Diamantähnliche Kohlenstoffschichten (DLC) zeichnen sich durch ein sehr günstiges Reibungs- und Verschleißverhalten aus. Auf vielen Werkzeugen und hochbelasteten Bauteilen ist DLC daher bereits erfolgreich im Einsatz. In naher Zukunft wird die Bedeutung dieser Schichten als Oberflächenschutz in tribologischen Systemen weiter ansteigen.
Wie viele Applikationsbeispiele zeigen, ist die Leistungsfähigkeit von DLC als Schicht zur Verringerung von Reibung und Verschleiß zwar groß, weist aber auch Grenzen auf. Vor allem bei höheren Temperaturen (> 300 °C) treten Strukturveränderungen oder sogar Oxidationsvorgänge auf, die auch die tribologischen Eigenschaften der Schichten verschlechtern können.
Reibungs- und Verschleißuntersuchungen (Schwingungsverschleiß) von DLC-Schichten wurden im Temperaturbereich von 25 °C bis 250 °C durchgeführt und zeigen ein schnelleres Durchreiben der Schicht bei höheren Temperaturen. Die Lebensdauer der Schichten wird mit zunehmender Prüftemperatur reduziert. Einsatzgrenzen für DLC-Schichten können abgeleitet werden.
The tribological behaviour of unfilled thermoplastic polyurethane (TPU) and a polymer sphere filled (TPUG) thermoplastic polyurethane have been studied under oscillating sliding condition against cast iron as a counterpart. In the case of unfilled TPU, the wear mechanisms are dominated by particle detachment and roll formation. In principle, TPUG also showed a similar wear mechanism as that of unfilled TPU; in addition, particle pull-out and delamination are also observed. Wear volume of TPUG was significantly higher than that for the unfilled TPU and this is attributed to the different material removal processes taking place in the material during sliding. The polymer spheres as a filler material deteriorated the wear resistance of TPU because of improper adhesion and bonding of filler in the TPU matrix and therefore it contributed to more wear. In case of TPU the friction behaviour was strongly dependant on the temperature and surface roughness of the counter body. The results showed that below the glass transition temperature higher friction values are observed with higher counter body surface roughness. However, above the glass transition temperature, higher friction values are observed with a smoother surface roughness of the counter body. In case of TPUG, the friction behaviour was not significantly dependent on surface roughness of the counter body.
The influence of temperature and counterbody material on the tribological properties of a-C:H
coatings deposited on Cronidur 30 steel has been investigated in a lubricated ball on disk
contact situation with alpha-alumina and silicon nitride as counterbodies. The results show, that the wear volumes of the systems increase exponentially with increasing temperature, for alpha-alumina more than for silicon nitride. Two different wear mechanisms seem to have a
major influence: First, the abrasive action due to materials hardness and second, the tribo-oxidation when silicon nitride is counter material.
The influence of temperature and counterbody material on the tribological properties of a-C:H coatings deposited on Cronidur 30 steel has been investigated in a lubricated ball on disk contact situation. The results show, that the wear volumes of the system increase exponentially with increasing temperature. Two different wear mechanisms seem to have a major influence: First, the abrasive action due to materials hardness and second, the tribooxidation when silicon nitride is counter material.