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- 2014 (22) (entfernen)
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- Vortrag (8)
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- Ceramic (3)
- Cobalt (3)
- Friction (3)
- Hard metal (3)
- NbC (3)
- Niobium carbide (3)
- Oscillation (3)
- Wear (3)
- High temperatures (2)
- Modulus (2)
Eingeladener Vortrag
- nein (8)
Polyalkyleneglycols are oxygen containing base oils, which enable a) polymer-free formulations with high intrinsic viscosity indices favorable for fuel economy, b) bio-no-tox properties and c) low viscosity formulations with low evaporaions. The oxygen present in each monomer of the backbone of polyalkylene glycols defines intrinsic properties, such as high viscosity indices, low NOACK-evaporation, extreme pressure, high hear capacities, etc., thus enabling metal-, ash- and polymer-free engine oil formulations supporting the functional benefits, such as improved of fuel economy or no adverse effects on after-treatment devices.
Stribeck curve
(2014)
The importance of lubricants in virtually all fields of the engineering industry is reflected by an increasing scientific research of the basic principles. Energy efficiency and material saving are just two core objectives of the employment of high-tech lubricants. The encyclopedia presents a comprehensive overview of the current state of knowledge in the realm of lubrication. All the aspects of fundamental data, underlying concepts and use cases, as well as theoretical research and last but not least terminology are covered in hundreds of essays and definitions, authored by experts in their respective fields, from industry and academic institutes.
Wear
(2014)
Original equipment manufacturers (OEMs) and end-users perceive “wear” or “oil drain” differently. Spare parts, Services, and accessories contribute to an important portion to the profit of the OEMs. Maintenance and shutdowns define the operational costs of end-users. Thus, the strategy in order to exploit “wear” depends from the market structure and is up to the reader and/or applicant. The topic “Service Life/Durability/Life Cycle” represents a very ambiguous one and was already thematized in earlier times.
Coatings for slip-rolling
(2014)
We review contact mechanics with emphasis on the rheological (time dependent) properties of polymers and their relations to surface roughness, material properties, and friction as well as wear behavior of rubbing polymer surfaces. The main concept of polymer mechanics related to tribology consists of three basic elements involved in friction: deformation resulting in the real area of contact of rough surfaces, contact adhesion, and shear and rupture of materials in the contact during the sliding friction. The results of classical work are included, which addresses the real contact area calculation and the description of adhesion interaction between rough surfaces. A brief review of experimental investigations concerning the surface characterization by means of bearing curves, the intermolecular force interaction using the adhesion parameter, the effect of temperature on the real contact area, the formation of transferred polymer film during friction, and tribological behavior of ultrathin polymer layers are presented and their implications discussed.
Das triboiogische Profil von binderlosem NbC und mit 8% bzw. mit 12% Cobalt oder 12% FeaAl gebundenem NbC wird unter unidirektionaler Gleitreibung (v= 0,1-10 m/s, T= 22°C und 400°C) und unter oszillierender Gleitreibung vergleichend gegenüber Ingenieurkeramiken und Hartmetallen dargestellt. Zusätzlich werden die 4-Punkt-Biegebruchfestigkeit, elastische Eigenschaften (E,G) bis 1.000°C die lastabhängige Mikrohärte sowie die Phasenzusammensetzung und Gefügestrukturen vorgestellt.
Die Verschleißkoeffizienten des binderlosen NbC lagen bei T unterhalb von 10'6mm31 / *N* m, während diejenigen der cobaltgebundenen NbCs mit ansteigender Gleitgeschwindigkeit von 2-4 10‘6 mm3/Nm bei 0,1 m/s auf 5-7 10"7 mm3/Nm bei 10 m/s abnahmen. Die Verschleißkoeffizienten bei 400°C lagen für die NbCs generell unterhalb von 10‘6 mm3/Nm. Das triboiogische Lasttragevermögen im Trockenlauf, ausgedrückt als PV-Wert, nimmt mit ansteigender Gleitgeschwindigkeit auf 100 W/mm2 zu. Bedingt durch die geringe Löslichkeit von NbC in Legierungen offenbarten erste Zerspanversuche mit verschiedenen Stählen eine gegenüber WC-basierten Schneidstoffen signifikant angehobene Zerspanungsvolumina. Somit offenbart NbC in offenen und geschlossenen Tribosystemen Anwendungspotentiale.
Niobkarbid
(2014)
3 different base-stocks (poly-a-olefin, polypropylene glycol and unsaturated TMP ester) and these blended with 2 different additives (1wt% ZnDTP or 1wt% dibenzyl disulfide(DBDS)) were used as lubricants to evaluate the tribological properties of AA6061-T6 treated by means of plasma electrolytic oxidation in a SRV tribometer (Toi|=80 °C, Fn = 50N, v= 50 Hz, 2mm stroke, 2hrs). The base oils of PPG and the TMP-ester had better lubricities than the PAO with/without the additives. ZnDTP tend to reduce wear, but when added to PAO and PPG increased the friction. The unsaturated TMP-ester +1wt%DBDS showed 45% lower friction than PAO + ZnDTP (reference), whereas PPG + DBDS had 30% lower friction.
This paper presents a dry sliding tribo-couple (DLC/monolithic oxide ceramics), where the tribological quantities are more or less in a wide ränge independent of the sliding speed. The DLC film is composed of a specific mixture of sp3 /sp2 hybridized carbon. Self-mated ceramic/ceramic couples of MgO-Zr02, alpha-AI203 or SSiC are with their coefficients of friction above 0.45 not so lubricious, whereas the coefficients of friction of the tribocouples MgO-Zr02/DLC and alpha-AbOVDLC ranged between 0.075 and 0.15 under dry sliding. The coefficients of friction for these tribo-couples tend to decrease with increase sliding speed from 0.03 m/s to 6 m/s. The dry wear rates of the thin film is low (<10‘7 mm3/Nm) and perfectly independent from sliding velocity.
