY alloy (uncoated) were tested by a continuous sliding test (cylinder-on-disk) under mixed/boundary lubrication with commercially available EALs at 80°C against 100Cr6 Steel. Appropriate combinations of aluminium alloys (coated or uncoated) and commercially available EALs have the potential to compete with conventional tribo-system like steel/steel lubricated with mineral hydraulic fluids under mixed/boundary lubrication.
The tribological profile of alumina (99.7%) mated against rotating disks in two niobium Carbide (NbC) grades were determined in unidirectional sliding tests (0.1 m/s to 7.5 m/s; 22°C and 400°C) as well as in oscillation tests (f= 20 Hz, Ax= 0.2 mm, 2/50/98% rel. humidity, n= 1062 c* y*c *l es) under unlubricated (dry) conditions. In addition, the microstructure and mechanical properties of NbC were determined as well. The reason for testing hot-pressed NbC was to avoid side effects generated by sintering additives and/or second phases. The tribological data obtained were benchmarked with different ceramics, cermets and thermally sprayed coatings. NbC exhibited low wear rates under dry sliding associated with high load carrying capacity. The tribological profile established revealed a strong Position of NbC under tribological considerations and for closed tribo-systems against traditional references, such as WC, Cr3C2, (Ti,Mo)(C,N), etc..
Highly concentrated or loaded contacts in powertrain and gear applications offer significant weight savings in C02 emissions. Today, thin film coatings, alternative base oils and new additives are populär as working fields and strategies of OEMs to realize low friction tribosystems. Especially the automotive industry anticipates environmental and performance benefits in applying light-weight construction of mechanical parts, for instance in gears and engines. Light-weight strategies increase the contact stresses above 2.14 GPa (or FZG load stage 14) due to the reduction of component sizes. These demands directly raise questions about the suitability of the most promising technical solution. Alternative steels with improved mechanical properties, i.e. toughness values, which offer low coefficients of friction, optimal resistance to high contact pressure and potential to apply low friction surface coatings representing a valid alternative to conventional gear steels. Traditional bearing and gear steels, such as 100Cr6 (SAE E52100) or 16MnCr5 (1.7131) have reached their mechanical limits at contact pressures above FZG load stage 14.
The tribological profile of alumina (99.7%) mated against rotating disks in two niobium carbide (NbC) grades were determined in unidirectional sliding tests (0.1 m/s to 7.5 m/s; 22°C and 400°C) as well as in oscillation tests (f= 20 Hz, δx= 0.2 mm, 2/50/98% rel. humidity, n= 106 cycles) under unlubricated (dry) conditions. In addition, the microstructure and mechanical properties of NbC were determined as well. The reason for testing hot-pressed NbC was to avoid side effects generated by sintering additives and/or second phases. The tribological data obtained were benchmarked with different ceramics, cermets and thermally sprayed coatings. NbC exhibited low wear rates under dry sliding associated with high load carrying capacity. The tribological profile established revealed a strong position of NbC under tribological considerations and for closed tribo-systems against traditional references, such as WC, Cr3C2, (Ti,Mo)(C,N), etc.