The tribological profile of rotating disks made in binder-less niobium Carbide (hot-pressed NbC) and cobalt-bonded NbCs (NbC-8Co and NbC-12Co) mated against alumina (99.7%) were determined under unidirectional sliding tests (0.1 m/s to 8.0 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= 105/l 06 cycles) under unlubricated (dry) conditions. In addition, the microstructure and mechanical properties of HPNbCl and NbC bonded with 8 vol.-% and 12 vol.-% cobalt were determined as well. The tribological data obtained were benchmarked with different ceramics, cermets, hard metals and thermally sprayed coatings, where the NbCs bonded with 8% and 12% Co presented above 7 m/s the lowest wear rates so far in such a bench mark. HP-NbCl, NbC-8Co and NbC-12Co exhibited low wear rates under dry sliding associated with PV high load carrying capacities. The tribological profile established revealed a strong position of NbC bearing materials under tribological considerations and for closed tribo-systems against traditional references.
Die Ausbildung von tribologisch günstigen Grenzschichten ist eine häufig für die Phase des Einlaufs angenommene Modellvorstellung. Solche tribologisch günstige, durch Reibungsvorgänge im Kontaktbereich induzierte Triboschichten, werden in der Fachliteratur auch als sog. Beilby- und Cervovit-Schichten oder auch als Tribomutationen bezeichnet. Durch eine Vorkonditionierung mittels modifizierter Schmierstoffe oder durch Kaltverfestigung kann der Verschleiß in Wälzkontakten signifikant erniedrigt werden. Bislang ausgeblieben ist eine deutliche Reibungsminderung, aber es wurde keine Reibungserhöhung gemessen. Es waren die Ziele, mithilfe geeigneter Schmierstoffadditive in Verbindung mit dem Prozess des Kaltverfestigens durch das „Dichtwalzen“ (unter Hertz’schen Kontaktpressungen oberhalb von Pmax = 3,0 GPa), ohne Vorschädigung, eine metallurgische Veränderung zu erzielen und gleichzeitig durch einen induzierten Tribofilm geschützte Stahloberfläche zu erhalten, sodass thermochemische Behandlungen durch diese Konzepte einzeln oder kombiniert substituiert werden können.
The tribological and mechanical properties of niobium carbides (NbC) bonded with cobalt of Fe3Al
(2014)
The tribological and mechanical properties of niobium carbide bonded with 8 vol.-% (NbC-8Co), 12 vol.-% of cobalt (NbC-12Co) or 12 vol.-% of Fe3Al (NbC-12Fe3Al) are presented. Rotating discs made of metal-bonded niobium carbide were mated against alumina (99.7%) under unlubricated (dry) unidirectional sliding tests (0.1 m/s to 12.0 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=105/106 cycles). Microstructure and phase compositions were determined as well. The tribological data obtained were benchmarked with different ceramics, cermets, hard metals and thermally sprayed coatings, where NbC bonded with 8% and 12% Co presented above 7 m/s the lowest wear rates so far in such a benchmark. Binderless NbC (HP-NbC1) and the metal-bonded NbCs exhibited low wear rates under dry sliding associated with P·V high load carrying capacities. NbC-based hard metal bonded with 12 vol.-% of Fe3Al resulted in a higher hardness level than for 12 vol.-% cobalt. The tribological profile established revealed a strong position of NbC-bearing materials under tribological considerations and for closed tribosystems against established reference tribo-couples.
Tribologie
(2014)
Tribologie ist die Wissenschaft und Technik von aufeinander einwirkenden Oberflächen in Relativbewcgung (DIN 50 323, Teil I). Diese Definition ist aus der englischen Originalfassung abgeleitet: Tribology - Science and tcchnology of interacting surfaces in relative motion and the practiccs related thereto 11 ]. Die Tribologie umfasst die Teilgebiete Reibung, Verschleiß und Schmierung. Sie steht in enger Beziehung zu den Werkstoffen der beteiligten Körper, deshalb ihre Behandlung in Teil H.
The tribological profile of rotating disks made of binder-less niobium carbide (hot-pressed NbC) and cobalt-bonded NbC (NbC-8Co) mated against alumina (99.7%) were determined under unidirectional sliding tests (0.1 m/s to 8.0 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= 105/106 cycles) under un-lubricated (dry) conditions. In addition, the microstructure and mechanical properties of NbC and NbC bonded with 8% cobalt were determined as well. The tribological data obtained were benchmarked with different ceramics, cermets, hard metals and thermally sprayed coatings, where the NbC-8Co presented above 7 m/s the lowest wear rates so far in such a bench mark. NbC and NbC-8Co exhibited low wear rates under dry sliding associated with P·V high load carrying capacity. The tribological profile established revealed a strong position of NbC bearing materials under tribological considerations and for closed tribo-systems against traditional references.
Wear tests are often used in engine development in order to characterize the functional profile of surfaces interacting with lubricants. This paper proposes a new test procedure to determine Stribeck-type curves for the tribosystem piston ring/cylinder liner involving test pieces prepared from engine components. The variation of the friction coefficient with sliding speed depends on the structure and constitution of the base oil, the viscosity index, the surface topography of the liner and ring, and the friction modifiers used. Novel organic friction modifiers of low molecular mass not only reduce the friction coefficients under mixed / boundary lubrication, but also in the fluid film regime. In addition, the influence of surface roughness on the wettability of surfaces can be significant for both static and dynamic wetting. For this reason, the interaction of the lubricant with the surfaces was also investigated to enable a correlation between the surface properties of the liquid and solid phases and the tribological behavior.